Computational Techniques for Eye Movements Analysis towards Supporting Early Diagnosis of Alzheimer's Disease: A Review <s> Eye Movements Analysis in Naturalistic Tasks. <s> The aim of this study was to determine the pattern of fixations during the performance of a well-learned task in a natural setting (making tea), and to classify the types of monitoring action that the eyes perform. We used a head-mounted eye-movement video camera, which provided a continuous view of the scene ahead, with a dot indicating foveal direction with an accuracy of about 1 deg. A second video camera recorded the subject's activities from across the room. The videos were linked and analysed frame by frame. Foveal direction was always close to the object being manipulated, and very few fixations were irrelevant to the task. The first object-related fixation typically led the first indication of manipulation by 0.56 s, and vision moved to the next object about 0.61 s before manipulation of the previous object was complete. Each object-related act that did not involve a waiting period lasted an average of 3.3 s and involved about 7 fixations. Roughly a third of all fixations on objects could be defin... <s> BIB001 </s> Computational Techniques for Eye Movements Analysis towards Supporting Early Diagnosis of Alzheimer's Disease: A Review <s> Eye Movements Analysis in Naturalistic Tasks. <s> Two recent studies have investigated the relations of eye and hand movements in extended food preparation tasks, and here the results are compared. The tasks could be divided into a series of actions performed on objects. The eyes usually reached the next object in the sequence before any sign of manipulative action, indicating that eye movements are planned into the motor pattern and lead each action. The eyes usually fixated the same object throughout the action upon it, although they often moved on to the next object in the sequence before completion of the preceding action. The specific roles of individual fixations could be identified as locating (establishing the locations of objects for future use), directing (establishing target direction prior to contact), guiding (supervising the relative movements of two or three objects) and checking (establishing whether some particular condition is met, prior to the termination of an action). It is argued that, at the beginning of each action, the oculomotor system is supplied with the identity of the required object, information about its location, and instructions about the nature of the monitoring required during the action. The eye movements during this kind of task are nearly all to task-relevant objects, and thus their control is seen as primarily ‘top-down’, and influenced very little by the ‘intrinsic salience’ of objects. © 2001 Elsevier Science Ltd. All rights reserved. <s> BIB002 </s> Computational Techniques for Eye Movements Analysis towards Supporting Early Diagnosis of Alzheimer's Disease: A Review <s> Eye Movements Analysis in Naturalistic Tasks. <s> We examined eye movements in a patient, FK, who has action disorganisation syndrome (ADS), as he performed the everyday task of making a cup of tea. We compared his eye movements with those of a person with Alzheimer's disease and with healthy volunteers. Despite showing very disorganised behaviour many aspects of FK's eye movements were relatively normal. However, unlike normal participants FK made no advance glances to objects that were about to be used, and he made increased numbers of fixations to irrelevant objects during the task. There were also differences in the durations of his eye movements during correct actions and during his perseverative and task-addition responses. We discuss the implications for understanding ADS and the cognitive processes required for correctly performing everyday tasks. <s> BIB003 </s> Computational Techniques for Eye Movements Analysis towards Supporting Early Diagnosis of Alzheimer's Disease: A Review <s> Eye Movements Analysis in Naturalistic Tasks. <s> Mild cognitive impairment (MCI) refers to the intermediate period between the typical cognitive decline of normal aging and more severe decline associated with dementia, and it is associated with greater risk for progression to dementia. Research has suggested that functional abilities are compromised in MCI, but the degree of impairment and underlying mechanisms remain poorly understood. The development of sensitive measures to assess subtle functional decline poses a major challenge for characterizing functional limitations in MCI. Eye-tracking methodology has been used to describe visual processes in everyday, naturalistic action among healthy older adults as well as several case studies of severely impaired individuals, and it has successfully differentiated healthy older adults from those with MCI on specific visual tasks. These studies highlight the promise of eye-tracking technology as a method to characterize subtle functional decline in MCI. However, to date no studies have examined visual behaviors during completion of naturalistic tasks in MCI. This review describes the current understanding of functional ability in MCI, summarizes findings of eye-tracking studies in healthy individuals, severe impairment, and MCI, and presents future research directions to aid with early identification and prevention of functional decline in