several categories, including basket cells, chandelier cells, bipolar cells, double bouquet cells, bitufted cells, and neurogliaform cells (Markram et al., 2004). These different cell types specialize in their location of axon innervation of target neurons, including soma and proximal dendrites (basket cells), more distal dendrites (double bouquet, bipolar, bitufted, neurogliaform, Martinotti cell), and axon initial segments (chandelier). These distinct patterns of target neuron innervation allow for precise control of both input (dendritic processing and integration) and output (somatic and initial segment) functions of the postsynaptic neuron. Interneurons are also classified according to their expression of different calcium binding proteins (parvalbumin, calbindin, and calretinin) and neuropeptides (neuropeptide Y, vasoactive intestinal peptide, somatostatin, and cholecystokinin). In terms of electrophysiological responses, neocortical interneurons display a wide range of spiking patterns in response to steady-state current injection. These include non-accommodating, accommodating, stuttering, irregular spiking, and bursting. Within the prefrontal cortex, most studies have recognized four different classes of interneurons based on spiking patterns during current injection (Kawaguchi, 1995; Gorelova et al., 2002). Fast-spiking (FS) neurons are the most numerous and display very rapid action potentials (~0.5ms half-width) each followed by a deep after-hyperpolarization. FS neuron firing is non-accommodating and rarely do these neurons show
