Multidisciplinary investigation of shape and motion processing in the rat visual cortex

This thesis describes a multidisciplinary effort aimed at characterizing processing of visual shape and motion information, as well as the experience dependent development of the former, in the rat visual cortex. The methodological approaches employed include in-vivo electrophysiology, computational modelling and behavioral testing of both naïve rats and rats reared in controlled visual environments. In the first chapter of the thesis the progression of neuronal tuning properties across the putative rat shape processing stream is characterized. The trends observed from rat V1 to LL areas are then compared with what observed across the monkey ventral areas and, in-silico, in a classical computational model of object recognition as well as in a modern deep neural network. In the second chapter the development and validation of an automated method to identify the laminar position of recording sites of a multichannel silicon probe is described. In the third chapter a causal test of the unsupervised temporal learning hypothesis is provided by evidencing a key role for the temporal continuity of the visual-input experienced during early postnatal development in building-up position tolerance of V1 complex cells. In the fourth chapter rats are shown to be able to spontaneously perceive global motion of plaids, validating them as a promising animal model for the study of the neural mechanisms of motion integration. In the fifth chapter the neural substrate of motion integration in rat visual cortex is investigated reporting the presence of global motion sensitive units in both and V1, LM areas.