Sleep quality and its association with the insular cortex in emotional empathy.

The human ability to vicariously share someone else's emotions (i.e., emotional empathy) relies on an extended neural network including regions in the anterior cingulate and insular cortex. Here, we tested the hypothesis that good sleep quality is associated with increased activation in the brain areas underlying emotional empathy. To this aim, we assessed subjective sleep quality in a large sample of healthy young volunteers, and asked participants to complete a computerized emotional empathy task. Then, we asked 16 participants to complete the same task while undergoing functional Magnetic Resonance Imaging (fMRI). After confirming the behavioral relationship between quality of sleep and emotional empathy in the large sample, we conducted a Region of Interest (ROI) analysis on selected ROIs involved in emotional empathy, and measured Blood Oxygen Level Dependent (BOLD) signal change in participants who performed the emotional empathy task in the MRI scanner; additionally, we assessed how the BOLD signal in different brain areas temporally correlated with performance throughout the task (i.e., task-based functional connectivity). We found increased BOLD signal change in a selective region within the left insula for individuals with better subjective sleep quality. These findings provide the very first evidence that individuals' sleep quality relates to emotional empathic responses through increased neural activation of a specific area within the insular cortex.