Representation of vibrissae inputs through the climbing fiber pathway in lobule VII of the adult rat cerebellar vermis.
The present study gives a detailed description of the functional characteristics and of the topographic distribution of Purkinje cell (PC) responses, mediated through the climbing fiber pathway and elicited by mechanical stimulation of two different rows (A and C) of vibrissae in a circumscribed region of the posterior vermis of the rat cerebellum. Experiments were carried out on normal adult rats under barbiturate anesthesia. PCs were recorded in an area extending 1500 microns laterally to the midline in the vermal part of lobule VII contralateral to the stimulation. Using micromapping techniques and computer analysis, we located the cells on the map of the unfolded PC layer. Taking into account the mean latency of the responses and the probability of discharge of PCs, restricted areas of projection were found. For each row, these areas formed two longitudinal patches located between midline and plane 1100 microns and separated by a non-responsive plane at 500 microns. Cells having the best characteristics of responses to the stimulation of row C were located mainly in plane 200 microns. Cells giving the best responses to the stimulation of row A were located mainly in the posterior part of plane 200 microns which was therefore a zone of convergence for both rows.