Early cortical orientation selectivity: how fast inhibition decodes the order of spike latencies.
Following a flashed stimulus, I show that a simple neurophysiological mechanism in the primary visual system can generate orientation selectivity based on the first incoming spikes. A biological model of the lateral geniculate nucleus generates an asynchronous wave of spikes, with the most strongly activated neurons firing first. Geniculate activation leads to both the direct excitation of a cortical pyramidal cell and disynaptic feed-forward inhibition. The mechanism provides automatic gain control, so the cortical neurons respond over a wide range of stimulus contrasts. It also demonstrates the biological plausibility of a new computationally efficient neural code: latency rank order coding.
Delorme
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CNL, Salk Institute, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA. arno@salk.edu
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D015350:Contrast Sensitivity; D019706:Excitatory Postsynaptic Potentials; D005829:Geniculate Bodies / Q000033:anatomy & histology / Q000502:physiology; D006801:Humans; D008954:Models, Biological; D009433:Neural Inhibition / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D009949:Orientation; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology*; D013997:Time Factors; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology