Supplementary Figure 6: Memory performance is associated with illness and ECT parameters

We assessed whether screening scores or elements of ECT treatment were related to memory performance. Top: Cumulative illness rating scale scores (CIRS, y-axis) correlated with memory performance (x-axis) over all groups (Pearson r = –0.32, N = 38, P = 0.047), thus the lower the comorbid physical problems or illnesses the better memory performance. Middle: Limiting the analyses to group A and group B, we tested whether ECT treatment parameters were related to memory performance. An independent t-test showed that memory impairment was greater for bifrontotemporal electrode placement compared to right unilateral stimulation (t(24) = 2.28, P = 0.032, right unilateral mean: 36.27, s.e.m: 2.45; bifrontotemporal mean: 28.91, s.e.m.: 1.96). Bottom: Given that bilateral stimulation leads to more memory impairment, we specifically tested for a modulation of reconsolidation by electrode placement in group A. No effect was observed (P > 0.05), but this null finding may reflect the size of our sample (unilateral N=4, bilateral N=9). The reconsolidation impairment observed in group A was still evident when controlling for electrode placement. The relation between electrode placement and memory performance suggests that the observed memory impairments are a result of the electrical stimulation and/or the convulsion itself and not other elements of the ECT treatment such as the anaesthesia. Error bars depict s.e.m.