Investigation of cerebral dominance in 'left-handers' and 'right-handers' using unilateral electroconvulsive therapy.

Twenty-four patients receiving unilateral electroconvulsive therapy for depression were given the first treatment with electrodes on the left or right side of the head and the second treatment with electrodes on the opposite side. They were tested with the Word Associate Learning subtest of the Wechsler Memory Scale when fully responsive after the first ECT and after the same time interval following the second ECT. Twelve were left-handed and 12 were right-handed writers. In both groups, better scores were usually obtained after right-sided treatment. Redistribution of patients into sinistral, mixed, and dextral groups showed that this difference between the effects of left and right-sided ECT was significant only in dextrals. Only two right-handed writers had scores indicating right-sided dominance for speech; both were 'shifted sinistrals'. Left hemisphere dominance was indicated in 67% of all non-dextrals. Eight of nine patients in whom testing was repeated after a second pair of treatments on alternate sides obtained scores favouring the same side in both pairs of testing. Findings indicate the need for closer inquiry into handedness than is often made before unilateral ECT is prescribed. Further development of unilateral ECT for establishing cerebral dominance in individuals is supported by the results.