Chapter 18 Cortical convergence of ON- and OFF-pathways and functional adaptation of receptive field organization in cat area 17

Abstract

Publisher Summary The chapter discusses different connectivity schemes proposed for the genesis of simple and complex receptive fields (RFs) and discuss the relative degree of convergence of ON and OFF-afferents along the retino-geniculo-cortical pathway. Studies of development and plasticity provide an additional understanding of the spatial organization of cortical receptive fields, by describing the processes that lead to their formation. In addition, these studies make it possible to test the validity of proposed connectivity models indirectly. The experimental approach presented in the final part of the chapter is to artificially impose different activity levels in ON- and OFF-pathways, and look for possible refinements or shaping of the spatial RF structure of cortical cells. These changes can be interpreted in terms of adaptive geniculo- and cortico-cortical connections, and support specific models of RF structure. After a brief overview of data supporting activity dependence in the development of the spatial organization of cortical receptive fields, a report is given on recent electrophysiological experiments demonstrating that, it is possible to modify the spatial structure of the receptive field during the time of recording of a single cell in the paralyzed and anesthetized animal. It is shown that differential conditioning of ON- and OFF-responses induces long-lasting changes of spatial receptive field organization in kitten and cat visual cortex. Finally, various models of connectivity that could sub-serve the selection of simple and complex RF organizations through activity-dependent processes during development are discussed.