Disruption of component processes of spatial working memory by electroconvulsive shock but not magnetic seizure therapy

Abstract

Self-ordered spatial working memory measures provide important information regarding underlying cognitive strategies, such as stereotypy. This strategy is based on repetitive sequential selection of a spatial pattern once a correct sequence has been identified. We previously reported that electroconvulsive shock (ECS) but not magnetic seizure therapy (MST) impaired performance on a spatial working memory task in a preclinical model. Here we tested the hypothesis that ECS disrupted stereotyped patterns in the selection of spatial stimuli. In a within-subject study design, we assessed the effects of ECS, MST, and sham on stereotypy and reaction time in a preclinical model. Stereotypy was assessed by the correlation of actual and predicted response patterns of spatial stimuli. Predicted patterns were based on performance during baseline sessions. ECS resulted in lower correlations between predicted and actual responses to spatial stimuli in two of the three subjects, and it also disrupted stereotypy. For one subject, there was change in the predictability of the spatial locus of responses between experimental conditions. For all three subjects, reaction time was significantly longer in ECS, relative to MST and sham. This is the first study to examine the effect of ECS, and to contrast the effects of ECS and MST, on spatial working memory component processes. Our preliminary findings show that ECS, but not MST decreased stereotypy and increased reaction time. This line of investigation may have significant implications in our understanding cognitive component processes of memory function and impairment.

Figures

Fig. 1

Typical learning curve on the Columbia University Primate Cognitive Battery (CUPCB) spatial working memory measure. The subjects were trained on the CUPCB spatial working memory measure with stimuli incrementally increased as mastery of the measure was obtained. This figure shows the learning curve for four, five and six spatially represented stimuli.

Fig. 2

Columbia University Primate Cognitive Battery (CUPCB) spatial working memory task. A number of identical geometrical shapes were presented simultaneously on the monitor. Subjects touched each spatial position once to complete the trial. Successive touches to a position that differed from the current position produced positive visual/auditory feedback. Touches that were not directed at a near position resulted in negative visual/auditory feedback. Items could be touched in any order. A new set of objects, in new locations that were randomly selected, were presented on each trial. The subject had to select each stimulus in turn without repeating an earlier selection. Between selections, the subject had to return to the centre and select a ‘reset’ stimulus.

Fig. 3

Kendal’s tau correlation rank coefficients between actual and predicted touch for correct and incorrect trials. This figure represents the correlation coefficient (squares) and the 95% confidence intervals (bars) for (a) correct and (b) incorrect trials. For correct trials, the correlations were significantly lower in the ECS condition relative to baseline, MST, and sham. For incorrect trials, there were no significant differences between the conditions. ECS, Electroconvulsive shock; MST, magnetic seizure therapy; sham, anaesthesia only.

Fig. 4

Stereotypic first touch on the spatial working memory measure. This figure represents the pattern of the first touch for each subject when completing the spatial working memory measure. The orange regions show the preference for starting in the same region whereas the blue regions show the lack of preference for starting in the same region. ECS, Electroconvulsive shock; MST, magnetic seizure therapy; sham, anaesthesia only.

Fig. 5

Reaction time on the spatial working memory measure. This figure represents the reaction time (in seconds; mean and error bar) on the spatial working memory task for the subjects for each condition, and by (a) correct or (b) incorrect trials. For correct and incorrect trials, reaction time was significantly longer in the ECS condition relative to baseline, MST, and sham. There were no other significant differences. ECS, Electroconvulsive shock; MST, magnetic seizure therapy; sham, anaesthesia only.