Abstract
Animals vocalize for different reasons: to express their feeling and mood, to emit warning signals, to communicate with individuals of the same species. Vocalization plays a specific role in bats and other echo-locating animals where it serves for the scanning of space. Of the vertebrates, birds in particular are known for their repertoire of vocalizations or singing. Vocalization also plays an important role in the behavior of primates. Undoubtedly an unprecedented and yet unknown process of the perfection and refinement of vocalization in primates resulted in the emergence of a unique feature of the human brain — speech. Although a great deal of knowledge has been accumulated about the production of animal calls and their acoustical features, an understanding of the mechanisms which subserve the processing of these signals in the brain of animals still remains to be elucidated. In the first studies, which were mostly performed in the auditory cortex of awake monkeys in the seventies (Wollberg and Newman, 1972; Winter and Funkenstein, 1973; Newman and Wollberg, 1973; Manley and Muller-Preuss, 1978; Newman, 1978; Newman and Symmes, 1974), the authors expected that they would find neurons utilizing a feature extraction like the neurons in the visual cortex. The existence of specific cells which function as “call detectors” was not confirmed in these studies, and the authors later came to the conclusion that the pattern discrimination of a complex sound can be accomplished by a functional ensemble of neurons (Pelleg-Toiba and Wollberg, 1991). (1981) demonstrated that many cells in the auditory cortex of the squirrel monkey were inhibited during self-produced vocalizations. New interest in the investigation of the perception of species-specific vocalizations has recently emerged.