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Titolo:
Contrast-dependent nonlinearities arise locally in a model of contrast-invariant orientation tuning
Autore:
Kayser, A; Priebe, NJ; Miller, KD;
Indirizzi:
Univ Calif San Francisco, Dept Physiol, San Francisco, CA 94143 USA Univ Calif San Francisco San Francisco CA USA 94143 ancisco, CA 94143 USA Univ Calif San Francisco, Dept Otolaryngol, San Francisco, CA 94143 USA Univ Calif San Francisco San Francisco CA USA 94143 ancisco, CA 94143 USA Univ Calif San Francisco, Grad Program Neurosci, San Francisco, CA 94143 USA Univ Calif San Francisco San Francisco CA USA 94143 ancisco, CA 94143 USA Univ Calif San Francisco, WM Keck Ctr Integrat Neurosci, San Francisco, CA94143 USA Univ Calif San Francisco San Francisco CA USA 94143 rancisco, CA94143 USA Univ Calif San Francisco, Sloan Ctr Theoret Neurobiol, San Francisco, CA 94143 USA Univ Calif San Francisco San Francisco CA USA 94143 ancisco, CA 94143 USA
Titolo Testata:
JOURNAL OF NEUROPHYSIOLOGY
fascicolo: 5, volume: 85, anno: 2001,
pagine: 2130 - 2149
SICI:
0022-3077(200105)85:5<2130:CNALIA>2.0.ZU;2-F
Fonte:
ISI
Lingua:
ENG
Soggetto:
CAT VISUAL-CORTEX; LATERAL GENICULATE-NUCLEUS; NEOCORTICAL PYRAMIDAL NEURONS; RECEPTIVE-FIELD PROPERTIES; CORTICAL SIMPLE CELLS; STRIATE CORTEX; GAIN-CONTROL; TEMPORAL INTERACTIONS; SYNAPTIC DEPRESSION; SHUNTING INHIBITION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
78
Recensione:
Indirizzi per estratti:
Indirizzo: Miller, KD Univ Calif San Francisco, Dept Physiol, 513 Parnassus, San Francisco, CA 94143 USA Univ Calif San Francisco 513 Parnassus San Francisco CAUSA 94143
Citazione:
A. Kayser et al., "Contrast-dependent nonlinearities arise locally in a model of contrast-invariant orientation tuning", J NEUROPHYS, 85(5), 2001, pp. 2130-2149

Abstract

We study a recently proposed "correlation-based," push-pull model of the circuitry of layer 4 of cat visual cortex. This model was previously shown to explain the contrast-invariance of cortical orientation tuning. Here we show that it can simultaneously account for several contrast-dependent (c-d)"nonlinearities" in cortical responses. These include an advance with increasing contrast in the temporal phase of response to a sinusoidally modulated stimulus; a change in shape of the temporal frequency tuning curve, so that higher temporal frequencies may give little or no response at low contrast but reasonable responses at high contrast; and contrast saturation thatoccurs at lower contrasts in cortex than in the lateral geniculate nucleus(LGN). In the context of the model circuit, these properties arise from a mixture of nonlinear cellular and synaptic mechanisms: short-term synaptic depression, spike-rate adaptation, contrast-induced changes in cellular conductance, and the nonzero spike threshold. The former three mechanisms are sufficient to explain the experimentally observed increase in c-d phase advance in cortex relative to LGN. The c-d changes in temporal frequency tuning arise as a threshold effect: voltage modulations in response to higher-frequency inputs are only slightly above threshold at lower contrast, but become robustly suprathreshold at higher contrast. The other three nonlinear mechanisms also play a crucial role in this result, allowing contrast dependence of temporal frequency tuning to coexist with contrast-invariance of orientation tuning. Contrast saturation, and the observation that responses to stimuli of increasing temporal frequency saturate at increasingly high contrasts, can be induced both by the model's push-pull inhibition and by synaptic depression. Previous proposals explained these nonlinear response properties by assuming contrast-invariant orientation tuning as a starting point, and adding normalization by shunting inhibition derived equally from cells of all preferred orientations. The present proposal simultaneously explains both contrast-invariant orientation tuning and these contrast-dependent nonlinearities and requires only processing that is local in orientation,in agreement with intracellular measurements.

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Documento generato il 10/07/20 alle ore 17:39:59