Discrimination of object orientation by visual cortex

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DESCRIPTION (provided by applicant): The goal of the proposed studies is to characterize the role of the inferotemporal cortex and parietal cortex (area LIP) in the discrimination of object orientation. It has been shown in animal studies that lesions of the temporal cortex, while disrupting the ability to discriminate among different objects, leave intact the ability to discriminate among different orientations of the same object. Conversely, lesions of parietal cortex impair object orientation discrimination but spare object recognition. Parallel results have been obtained in clinical studies of humans. Thus it seems reasonable to hypothesize that the discrimination of object orientation involves primarily parietal and not inferotemporal (IT) cortex. To test this hypothesis, we will record the activity of neurons in IT and area LIP of the macaque monkey during the performance of fixation and object orientation discrimination tasks. Monkeys will be initially trained to discriminate between different orientations of ten objects. Following training, neural activity in IT and LIP will be collected using extracellular electrophysiological recording techniques. The data will be analyzed to test two predictions: (a) that neurons in LIP are more selective for object orientation than neurons in IT and (b) that neuronal activity in LIP is better correlated with the monkey?s orientation discrimination performance than neuronal activity in IT. The results of these studies will elucidate the manner in which object orientation is encode in the brain and provide insight into the nature of processes impaired following parietal lobe injury.