A basic property of cortical neurons is that particular features of sensory stimuli preferentially drive the spike output of individual cells. For example, neurons in visual cortex can fire selectively to visual stimuli that have a particular orientation or direction (Fig. 2A). Stimulus selective responses are observed in cortical regions devoted to all sensory modalities and understanding the mechanisms governing this tuning of responses to preferred stimuli is critical for unraveling how the cortex represents sensory information. Since the selectivity to certain stimuli (e.g. orientation tuning) emerges for the first time in the cortex, (i.e. it is not present in any of the neurons along the chain that conveys the signal from the sensory interface to the cortex), cortical circuitry must contribute to generating this stimulus selectivity (Hubel and Wiesel, 1962). What role does synaptic inhibition play in the tuning of cortical neurons to sensory stimuli?
