Musical Tests for Functional Lateralization with Intracarotid Amobarbital

Abstract

WHEN brain surgery which may affect language mechanisms is being contemplated, lateralization of speech is sometimes ascertained before operation by injecting 200–250 mg of sodium amobarbital (‘Amytal’) into either right or left common carotid artery, which depresses for several minutes the corresponding cerebral hemisphere¹; transient contralateral hemiparalysis and temporary loss of the higher functions dependent on the depressed hemisphere are produced. Although usually used when speech dominance is questionable^2–4, amobarbital testing is also indicated in persons with apparently well established laterality when they are to undergo commissural section as a treatment for seizure disorder⁵. Even where definite right-handedness clearly implies left hemisphere speech dominance, right carotid amobarbital testing can ensure that the preservation of speech does not require right hemisphere participation. This affords an independent approach to the further exploration of the higher functions, for which the right hemisphere may be dominant⁶. We report here some of the results of right carotid injection in six patients (of P. J. Vogel) who had no previous operative intervention, and had a consistent right-handed preference for a wide variety of tasks including writing, eating and tool use.