Neural processing in the ventral visual pathway during object search

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Project summary The goal of this proposal is to arrive at an accurate description of the multiple roles that visual areas in the brain play when we are looking for a specific visual object. Locating a specific object requires that we 1) activate a remembered, neural representation of our sought target, 2) develop a neural representation of each item we encounter as we search, and 3) compare these two representations to determine whether the object currently in view matches the object that we seek. We know that the process of remembering an object activates neurons in classically defined 'visual' areas of the brain, suggesting that these visual areas may play a role beyond statically processing the visual scene when searching for an object. This notion is supported by other lines of evidence, including our own preliminary data. In Specific Aim 1, we propose to characterize this role by measuring the degree to which the visual representation of a currently viewed stimulus also depends on the identity of a sought target at different levels of visual processing (i.e. areas V4 and IT). Upon finding such dependencies, we will seek to determine what they accomplish. For example, the visual system might adjust its detectors to increase the discriminability of a target. Similarly, the responses of these visual neurons may represent the outcome of a comparison between the target and the scene currently held in view. In Specific Aim 2, we are motivated by the notion that real-world object search involves finding an object across changes in position, size, background and pose, and we propose to characterize the role of the visual system in searching for a target across a subset of these identity- preserving object transformations. Finally, in Specific Aim 3, we propose to characterize the activity of visual neurons when a visual stimulus is held in memory but no visual stimulus is physically present ("persistent activity") to better understand the neural signature of the remembered and sought target in the visual system.