Cutaneous sensory projections to the avian forebrain

Abstract

The diencephalon and the telencephalon of pigeons were explored for cutaneous evoked potentials and multiple unit responses. Three projection areas were found, one located in the dorsal thalamus, one in the medial neostriatum caudale and another in the anterior hyperstriatum. The thalamic evoked potentials were small (20–30 μV), even when many units fired in response to light tactile stimulation with a latency of 9–10 msec. Of the two telencephalic projections the neostriatal responded with a latency of 11–12 msec and potentials of 80–100 μV while the hyperstriatal reacted with potentials of similar amplitude and 14–16 msec latency. All projection areas were driven by stimulation mainly of the contralateral body surface including the head the extremities. Direct stimulation of a cutaneous nerve, electrical stimulation of the skin, mechanical taps, and puffs of compressed air were all similarly effective stimuli. The telencephalic potentials decayed in amplitude with stimulation rates above 0.5 c/sec. The cutaneous sensory projections of birds are reviewed, earlier work being incorporated. On the basis of preliminary experiments it is concluded that at least one of the telencephalic projections originates in the dorsal thalamic n nuclei.