Information about movement direction obtained from synchronous activity ofmotor cortical neurons

Although neuronal synchronization has been shown to exist in primary motor cortex (MI), very little is known about its possible contribution to coding of movement. By using cross-correlation techniques from multi-neuron recor dings in MI, we observed that activity of neurons commonly synchronized aro und the time of movement initiation. For some cell pairs, synchrony varied with direction in a manner not readily predicted by the firing of either ne uron. Information theoretic analysis demonstrated quantitatively that synch rony provides information about movement direction beyond that expected by simple rate changes. Thus, MI neurons are not simply independent encoders o f movement parameters but rather engage in mutual interactions that could p otentially provide an additional coding dimension in cortex.