Voluntary movements are driven by coordinated activity across a large population of neurons. Here we study how remote areas of the brain communicate with motor cortical neurons to drive movement effectively. We combine electrophysiological and pharmacological tools to identify cell types and pathways in the motor cortex of behaving animals. We find that thalamic input to the motor cortex triggers a strong inhibition by contacting inhibitory cells via highly effective synapses. We also find that the movement-related activity of inhibitory cells precedes the firing of pyramidal cells. This counterintuitive [JB1] [JB2] sequence of events, whereby inhibitory cells are recruited more strongly and before excitatory cells, could amplify the cortical effect of thalamic signals by suppressing competing inputs.

Figure: