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Archie, Kevin Dendritic interactions could account for stimulus competition and attentional modulation in visual cortical neurons. Reynolds, Chelazzi, and Desimone (J. Neurosci. 19:1736, 1999) showed that when two stimuli are presented simultaneously within the receptive field of neurons in area V2 and V4 in macaque, the firing rate of some cells is a weighted average of the responses evoked by the two stimuli presented in isolation, reflecting a fundamentally competitive stimulus interaction. Thus, a stimulus that boosts the response of the cell when presented alone can suppress the response of the same cell when presented together with a more effective visual stimulus. They showed further that attention biased the competition, boosting cell responses when attention was directed to the more effective stimulus and suppressing cell responses when attention was directed to the less effective stimulus. Using a biophysically-detailed compartmental model, we tested the hypothesis that this form of competition could arise via interactions between excitatory and inhibitory inputs onto the active dendrites of a single visual cortical neuron. We observed the appropriate patterns of response boosting and suppression when it was assumed that each visual stimulus, or attention to that stimulus, activated both excitatory and inhibitory inputs to the cell -- but on different dendritic branches -- i.e., in a wiring pattern consistent with a Hebbian developmental rule. Given the strong compartmentalization of the cell, inhibition caused by one stimulus was most effective at suppressing the active dendritic responses driven by the other stimulus.
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