Intracortical microstimulation of somatosensory cortex generates evoked responses in motor cortex

The complex nature of neural connections throughout the cerebral cortex has led to broad interest in understanding cortical functional networks of tactile perception and sensorimotor integration. Cortico-cortical evoked potentials (CCEPs) can be used as physiological markers to study and map cerebral networks in the brain. In a human participant with bi-hemispheric microelectrode array implants in sensorimotor regions of the brain, we found that intracortical microstimulation (ICMS) of the primary somatosensory cortex can lead to evoked responses in the motor cortex in the same hemisphere, indicating connectivity between these sensorimotor regions. Single ICMS pulses were not consciously perceived, but elicited a rapid evoked potential approximately 20 ms after stimulus onset. Multi-pulse ICMS trains, perceived as tactile sensations in the thumb, sustained over an approximately 33 ms period, led to a delayed evoked response roughly 80 ms after stimulus onset. This work is important not only for better understanding the functional relationship between cortical areas, specifically somatosensory and motor cortices, but also to provide insight on pathways where neuromodulation techniques could be employed for rehabilitation or mitigation of sensorimotor neurodegenerative effects.