12
October
2011

Neuroscience Lecture by Yves Fregnac (Department of Neuroscience, Information and Complexity (UNIC) and the Institute of Neuroscience Alfred Fessard (INAF), CNRS Campus of Gif-sur-Yvette, France)

Title: "Reconstructing Visual Perception from Synaptic echoes in V1"

Yves Fregnac

Time and venue: 11.00 a.m. at the Lecture Hall (room 0.10 of the Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, 60438 Frankfurt am Main, Campus Riedberg)

Abstract
In vivo intracellular electrophysiology offers the unique possibility of listening to the “synaptic rumour” of the cortical network captured by the recording electrode in a single cell. The analysis of synaptic echoes evoked in primary visual cortex (V1) during sensory processing is used here to reconstruct the distribution of input sources in visual space and in time. It allows to infer, with minimal assumptions, the dynamics of the effective input network in cortical space, afferent to the recorded cell.

We have first applied this method in the mammalian visual cortex to re-examine the contribution of local intracortical connectivity to the expression of the Simple vs Complex feature of visual receptive fields. By submitting the same single cell to different input statistics, we have been able to show that both Simple and
Complex V1 RFs integrate a high diversity of subthreshold functional synaptic contributions, much larger than previously assumed or reported. Comparison of synaptic responses for different types of visual noise shows that the individual gains of hidden complex-like subunits can adapt to the high-order statistics of the sensory input, making the same receptive field look more “Simple” for complex inputs and more “Complex” for simple stimuli.

Using the same technique, but different types of stimuli (apparent motion noise) shown outside the classical receptive field, we are currently studying the long-distance propagation of visually evoked activity through lateral (and possibly feedback) connectivity. Our results demonstrate the propagation at the map level of intracortical depolarizing waves, broadcasting an elementary form of collective “belief” to distant parts of the network. The functional features of these slow waves support the hypothesis of a dynamic association field,
facilitating synaptic modulation in space and time and may serve as a substrate for implementing the perceptual Gestalt principles of common fate and axial collinearity.

This work is supported by CNRS and grants from ANR and the European Community (Brain-i-nets, BrainScales, Facets).

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