Neural Substrates of Vocalizations in Gulls and Pigeons

Abstract

Vocalizations were obtained by electrically stimulating the inferior co]liculus, the auditory thalamic nucleus and a media] hypothalamic nucleus of awake, unrestrained herring gulls, lesser black-backed gulls and pigeons. The significance of the involvement of auditory centres in the motor control of avian calling is discussed. The wide gammut of calls and accompanying behaviour that was elicited is described and related to the normal behaviour, typical of the species concerned. A difference between immature gulls and adult pigeons regarding this relationship is attributed to their differing hormonal states. Attention is drawn to the heterogeneity of temporal characteristics associated with the stimulus induced responses even when elicited from virtually the same site. Incorporating earlier work on the central mechanism of avian vocalizations and based on anatomical, physiological and behavioural considerations it is tentatively concluded that the neural structures involved are linearly organized into a teleneephalofugal, efferent system. It is suggested that the inferior colliculus incorporates the origin of a final common pathway to medular motor centres for all vocalization generating structures.