Single-pulse TMS functional mapping of sensorimotor cortex during decision-making task

Perceptual decision-making involves distinct sub-processes, including sensory encoding, decision formation, and motor execution. Studying the specific contributions of cortical areas to these components could deepen our understanding of decision-making mechanisms and inform therapeutic approaches for cognitive impairment. Single-pulse transcranial magnetic stimulation (spTMS) enables the functional investigation of cortical involvement during task performance, revealing the participation of specific regions in cognitive processes. When combined with the drift diffusion model (DDM), spTMS can precisely characterize effects on different decision sub-processes. In this study, 30 healthy participants performed a perceptual decision-making task requiring right-hand finger responses to complex visual stimuli. We delivered spTMS to sensorimotor cortex regions at two time points during task performance (200 ms and 800 ms post-stimulus onset). Results demonstrated region-specific modulation patterns: stimulation of the premotor dorsal caudal cortex (PMdc) selectively reduced reaction time (RT) by decreasing non-decision time (NDT), indicating its role in motor preparation. In contrast, primary motor cortex (M1) and primary somatosensory cortex (S1) stimulation produced opposing effects - decreased NDT coupled with increased evidence accumulation time (EAT) - resulting in no net RT change. These findings highlight how spTMS combined with DDM can dissect distinct cortical contributions to decision-making sub-processes.