Orientation selectivity in a model of primary visual cortex with and without orientation map

G. MATO; S. GONZALO COGNO

Praga

Conferencia; CNS 2015; 2015

Organization for Computational Neuroscience

Since its discovery by Hubel and Wiesel in 1959, orientation selectivityhas been observed in every mammal for which the neuronal responseselectivity of primary visual cortex (V1) has been examined. In someanimals, like cat and monkey, anatomically close V1 neurons have similarpreferred orientations, giving rise to *maps of orientation* preferences.However, sharp selectivity is also observed in animals, like mice, squirrelsand rats, whose V1 has no orientation map. It means that neurons withdifferent preferred orientation are intermixed. This second scenario iscalled *salt-and-pepper organization*. This scenario leads to question the rolof intracortical connections because a purely topographical organization of the connections would not generate reinceforcement of orientation selectivity as in the case with orientation maps.Recent studies have shown that connections are formed selectivelybetween neurons with similar response properties, and connections are eliminatedbetween visually unresponsive neurons. The overall connectivity rate is kept constant.Though, the effect of this plastic behavior on orientation selectivity is unclear, The present work focuses on analying the effect of plasticity on orientation selectivity for the salt-and-pepper organization. We simulate a patch of layer 4composed by two populations of neurons (excitatory and inhibitory) with weakly orientation selective inputs and update the excitatory-excitatory connections. The updating rule depends on the relative timing of the pre and post-synaptic spikes. We find that even if the connections are substabtially altered  this does not lead to a substantial oncrease is selectivity (see figure). IN future work we plan to compare this phenomenon with the results of systems with orientation maps.