Short-latency auditory projection to the frontal telencephalon of the pigeon

Abstract

An auditory projection to the frontolateral telencephalon of birds, originally described by Iljitschew, is confirmed for the pigeon. Potentials evoked by acoustic stimuli were recorded from the neostriatum frontale closely surrounding the nucleus basalis, in anesthetized and awake subjects. The latency of these responses was short (5 to 8 ms) compared to that of responses recorded from the orthodox avian telencephalic auditory projection in the neostriatum caudale, field L (12 to 14 ms). The intensity and frequency sensitivities of the frontal auditory potentials, however, were similar to those of the area L responses. Clicks delivered to the auditory meati were more effective than the same stimuli directed at other parts of the head or beak. Ipsilateral and contralateral auditory stimuli were equally effective. Occlusion of the ear openings attenuated the responses; thick pasting of the remainder of the head or beak did not affect them. Trigeminal deafferentation similarly did not attenuate the frontal auditory potentials, but alblation of the cochleae totally abolished them. The hypothesis that the frontal auditory responses are due to an artifactual stimulation of trigeminal mechanoreceptors projecting to the nucleus basalis is thus rejected. The neural pathway subserving this projection and the functional role that it may play are discussed.