disorders of aging. <s> BIB004 </s> Computational Techniques for Eye Movements Analysis towards Supporting Early Diagnosis of Alzheimer's Disease: A Review <s> Eye Movements Analysis in Naturalistic Tasks. <s> This study aimed to examine simple locomotion and eye behaviour of individuals with Posterior Cortical Atrophy (PCA) and typical Alzheimer's disease (tAD) within a simulated real-world environment. Posterior cortical atrophy (PCA) is a neurodegenerative condition characterised by parietal, occipital and occipito-temporal tissue loss and progressive impairment of higher-order visual function in contrast to relatively spared memory and language. Targeted types of locomotion were walking in a series of corridors, up or down stairs, and across an open room with or without the presence of an obstacle. Eye tracking measures and inertial moment units (IMU) were used in this experiment, and resultant acceleration of left foot and fixation duration were extracted. Findings from three participants are presented as a case series: one control, one PCA and one tAD patient. The averaged resultant acceleration of PCA patient was the slowest in all types of locomotion, especially in stairs. The averaged resultant accelerations of PCA and tAD participants were slower than the control participant. The PCA participant had longer mean fixation durations than the tAD and control participants, however, mean fixation duration was similar between tAD and control participants. Results may help characterise locomotion and eye behaviour in PCA and tAD and may suggest ways to support effective diagnosis and assessment of disease progression. <s> BIB005 </s> Computational Techniques for Eye Movements Analysis towards Supporting Early Diagnosis of Alzheimer's Disease: A Review <s> Eye Movements Analysis in Naturalistic Tasks. <s> Yarbus' pioneering work in eye tracking has been influential to methodology and in demonstrating the apparent importance of task in eliciting different fixation patterns. There has been renewed interest in Yarbus' assertions on the importance of task in recent years, driven in part by a greater capability to apply quantitative methods to fixation data analysis. A number of recent research efforts have examined the extent to which an observer's task may be predicted from recorded fixation data. This body of recent work has raised a number of interesting questions, with some investigations calling for closer examination of the validity of Yarbus' claims, and subsequent efforts revealing some of the nuances involved in carrying out this type of analysis including both methodological, and data related considerations. In this paper, we present an overview of prior efforts in task prediction, and assess different types of statistics drawn from fixation data, or images in their ability to predict task from gaze. We also examine the extent to which relatively general task definitions (free-viewing, object-search, saliency-viewing, explicit saliency) may be predicted by spatial positioning of fixations, features co-located with fixation points, fixation dynamics and scene structure. This is accomplished in considering the data of Koehler et al. (2014) 30 affording a larger scale, and qualitatively different corpus of data for task prediction relative to existing efforts. Based on this analysis, we demonstrate that both spatial position, as well as local features are of value in distinguishing general task categories. The methods proposed provide a general framework for highlighting features that distinguish behavioural differences observed across visual tasks, and we relate new task prediction results in this paper to the body of prior work in this domain. Finally, we also comment on the value of task prediction and classification models in general in understanding facets of gaze behaviour. <s> BIB006 </s> Computational Techniques for Eye Movements Analysis towards Supporting Early Diagnosis of Alzheimer's Disease: A Review <s> Eye Movements Analysis in Naturalistic Tasks. <s> We present a novel computational model that describes action perception as an active inferential process that combines motor prediction (the reuse of our own motor system to predict perceived movements) and hypothesis testing (the use of eye movements to disambiguate amongst hypotheses). The system uses a generative model of how (arm and hand) actions are performed to generate hypothesis-specific visual predictions, and directs saccades to the most informative places of the visual scene to test these predictions – and underlying hypotheses. We test the model using eye movement data from a human action observation study. In both the human study and our model, saccades are proactive whenever context affords accurate action prediction; but uncertainty induces a more reactive gaze strategy, via tracking the observed movements. Our model offers a novel perspective on action observation that highlights its active nature based on prediction dynamics and hypothesis testing. <s> BIB007
