Fact and theory in recovery from the aphasias

Clinical evidence has suggested that the form of an aphasia--and perhaps potential for recovery therefrom--can be related to an exceedingly wide range of variables. Such anatomico-physiological considerations as size, depth, location and nature (e.g. penetrating missile injury, stroke, tumour, closed head injury) of the injury are frequently held to be crucial correlates, as are associated neurological deficits (e.g. presence of hemiplegia, sensory and visual field defects). Subject variables, such as age, sex and 'handedness" (including familial handedness), complicate the picture still further, as may differences in education personality and cognitive style. Given a multidimensional problem of this magnitude the first objective of theory is to indicate putative constrainst on patterns of impaired performance. Studies of the normal population--that is, the population from which cases of brain injury are later drawn--may, we believe, aid in the elucidation of individual differences seen after injury. A more detailed knowledge of the range of possibilities concerning cerebral specialization of function and variations in task strategies seems to be required. In this context we shall review some recent reports on dichotic listening and split visual field experiments with both normal and brain-damaged subjects and also consider the role that linguistic descriptions of aphasic impairment could play in suggesting retraining procedures appropriate to the individual patient.