Relative spike time coding and STDP-based orientation selectivity in the early visual system in natural continuous and saccadic vision: a computational model |
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Authors: | Timothée Masquelier |
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Institution: | (1) Unit for Brain and Cognition, Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona, Spain |
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Abstract: | We have built a phenomenological spiking model of the cat early visual system comprising the retina, the Lateral Geniculate
Nucleus (LGN) and V1’s layer 4, and established four main results (1) When exposed to videos that reproduce with high fidelity
what a cat experiences under natural conditions, adjacent Retinal Ganglion Cells (RGCs) have spike-time correlations at a
short timescale (~30 ms), despite neuronal noise and possible jitter accumulation. (2) In accordance with recent experimental
findings, the LGN filters out some noise. It thus increases the spike reliability and temporal precision, the sparsity, and,
importantly, further decreases down to ~15 ms adjacent cells’ correlation timescale. (3) Downstream simple cells in V1’s layer
4, if equipped with Spike Timing-Dependent Plasticity (STDP), may detect these fine-scale cross-correlations, and thus connect
principally to ON- and OFF-centre cells with Receptive Fields (RF) aligned in the visual space, and thereby become orientation
selective, in accordance with Hubel and Wiesel (Journal of Physiology 160:106–154, 1962) classic model. Up to this point we dealt with continuous vision, and there was no absolute time reference such as a stimulus
onset, yet information was encoded and decoded in the relative spike times. (4) We then simulated saccades to a static image and benchmarked relative spike time coding and time-to-first
spike coding w.r.t. to saccade landing in the context of orientation representation. In both the retina and the LGN, relative
spike times are more precise, less affected by pre-landing history and global contrast than absolute ones, and lead to robust
contrast invariant orientation representations in V1. |
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Keywords: | |
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