Klinefelter syndrome (KS)  is the most common sex chromosome disorder, with a prevalence of 1 in every 660 newborn males. Despite the profound adverse effects of anxiety and depression, and their greater prevalence in KS populations, no research has been conducted to date to identify the determinants of anxiety and depression among patients with KS. We examined the relationships between personality traits, social engagement, and anxiety and depression symptoms among KS patients (n = 69) and a group of male controls (n = 69) matched for age and years of education. KS patients experienced more anxiety and depression symptoms than control participants. Neuroticism was the strongest and most consistent mediator between KS and both anxiety and depression symptoms. This research suggests that neuroticism may play a central role in attention switching, anxiety and depression among patients with Klinefelter syndrome. The central role of neuroticism suggests that it may be used to help identify and treat KS patients at particularly high-risk for attention-switching deficits, anxiety and depression. Klinefelter syndrome (KS) 47, XXY) is the most common sex chromosome disorder, with a prevalence of 1 in every 660 newborn males . KS is a7, XXY isvulnerability model of psychopathology, which hypothesizes that personality traits contribute significantly to the development of psychiatric disorders[Personality traits represent an important group of potential predictors of KS patients’ anxiety and/or depression, as they develop early in life, they are stable over time, and they have been linked to various forms of psychopathology –14. Incrdisorders;19. Prevdisorders. HoweverIn addition to personality traits, social engagement has also been proposed as an important factor in relation to psychopathology –24. SociTo address these issues, we examined the relationships between personality traits, social engagement, and anxiety & depression symptoms among KS patients and a group of male controls matched for age and years of education. Both zero-order and path analyses were performed to identify direct and indirect relationships between these study variables.Patients with verified KS were recruited from endocrinology, genetics and fertility clinics in Denmark. Participants included 69 KS patients with 47,XXY karyotype, with a mean age of 36.4 years (SD = 10.0), and an average of 12.6 years (SD = 2.35) of formal education. At the time of participation, 48 (70%) of the patients with KS were receiving testosterone, and 21 (30%) were not. Fourteen of these 21 KS patients had never received testosterone treatment, while 6 had been treated with testosterone in the past . One patient with KS reported being treated with testosterone for an unspecified period in the past.In addition, 69 matched male controls—with a mean age of 36.4 years (SD = 9.6) and an average of 12.8 years (SD = 2.21) of formal education—were recruited through advertisement in local hospitals, newspapers, fire departments, and other civil service offices. There were no significant differences between KS and control participants in either age or education level (ps >.84). Inclusion criteria required that participants be between the ages of 18 and 60, and exclusion criteria included a history of substance use, and neurological disease or head injury more severe than simple concussion. All participants received oral and written information about the requirements of the study before written consent was obtained, and informed consent was obtained before participation was initiated. The study was approved by The Danish Data Protection Agency and local ethics committee  and registered at ClinicalTrials.gov . Certain neuropsychological data from this research has been presented previously to address separate research questions ;33.Personality traits were assessed using the Revised NEO Personality Inventory (NEO PI-R) short form. This foSocial engagement was assessed using the Autism Spectrum Quotient (AQ) . This quSymptoms of anxiety and depression were assessed using the anxiety (SLC-ANX) and depression (SLC-DEP) subscales of the Symptom Checklist (SLC-90);37. The Testosterone levels for all participants were measured by liquid chromatography tandem mass spectrometry, using Perkin Elmer´s CHS steroid MS kit. The lower limit of detection was 0.1nmol/L and the working range 0.2-100nmol/L.In preliminary analyses, KS patients were first compared with controls in terms of testosterone, personality, social engagement, and anxiety and depression symptoms. Bivariate relationships were then calculated between the continuous study measures. In the primary analyses, two sets of three regressions—one set for anxiety, and one for depression—were conducted in which each of these two dependent measures (anxiety and depression) was regressed simultaneously on 1) personality traits, 2) social engagement measures, and 3) testosterone status, while controlling for KS status. Finally, a path analysis was conducted which included both anxiety and depression, as well as their respective bivariate predictors. Because path analysis is the functional equivalent of a series of multiple regressions in which each variable in the model is successively regressed on the other variables, it controls for multicollinearity and indicates the independent relationship between each of the factors in the model. As with the preceding regression analyses, variables in the path model were entered simultaneously—rather than hierarchically—and statistically significant relationships were included in the final path model, while non-significant associations were not.Continuous data were tested for normality using Kolmogorov-Smirnov test, and those with distributions of Dα > 0.23 were considered non-normal, and were normalized using a loglinear (ln+1) transformation. Differences between groups were analyzed with parametric Student´s t-test for normally distributed data. Otherwise, data were analyzed using the Mann–Whitney–Wilcoxon test. Chi-Square tests were used for nominal variables. P-values lower than 0.05 were considered significant. SPSS version 19.0  was used for statistical data analysis.KS patients exhibited significantly higher neuroticism than controls, as well as significantly lower extraversion, openness to experience, and conscientiousness . KS and KS patients scored significantly lower than controls on attention switching, imagination, communication, and social skills. However, KS patients and controls did not differ in attention-to-detail, nor did KS patients treated with testosterone differ in social engagement from untreated KS patients.KS patients reported significantly more anxiety and depression symptoms than controls, although there were no differences between KS patients treated with testosterone and those who were not.KS patients had a significantly higher levels of testosterone than controls, reflecting the fact that the majority of these KS participants were receiving high doses of exogenous testosterone. Similarly, testosterone levels among KS patients receiving testosterone therapy were significantly higher than those not receiving this therapy.In addition to being related with each other, less neuroticism and more extraversion, conscientiousness, communication, attention switching and social skills were all associated with fewer anxiety and depression symptoms . No sign2 = .30, p<0.001), but neuroticism was the only significant individual predictor , with both KS status and attention switching emerging as significant predictors (ps<0.05). When KS status and testosterone levels were combined to predict anxiety, the full model was again significant , but this was attributable solely to the impact of KS status.When KS status and personality measures  were combined to predict anxiety symptoms, the overall model was significant , with neuroticism emerging as the lone significant predictor (p<0.001). Depression was also predicted by KS status and social engagement  , with attention switching as the significant predictor (p < .001). When combining KS status and testosterone status, the overall model was significant , but this was attributable to the impact of KS status (p = .01).As shown in When the significant personality and social-engagement predictors were combined with both anxiety and depression symptoms in an overall path analysis, neuroticism fully mediated the impact of KS status on both anxiety and depression (ps < .05), as seen in This research examined the influence of personality, social engagement and testosterone treatment on anxiety and depression levels among KS patients. Although many of these measures were significant bivariate predictors of anxiety and depression symptoms, subsequent regressions indicated that only neuroticism and attention switching helped to explain the effect of KS on these indices of mental health. Finally, a combined path analysis found that KS increased both anxiety and depression symptoms through greater neuroticism.These results are consistent with previous studies that have found more anxiety and depressive symptoms among patients with KS ;4;7, butIn this research, higher levels of neuroticism also mediated KS patients’ deficits in attention switching. Attention switching is related to control processes of cognition such as perception, initiation, inhibition, and executive function;45. As sThe current results also have a number of practical implications for interventions to improve the well-being of individuals with KS. First, the central role of neuroticism suggests that it may be useful as a marker to identify KS patients at particularly high-risk for anxiety, depression and attention-switching problems, who would benefit most from assistance in these areas. A second possibility is suggested by studies finding that neuroticism levels can be raised or lowered through experience and/or training . These rWe did not find any influence of testosterone treatment on anxiety and depression levels among KS patients, which is in contrast with meta-analyses showing a positive impact of testosterone treatment on depressive symptoms in non-KS hypogonadal men from the general population –49. The The limitations of this study include the cross-sectional nature of the research design. Although it takes advantage of the early development of personality—and even earlier onset of KS—it cannot determine the directionality or causal relationships between the study variables. Future longitudinal and experimental research will be useful to confirm the directionality of these effects, as well as their effectiveness in enhancing the well-being of KS patients, and perhaps other at-risk populations.Another limitation of this study is that we did not assess socioeconomic variables. KS is associated with lower socioeconomic status—including lower educational and income, earlier retirement and fewer partnerships —which inAs the first study to assess the influence of personality traits and social engagement on anxiety and depression among KS patients, this research suggests that personality, particularly neuroticism, plays a central role in attention switching and both measures of mental health. Future studies with larger sample sizes, longitudinal and experimental designs, and additional factors may help address many of the remaining questions, and further our understanding of KS-related deficits, and in turn, improve these and other important health outcomes.


