The Neurological Foundations of Language

This chapter reviews some of the available evidence about the neurological foundations of language. Global aphasia without hemiparesis can be observed with two separate lesions of the anterior and posterior parts of the language areas. In the area of written language, a psycholinguistic approach has largely superseded the anatomo-clinical classification, with which, however, it partially overlaps. A striking dissociation between sign language aphasia and preserved nonverbal gestural communication has been observed in a deaf signer with a left hemispheric lesion. The hypothesis of a different cerebral organisation of language in speakers of non-indoeuropean languages has been suggested on the basis of clinical observations. The introduction of positron emission tomography marks the most important advancement for the investigation of language activation in normal subjects. The activation is actually greater for nonwords than words, suggesting that all level of linguistic processing can be engaged by unfamiliar, but “language-like” stimuli.