Differential organization of thalamic projection cells in the brain stem trigeminal complex of the rat.

Following large injections of horseradish peroxidase into the thalamus of the adult rat, labeled neurons can be detected in the contralateral principal sensory nucleus and the subnucleus interpolaris of the spinal trigeminal nucleus. Thalamic projection neurons in the principal sensory nucleus are arranged in discrete aggregates which replicate the organization of the vibrissae and other parts of the face. This cellular organization corresponds very well with the pattern of vibrissae related afferent termination in this region of the nucleus as seen in SDH preparations. There is no such cellular organization in the subnucleus interpolaris.