Somatosensory input and thalamic projection of pedunculopontine tegmental neurons

The cholinergic pedunculopontine tegmental area of the anesthetized rat was explored for single units responsive to somatosensory stimulation. Units projecting to the intralaminar thalamus were identified by antidromic stimulation. Approximately one half of the somatosensory units consisted of low threshold units responsive to light tapping and stroking; the others were high threshold mechanoreceptive units. Most receptive fields were tri- geminal and contralateral. These results suggest that somatosensory information is an important element in a subcortical system linking this area with the basal ganglia, superior colliculus and thalamus.