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LEARN2SEE Report Summary

Project ID: 616803
Funded under: FP7-IDEAS-ERC
Country: Italy

Mid-Term Report Summary - LEARN2SEE (Invariant visual object representations in the early postnatal and adult cortex: bridging theory, model and neurobiology)

The goal of the project is to understand what neuronal processes underlie visual object recognition in rats, and what learning principles drive the development of such processes during early postnatal development. Our research is based on a variety of experimental and theoretical/computational approaches, including high-throughput behavioral testing (i.e., psychophysics), neurophysiology, histology, rearing of newborn rats in visually-controlled environments, and machine learning tools (such as information theory, pattern classification, convolutional neuronal networks, and generalized linear models). At the behavioral level, we have performed two studies to investigate high-level processing of both shape and motion information in rats engaged in visual discrimination tasks. The first study has revealed that rats’ proficiency in visual object recognition is accounted for by the complexity of their perceptual strategy. In the second study, we have shown that rats are able to correctly discriminate the direction of drifting plaids (i.e., complex patterns, typically used to study high-level motion processing in primates), thus providing the first behavioral evidence, to our knowledge, of the processing of global motion in rodents. At the neurophysiology level, we have started (and, in some case, completed) a number of studies, aimed at understanding how shape and motion information is coded in rat primary visual cortex (V1), as well as the progression of higher-order visual cortical areas that run laterally to V1: areas LM, LI and LL. In a first study, we have found evidence that the ability of neuronal representations to successfully support object recognition increases along the areas progression, being maximal in LL, thus providing very compelling evidence about the existence of a rodent object-processing pathway. Another study is exploring these same areas using a very rich set of object conditions (tens of objects, each shown under tens of different appearances) with the goal of further exploring the structure of object representations from V1 to LL. In a third study, we are probing V1 and LL with simpler visual stimuli (e.g., drifting gratings) to check the tuning of neurons in these areas to basic spatial and temporal properties of the visual input, similarly to what done in recent studies of the mouse visual system. In yet another study, we are testing how visual neurons recorded from V1 trough LL encode natural movies. Finally, we have designed and built a system that allows rearing newborn rats in visually controlled environments, where the statistics of the visual input is under full control of the experimenter. This apparatus will allow testing computational hypotheses about the impact of the environment on the development of visual cortex with unprecedented accuracy and flexibility. Two neurophysiology studies employing rats reared in such visually controlled environments have just started and one behavioral study is about to begin. Overall, we believe that the array of scientific questions and methodologies at the core of our project will substantially improve our understanding of visual processing in the rat brain and will significantly foster the use of rodents in vision studies.

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