Seven Glimpses into the Emotional Brain
In the last century, and particularly since the 1950’s, we’ve witnessed a shift in our efforts to understand the human mind. Cognition—the term that includes mental processes such as attention, memory, problem-solving, planning, and language—stopped being exclusively a philosophical subject approached by introspection and became a matter of empirical investigation and objective quantification. However, the traditional approaches to study cognition have focused on the information-processing functions and have generally excluded emotions. Today researchers acknowledge a close relationship between our feelings and our thoughts, and have begun to disentangle how this relationship affects how we view the world, what we learn from it, and how we adjust our behavior accordingly. In this short article, I summarize recent research published in Open Access journals that explores the quantification and manipulation of emotions and investigates the interactions between emotions and cognitive processes such as attention and memory. This work provides insights from human subjects and animal models on the underlying neural mechanisms of cognition. In a recent study published in PLOS Biology [1], the authors investigated how emotions impact visual attention. To do so, they used a combination of psychophysical experiments and functional Magnetic Resonance Imaging (fMRI), which measures brain activity by detecting changes associated with blood flow. When human subjects were shown emotionally loaded stimuli, the size of the attention field changed depending on whether the stimuli had a positive or negative valence. For example, a smiling face has a positive valence, and when presented to the subject, their attention field broadened. However, when the subjects were presented with a face with a negative valence (frowning or angry), the subject’s attention field narrowed. Interestingly, the emotional strength of the negative or positive faces, as explicitly reported by the participants, closely matched the size of the effects in the behavioral and brain-imaging experiments. The authors could establish that the effects of emotional valence on the size of the attention fields were mediated by a feedback from the dorsolateral prefrontal cortex—a functional brain structure that contributes to executive functions such as working memory, cognitive flexibility, planning, and abstract reasoning—to the primary visual cortex. These findings pave the road for understanding how the interaction between emotion and attention shapes our experience of the world. In a complementary study published in PLOS Computational Biology [2], researchers explored additional neural mechanisms that could account for the emotional regulation of attention. The scientists developed a computational model to investigate how the amygdala— the gateway of the brain’s emotional system—controls the inhibitory thalamic reticular nucleus, which is central to the attentional system. Lesions in the thalamic reticular nucleus, for example, result in attentional deficits. The computational model indicates that the amygdala-thalamic reticular nucleus pathway can select emotionally salient stimuli and inhibit transmission of irrelevant signals to the cortex, thereby determining the information available for subsequent cortical processing. In this way, the model accounts for both flexible bottomup and focused top-down attention guided by emotions. Bottom-up (or stimulus-driven)