The Neural Basis of Language

Until the middle of the 1960s, the understanding of the anatomical basis of language in humans had grown on the strength of a handful of methods. The oldest and admittedly the most fruitful of them was the neuropathological study of focal cerebral lesions in patients with aphasia. A closely related method was the behavioral study of patients who had undergone surgical interventions, such as the ablation of a cerebral lobe or even an entire hemisphere. Other approaches were provided by (a) the electrical stimulation of the human cerebral cortex, in awake patients, during surgical interventions, aimed at studying the effect of stimulation on language behaviors; (b) the use of estab­ lished neuroradiological techniques, such as cerebral angiography and pneumoencephalography, for indirect localization of lesions related to lan­ guage disturbance; and (c) the study of language behavior after transient hemispheric inactivation caused by a barbiturate injected into the carotid artery of one side (the Wada Test). Unquestionably, the advances brought about by the combination of those methods were remarkable. For instance, from about the middle of the nineteenth century and for a period of nearly 100 years, neurologists collected a large number of single case studies in which distinctive disturbances of the use of language were correlated with specifically located