Single-Unit Activity in the Human Medial Temporal Lobe Reflects Reduced Error Monitoring During Mind Wandering.

Mind wandering (MW) has been frequently reported to impair task performance. In this study, we investigated the hypothesis that it also affects error monitoring and adjustment. Several recent studies suggest that the hippocampus and adjacent regions significantly contribute to error monitoring. Therefore, we analyzed single-unit recordings from the medial temporal lobe (MTL) in presurgical epilepsy patients performing an attention task, which included interspersed experience sampling probes. Behavioral performance data revealed reduced error adjustment during periods of MW compared to task-focused attention. Analysis of single-unit recordings showed population responses related to performance errors within the hippocampus and adjacent regions, supporting the idea that MTL regions contribute to error monitoring. Importantly, this error-related population activity was significantly reduced during periods of MW compared to task focus. Together, our findings clearly support the hypothesis that MW impairs both error monitoring and adjustment.