IVOR

Neuronal substrates of invariant visual object recognition in rats

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 Obiettivo del progetto (Objective)

'One of the key issues in the field of system neuroscience is to understand how the mammalian visual system is able to recognize visual objects in spite of tremendous variation in their appearance (e.g., lighting and viewpoint). So far, this issue has been mainly investigated in non-human primates, while simpler model systems (such as rodents) have been largely overlooked. However, recent work of Dr. Zoccolan and colleagues has shown that rats are fully capable of invariant recognition, rising the question of what neuronal machinery endows them with a visual processing ability that heretofore has only been ascribed to a select few species. Our project aims at addressing this question, by measuring the degree of overlapping/tangling of the neuronal representations of distinct visual objects across rat’s known (i.e., occipital), as well as putative (i.e., temporal) visual cortical areas. Our approach will be based on a combination of psychophysics, multi-units neuronal recordings, early genes dual-activity mapping, and machine learning tools. Our hope is to understand where and how, in the rat cortex, the gradual untangling of object representations happens, and to shed new light on a fundamental process that, in spite of several decades of monkey studies, remains elusive and poorly understood.'

Introduzione (Teaser)

Visual object recognition in varying environments or scenarios is a complex process. EU-funded researchers are investigating this process in the rat model.

Descrizione progetto (Article)

Scientists working on the project 'Neuronal substrates of invariant visual object recognition in rats' (IVOR) combined psychophysics, multi-units neuronal recordings, mapping of immediate-early genes (IEGs) expression, and machine learning tools to study how the rat brain processes visual object information.

During the first project period itself, considerable progress was made. Scientists completed the behavioural study underlining the shape processing strategy in the rat brain and results were published in the Journal of Neuroscience. The rat brain processes visual objects using a combination of invariant multiple features for recognition or discrimination between objects.

The IEGs-based neuroanatomy study of the rat visual and association cortex is also almost complete. c-fos is a transcription factor often expressed during neuronal activity. Researchers mapped the expression of IEG c-fos in the rat brain after exposure to different visual, tactile or visuo-tactile environments.

Stained cell density counts indicate that visual object recognition in the rat brain involves a cascade of cortical areas. The signals begin in the primary visual cortex (V1), spreads laterally to the secondary visual areas (V2L) untilit reaches the temporal association cortex (TeA) and terminates in the perirhinal cortex.

Preliminary findings from the neuroanatomy study proved useful while performing the neurophysiology experiments. Multi-electrode neuronal recordings of the V1, V2L and TeA areas in anaesthetised and awake rats is currently ongoing. The rats are exposed to ten objects presented in differing conditions and made to perform a visual discrimination task.

So far, results indicate an increase in object selectivity and transformation-tolerance of neuronal responses from V1 to TeA. Based on previous studies on primates, results indicate that the rat visual system processes visual information in a similar manner.

Project activities should provide unprecedented insight into visual processing in rodents. The similarity in visual processing between primates and rats suggest that rats can be used to study higher level visual functions. Future research activities employing rodent models will not only be cheaper but will also produce faster results.