Objective: We investigated whether the ability to learn new information, as opposed to recall information, would change significantly in depressed individuals treated by low- or high-dose right unilateral electroconvulsive therapy and tested whether change in learning explained changes in recall.
Method: Fifty-four depressed patients randomized to receive right unilateral electroconvulsive therapy (ECT) at approximately 2.25 times their seizure threshold (ST) or at doses greater than 2.25 times ST were evaluated for verbal and figural memory as well as verbal and figural learning both pre- and post-ECT. A subset of scores from the Rey Auditory Visual Learning Test and the Rey Figure Test were analyzed using analysis of variance and linear regression techniques.
Results: Scores reflecting verbal learning decreased by a mean of approximately 50% immediately after a completed course of ECT as compared with pre-ECT verbal learning scores. Stratification of effect by dose of electrical charge revealed trends that did not achieve statistical significance. Approximately 8% of the change in delayed verbal recall was predicted by changes in verbal learning. Figural learning was not significantly changed in the aggregate (pre-versus post-treatment) or when the effect was stratified by electrical charge.
Conclusions: Verbal learning scores declined immediately after ECT, but the change in learning scores explained only a minor part of the observed changes in verbal recall. These findings support the notion that the deficits in delayed recall after ECT represent a relatively specific cognitive effect that is not completely explained by changes in other aspects of cognition such as learning.