We provide evidence that the discrete clustered distribution of the trigeminothalamic projection neurons in the principal sensory nucleus of the trigeminal is dependent on the integrity of the trigeminal nerve during development. Nerve section at birth abolishes all evidence of cellular clustering in the principal sensory nucleus, while more discrete damage to specific rows of follicles results in changes in the cellular clustering pattern only in the portion of the nucleus related to the afflicted rows of vibrissae.