Midbrain dopamine seems to play an outsized role in motivated behavior and learning. Widely associated with mediating reward-related behavior, decision making, and learning, dopamine continues to generate controversies in the field. While many studies and theories focus on what dopamine cells encode, the question of how the midbrain derives the information it encodes is poorly understood and comparatively less addressed. Recent anatomical studies suggest greater diversity and complexity of afferent inputs than previously appreciated, requiring rethinking of prior models. Here, we elaborate a hypothesis that construes midbrain dopamine as implementing a Bayesian selector in which individual dopamine cells sample afferent activity across distributed brain substrates, comprising evidence to be evaluated on the extent to which stimuli in the on-going sensorimotor stream organizes distributed, parallel processing, reflecting implicit value. To effectively generate a temporally resolved phasic signal, a population of dopamine cells must exhibit synchronous activity. We argue that synchronous activity across a population of dopamine cells signals consensus across distributed afferent substrates, invigorating responding to recognized opportunities and facilitating further learning. In framing our hypothesis, we shift from the question of how value is computed to the broader question of how the brain achieves coordination across distributed, parallel processing. We posit the midbrain is part of an “axis of agency” in which the prefrontal cortex (PFC), basal ganglia (BGS), and midbrain form an axis mediating control, coordination, and consensus, respectively. Dopamine is widely associated with providing value-related signals that serve activational and teaching functions. We shift focus from computing value-related signals and develop a hypothesis that suggest midbrain dopamine is sampling and integrating distributed neural activity to recognize and signal consensus across distributed, parallel processing. We posit each dopamine cell acts like an index of afferent activity and serves as a Bayesian unit detecting opportunity reflected in activity across distributed substrates. When cells across a dopamine population converge on the same temporal patterns, dopamine cell synchrony emerges generating a consensus signal that facilitates responding and learning. In this view, the fundamental role of dopamine is to signal consensus across parallel processing to facilitate unified behavioral responding.The midbrain dopamine system is integral to mediating value-based neural activity underlying adaptive behavior . EvidencThe nature of dopamine’s contribution to value-based adaptive behavior continues to be contentious. While evidence demonstrates that dopamine can encode prediction errors , dopaminMany excellent reviews discuss the various issues outlined . Here, wt, obtained reward rt) were delivered to the midbrain. These models centered around the basal ganglia (BGS) connections with the midbrain  in a region such as the amygdala translated into a single quantity  and then distributed broadly across a population of dopamine cells? Short of every neuron in an ensemble within a particular afferent region being connected with every dopamine cell, it is not clear how this ensemble->scalar translation could be achieved and uniformly deliver the required quantity across the midbrain.Together, these issues argue that the notion that discrete quantities are computed in particular afferent regions and delivered to the midbrain is not consistent with the anatomy and largely untenable. Instead, it appears that the midbrain is integrating a highly diverse set of inputs drawn broadly from across the brain and that these inputs may contain various, non-segregated value-related information. While this provokes the question of what information is being integrated, how and to what end, before considering this we have to consider the particularities of the output side of the dopamine system.The midbrain dopamine nuclei contain a modest number of neurons, in rodents ∼20,000–40,000 tyrosine hydroxylase expressing neurons, estimated to be between 400,000 and 600,000 in humans . Each neKm/Vmax , release will integrate and generate temporally resolved peaks and troughs in extracellular dopamine that maximize information transfer to postsynaptic targets. When spike activity is asynchronous, including asynchronous bursting activity, dopamine concentration will be distributed across time, reflecting the average spike rate. We will refer to “tonic” and “phasic” in terms of whether population spiking activity generates temporally resolved fluctuations in extracellular dopamine  or a distributed averaging of activity . Rather than reflecting two distinct modes of signaling, tonic and phasic represent two ends of a spectrum in temporal partitioning of dopamine cell activity. Phasic dopamine signaling has been construed as arising from uniformity in bursting activity, consistent with electrophysiological evidence where dopamine cell recordings show a high percentage of tested cells exhibit similar and consistent responses to stimuli  to fluctuations in extracellular dopamine concentration (amplitude modulation). While many factors can modulate this transformation, the critical determinant is the degree of synchrony among spiking neurons relative to the clearance rate of the dopamine transporter . When sp stimuli , as well stimuli .While initially it was thought that dopamine cells are in some way coupled generating obligate synchrony, accumulating evidence favor emergent synchrony in which cells function autonomously, but independently come to generate the same temporal patterns of activity. Gap junctions between dopamine cells  have beeIn studies examining pairs of dopamine cells, roughly 25% of dopamine cell pairs show significant correlation in spiking rate  with litWe are presented then with a stark contrast between midbrain dopamine input, highly diverse afferent inputs drawn broadly from across brain regions in which value-related information does not appear to be neatly compartmentalized by region but rather widely distributed and intermixed, and the dopamine output system, which relies on relative uniformity of spiking activity across dopamine cell populations to transmit a simple scalar to target regions. It is this transformation from heterogeneity of input to homogeneity of output that will concern us: we propose the transformation from polyglot to monosyllable is fundamental to dopamine’s function within the brain, and that the emergence of dopamine cell synchrony is the core mechanism mediating this function.Before describing our hypothesis, we want to tentatively reframe the putative problem the dopamine system evolved to solve. Widely viewed as the “reward transmitter,” various theories of dopamine describe a system that, in one way or another, helps the organism recognize and act on opportunities for value. In its most simplistic terms, the core evolutionary problem addressed is helping an organism to engage in actions that are advantageous, specifically by signaling value in some form .We wish to consider dopamine in the context of a different core evolutionary problem. A fundamental question in neuroscience is how distributed, parallel processes are integrated into a functional “whole-brain” model to generate unitary organismal action . The braThe function broadly associated with dopamine involves recognizing available reward opportunities, weighting decision making to act on opportunity, energizing responding and facilitating learning about the context and predictors in which the reward occurred: in short, to facilitate adaptive choices in the face of opportunity. Is this not what the entire brain evolved to do? “Value” is a (perhaps the) fundamental organizing principle of the brain. It is not merely that value is reflected in on-going neural processing broadly across neural substrates  but that the brain is structurally shaped and modified by value. During early development, synapses are pruned to select those that yield functionality  to the organism. Throughout life, neural plasticity shapes circuits and weights synapses to benefit the organism, i.e., obtain value.The challenge is ascertaining the root of the evaluative mechanisms that guide this value organization. How does the brain know what is good for it? While there are many potential answers to this question, one common answer is that dopamine distributes value information. Indeed, that is the core role of the reward transmitter regardless of one’s view on the form in which this information is delivered. But this immediately begs the question “how does midbrain dopamine ‘know’?” Who teaches the teacher? That is, how is this signal derived? All extant theories suggest that the midbrain obtains value information from afferent regions, but this quickly becomes circular. If dopamine is the teacher, how do afferent regions learn about value to inform the midbrain, and if afferent regions already recognize value, what need is there for a teaching signal in the first place? In short, the notion that dopamine distributes value information across the brain begs the question of how and where value is originally determined. Where is the ghost in the machine?While the brain must select stimuli to which to direct its attention and generate advantageous responses, the most fundamental selection process is how the brain represents self and world in the first place. That is, it is neural activity itself that must be selected to create adaptive, productive self-in-world models that, in turn, yield adaptive behavior. This assertion does not resolve the question posed above about how value is determined, but simply restates it in neural terms. However, doing so provides a different perspective. Rather than construe value as some quantity computed somewhere, we view the brain as being in a constant process of selecting productive and diminishing non-productive neural activity. While we cannot pretend to explain how this happens, we do not know where the “ghost” resides, we can draw a tentative corollary: value is implicit in neural activity. While this may sound radical, it is consistent not only with a broad construal of the fundamental function of the brain in mediating adaptive behavior, it is consistent with empirical studies that tend to find value information, in a variety of forms, distributed broadly across the entire brain  intersect in the ventral striatum, While most brain regions have been associated with particular kinds of information, the striatum exhibits remarkable malleability in its encoding. In virtually every task in which striatal activity has been monitored, every aspect of the task has been represented: stimuli/cues, actions, rewards as well as putative predicted value associated with these representations. Moreover, medium-spiny neurons will come to represent whatever is relevant in a task. If spatial locations are relevant, spatial locations will be represented in phasic MSN activity . If timeIn our characterization of the BGS and midbrain dopamine, we suggest both are integrating disparate afferents drawn broadly from across the brain, but the function of this integration is essentially opposite. During learning, dopamine cell activity becomes increasingly synchronous and homogeneous across a population of dopamine cells . In contWe propose that midbrain dopamine functions at the intersection of two axes : (1) a lIn our Bayesian construal, the computational goal is to determine the probability, the posterior, that distributed, parallel processes are responding to the same events in the on-going sensorimotor stream , reflecting