Intracranial EEG Reveals a Time- and Frequency-Specific Role for the Right Inferior Frontal Gyrus and Primary Motor Cortex in Stopping Initiated Responses

Inappropriate response tendencies may be stopped via a specific fronto/basal-ganglia/primary-motor-cortical network. We sought to characterize the functional role of two regions in this putative stopping network, the right inferior frontal gyrus (IFG) and the primary motor cortex (M1), using electocorticography from sub-dural electrodes in four patients while they performed a stop signal task. On each trial, a motor response was initiated, and on a minority of trials a stop signal instructed the patient to try to stop the response. For each patient, there was a greater right IFG response in the beta frequency band (∼16 Hz) for successful vs. unsuccessful stop trials. This finding adds to evidence for a functional network for stopping because changes in beta frequency activity have also been observed in the basal ganglia in association with behavioral stopping. In addition, the right IFG response occurred 100 - 250 ms after the stop signal – a time range consistent with a putative inhibitory control process, rather than stop signal processing or feedback regarding success. A downstream target of inhibitory control is M1. In each patient, there was alpha/beta-band desynchronization in M1 for stop trials. However, the degree of desynchronization in M1 was less for successfully than unsuccessfully stopped trials. This reduced desynchronization on successful stop trials could relate to increased gamma-aminobutyric acid inhibition in M1. Taken together with other findings, the results suggest that behavioral stopping is implemented via synchronized activity in the beta-frequency band in a right IFG/basal-ganglia network, with downstream effects on M1.