The Direction of Tilt Aftereffects Depends on Short-term Inhibitory Facilitation

J.M. Cortes, D. Marinazzo, T.J. Sejnowski and M.C.W. van Rossum. The Direction of Tilt Aftereffects Depends on Short-term Inhibitory Facilitation. NIPS 2011, Submitted but Rejected [pdf]

Neural adaptation leads to changes in the responses of single neurons and neural populations during continued exposure to a stimulus. At the single neuron level, adaptation reduces responses to a constant stimulus. At the perceptual level, adaptation can manifest itself as aftereffects. For instance, prolonged adaptation to a grating briefly shifts the perceived orientation of a test grating, which is called the tilt aftereffect (TAE). Although phenomenological models of the perceptual effects of adaptation are common, models at the single neuron level based on physiological mechanisms resulting in TAEs at population level are rare. Here we examined a model of adaptation in populations of cortical neurons based on short-term synaptic plasticity (STP). Neurons organized in a ring model were connected by center-surround interactions. Synaptic depression, affecting both excitatory and inhibitory synapses, produced reduction in neural responses, while inhibitory facilitation increased inhibitory efficacy. For strongly facilitory synaptic inhibition the peaks of the tuning curves shifted away from the adapting stimulus (repulsive shift), but for weak inhibitory facilitation, the tuning curves shifted towards the adapting stimulus (attractive shift). Using both population vector and winner-take-all decoders, the TAE reflected in the population was attractive for high values of inhibitory facilitation and repulsive for low values. Psychophysical experiments report repulsion close to the adapting stimulus and attraction farther away, consistent with the predictions of facilitory inhibition.

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