THE EVOLUTIONARY ORIGIN OF THE LANGUAGE AREAS IN THE HUMAN BRAIN - A NEUROANATOMICAL PERSPECTIVE

The capacity to learn syntactic rules is a hallmark of the human speci es, but whether this has been acquired by the process of natural selec tion has been the subject of controversy. Furthermore, the cortical lo calization of linguistic capacities has prompted some authors to sugge st a modular representation of language in the brain. In this paper, w e rather propose that the neural device involved in language is embedd ed into a large-scale neurocognitive network comprising widespread con nections between the temporal, parietal and frontal (especially prefro ntal) cortices. This network is involved in the temporal organization of behavior and motor sequences, and in working (active) memory, a sor t of short-term memory that participates in immediate cognitive proces sing. In human evolution, a precondition for language was the establis hment of strong cortico-cortical interactions in the postrolandic cort ex that enabled the development of multimodal associations. Wernicke's area originated as a converging place in which such associations (con cepts) acquired a phonological correlate. We postulate that these phon ological representations projected into inferoparietal areas, which we re connected to the incipient Broca's area, thus forming a working mem ory circuit for processing and learning complex vocalizations. As a re sult of selective pressure for learning capacity and memory storage, t his device yielded a sophisticated system able to generate complicated utterances (precursors of syntax) as it became increasingly connected with other brain regions, especially in the prefrontal cortex. This v iew argues for a gradual origin of the neural substrate for language a s required by natural selection. (C) 1997 Elsevier Science B.V.