Microelectrode mapping of modality-specific somatic sensory cerebral neocortex in slow loris.

Microelectrode mapping methods and strategies were developed to map fine details of the somatotopic organization of somatic sensory cortex (SI) in slow loris. In-depth, multiple-unit recording, and threshold natural stimulation of skin and hari revealed three modality-specific cortical areas. The centrally located one was activated by extremely light touch and the somatopic organization of peripheral projections to it was mapped in detail. As many as 25 punctures/mm2 were made in delineating these details. The microelectrode mapping method used revealed smaller receptive fields, lesser degrees of overlap, a more differentiated pattern of peripheral projections, and a more precise correlation of electrophysiological results with underlying cytoarchitectonic details than did the usual macroelectrode surface recording method. These results and the correlations found between different physiologically defined areas and cortical sulci are discussed as they pertain to methodological advances in studies of cerebral localization of function.