The role of gamma connectivity in the human prefrontal cortex in the Bereitschaftspotential

Abstract

Objects: The Bereitschaftspotential (BP) is a slow negative cortical potential related to the intention, decision, execution, and control of a movement. The prefrontal cortex (PFC) is known to be one of the generators of BP and to play an important role in cognitive preparation and decision making. Since movement preparation needs the synchronous activity of various neurons, BP may be developed through the exchange of information between motor-related neurons. However, the relationship between BP and information flow is not yet well-known. In the present study, we aim to investigate how the connectivity in the PFC changes during the occurrence of BP.

Method: Electrocorticography (ECoG) was recorded in 5 patients with epilepsy. The subjects performed self-paced hand grasping for 5 minutes during each session, and 3 sessions were recorded for each subject. In the PFC region, electrodes showing prominent BP were selected by visual inspection. An equal number of electrodes distant from the PFC were chosen as a comparison model. We compared the intraregional connectivity between the PFC and non-PFC regions using partial directed coherence (PDC, range 0-1, 0 denoting no coherence and 1 denoting complete coherence).

Results: In the PFC, the connectivity of beta and gamma bands in the BP period increased by an average of 24.4% compared with the baseline connectivity. Conversely, the gamma connectivity in the non-PFC regions decreased by 31.4%. Moreover, the intraregional connectivity in the PFC increased according to the stage of BP, i.e. baseline (0.24) early (0.30) and late (0.32) periods.

Conclusion: The increased gamma band connectivity in the PFC implies that the increased communication among neurons in the PFC is associated with the development of BP. This finding shows that voluntary movement is developed by intraregional connectivity in the PFC, and reflects the activation of brain networks related to movement preparation.