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Synaptic plasticity changes orientation tuning and provides a mechanistic explanation for the tilt aftereffect in network models of V1
Zitatschlüssel wimm09
Autor K. Wimmer and K. Obermayer
Buchtitel Society for Neuroscience Abstracts
Seiten Program No. 850.15
Jahr 2009
Zusammenfassung The temporal context of a sensory stimulus influences the representation of the stimulus by neural populations and, in turn, how the stimulus is perceived. A well studied psychophysical phenomenon is the tilt aftereffect, in which an adapting context stimulus causes a vertically orientated test stimulus to appear repulsed away from the context orientation. Physiological studies have identified the accompanying changes in orientation tuning of individual neurons in primary visual cortex: Tuning curves shift away from the adapting stimulus, and responses close to the adapting stimulus are suppressed. Previous modeling studies have been purely conceptual or have focused exclusively either on the perceptual (tilt aftereffect) or physiological (tuning curve changes) effects. Here, we investigate whether synaptic plasticity evokes adaptive changes in orientation tuning that correctly predict the magnitude of the tilt aftereffect. We use two-dimensional fire rate models [1] of primary visual cortex that incorporate a biologically plausible topographic orientation preference map. The model cells receive strong recurrent excitation and inhibition, both dominating the feed-forward input, in order to account for fundamental physiological data on orientation tuning. We then systematically vary the strength of synaptic depression for the four types of recurrent connections (exc -> exc, exc -> inh, inh -> inh, and inh -> exc) and simulate adaptation experiments. Depending on the relative strength of the depression parameters, tuning curves of individual cells as well as the population responses show either attractive or repulsive shifts, and adaptation leads either to response suppression or facilitation. A wide range of models with strong depression of excitatory to excitatory connections is compatible to the experimental data. We additionally investigate how the tuning curve shifts of model neurons depend on the local intercortical interactions. It has been found experimentally, that adaptation-induced changes are more pronounced close to pinwheel centers. In the model, adaptation affects the broadly tuned recurrent inputs near pinwheels more strongly, which in turn leads to larger tuning curve shifts. We do not observe this difference between pinwheel and orientation domain cells in models with weak recurrent interactions. Thus, the pronounced adaptation near pinwheel centers is a consequence of the enhanced sensitivity to modulations of connection strengths in the strong recurrent network regime. [1] M Stimberg, K Wimmer, et al. The Operating Regime of Local Computations in Primary Visual Cortex. Cereb Cortex, Epub ahead of print (2009).
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