Volitional control of single cortical neurons in a brain–machine interface

Abstract

Volitional control of cortical activity is relevant for optimizing control signals for neuroprosthetic devices. We explored the control of firing rates of single cortical cells in two M. Nemestrina monkeys by providing visual feedback of neural activity and rewarding changes in cell rates. During ‘brain control’ sessions monkeys modulated the activity of each of 246 cells to acquire targets requiring high or low discharge rates. Cell control improved by more than 2-fold from the beginning of practice to peak performance. Activity of all cells was modulated substantially more during brain control than during wrist movements. When recording stability permitted, monkeys practiced controlling activity of the same cells across multiple days. Performance improved substantially for 27 of 36 cells when practicing brain control across days. Monkeys maintained discharge rates within each target for 1s, but could maintain rates for up to 3s for some cells. Monkeys performed the brain control task equally well using cells recorded from pre-central cortex compared to cells in post-central cortex, and independently of any directional tuning. These findings demonstrate that arbitrary single cortical neurons, regardless of the strength of directional tuning, are capable of controlling cursor movements in a one-dimensional brain-machine interface. It is possible that direct conversion of activity from single cortical cells to control signals for neuroprosthetic devices may be a useful complementary strategy to population decoding of intended movement direction.