A simple method for creating wide-field visual stimulus for electrophysiology: Mapping and analyzing receptive fields using a hemispheric display

Modern neurophysiological and psychophysical studies of vision are typically based on computer-generated stimuli presented on flat screens. While this approach allows precise delivery of stimuli, it suffers from a fundamental limitation in terms of the maximum achievable spatial coverage. This constraint becomes important in studies that require stimulation of large expanses of the visual field, such as those involving the mapping of receptive fields throughout the extent of a cortical area or subcortical nucleus, or those comparing neural response properties across a wide range of eccentricities. Here we describe a simple and highly cost-effective method for the projection of computer-generated stimuli on a hemispheric screen, which combines the advantages of computerized control and wide-field (100 degrees x 75 degrees) delivery, without the requirement of highly specialized hardware. The description of the method includes programming techniques for the generation of stimuli in spherical coordinates and for the quantitative determination of receptive field sizes and shapes. The value of this approach is demonstrated by quantitative electrophysiological data obtained in the far peripheral representations of various cortical areas, including automated mapping of receptive field extents in cortex that underwent plasticity following lesions.