In primates area Vl serves as the gate through which visual information reaches the rest of the cerebral cortex, influencing the conscious behavior of the animal. Adjacent area V2 receives parallel inputs from each of the Vl efferent cortico-cortical projection channels and retransmits each channel to more distant specialized cortical association areas. The studies proposed explore anatomical and physiological aspects of the internal circuitry of areas Vl, V2, and the more distant area V4. The long-term objectives are to arrive at a clearer understanding of the interactions of different channels of visual information within these areas, the pattern of information flow between them, and the nature of internal controls on their efferent projections.
The specific aims are: 1) Anatomical analysis of intrinsic pattern of connections in visual areas Vl, V2 and V4 to determine the extent of links made between different visual channels and the patterns of intrinsic organization characterizing each area. Techniques include analysis of Golgi preparations, and use of biocytin and HRP tracer substances. 2) Physiological exploration of area V2 to examine the transformation of properties between afferents and postsynaptic neurons and the role of intrinsic lateral connections in shaping V2 neuron response properties. Techniques include kainic acid destruction of postsynaptic neurons and unit recording with use of pharmacological block of intraareal connections. 3) Anatomical investigation of key local circuit neurons controlling efferent neuron activity in Vl, V2 and V4. Techniques include electronmicroscopy, Golgi preparations, and immunocytochemistry. 4) Exploration of the CFos gene product as a label for cells and circuits active in Vl, V2 and V4 under different conditions of visual stimulation. Immunocytochemical techniques will be used. These studies use the visual cortical areas of the primate as a model for understanding the functions of local circuits and association pathways in cerebral cortex. This understanding is essential for progress in determining the courses and appropriate treatments for cortical malfunctions in man, both in vision and in diseases such as Alzheimer's, schizophrenia, and other dementias.
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