the ability of those events to broadly organize neural activity, reflecting in turn implicit value; that is, to determine the probability that disparate primary substrates are organizing around and responding to the same events, consensus. Taking the excitatory (E) and inhibitory (I) axes proposed above as advocate and skeptic, respectively, we formulate our Bayesian construal as follows :The prior is comprised of the excitatory drive, P(E), reflecting the sampling of distributed processing discussed above. This afferent activity reflects “prior belief” because, as events enter the sensorimotor stream, the response of distributed afferents is shaped by prior experience and learning (response to novel stimuli addressed below). Thus, when multiple afferent regions respond to a sensorimotor event, this increases P(E), reflecting the prior probability that this event has an organizing impact on distributed processing.The likelihood, P(I | E)/P(I), is a function of striatal inhibition of dopamine. The denominator, P(I) reflects tonic inhibitory tone; this is the skeptic, maintaining a basal, inhibitory non-belief that diminishes the excitatory prior. This basal inhibitory tone is modulated by afferent input to the striatum (from many of the same regions contributing to the midbrain), P(I | E); that is, striatal inhibitory tone given the excitatory drive on the striatum. Thus, as events in the sensorimotor stream, such as a cue light, disinhibit striatal inhibition of the midbrain, the skeptic is diminished granting greater weight to the prior. We note that the “E” in P(E) and P(I | E) reflect the excitatory drives on the midbrain and striatum, respectively, and are not strictly the same quantity. We construe them as serving the same function in our construal, reflecting activity across distributed, parallel processing, i.e., primary processing, funneled to both the striatum and midbrain for different purposes.We propose that this Bayesian selector operates both at the level of individual cells and the population level. We suggested above that each dopamine cell is sampling afferent activity and serving as an index; here we elaborate this as a Bayesian index. As greater numbers of individual dopamine cells respond to the same events, emergent synchrony will increase, and with it a temporally defined phasic dopamine signal. Thus, the selector operates at the population level simply as a summation across cells, an index of indices, the sum of posterior probabilities from a population of afferent samples.t. P(E) can be construed as evidentiary without constraining the representational content of the afferent activity. Such activity, as While we present here apparent mathematical quantities, P(E), etc., these are very different from discrete quantities proposed in prior models, such as expected reward, VIn sum, we propose that midbrain dopamine is constantly sampling distributed neural activity monitoring for occasions when the input from both the advocate, P(E) and the skeptic, P(I | E)/P(I) agree that the current activity distributed across the brain reflects coordinated neural activity in response to an event in the sensorimotor stream that organizes distributed, parallel processing, reflecting implicit value: and as such, likely an opportunity to be acted on and learned about. When a large percentage of dopamine cells arrive at the same “conclusion,” synchrony arises and a temporally resolved fluctuation in extracellular dopamine emerges and encodes opportunity to act and learn.The notion that phasic dopamine signals consensus may at first seem contradictory to the widely accepted idea that dopamine provides a teaching signal. In our hypothesis, it appears that midbrain dopamine is the last to learn, not the teacher. This is consistent with studies that observe dopamine prediction errors emerge following, not preceding learning . We willFirst, primary learning occurs in afferent regions contributing to midbrain dopamine, such as the PFC, amygdala, hippocampus; that is, across the distributed substrates we called primary processing and identify as the prior, P(E). Second, learning occurs in the striatum and BGS system, altering inhibitory drive on dopamine, the likelihood, P(I | E)/P(I). Finally, learning occurs in the midbrain itself via synaptic plasticity, selectively strengthening and weakening particular synaptic inputs. We view this learning as cascading because it occurs in an interleaved fashion where each axis of learning modulates the others. For example, as primary substrates undergo learning, this alters the input driving both the BGS and midbrain, modulating both P(E) and P(I | E) in our Bayesian construal. Learning and activity in the primary substrates are, in turn, modulated by both BGS output and dopamine signals. Similarly, learning in the BGS alters inhibitory input to the midbrain, and modulated dopamine in turn alters learning in the striatum. The core idea here is that learning does not occur discretely in one substrate and then get transferred to another as a teaching signal, but that learning occurs simultaneously across all substrates in an interdependent fashion.A crucial objective for learning in distributed substrates is to coalesce into an organized whole-brain model to facilitate unitary action. The interleaving of BGS and midbrain learning contributes to the development of this coordinated organization. Midbrain dopamine signals growing consensus as learning progresses, arising through emergent synchrony , increasThis provides an alternative perspective on the emergence of prediction errors. Learning is initiated when an animal encounters known value  at an unexpected place and time. The prediction error hypothesis argues that surprise, the unexpectedness of that initial encounter, generates the dopamine teaching signal. Our hypothesis focuses on the known value aspect of that initial encounter: the encountered food pellet is well known to distributed neural substrates and induces a consistent, organizing response in those substrates that drives a dopamine consensus signal to facilitate further learning about the features of time and place that yielded the food opportunity, such as a cue light predicting the reward. We would further suggest that the emergent phasic dopamine response to the cue light does not reflect dopamine teaching target regions about the value of the cue light but, rather, that the “rest of the brain” has learned the value of the cue light and, as the cue light becomes a stimulus of “known value” across the brain, dopamine now signals consensus regarding the cue light: the last to learn.We wish to briefly touch on two possible objections to our notion that dopamine signals consensus. In one, a lack of phasic dopamine can be observed when one might, according to our hypothesis, expect it. In the other, conversely, dopamine cell bursting is observed when there would seem to be no basis for consensus across distributed processing.First, sometimes a well-predicted reward does not generate a phasic dopamine response. If the reward induces an organized, consistent response across distributed substrates, consensus, why does the dopamine signal disappear? We note first that this is not always the case, perhaps mostly not the case, and that a persistent dopamine signal in response to reward, even in well-learned tasks, has been repeatedly observed , where oSecond, novelty is known to induce increased dopamine cell activity , which sTemporal-difference theories of dopamine have been largely based on the idea that dopamine signals arise from a model-free system . The valWe suggest the crucial characteristic of dopamine signaling is when, not what. Dopamine mobilizes and energizes responding and facilitates learning. As a consensus signal, phasic dopamine is effectively saying “now,” which serves to activate and coordinate diverse target regions to collectively respond rapidly and vigorously in order to seize upon an opportunity. The crucial question, when is now?, can be answered with varying degrees of temporal precision: from a cue light indicating reward in one second to contextual stimuli, such as being in an task environment with a higher rate of reward availability . In our The point above begs the question, temporal model of what? We argue the “what” is when an event in the sensorimotor stream impacts neural activity and processing across multiple afferent substrates indicating the event has an organizing effect on distributed, parallel processing, reflecting implicit value. Such implicit value may correspond to the traditional economic sense, such as when a cue light predicts the imminent arrival of a delectable, tasty treat, but may also reflect implicit value in stimuli that organize neural activity to achieve non-traditional value, such as the ability to run the rotarod without falling off, or to execute a killer tennis serve. In essence, it is the neural activity itself that is being assigned a valuation for its utility in achieving some goal rather than valuation of what it is that neural activity is putatively representing. In short, the what corresponds to “when this neural activity arises, it reflects an opportunity for advantage and should be promoted and acted upon.”In our view, dopamine cells are collecting evidence, the midbrain is an evidentiary system, and that the representational nature (the content) of that evidence is unconstrained: basically, it can be anything and reflect whatever representational content is being processed in afferent regions driving midbrain dopamine activity. In our metaphor of a dopamine cell as analogous to an index of stocks, if one stock has a disproportionate effect on the index, say an automobile company, this does not mean that the index is “signaling automobile,” but if you look at what the index corresponds to in economic activity, it will correspond to increased car sales. Similarly, midbrain dopamine may generate a phasic response, signaling consensus and implicit value, that may correlate with any number of events, stimuli and actions depending upon the task. During a motor task such as the rotarod, dopamine cells may correlate to proprioceptive, vestibular and motor activity. During a task with visual cues, visual information may be embedded in and even dominate dopamine cell activity while in a task with auditory cues, auditory information dominates. In short, rather than encoding an abstracted value associated with different events, stimuli and actions, we propose that these appear in dopamine cell activity precisely to the extent to which they organize distributed, parallel processing in afferent regions, reflecting implicit not abstracted value.As noted above, many aspects of our hypothesis are consistent with extant data, including heterogeneity of afferents from distributed brain regions, the requirement for dopamine cells to fire synchronously to generate a temporally resolved phasic signal, evidence that dopamine cell synchrony can increase with learning, evidence that various types of value information are mixed and distributed across multiple afferent substrates, the mixed nature of the dopamine value signals , as well as accumulating evidence that dopamine signals can correlate to diverse phenomena beyond abstracted value , including both features of stimuli associated with value  as well as “non-value” related activity, such as observed in non-reward related tasks . What we offer is a different framework in which to interpret these data and an alternative hypothesis on what the “basic function” of dopamine might be, shifting from signaling and teaching about reward or value to mediating coordination across distributed, parallel processing.This initial description of