Somatotopic organization of the tactile thalamus in normal adult and developing mice and in adult mice dewhiskered since birth

Abstract

This paper describes the somatotopic organization in dorsal thalamus of the mystacial vibrissae and of the common fur of the muzzle in normal adult and developing mice. The reorganization of these projections was studied in mice whose vibrissae follicles were destroyed at birth. In the normal adult the vibrissae project to the medial part of the ventrobasal complex (VBm): projections for each individual vibrissa are arranged in rows, with vibrissae of peripheral row A caudal in the nucleus, and vibrissae of peripheral rows D and E, rostral. Caudal vibrissae project to the lateral part of the VBm, and rostral vibrissae to the medial part. A second region of projections for vibrissae was found below the VBm. This region differs from Emmer's thalamic area SII, and seems to consist of fibers of the trigemino-thalamic tract. The fur of the body projects to the lateral part of the nucleus (VB1), and the common fur of the mystacial pad projects to a small region rostrally situated in the VB complex. Development of the projections of vibrissae and hairs of the mystacial pad was followed from 4 to 22 postnatal days. In mice with vibrissae follicles destroyed at birth, projections from the common fur of the mystacial pad were found to spread over most of the VBm nucleus, which appeared to be reduced in size.