Functional Properties of Neurons Providing Feedback to Visual Cortex

Cuny City College, New York NY

Investigators

Abstract

Neurons in the mammalian visual cortex are intensively studied, making them perhaps the best understood cells in the brain. Research now shows that the modulatory effect of visual stimuli presented outside the classical receptive field (CRF), the area of the visual field from which responses to visual stimuli can be evoked, is not well understood and can be profound. Previous anatomical studies characterizing feedback circuits to primary visual cortex (V1) describe which cortical areas provide feedback to V1, and show that feedback links cells with nonoverlapping receptive fields. These results sugest that V1 cannot be understood purely on the basis of inputs from the eyes or local anatomical connections within V1. Therefore, understanding feedback signals to V1 is crucial to understanding how V1 works. The research develops a comprehensive physiological characterization of fundamental brain circuits to understand better how they are organized, and to discover their contribution to the functional properties of their targets. Multiple areas of cerebral cortex provide feedback to V1 and the hypothesis that different feedback signals are provided to V1 by different cortical areas will be tested. Electrical stimulation will be used to identify neurons in areas 18 and 19 projecting to V1 using adult ferret cerebral cortex. The spatial extent and stimulus selectivity of the CRF, and the modulatory surround field of single neurons, will be studied. The functional properties of cells providing feedback to V1 from each area will be compared. In each area, the properties of cells projecting to V1 will also be compared to those of cells not providing feedback. This will permit a direct test of how different areas of cerebral cortex contribute information to V1. The proposed work will provide critical knowledge about the mammalian cerebral cortex thereby improving understanding of mental functions. The results of this work will be published in journals, and presented at scientific meetings and academic institutions. The proposed work will enhance interactions among the burgeoning neuroscience community at City College, and will enhance research training by funding one doctoral student. Resources will enable motivated undergraduate students from underrepresented groups, which make up the majority of the student body at the City College of New York, to become involved in research in neuroscience.