our hypothesis, laying out the basic ideas and claims, lacks the rigor of a formal theory, which will emerge over time as the ideas presented are further developed. Nonetheless, the hypothesis does yield many predictions that can be tested empirically. For example, the notion that “dopamine is the last to learn” can be tested in a design similar to First, it is becoming increasingly evident that both dopamine and midbrain GABA neurons form a functional midbrain unit , includiOur hypothesis posits that dopamine cells comprise a layer in cascading learning. While dopamine cells exhibit synaptic plasticity, this plasticity and its regulation has not been as extensively characterized as, for example, corticostriatal plasticity. We suggest here that synaptic plasticity in dopamine cells is regulated by inhibitory GABA inputs from the striatum, analogous to how dopamine regulates corticostriatal plasticity. In this way, selective activity-dependent long-term potentiation of excitatory synapses would be gated by disinhibition of striatal inputs. Although there is evidence for this notion , it has Another area for exploration is how different inputs are actually integrated at a cellular level. Our Bayesian construal would on first glance suggest that inhibitory inputs from the striatum and excitatory inputs from distributed afferents should be multiplicative, but this is not exactly right. The likelihood, P(I | E)/P(I) is not computed in the midbrain where excitatory activity, P(E) is multiplied by P(I | E) and both quantities divided by P(I). Rather, in our construal, the likelihood is computed in the striatum and delivered as a single quantity of disinhibition to the midbrain; mathematically, P(E) is not divided directly by P(I). The question might be whether P(E) + P(I | E)/P(I), likely a more accurate rendering, is functionally equivalent. Using cortical activity as an example, if specific cortical activity (say that encoding a cue light) contributes afferent drive to both midbrain, i.e., P(E) and the striatum, i.e., P(I | E), could an increase in this cortical activity transmitted to the midbrain both directly and via disinhibition be multiplicative in the degree to which that specific cortical activity drives midbrain dopamine? The answer is unknown. Demonstrating how mathematical operations comprising formal theories are implemented in neural machinery is a continuing challenge , 2011.Finally, our initial description of the hypothesis provided here requires more formal theoretical elaboration. However, doing so entails rethinking what a normative description of dopamine function might mean if its primary role is construed as mediating coordination across distributed processing rather than signaling value per se. As long as dopamine is viewed in some fashion as the reward transmitter, computational approaches can build formal algorithms whose functional goal is maximizing value. Our hypothesis posits “maximizing value” as a distal goal mediated by multiple neural substrates where the proximal problem is getting those substrates to function in a coordinated manner to achieve maximal value. If dopamine is construed as a solution to that proximal problem of coordination, then thinking through formal models of this idea requires developing notions on how “coordination” is maximized or even quantified and evaluated. We believe our Bayesian construal of dopamine and notion of cascading, distributed learning offers some initial fodder for more formal efforts.A good hypothesis should provoke novel investigations and generate deeper understanding, whether ultimately proven true or not. The prediction error hypothesis makes clear, simple predictions: that phasic dopamine signaling will correspond to discrepancies in expected and actual outcomes. Nonetheless, twenty years later we are still testing this hypothesis , which hVarious theories of dopamine function have been proposed. Data have accumulated supporting each of these theories and, strictly speaking, falsifying each other. If a value instead of error signal is observed, then strictly speaking the prediction error hypothesis cannot be a complete account. The taste for pitting these different accounts of dopamine against each other seems to be waning, with a growing appreciation that each likely captures some aspect of dopamine signaling. Increasingly, the most pressing question seems to be how to conceive of a framework where these different theories can be integrated rather than viewed as competing accounts.By shifting from a presupposition that dopamine fundamentally signals value information in some fashion, the reward transmitter, to positing that dopamine plays a role in mediating coordination across distributed, parallel processing, the hypothesis outlined here provides an alternative perspective in thinking about how to assimilate and interpret the diverse data that have accumulated for decades on dopamine. Moreover, it suggests new avenues for both theoretical and empirical exploration and model development. This is particularly true in light of data emerging in recent years showing much greater richness and complexity to dopamine signals, as well as its connectivity, architecture and physiology, than originally imagined. As it becomes increasingly difficult to shoehorn this apparent complexity into one or another extant theories, the need for alternative frameworks, perspectives and accounts may grow. Although only an initial description, we offer the current hypothesis in the spirit of this need for new perspectives.


Antimicrobial resistance (AMR) is a global public health threat that warrants urgent attention. However, the multifaceted nature of AMR often complicates the development and implementation of comprehensive policies. In this study, we describe the policy context and explore experts’ perspectives on the challenges, facilitators, and strategies for combating AMR in Singapore. We conducted semi-structured interviews with 21 participants. Interviews were transcribed verbatim and were analyzed thematically, adopting an interpretative approach. Participants reported that the Ministry of Health (MOH) has effectively funded AMR control programs and research in all public hospitals. In addition, a preexisting One Health platform, among MOH, Agri-Food & Veterinary Authority , National Environment Agency, and Singapore’s National Water Agency, was perceived to have facilitated the coordination and formulation of Singapore’s AMR strategies. Nonetheless, participants highlighted that the success of AMR strategies is compounded by various challenges such as surveillance in private clinics, resource constraints at community-level health facilities, sub-optimal public awareness, patchy regulation on antimicrobial use in animals, and environmental contamination. This study shows that the process of planning and executing AMR policies is complicated even in a well-resourced country such as Singapore. It has also highlighted the increasing need to address the social, political, cultural, and behavioral aspects influencing AMR. Ultimately, it will be difficult to design policy interventions that cater for the needs of individuals, families, and the community, unless we understand how all these aspects interact and shape the AMR response. Antimicrobial resistance (AMR) has gained considerable recognition as a major global public health threat ,2,3,4. TSingapore is an island nation with a diverse population of 5.6 million people . There iStaphylococcus aureus (MRSA), coupled with an increase in resistant Gram-negative bacteria in the hospitals and the community [In line with the Global Action Plan for AMR, Singapore launched its own National Strategic Action Plan on AMR in November 2017 . This muommunity ,16,17,18ommunity .The AMR issue has been described as a “wicked problem”, where there are many stakeholders involved from the various sectors and several ways to frame the problem . This reThis qualitative study was conducted from September 2017 to May 2018. We used a purposive sampling method to recruit informants in key roles across sectors relevant to the issue of AMR in Singapore. Potential participants were identified from experts in the area of AMR in Singapore, and were approached for an in-depth interview via email explaining the purpose of research. A total of 21 participants from within and outside Singapore were recruited in this study . The parFace-to-face in-depth interviews were conducted by three of the researchers  in English. Among the interviewers, two were Research Associates and one was an Associate Professor. All interviewers were trained in qualitative research. The interviews were conducted in a quiet space at the preferred location of the participants. Each interview lasted an hour on average and was audio-recorded. There were no repeat interviews. A semi-structured question guide was used to explore the main areas of concern for the participants, in their fields and areas of interest. The question guide was developed with questions focusing on participants’ experiences and perceptions of AMR policy and practice including awareness, key challenges and facilitators in their particular area of expertise, and possible strategies and solutions to address key challenges in the Singaporean context. Participants were not remunerated for the interview.Ethical approval was obtained from the National University of Singapore Institutional Review Board (NUS-IRB). Each participant was provided an information sheet stating the objectives and methods of the research, at the point of recruitment. The confidentiality and anonymity of participants’ responses was also highlighted. Written consent was sought before the beginning of each interview, requesting for permission to be audio-recorded and to be quoted anonymously in research outputs. Participants could refuse any of these options, as well as any questions posed to them during the interview itself. All participants were de-identified to maintain confidentiality.All interviews were transcribed verbatim and identifying data were removed from all research documents to ensure confidentiality. QSR NVivo 11 software was used to organize and share the data among study team members. We used an interpretive approach which focuses on the participants’ perceptions and interpretations of the topic of discussion. Thematic analysis was used to inductively identify themes from the data. We drew on techniques from the constant comparative method, such as line by line analysis, naming each line and segment of data, and the use of subsequent interviews to test preliminary assumptions. In addition, deviant cases were explored and examined ,21. The We present our findings under five main themes identified from analysis of participants’ responses. The first theme examines the policy context and discusses whether AMR as a policy issue is a priority in Singapore. The second theme discusses the level of AMR awareness among policymakers, professionals, and the general population. The third and fourth theme discusses the perceived facilitators and challenges to combat AMR in the Singaporean context. Finally, the fifth theme reflects on the reported strategies to increase awareness and combat AMR based on participants’ perceptions.“A lot of incidents drive behavior in Singapore, like for example SARS drove infection control to the front of everything. If you speak to some people, (they) will say infection control became prominent feature with SARS happening.”