Inhibitory Mechanisms in the Motor Cortical Circuit
Inhibitory mechanisms are crucial for the integrated operation of the motor cortical circuit. Local inhibition is exerted by interneurons that are GABAergic, nonpyramidal cells with short, nonprojecting axons. Interneurons can be classified into at least two groups: fast-spiking (FS) neurons and instrinsic bursting (IB) neurons. In the primary motor cortex, FS cells may sculpe the tuning dispersion of directionally selective putative pyramidal cells during reaching in behaving monkeys. Analysis of putative interneuronal activity also allowed to discard the role of inhibition as a gating mechanism in motor control. The development of high-density, semichronic electrode systems for extracellular recordings in behaving primates will allow a closer investigation of the role of interneuronal inhibition in directional tuning and voluntary motor control. The results discussed in this chapter agree with the authors’ proposal that local inhibitory mechanisms may be intimately involved in controlling the directional accuracy and speed of the reaching movement.