feedback and feedforward, represent fundamental building blocks of cortical architecture and account for the fact that cortical excitation and inhibition are inseparable (van Vreeswijk and Sompolinsky, 1996). GABAergic interneurons will be recruited no matter whether excitation is generated locally or received from distant sites. In addition to principal cells, GABAergic interneurons also make inhibitory contacts onto each other and the connectivity between interneurons is highly reciprocal (Galarreta and Hestrin, 2002; Gibson et al., 1999; Tamas et al., 1998). This mutual connectivity between interneurons is also poised to shape spatial and temporal features of cortical inhibition.