—I11, Human HealthPolicymakers that participated in the study reflected on the importance of addressing infectious diseases in the Singaporean context, especially after the outbreaks of severe acute respiratory syndrome (SARS) and H1N1 influenza which took place in 2003 and 2009, respectively. As a physician highlighted:“The Ministry keeps an eye out for how it compares itself to other countries. So that drives their interest in looking at where we stand, how good, how bad (…) They directly fund quite a lot of the manpower in the hospital systems, certainly for antimicrobial stewardship.”—I02, Human HealthIn 2009, the MOH initiated the National Antimicrobial Taskforce (NAT) that helped lay down the basics of mandatory surveillance, stewardship, and infection prevention principles in public restructured hospitals. The NAT was tasked to formulate hospital programs and policies, as well as to implement measure for monitoring and evaluation of these policies. It was later reorganized into the National Antimicrobial Resistance Control Committee (NARCC) in 2014. Participants highlighted that the strategy adopted to keep efforts sustainable was by working with people on the ground to reinforce the implementation of these programs. The MOH’s knack for looking at global health issues and comparing itself to other countries also helped in funding and formulation of AMR strategies. The next quote highlights the ways in which the MOH operates including the dedicated funding for antimicrobial stewardship programs:Participants also remarked that the ministry looked at other countries and international organizations, such as the WHO and the European Union, for inspiration and implemented policies relevant to the Singapore context.“What WHO or even the EU is recommending, (…) I have been trying to push for that. We follow what others are doing, we don’t want to reinvent the wheel, so that we can then compare ourselves.”—I07, Human HealthParticipants credited the proactive Singaporean government with forming a One Health platform, maintaining effective communication, and coordination between the agencies. One example of this was the formulation of the National Strategic Action Plan on AMR that was released in 2017. Despite establishing a One Health platform, participants suggested that the implementation of programs against AMR would be more challenging. They stressed on the necessity of advocating the importance of AMR to raise awareness.“Bringing different people to the table in the first instance in Singapore is easy, for somebody that is in charge (…). But at the end, (…) we need to get every single stakeholder to believe in the topic. There’s a lot of sales or advocacy involved.”—I12, Human Health“I guess AMR, this phrase (…) if you were to tell me it’s AMR, I would not know it’s antimicrobial resistance.”—I01, Human HealthMost participants recounted low awareness of AMR among Singaporeans. Furthermore, AMR was identified as a recently coined term and many professionals including physicians were not familiar with the term even though they were knowledgeable of the topic itself. The next quote is an example of such reports:“At the ground level, they were saying, “What is AMR?” People don’t really know. (…) How do we address it? This is a difficult question.”—I09, Environment HealthParticipants also remarked there was low awareness of AMR both as a topic as well a term among other One Health stakeholders including farmers and others within the environmental health sector. When we contacted potential participants from the environment sector, very few agreed to be interviewed since many reported not having conducted sufficient work related to AMR. The next quote highlights the concerns expressed by an environmental health expert who was worried about the lack of awareness among his colleagues at “the ground level”:“I think we need people who can inform on public policy in a way that would make our population understand. So we don’t have those communication agencies. I think we have think tanks, right? And we have scientific groups. But we don’t quite have that translation into a public health campaign.”—I02. Human HealthAwareness was also perceived to be low in the general population as expressed by participants. Timely awareness efforts by the academic sector had not yet reached the general population. Since 2016, Singapore has been actively participating in the annual World Antibiotic Awareness Week every November, reaching out to the public at various public forums, hospitals and national libraries ,23. In 2Some participants stated the importance of raising AMR awareness to counter its emergence. It was suggested that by raising awareness of the topic and getting more funds to drive AMR programs for the general population and stakeholders alike, AMR emergence could be tackled better.“The community somehow must come to feel that this is an important issue. And once they do, then, you know, naturally, I think all the other pieces will fall into place. The politicians will sing the same song. The private sector will start putting money into the issue.”—I06, Animal HealthMost stakeholders considered AMR a significant threat to Singapore and global health, but they also mentioned that it was not given the highest priority in the list of local healthcare challenges until several outbreaks of healthcare-associated infection changed the perception of policymakers and administrators with regards to its risk and standing. Until the early 2010s, issues such as ageing population and chronic diseases were rated much higher in priority compared to infectious diseases.“We had this roundtable discussion. Everybody, all the movers and shakers, public health systems… and they were asked to state these priorities. And believe it or not, infection, the scourge of infection wasn’t one of the top five.”—I02, Human Health“Patients will always come in and ask for antibiotics. So I think it’s something that we should control and not say that it all is well and then we ignore it. But like I said (…) I think the awareness may not be strong enough for us to continue to pursue.”—I01, Human HealthThere were many reports suggesting a lack of awareness of AMR from the public. Many participants reiterated the fact that General Practitioners (GPs) may succumb to the pressure of demanding patients to prescribe antibiotics even when they were not clinically indicated. The next quote highlights how patients are “always asking for antibiotics”:“As far as infection prevention goes, infection prevention and antimicrobial resistance is like stepchild of everyone. Because it’s not in anyone’s radar except for people who do infection control. So it’s about making it a culture in everyone’s mind, which is not an easy task.”—I11, Human HealthIt was also highlighted that there is a need for a firm drilling of infection prevention and control practices right in formative years of training for all healthcare professionals. Healthcare professionals needed to be more aware of and prioritize infection control, as it is not currently under “anyone’s radar except for the people who do infection control”:“It’s not really our fault. You are sitting here scolding us, that we have a lot of MRSA but it’s because, it’s not poor infection control. You are making us take care of patients in overcrowded hospitals. You know, it’s very different from the US or Europe where most of their rooms are two-bedders. If you have a six-bedder, even if I wash my hands, the uncle there who has a maid, and the maid is talking to the other maid and they all share, you know… and it’s practically, it’s all crowded, all these infrastructure issues.”—I04, Human HealthInadequate infrastructure to facilitate optimal infection prevention and control measures was the most commonly cited challenge in addressing AMR. Though infection prevention and control efforts were highly regulated in both the public and private hospital settings, certain contextual factors such as lack of sufficient single room facility were highly challenging to overcome. A few participants mentioned that the design of hospital wards with one room having six beds or eight beds was not conducive to prevent infections:“If the pharmacy notice that the patient is coming back repeatedly with antibiotics, they will alert the senior doctor to say that they’ve noticed that the doctor’s pattern tends to prescribe a lot of antibiotics. At the same time, we also conduct audits annually on antibiotics usage.”—I01, Human HealthOverall, participants reported that guidelines and antimicrobial stewardship policies were better established in public-sector hospitals and clinics than their private counterparts. Participants attributed this to strict adherence to the guidelines in the public sector, as well as regular audits and monitoring of antibiotic prescriptions by public-sector pharmacists. The following quote is an example of the audits conducted in the public sector:“I feel, in the restructured setting, you know, it’s much more, I wouldn’t say easier may not be the word, but maybe less challenging because it’s much more homogenous within that institution and you only have to work in your institution whereas we have to work across all these little and then we are spending a lot of time and cracking ourselves in bits and pieces whereas it can all be done, you know, under one, I think, more harmonization, less bickering, less fighting, and then we can get more funding.”—I18, Human HealthIn contrast, it was reported that private hospitals gave less priority to funding for infection control and stewardship policies than public hospitals. The stewardship element was not strictly monitored in the private hospitals and clinics, where it was reported that the MOH does not have so much leverage. This was raised as a concern by some physicians and policymakers when discussing the extension of AMR policies to the private sector:Many participants mentioned that there were practical difficulties in being able to perform adequate tests before dispensing or prescribing antibiotics. Hence physicians and veterinarians tended to practice defensive medicine by prescribing broad-spectrum antibiotics.“If you are not following the stories in Singapore, it’s not too long ago, you notice that the doctors have been held a lot in, they are being suspended for not diagnosing a certain condition (…) So, if you are going to hide under the umbrella of stewardship, are they going to get bailed out? Is someone going to come and rescue them, you know? Pertinent questions. It’s not that people want to practice defense medicine, but that is somehow being construed or misconstrued from what is happening out there.”—I18, Human Health“Textbook always tells us to do so (diagnostics) before you start on any medication. But, in a practical sense, hard to because how do I explain $60 more on top of what they are already paying, for them to get a culture and sensitivity back before we give antibiotics?”—I17, Animal HealthMoreover, veterinarians emphasized that the high diagnostics costs were difficult to justify to pet owners as the next quote exemplifies:“Even though the vets use a huge volume of antibiotic in farming, I think the quantity used per animal over a period of time is way less than what we can get from human clinics. Way, way less.”—I17, Animal HealthStakeholders differed on their take as to what contributes more to AMR and ultimately which policy may help in reducing it. Physicians reported being aware of the importance of antimicrobial stewardship policies and infection prevention measures to control AMR, but were unsure if these programs alone could alleviate AMR since they believed that AMR could also be generated by antimicrobial use in animal farming as growth promoters. On the contrary, animal health experts believed the animal food industry did not contribute much to the growing resistance since the volume of antimicrobial used over the lifespan of livestock was very low. As reported by an animal health expert:“It was still very much hospital-focused. The membership  still basically comprised representatives of every public-sector hospital, and the chairman and the members were still very much concerned about preventing the spread of AMR organisms in hospitals.”