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Summary of neocortical mechanisms of sparseness and reliabity with widefield stimulation

Figure 13. A. With normal CRF stimulation, the pyramidal cell (RSc) response is mediated by an interaction of local excitatory and inhibitory neurons. B. With widefield stimulation, neighboring regions of cortex are stimulated, resulting in lateral influences. This lateral influence is most likely excitatory and preferentially activates local inhibitory neurons owing to their steep input-output curves (see middle graphs). This preferential activation of inhibitory neurons results in an increase in activity of the GABAergic cells with widefield stimulation and a decrease in action potential response in the excitatory pyramidal cells. There is a sharpening of the pyramidal cell response through an "ice berg" phenomenon - they fire only at the peaks of depolarizing synaptic responses. This increase in "sharpness" increases the reliability of the network, by restricting spikes to narrow windows of time.