The neurobiological mechanisms of the visual system involves the primary visual cortex (V1) transmitting retinal input to multiple higher visual areas (HVAs) such as the posteromedial (PM) area. Each V1 or HVA neuron has a unique receptive field, or region of sensory space that affects the neuron’s firing rate in response to incoming stimuli. When the stimulus enlarges to a certain size, the average firing rate of individual neurons will drastically decrease; however, it is unclear why this pattern, or surround suppression, is not as radical in PM neurons. We hypothesize that V1 axonal inputs converge, or overlap, more to PM than those to alternative HVAs. We inject fluorescent tags, tdTomato, in-vivo in mouse V1 and wait for the tags to express in V1 to HVAs axons. The brains are then sliced, and tdTomato is imaged in-vitro under a microscope. MatLab is then used to analyze the width of the fluorescent tdTomato area, or the width of axon spread for each HVA. We expect PM’s axon spread width will be larger than the other HVAs, suggesting higher convergence of V1 to PM input. These findings will ultimately benefit our neurobiological understanding of the visual circuits that lead to perception.

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