—I07, Human HealthMany participants also expressed that AMR in Singapore had so far only been addressed in the hospital sector and not much had been done regarding the prevention of AMR in the animal and environment health domains. It was also mentioned that within NAT most of its members and emphasis was still focused on the hospital sector:Environmental health stakeholders expressed the potential of AMR emergence from farms, the community, and the environment as a whole. In general, the perception was that Singapore has not established strategies to deal with environmental contamination. Untreated effluents from hospitals was noted to serve as one of the potential threats in case of a sewage leak.“The primary source for us (…) is, of course, our hospitals, also hospital effluents. We know that there are very high concentrations of all these last resort antibiotics, especially from the ICUs (Intensive Care Units) and all that, and it gets into the wastewater which then goes into the sewerage system, all the way to the wastewater treatment plant.”—I14, Environment HealthAlso, there was a scope for improving the wastewater treatment standard to treat some antibiotic residues so that they do not harbor AMR.“Even if you look at the wastewater treatment plants, they’re not doing so well in removing all the pharmaceuticals, all the antibiotics. Some can be removed very well, but some cannot. And so, that means they will be discharged and be effluent.”—I14, Environment Health“At the treatment end, there’s no problem because their treatment process is rigorous enough to remove all these bugs and all that…But, of course, I think it’s more from the environmental leakage (of antibiotics).”—I09, Environment HealthParticipants reported that antimicrobial laced water leeching in the environment served as breeding sites for AMR as the next quote emphasizes:In addition to the above factors, participants also hinted on the vested interest of different stakeholders. For example, it was mentioned that private practitioners make substantial profits when dispensing antibiotics as it added to their income.“And by dispensing (antibiotics) they (GPs) are also getting the profits. So, there is already a misaligned incentive.”—I04, Human HealthAlso, some participants reflected on the vested interests of pharmaceutical companies in marketing for higher sales of their antibiotics for their own profits.“There is a conflict of interest already, because, they  are producing, they are just selling to the farmers (…) in a way they are trying to encourage certain resistance.”—I17, Animal HealthAnimal health stakeholders expressed that the not so strict regulations on the import of newer antibiotics with a broader spectrum of activity served as a leeway for some veterinarians to prescribe them even when not clinically needed. Participants pointed out that the abuse of reserved antibiotics favored acquisition of resistance genes by microorganisms, resulting in loss of antibiotic efficacy.“There are those not very good ones out in the market that actually goes for the most exotic antibiotics because they distinguish themselves in that sense. Some of them actually use what I call the third-level antibiotic as a first line treatment which I personally don’t agree. Of course, they charge exorbitant amount because it’s ‘special’ antibiotics.”—I17, Animal HealthIn addition, owing to a small farming sector, existing veterinarians had limited expertise in agriculture and aquaculture and hence farmers in Singapore were not mandated to attain prescription for accessing antibiotics independently. Participants alluded that farmers not needing to consult a veterinarian for a prescription for antibiotics served in the farmer’s interest.“Vets were not familiar to treat fish, so farmers didn’t trust the vets to treat their fish, and vets then became very unwilling to treat farm fish. That’s not changed very much, and there are still issues in Singapore. For example, fish farmers can now buy any antibiotic they want by themselves.”—I15, Animal HealthSingapore’s MOH was unanimously praised by all participants in its proactive approach towards AMR and making way for changes amid very complex issues. It was mentioned that the MOH was transparent and accountable and was operating an efficient public healthcare system in Singapore. Yet, as a drawback some participants argued that having a system that relies too much on decisions made at the highest political level makes the general population and service providers inert.“That’s why I think in Singapore, unless it comes directly from the Prime Minister’s office, it will never move anything.”—I11, Human HealthIn terms of the resources made available to fund AMR programs, it was reported that MOH had effectively funded AMR control programs and research in all public hospitals.“When the Singaporean government gets into doing something, they tend to do it very thoroughly. (…) You may not always agree with the strategy, but you have to give them full marks for trying.”—I04, Human HealthMost participants affirmed that the Singaporean population and healthcare professionals bestow trust in government programs and policies. The next quote highlights that whether participants agreed or not with the proposed policy, there was a sense that the government is “trying to do a good thing”:In addition, a preexisting One Health platform among MOH, SFA, AVS, NEA, and PUB was perceived to have facilitated the coordination and formulation of Singapore’s AMR strategies.Laying the foundation of surveillance in public hospitals and making the data transparent was appreciated by all participants. Participants also shared recent advances in the capacity to implement stewardship and infection prevention and control policies among different Singapore institutions including nursing homes.“We are looking to reaching out to even nursing homes to provide that kind of bold infection prevention, but also infection control.”—I03, Human HealthAMR indicators, segregated mainly into process and outcome indicators, were set up in the public hospital surveillance system. Some of the process indicators were antimicrobial use for human and animal health, and infection prevention and control measures such as hand hygiene in hospitals. It was suggested that the Singapore government played a prime role in mandating the standardization, transparency, and sharing of data with the NAT.“We wanted to measure stuff in Singapore, but really to do that you really need the government involved, (…) otherwise if it’s a voluntary basis, and there are certain biases about data. Whereas if it’s systematic surveillance and it’s mandatory you get a more comprehensive and representative sample.”—I04, Human HealthParticipants mentioned that though the AMR surveillance indicators were defined and well set up in the public hospital domain, surveillance needed to be at a national level, extended to private hospitals, primary care and intermediate/long-term care facilities , as well as animal and environment sectors.“The indicators we sort of have been following is still hospital-based indicators. We don’t have country-wide, AMR indicators which internationally people are talking about. For example, we don’t know what is the level of antibiotic consumption at the country level, we don’t know what, for example, when people are talking about “oh, for this bacterial infection, what proportion of this bacterial infection is resistant to what antibiotics” you know? We haven’t gone to measuring that kind of level.”—I07, Human Health“More important I think is the peer pressure and peer standing. And when it’s made the department target and communicated by the head of the department, no one wants to be the worst department in the stats when they are shown up. So there’s lot of department pride and that’s what drives stuff. Doctors are often competitive, some of the nurses too. And no one wants to be the idiot that lets the team down.”—I03, Human HealthThe motivation of the workforce was attributed to the competition, prestige, and reputation of the workforce. In the hospital setting, metrics and outcomes of antimicrobial stewardship such as average defined daily dose and percentage of appropriate antibiotics prescribed, and length of hospitalization for each department are often reported and shared among the various departments within the hospital. The transparency of data highly motivated the workforce to perform well in these benchmarking exercises. The following quote is an example of such occurrence:“One of the key reasons in the national action plan is research. And among the research activities there have been sort of highlighted in terms of priority, is better surveillance. You know, how to better measure the different perspectives and areas that we need to, outside the hospitals: primary care, the community and understanding the sort of pathways of antibiotic resistances, what is driving, the drivers of antibiotic resistance locally…”—I07, Human HealthResearch in Singapore was unanimously considered to be well promoted and funded, albeit it was also rated to be very competitive in terms of securing research funding. There was ongoing AMR research including in the areas of surveillance, prevention of transmission, whole genome sequencing, among others. Of the various arms of AMR research, surveillance was considered to be one of the main pillars in AMR research:“There’s that translation angle number one. There is the One Health angle number two, and then of course number three we also engage with basic science collaborators, to try to understand the basic science mechanisms of this issue.”—I08, Human HealthThe researcher and academic participants mentioned that the government and ministry were very tightly knit in Singapore. Leadership was very open and attentive to research findings that could be translated into better health practices in Singapore. As the following quote highlights:As AMR is a global health issue, participants remarked that Singapore alone could do very little in controlling AMR as a whole. Despite all policies Singapore will not be untouched by rising AMR in the region which can be ultimately transmitted via large imports of agricultural products and humans travelling for trade and tourism. However, most participants mentioned that Singapore could play a role by coordinating and sharing expertise with neighboring member states of the Association of Southeast Asian Nations (ASEAN).Many participants proposed the idea that Singapore can serve as a research hub owing to its unique positioning and research capacity. Sharing innovative findings both on science, clinical practice and exemplary policy implementation strategies could prove helpful to neighboring countries that share some contextual factors with Singapore.“It is an ideal geographic position as well as possibly a good political one with the recognition by the west that Singapore is a high-income country as well as intellectually advanced. That bridge between the west and low- and middle-income countries especially in the Asia Pacific region could really be bridged by your university and your researchers.”—I20, Human HealthA few ministerial participants affirmed Singapore’s role of coordinating regional efforts on AMR.“What Singapore is trying to do is trying to harmonize efforts in the agriculture sector and the livestock sector because these are under different ASEAN stream workgroups. So we also work with FAO to coordinate these.”