Detail, Proportion, and Foci among Face Receptive Fields of Climbing Fiber Responses in the Cat Cerebellum

Abstract

This paper reports a theoretical analysis of the transformation from a tactile stimulus of the face to climbing fiber responses in three regions of the cat cerebellum. The database consisted of climbing fiber receptive fields on the face from 75 responses from the anterior lobe, 33 responses from the paramedian lobule (PML), and 52 responses from the crus IIp of the anesthetized cat. The receptive fields were similar in being composed of discrete areas on the skin, or skin compartments. The regional differences in the configurations of the receptive fields were reflected in which compartments most often combined to form receptive fields. Each region had a distinct pattern of the preponderance of skin compartments that combined to form receptive fields, and yet the preponderant compartments were all chosen from one composite set of compartments that applied to all three regions. The climbing fiber representation of the face differed over the three regions (1) in the parts of the face that were represented; (2) in the frequency with which certain areas were included in the receptive fields; and (3) in the details of the face that could be distinguished by differing ensembles of climbing fiber responses. The majority of the climbing fiber receptive fields from either the anterior lobe or the crus IIp were unique to the region, whereas the majority of the receptive fields of responses from the PML were encountered in one or both of the other regions. Overlapping all face receptive fields from each of the three regions revealed that the receptive fields were differentially focused on or around the cornea, nose, or chin. In the anterior lobe, the face receptive fields mainly included the chin (43%) and the glabrous tip of the nose (40%), but few included the cornea (1%). In the PML, the receptive fields included the cornea (24%) and the chin (58%), but none included the nose. In the crus IIp, the cornea was included in the greatest number (37%) of receptive fields, whereas the nose and the chin were included equally (24%). The different sets of climbing fiber receptive fields in each of the three regions afforded the regions differing abilities to distinguish among complex patterns of stimuli, depending on the portion of the face stimulated.