Lateral Excitation between Dissimilar Orientation Columns for Ongoing Subthreshold Membrane Oscillations in Primary Visual Cortex
Primary visual cortex (V1) is the first stage of visual information processing; detection of particularly oriented bars. These elemental visual features are sent to higher visual regions including V2, in which their combinations such as ”corners” and ”junctions” are processed. A recent study has demonstrated that corners and T-junctions could be processed even at the early visual stage (V1), raising the question of why the binding of bars by V1 is necessary. We simulated a V1 neural network model, in which the so-called ”orientation-columns” were connected through both excitatory and inhibitory synapses. The lateral excitatory connections contributed not only to binding paired bars constituting corners but also to making membrane oscillations near firing-threshold during ongoing (spontaneous) neuronal activity periods. This ongoing subthreshold neuronal state led to accelerating the reaction speed of neurons to paired bar-stimuli. The lateral inhibitory connections effectively enhanced the selective responsiveness of neurons to the stimuli. We suggest that coordinated lateral excitation and inhibition between orientation-columns in V1 could send angular information such as corners and junctions, presented to retina, rapidly to the next stage V2 for its full and precise analyses.
KeywordsNeural network model Lateral excitation Feature binding Orientation map Ongoing subthreshold membrane oscillation Primary visual cortex
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