Effects of Stimulus Parameters on Cognitive Side Effects

This symposium has already focused on recent experimental data directed toward an understanding of the differential effects of electrode placement upon both therapeutic response and adverse cognitive effects with electrmnvulsive therapy (ECT). In addition, we have yet to hear a number of further expositions on this subject. The available data, presented both here and elsewhere, suggest that unilateral nondominant (UL) ECT is roughly as effective as bilateral (BL) ECT in producing a remission in severely depressed patients.’” At the same time, it must be pointed out that technical factors such as sufficient interelectrode distance and the assurance of suprathreshold stimuli also appear to play a role in the efficacy of UL treatments. In addition, there is also a possibility that some patients might respond better to the combination of more intense seizures and denser organic interictal changes produced by bilateral stimulation. The situation with regard to adverse effects, however, is considerably clearer: unilateral nondominant ECT offers a distinct advantage to bilateral treatments with regard to the presence and extent of cognitive disruption, a t least with respect to those functions that depend on the dominant herni~phere.~ Still, the extent of data indicating that such amnestic differences exist longer than a few weeks has been largely limited to reports of self-ratings.Another form of ECT modification, discussed both within this volume as well as elsewhere in the literature, though to a lesser degree than electrode placement, is the