The significance of laterality effects.

Language laterality can be unequivocally ascertained by comparing the effects of unilateral ECT to the right and the left hemisphere. It has been shown in right-handed depressed patients that a unilateral treatment to the left hemisphere resulted in transient dysphasia whereas unilateral ECT to the right hemisphere did not. The language laterality in a small group of left-handed depressed patients has been ascertained. Evidence is presented to show that neither dichotic listening nor hand position for writing provide satisfactory indices of language laterality. The ear advantage was more closely related to strength of sinistrality than to language laterality--that is sidedness appears to overide brainedness. The results favour a spatial attention hypothesis rather than a structural hypothesis as the main determinant of laterality effects.