Utilizing fNIRS to Map the Dynamics of the Motoric Readiness Potential During Reactive Response Inhibition Tasks

The ability to inhibit a response before the motoric point of no return could mean the difference between an organism's success or failure. Despite decades of research, a disagreement persists regarding the roles of the right inferior frontal gyrus (rIFG) and the pre-SMA in reactive motor inhibition, specifically, which region plays the initiating role. The Bereitschaftspotential (BP), which reflects preparatory activity in motor-related regions of the pre-SMA, SMA, and motor cortices, provides a unique vehicle for visualizing and quantifying motoric activity. Traditionally, this has been investigated utilizing fMRI; however, this study focused on determining the feasibility of leveraging fNIRS during a modified Stop Signal Task to map the neurovascular coupling in these regions. A channel-based analysis during inhibitory control trials revealed significantly greater oxygenated hemoglobin (HbO) in the right inferior frontal gyrus (rIFG) during successful stop trials when compared to go trials. In contrast, when comparing failed to successful stop trials, increased HbO relative to deoxygenated hemoglobin (HbR) was observed in the premotor cortex (PMC) and primary motor cortex (M1), reflecting motor activation in the absence of inhibitory engagement from the rIFG. These findings suggest a dominant role of the rIFG over the pre-SMA when reactive motoric response inhibition is required, initiated, and successful, and validates the use of fNIRS as a robust approach to resolving the temporal and spatial contributions of these structures.