Slow-wave sleep in the TPJ is linked to individual differences in implicit bias

Implicit biases can profoundly impact social interactions and decision-making processes. Here, we investigate whether the heterogeneity of implicit racial bias can be explained by interindividual differences in the intracortical distribution of slow-wave activity (SWA), a marker of sleep depth. Using high-density EEG, we recorded sleep data from 52 healthy adults (27 females) during a typical night's sleep in their homes. Implicit racial bias was measured using the race Implicit Association Test (IAT). Whole-brain corrected source localization analysis identified a significant association between higher relative SWA current density in the left temporoparietal junction (TPJ) and lower levels of implicit racial bias. The TPJ plays a crucial role in social cognitive processes such as mentalizing - the process of understanding others' mental states. We propose that deeper sleep in this region, as indicated by higher SWA current density, may reflect higher inherent mentalizing abilities, leading to reduced implicit racial bias. Applying a novel approach to investigate the link between sleep and social functioning, our data suggests that local aspects of sleep could explain inter-individual differences in social cognition.