Yves Fregnac

CNRS-UNIC - Unité de Neuroscience, Information et Complexité, Gif-sur-Yvette, France

Title: Role of Horizontal connectivity in contour co-linearity and filling-in prediction in the Primary Visual Cortex

Abstract:

We explore here the role of the "horizontal" long-distance intra-cortical connections in the dynamic emergence of predictive responses in the primary visual cortex (V1) of the anesthetized cat. Our stimulation paradigms interleave a variety of apparent motion (AM) or continuous animations of local oriented stimuli along trajectories, whose perceptual saillance could be varied according to the specific spatial and temporal properties of local and global features.

The picture drawn from our intracellular observations is that synaptic activity in cat V1 reveals a built-in bias for co-linearity detection in primary visual cortical areas. This bias is already detectable in the anesthetized animal, in the absence of attention-related feedback from higher cortical areas. In a recent series of experiments we could demonstrate that collinear centripetal AM flow restricted to the far "silent surround" of V1 cells (from 25° to 5° of eccentricity) induced "filling-in" response in 30% of recorded cells. This effect was found most prominent at saccadic-like speeds (150-250°/s) along the orientation preference RF axis.

Taken together with findings obtained in collaboration with Frederic Chavane's lab (INT, Marseille), our results point to two specific roles of horizontal propagation in V1, with possibly different spatial anisotropy profiles, different spatial scales and different speed selectivities. The first one concerns collinear-biased propagation of iso-orientation preference at high speed (0.1-0.3 m/s; 100°/sec (monkey) -250°/sec (cat)) and fits the general concept of the "perceptual" association field. The second one concerns isotropic horizontal propagation (10-30°/sec (cat and monkey)) and the build-up of anticipatory activity facilitating integration of a moving object along a trajectory. This propagation process could operate at lower speed than the orientation selective component, and most likely imply a cascade of shorter-range horizontal interactions triggered by a sequence of feedforward inputs. Its synaptic correlates are still unknown.

Supported by CNRS and the ANR (Horizontal-V1).

Bio-sketch:

Yves Frégnac is Emeritus Research Director at the Centre National de la Recherche Scientifique (CNRS). He has been the Head of the Unit of Neuroscience, Information and Complexity (UNIC) until 2017, and Full Professor in Cognitive Sciences at the Ecole Polytechnique. His interdisciplinary research explores the phenomenon of complexity related to the natural dynamics of cortical neural networks. He was awarded the Grand Prix thématique de l'Académie des Sciences (Prix Jaffé) in 1999 and the Grand Prix de l'Institut de France (Prix Louis D.) in 2008. For the past 20 years, Yves Frégnac has been CNRS coordinator in Integrated Projects of the FET (Future Emerging Technologies) EC-Programs: SenseMaker, Facets, Facets-ITN, Brain-i-nets and BrainScales.

Selection of recent publications :

Frégnac, Y. and Bathellier, B. (2015). Cortical correlates of low-level perception: from neural circuits to percepts. Neuron. 88(1): 110-126.

Gerard-Mercier, F., Pananceau, M., Carelli, P., Troncoso, X. and Frégnac, Y. (2016). Synaptic correlates of low-level perception in V1. The Journal of Neuroscience. 36(14): 3925-3942.

Frégnac, Y. (2017). Big Data and Neuroscience industrialization: A safe roadmap for understanding the Brain? Science. 358 (6362): 470-447. DOI: 10.1126/science.aan8866.