When performing daily activities such as cooking or gardening, subjects interact with several objects, for example knifes, pans, or remote controls. During these interactions, a succession of different actions is involved, for example, cutting a vegetable or watering a plant. While executing these actions, humans use their vision to locate the objects and to manipulate them BIB001 . Indeed, the eye movements during everyday tasks provide relevant information about complex cognitive process related to object identification, place memory, tasks execution, and monitoring BIB004 . Studies attempt to understand the relation between activity execution and eye movements by investigating the eye patterns and eye-hand coordination on actions BIB002  . For example, results support that people shift their gaze to target sites anticipating actions BIB007 . Also, results indicate that subjects rarely fixate on objects irrelevant to a performed action  . In fact, almost all eye movements during activities are targeted to fixation of task relevant objects, suggesting that visual attention can be modelled as "top-down" having little influence of the "intrinsic saliency" of the scene BIB002 . Topdown modelling refers to aspects of attention and gaze that are under executive control and may be influenced by tasks' directives and working memory BIB006 . Thus, top-down models require prior knowledge from the context  . On the other hand, bottom-up modelling refers to attention that is driven by properties of the visual stimulus being independent from tasks or semantic BIB006 . The described findings so far have arisen from experiments with healthy subjects. While the results are important to understand the eye movements in ADL, experiments with AD patients are scarce. This later is critical to support the diagnosis in early stages and to monitor changes of the disease. Healthy subjects have demonstrated different results when conducting specific oculomotor task when compared with PwAD and we expect the same in naturalistic scenarios. In the work by Forde et al. BIB003 the eye movements in an ADL task are analyzed from a patient with action disorganization syndrome (ADS), from a PwAD, and from control subjects. The results show difference in the visual behavior from the participants while they were preparing a cup of tea. For example, the ADS patient made no glances to objects anticipating their use and had an increased number of fixations to irrelevant objects during the task. This shows different results from those stated in  BIB007 . The AD patient showed fewer fixations overall than control subjects and the ADS patients. In addition, the PwAD showed a lower proportion of relevant fixations compared to control subjects. In the work by Suzuki et al. BIB005 eye movement is investigated during locomotion. One AD patient, one Posterior Cortical Atrophy (PCA) patient, and one healthy subject used an eye tracking device while performing locomotion activities (walking along corridors, up and down stairs, and across a room with or without obstacles). The results show that the PCA patients were the slowest in performing the locomotion activities. Also, the PCA patient had longer fixation than the PwAD and the healthy subject. The PwAD required prompting during task competition showing memory impairment. Both studies show important findings toward understanding eye movements from PwAD; however more experiments with more participants are required. A research goal is to understand eye movements abnormalities when performing ADL that serve to identify early signs of AD and to alert about a possible development of the disease. However, several challenges must be addressed first. For example, despite finding differences between PwAD and control groups, several abnormalities on visual deficits are not unique to AD but they are also present in other pathologies. In addition, it is important to find a visual marker that can be used to measure the progression of the disease; that is, the longitudinal studies must be conducted. Additionally, the clinical and personal history of each patient must be considered. PwAD might have differences in their visual behavior due to their physiological and personal context. Such is the case, for example, if they have sensorial impairments or a determining event in their lives. For example, a manual worker might have a different behavior than a white-collar worker. The analysis of visual behavior during ADL has the potential to become a tool for AD assessment and for monitoring progression. Its success strongly relies on the development of technology able to measure eye movements. To be a pervasive tool it has to measure eye movements easily and in a noninvasive way allowing subjects to perform their activities in a natural manner. Currently, there are clinical trials registers describing ongoing research with the objective to analyze eye movements in naturalistic tasks. For example, by doing a search with the terms "Alzheimer's disease" and "eye movements" in the database ClinicalTrials.gov provided by the US National Library of Medicine, there are 10 results currently recruiting participants. We identified 2 as relevant ongoing studies of eye movements in naturalistic scenarios for AD. In  , researchers aim to analyze eye movements when reading sentences. In  , researchers aim to analyze deficits in visual exploration in ADL. Researchers in  expect to encounter that persons with AD have less ability of using scene semantic when locating objects. In this sense, the understanding of scene is paramount. In the next section we describe how the use of computational techniques can leverage the analysis of eye movements and AD by scene understanding.