Modulation of neocortical interneurons: extrinsic influences and exercises in self-control.

Neocortical GABAergic interneurons are a highly heterogeneous cell population that forms complex functional networks and has key roles in information processing within the cerebral cortex. Mechanisms that control the output of these cells are therefore crucial in regulating excitability within the neocortex during normal and pathophysiological activities. In addition to subtype-specific modulation of GABAergic cells by neurotransmitters released by afferents from subcortical nuclei, interneurons belonging to different classes are controlled by distinct self-modulatory mechanisms, each unique and powerful. In this article, we review the diverse responses of neocortical interneurons to extrinsic and intrinsic neuromodulators. We discuss how specificity of responses might differentially influence inhibition in somatodendritic compartments of pyramidal neurons and affect the balance of activities in neocortical circuits.