—I13, Animal HealthParticipants articulated that highlighting the increasing cost of managing patients infected with resistant organisms and the economic loss from AMR could be a potential way of drawing attention to the topic and getting funds to drive programs. As specific examples, participants illustrated not just the costs of treating resistant infections, but also the costs associated with implementing stricter infection control measures.“That is going to jack up costs in all kinds of ways. Number 1, you are going to have to pay for all those gowns, gloves, single rooms, for isolation, etc. Number 2 you need more manpower, because suddenly a nurse is going to be slowed down right? Or a doctor. You have to put on all this gear, you are going to be seeing fewer patients in the same amount of time, just because of … it’s a bother.”—I04, Human HealthSome participants believed that healthcare costs would increase due to AMR. These were attributed to many reasons, one of which was the cost of more effective antibiotics required to treat infections with resistant organisms. Another prominent reason mentioned was the costs towards infection prevention and control in healthcare settings. This was considered a necessary step to reduce the risk of healthcare-associated infections, especially in the face of worsening AMR. The following factors were suggested by one participant to prevent the spread of resistant pathogens and to cater to patients harboring resistant or infectious organisms:Many participants believed that unless AMR’s potential damage to the population and the economy is projected, people are not going to take AMR seriously. Some participants mentioned that only a grave incident such as an AMR outbreak would be able to catch the attention of the general public and extend the prevention efforts of AMR.A few participants articulated that rather than forcing a top-down policy approach, AMR could be better tackled by the sharing of best practices through communities of practitioners and creating social movements to encourage and sustain behavior change.“Practitioners come together to share best practices, through the ID networks, through the hospital networks, through the volunteer networks, you know, build communities of practice until this becomes a culture. And people are learning from each other (…) But whether it gets done is a question of culture, a culture needs strategy every day (…) so you want to do change, and you want to do large scale change and you want to sustain the change you need to create a movement not a directive… I think it’s more important to you to create the social movement around what that is, because if you are going to achieve this style change of behavior you need a more behavioral approach to this problem not a clinical approach.”—I05, Human HealthParticipants reflected on the need to develop public campaigns to sensitize people to become aware of and understand the fundamentals of programs and strategies against AMR. These include stewardship, adherence to vaccination guidelines, better infection prevention and control practices in hospitals as well as programs in the community. All these programs needed to take into account social, behavioral, and cultural aspects to accommodate the needs and perceptions of the community.“There is always a need to build a culture and to build a system for people to do the right thing. And the same applies outside the hospitals. So I think you know the schools have hand washing to teach the next generation.”—I05, Human HealthMost participants asserted that one of the probable strategies to counter AMR was to increase vaccination rates in children and adult population. However, increasing vaccination uptake will uncover another set of issues including population awareness, behavior changes, funding for regular vaccination, workforce to administer vaccination, and availability of vaccines.This paper has discussed the challenges and facilitators to addressing AMR in a well-resourced setting such as Singapore. Despite Singapore having an established One Health platform representing all the different stakeholders; appropriate funding to address the response; existence of stewardship and surveillance programs in public hospitals; an active program in research; and a motivated workforce; most participants raised several challenges to address AMR efficiently. These included, among other, vested interests among some stakeholders; disagreements between the human and animal health sectors; low public awareness; the need to address prevention of AMR in the animal and environmental sector; political and cultural aspects influencing AMR; and lax stewardship policies in the private sector.Therefore, the results of this paper highlight how difficult it can be to address AMR, especially when considering that Singapore has well-functioning stewardship programs, comprehensive hospital surveillance systems, and some of the latest technologies and innovations to address it. The example of AMR in Singapore brings to light the increasing need to address the social, economic, political, cultural, and behavioral aspects influencing AMR rather than just focusing on the technical solutions. Unless we understand how all these aspects operate and drive the response, it will be difficult to design appropriate policy interventions. In the next paragraphs we provide an example of each of these aspects to highlight their importance in the Singaporean setting. We address “the social” by analyzing how AMR has been socially constructed in Singapore; we discuss the influence of “politics” by considering power relations and governance approaches for the successful control of AMR; we address “behavioral aspects” by analyzing vested interests; and we consider “cultural components” by exploring how patients’ cultural beliefs influence antibiotic consumption.First, it is important to understand how AMR has been socially constructed in Singapore and how power relations operate between the different stakeholders. Wernli et al. distinguished five different frames that map the global policy discourse on AMR . These aSecond, considering governance approaches for the successful control of AMR requires a focus on both whole of society and sector specific approaches . This waIn the Singapore setting, many participants highlighted the leading role of the MOH in regulating the health sector, but acknowledged challenges in regulating the private and animal health sector. These challenges present examples where governance structures will need to weigh up the balance between regulation and persuasion as policy approaches. In the Singaporean context, differential policies in the public and private human healthcare sectors, whether by design or practice, are likely to be counterproductive, as patients use both sectors and the occurrence of resistant infections in one sector has implications for the other. On the other hand, the agricultural sector in Singapore is small and the availability of adequate veterinary expertise limited; imposing tight regulations on antibiotic access in the absence of qualified prescribers is therefore challenging, and persuasive strategies to reduce antibiotic use in this sector are likely to be more realistic, at least in the short term. On their collaborative approach towards governance, many participants highlighted the One Health platform as a good way of bringing stakeholders together. The good relationship between researchers and policymakers was also emphasized via the many avenues for researchers to discuss and share their research findings and discuss policy implications with policymakers. However, there were also conflicts reported specifically between human and animal health experts. This was crystalized on their different takes on what contributes more to AMR. Most physicians believed that antimicrobial use in animal farming as growth promoters might be a more significant driver of AMR, as has been explained by studies . In contThird, the AMR policy context represents a policy arena where certain groups engage in “behaviors” that might conflict with the overall goal of controlling AMR. Vested interests are more noticeable than in other health policy areas since different professional groups coexist in the AMR policy arena and there is substantial profit to be made from selling antibiotics ,30. In SFourth, many participants reported that “cultural aspects” and perception regarding medication influenced patients’ requests for antibiotics, with patients requesting them, and GPs recognizing feeling the pressure to prescribe them. Other research has found similar findings, with Lam et al. observing that primary healthcare physicians over-prescribed antibiotics in order to satisfy their patients . There wTo our knowledge, this is one of the first studies to explore the social, political, behavioral, and cultural aspects influencing AMR in a well-resourced setting. A key strength of this study is that we were able to gather the perspectives of multiple stakeholders in the human, animal, and environmental sector. However, we had difficulty in recruiting participants from the environmental sector, and we were only able to interview two participants. A limitation of this study is that participants could have downplayed some of the challenges and some strategies that are considered key to address AMR could have been missed. For example, the fact that Singapore has a well-functioning system for dispensing antibiotics in the human sector, with antibiotics only available with a physician’s prescription, was not mentioned as often as a facilitator as one might expect. This could be the case because it was already taken for granted as it has been in existence for several years.Escherichia coli bacteremia, as well as the influence different resistances have on them. Such findings will be useful for understanding the health and economic impact of future trends in resistance, and for prioritization of funding and strategies to tackle the problem [Finally, participants in this study were asked to describe the most important strategies to combat AMR and to raise awareness among the population. The most often mentioned responses were: the need to project AMR costs to draw more attention to the topic; pushing forward the AMR agenda by fear of no treatment; creating a community of practice; considering the social aspects of AMR in order to develop prevention efforts against AMR; engaging the community and public campaigns on the drivers of AMR; and increasing vaccination rates in children and adult population. One important step to realizing these strategies would be to have good quality data obtained from standardized surveillance platforms at the national level. This will allow the conduct of outcome research, which can eventually be translated into messages to increase awareness and to push forward the AMR agenda. For example, Naylor et al. used a national mandatory surveillance database in England to quantify the cost and mortality burden of  problem . In addiThe process of designing and implementing AMR policies is complicated even in a country such as Singapore, which has dedicated funding and has developed a multisectoral approach to address AMR. This paper has highlighted the increasing need to address the social, political, cultural, and behavioral aspects influencing AMR rather than just focusing on the technical solutions. Unless we understand how all these aspects operate and drive the response, it will be difficult to design policy interventions that produce the desired results and that cater for the needs of individuals, families, and the community as a whole.


