Intermittent theta burst stimulation as a potential intervention to enhance working memory after cardiac arrest: A proof-of-concept SCED feasibility study

Aim
Cognitive impairment affects approximately half out-of-hospital cardiac arrest (OHCA) survivors, yet no established treatments effectively improve cognitive functioning. Repetitive transcranial magnetic stimulation is a potential treatment candidate. This proof-of-concept feasibility study investigates whether intermittent theta burst stimulation (iTBS) targeting the left dorsolateral prefrontal cortex can enhance working memory performance, assessed via the N-back task.
Methods
A randomized ABAB single-case experimental design (SCED) study was conducted with six healthy participants and three OHCA survivors. Participants received alternating sham and active iTBS and completed the N-back task. The initial stimulation type and N-back length were randomly assigned. Sensitivity (d’) and reaction time were analyzed with visual analysis, non-overlap of all pairs (NAP), randomization tests, and multilevel regression analysis with Bayesian posterior model probabilities.
Results
No significant effect of iTBS on d’ was found at the individual or group level. Reaction time did not show differences on the individual level. On the group level, combined NAP indicates a slight reaction time improvement after iTBS (NAP = .41, 95 % CI [.33,.50]). Multilevel regression analysis showed a non-significant reduction of reaction time (β = − 13.4, t (157) = -1.90, p = .06), with posterior model probabilities suggesting 56 % chance of a real effect.
Conclusion
While iTBS did not significantly improve working memory performance on an individual level, group-level analyses indicated a small reduction in reaction time post-iTBS. This proof-of-concept study shows feasibility and potential benefit on a group level of iTBS on processing speed. Future studies should replicate and expand on these findings and investigate potential cumulative and longitudinal effects of iTBS on working memory.