Responses of cortical taste cells and chorda tympani fibers to anodal d.c. stimulation of the tongue in rats.

Single unit activities of the first-order taste neurons (chorda tympani), cortical field potentials and unit responses of cortical taste cells were recorded during anodal D.C. stimulation of the tongue surface in rats. This technique of anodal stimulation was found to be useful for accurate localization of the recording electrode in the cortical taste area, in order to record its unit activities. Salt-and/or cold-sensitive chorda tympani fibers were sensitive exclusively to anodal D.C. stimulation. The relationship between response magnitude and stimulus intensity corresponded approximately to Stevens' power function. In contrast to fibers in the chorda tympani, cortical cold-sensitive cells were less responsive to D.C. stimulation. Moreover, the dominant responsiveness of salt-sensitive cortical cells to D.C. stimulation of the tongue faded away within 1--5 s after onset of the stimulation.