Endemic Kaposi sarcoma (KS) was first described in African children over fifty years ago, but has recently been overshadowed by HIV-related disease. We aimed to evaluate the similarities and differences between endemic HIV-negative and epidemic HIV-positive pediatric KS in a KS-associated herpesvirus-endemic region of Africa.We describe clinical characteristics of 20 HIV-negative children with endemic KS over a six-year period and compare findings with a historical control—an HIV-related pediatric KS cohort from Lilongwe, Malawi.9/L) were found at time of original KS diagnosis in 45 and 40% respectively. In both HIV-negative and HIV-positive cohorts, lymphadenopathy was the most common presentation, prototypical skin lesions were often absent, severe cytopenias were a common clinical feature, and treatment outcomes were similar. Patients with endemic KS demonstrated less frequent oral involvement  and a lower proportion of patients with visceral involvement .The HIV-negative endemic KS cohort was 70% male with a median age of 9.3 years. Lymph node involvement was present in 50%, hyperpigmented skin lesions in 45%, and woody edema in 40%. One patient (5%) presented with oral KS involvement and no patients presented initially with visceral KS. Significant anemia (hemoglobin < 8 g/dL) and thrombocytopenia  contains supplementary material, which is available to authorized users. Descriptions of endemic Kaposi sarcoma (KS) of childhood originated more than fifty years ago in central and eastern Africa—decades before the emergence of HIV—offering details of the clinical characteristics and outcomes in HIV-negative African children living in regions with endemic human herpesvirus-8/KS-associated herpesvirus (KSHV) infection –5. UniquFollowing those initial descriptions, little has been published on endemic HIV-unrelated KS –9. With In this brief report, we describe the clinical features and treatment outcomes of endemic pediatric KS and compare it to our previously published experience with HIV-related pediatric KS in Lilongwe, Malawi.Medical records of HIV-negative children and adolescents (< 18 years) with a histological or clinical diagnosis of endemic KS between January 2011 and December 2016 were reviewed. HIV status was determined based upon standard clinical procedure using rapid antibody testing and all patients underwent repeat testing for confirmation to rule-out the potential for a false-negative result. The initial ten patients also underwent qualitative HIV DNA PCR testing for additional confirmation of their HIV-negative status. Diagnostic and therapeutic algorithms have been previously described, including supportive care strategies [Patients were staged according to the Lilongwe Pediatric KS Staging Classification, a pediatric-specific staging paradigm that attempts to address the unique clinical features of childhood KS observed in KSHV-endemic regions of Africa , 19. BriP-values were generated using either a k-sample equality-of-medians test, Chi-square test, or Fisher’s exact test, as appropriate. The study was approved by the Malawi National Health Sciences Research Committee and the Baylor College of Medicine Institutional Review Board for Human Subjects; a waiver of consent was obtained due to the retrospective nature of the study.Data from endemic KS patients were compared to data from a previously described cohort of HIV-related pediatric KS at the same institution . All sta9/L).There were 20 children  diagnosed with endemic KS between 2011 and 2016. In comparison, there were 140 new HIV-related pediatric KS diagnoses over the same six-year time period [At a median follow-up of 39 months (interquartile range 27–62), 13 patients (65%) were alive. Nine (45%) were in complete remission , 3 (15%) were alive with stable disease, and 1 patient had experienced relapse and was receiving salvage chemotherapy. Seven (35%) patients died at median time of 2 months (range 0.1–52) from the date of KS diagnosis. Six of those deaths were attributed to KS and there were no treatment-related deaths.Comparing this series of 20 children with endemic KS to our previously published cohort of 70 children with HIV-related KS, some similarities and differences emerged Table .P = 0.03). Approximately one-fourth of both cohorts presented with KS lymphadenopathy in the absence of prototypical skin/oral lesions or woody edema (P = 0.95). Hyperpigmented skin lesions were present in around half of both cohorts (P = 0.21). Moderate-severe anemia and/or thrombocytopenia commonly occurred in both epidemiological variants .In both cohorts, KS lymphadenopathy was the most common presenting feature, although this occurred more frequently among HIV-related KS cases (P = 0.03) compared to the HIV-related control group. None of the endemic KS patients originally presented with visceral disease compared to 16% of HIV-related KS patients (P = 0.06), and the endemic KS cohort was 70% male compared to 50% in the HIV-related KS cohort (P = 0.11). Ultimately, treatment outcomes were similar (P = 0.31).Distinctions between endemic and HIV-related KS were demonstrated as well. Patients with endemic KS had a lower frequency of oral KS involvement , 1 was in CR, 3 were alive with stable disease off chemotherapy, and 2 had died. One death occurred in a child that was lost to follow-up after six months of chemotherapy and was subsequently found to have died one year later, via telephone communication. The other death occurred in a child that originally presented with woody edema, hyperpigmented skin lesions, and lymphadenopathy, eventually evolving with the second relapse to include pulmonary visceral involvement with severe serosanguineous pleural effusions. All 4 of the patients categorized as stage 4 originally presented with disseminated cutaneous/oral KS  and without visceral involvement. Three of them were refractory to chemotherapy and their underlying KS rapidly progressed (time of death ranged 0.5–2 months). One patient achieved CR with up-front intensified chemotherapy (doxorubicin plus BV), however eventually experienced relapse 34 months after the original diagnosis and was alive with stable disease but receiving salvage chemotherapy with paclitaxel at the time of data analysis.This cohort of HIV-negative children and adolescents with endemic KS shows considerable overlap with HIV-related disease. Primary presentation with lymphadenopathy was a consistent clinical feature in both pediatric endemic and HIV-related KS cohorts. Additionally, in both epidemiological variants, presentation with severe cytopenias is frequent and approximately half of the patients lacked the prototypical hyperpigmented skin/oral lesions that are so often relied upon as a clinical indicator of KS. Distinctions between endemic and HIV-related pediatric KS were also observed, as we noted the uncommon occurrence of oral lesions in HIV-negative patients, as well as a lower frequency of visceral involvement in endemic KS.These findings are consistent with previously published reports on endemic KS in Africa Table . The preReviewing HIV-related parameters of the HIV-infected pediatric KS cohort, a few important observations are noted that may explain the clinical overlap with endemic disease. Severe CD4 count suppression was infrequent, observed in only 28% of the HIV-related cohort . AdditioThe occurrence of moderate-severe anemia and thrombocytopenia as a presenting clinical feature of pediatric KS has been consistent in the experiences with both HIV-negative and HIV-related disease in Malawi. Although numbers are too small in this cohort to evaluate clinical associations, presentation with cytopenias was not found to have an impact on survival in HIV-related pediatric KS . BaselinConsidering the frequent occurrence of cytopenias as well as the overlapping clinical patterns of disease in both epidemiological variants of pediatric KS, it is plausible that KSHV-driven pathways may play an important biological role in determining the clinical phenotype of disease. Recent pilot data from HIV-infected children in Malawi demonstrated associations between elevated plasma KSHV viral load and lymphadenopathic KS, and although sample size limited the statistical power of the results, it was notable that all 5 patients with anemia as well as all 4 patients with thrombocytopenia demonstrated detectable KSHV viral loads at the time of KS diagnosis . If the Cancer registry data and GLOBOCAN estimates demonstrate that alongside lymphoma , Wilms tumor, retinoblastoma, and leukemia, KS has become one of the top five most common overall childhood malignancies in several countries in eastern and central Africa including Malawi, Uganda, Kenya, Tanzania, Rwanda, Mozambique, Zambia, and Zimbabwe . ContempUltimately, it appears that there is significant overlap in the clinical features between endemic and HIV-related KS in children and adolescents in a KSHV-endemic region of Africa. The authors advocate for a universal risk-stratified treatment approach that applies to both endemic and HIV-related pediatric KS. Systematically characterizing the treatment response for children with endemic disease will be essential to improving overall outcomes.Additional file 1:Figure S1. Lymph Node Histopathology in Patients with Endemic HIV-Negative and Epidemic HIV-Positive Lymphadenopathic Kaposi Sarcoma. Lymph node biopsies from endemic HIV-negative (A) and epidemic HIV-positive (B) children with lymphadenopathic Kaposi sarcoma demonstrating diffuse spindle cell tumor infiltrates that stain positive for the Kaposi sarcoma herpesvirus/human herpesvirus-8 latency-associated nuclear antigen immunohistochemical stain at 200x magnification. (TIF 7072 kb)