22 - Towards a theoretical neurophysiology of language

Summary

We have discussed the neuroanatomical basis of language extensively in this volume, reviewing classical and modern connectionist theories, clinically derived “holist” theories of various sorts, modern studies of lateralization of language and cerebral dominance, localization of language functions in parts of the dominant hemisphere, and other related topics. Though we have considered evoked electrical correlates of language and the effects upon language of electrical stimulation of the cortex and subcortical areas, we have said practically nothing about the physiology of language – that is, the actual neural processes which are responsible for the coding of language. Nonetheless, this is a topic which is of crucial importance in neurolinguistics. Language must not only be carried out in portions of the brain; it must somehow or other actually be represented by elements and events in the brain. Caplan (1981) comments that the localization of a function would be, at most, a “convenient shorthand” for a statement of the actual physiological mechanisms which are responsible for the representation and processing of language. Marshall (1980) takes a further step, which, as we shall see in this chapter, may be correct: he argues that the physiological way a function is localized may be important in determining what is localized. These concerns are not new. Jackson (1878) also drew a distinction between the anatomical basis of a function (which he called “morphology”) and the physiological basis of a function (which he called “anatomy”). Most of what we have covered regarding language–brain relations in this book involves Jacksonian “morphology” (our “neuroanatomy”). In this chapter, we shall take a step towards a theory of the neurophysiology of language.