The subcallosal cingulate gyrus (SCG) is integral to cognitive function and mood regulation. Open-label SCG deep brain stimulation (DBS) studies demonstrate improvement or stabilisation of cognitive function in treatment-resistant depression (TRD).
This randomised controlled study aims to evaluate the neuropsychological effects of SCG-DBS.
35 participants with TRD received active or sham stimulation over two 3-month periods. A neuropsychological battery was administered to assess processing speed, learning and memory, and cognitive flexibility. Composite measures were derived for each domain after Period I. A mixed model for repeated measures analysis was performed for each test, with further analysis of significant measures to determine sustainability after Period II.
No significant differences in changes in depression scores were observed between groups. There were no significant deteriorations in cognitive performance following active SCG-DBS. Category Fluency Test performance improved after 3 months of active SCG-DBS (p=0.002); however, this was non-significant after correcting for multiple comparisons and was not observed after Period II (p=0.615).
While no cognitive deterioration was observed following SCG-DBS, significant improvements in cognitive function were not evident. There may be a transient enhancement in processing speed; however, this effect is not fully understood. Future studies should include larger cohorts and extended stimulation periods to explore the long-term effects of SCG-DBS in TRD and the sustainability of improvements in cognitive domains.