Hippocampal and cortical oscillatory dynamics support semantic processing and performance

While extensive work has mapped the anatomical regions that support semantic processing in healthy adults, the neural dynamics of such processing remain poorly understood. Herein, we use magnetoencephalography (MEG) to assess semantic-relatedness judgements (i.e., related versus unrelated) in 150 healthy adults. MEG data were transformed into the time-frequency domain and significant task-related oscillatory responses were imaged using a beamformer. Whole-brain, voxel-wise linear mixed-effects (LME) models were used to assess conditional differences while controlling for age. We find that participants respond slower during semantically-unrelated compared to -related trials and have stronger theta oscillations during unrelated trials in bilateral inferior frontal, parietal, and hippocampal areas, with the reverse pattern in the left superior parietal. In the gamma range, participants exhibit stronger gamma oscillations during related trials in prefrontal, hippocampal, and occipital regions. These findings suggest that theta and gamma oscillations may serve distinct roles in semantic processing.