Somatosensory cortex microstimulation modulates primary motor and premotor cortex neurons with extensive spatial convergence and divergence

Although intracortical microstimulation (ICMS) can affect distant neurons transynaptically, the extent to which ICMS pulses delivered in one cortical area actually modulate neurons in other cortical areas during voluntary behavior remains largely unknown. Here, we assessed how the individual pulses of multi-channel ICMS trains delivered in the primary somatosensory cortex (S1) modulate neuron firing in the primary motor (M1) and premotor (PM) cortex. S1-ICMS pulses modulated the majority of units recorded in both M1 and PM, producing more inhibition than excitation. Effects converged on individual neurons in both M1 and PM from extensive S1 territories. Conversely, effects of ICMS in a small region of S1 diverged to wide territories in both M1 and PM. Our findings may have ramifications for development of bidirectional brain-computer interfaces, where ICMS used to deliver artificial feedback in S1 could modulate the activity of neurons in M1 and PM, thereby hindering decoding of motor intent.

Highlights

• Somatosensory cortex microstimulation modulated motor and premotor cortex neurons.

• Inhibitory effects were more common than excitatory effects.

• Effects from stimulation on each ∼2x2 mm multielectrode array diverged widely.

• Effects in individual neurons converged from multiple somatosensory arrays.

eTOC blurb

Ruszala and colleagues show that multi-channel intracortical microstimulation in a small patch of somatosensory cortex modulates neurons distributed widely in both the primary motor and premotor cortex, with more effects being inhibitory than excitatory. Such modulation may complicate decoding motor intent when artificial sensation is delivered in bidirectional brain-computer interfaces.

Graphical Abstract