Role of the immediate-early genes arg3.1 and c-fos in activity-dependent development of sensory systems and information processing in normal or congenitally blind animal models

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A specific set of immediate-early genes (IEGs) are regulated by synaptic activity and play an important role in brain development giving rise to stable and functioning cortical circuits. The IEG arg3.1 has been shown to be involved in long-term changes and to directly modulate synaptic processes underlying memory and the encoding of novelty-related events. Novel stimuli involve a memory component in which the presented stimulus is compared to previously encoded stimuli for it to be considered novel or familiar. The first study will examine the brain expression of synaptic arg 3.1, compared to neuronal c-fos, activity-regulated IEGs either to novel auditory stimulation of normal (C57BL/6) and naturally blind (ZRDCT/An) mice or to novel visual stimulation (C57BL/6). These IEGs will also be investigated after repeated exposure to the same stimuli (familiarisation) as well as in animals raised in either enriched or standard environments. The congenitally blind ZRDCT/An mouse serves as an excellent model for cross-modal plasticity as auditory stimulation has been shown to produce neuronal activation of what is normally visual cortex, an effect that is enhanced by environmental enrichment (Piché et al. 2004). The second part of the work will examine arg3.1 and c-fos gene expression in the pigeon brain following exposure to novel visual stimuli or during either initial learning or recall phases of more complex visual-intensity discrimination tasks using touchscreen presented stimuli. The work will allow us to elucidate basic brain mechanisms involved in different levels of sensory processing (perceptual, encoding of novel stimuli, discrimination learning and memory). The studies will also allow us to better understand some cross-modal sensory phenomena observed in blind or deaf humans and have clinical or therapeutic implications with regard to the effect of sensory stimulation on cross-modal compensation.