Reproducibility and sources of interindividual variability in the responsiveness to prefrontal continuous theta burst...

Despite the increasing use of continuous theta burst (cTBS) protocols targeting the prefrontal cortex in clinical and research settings, very little is known regarding the interindividual factors that influence the magnitude and duration of cTBS aftereffects. The few existing studies have predominantly focussed on motor and corticospinal excitability, and the applicability of such findings to prefrontal modulation remains unclear. The current investigation aggregated published data from our laboratory to (1) assess the reproducibility of the effects of cTBS targeting the left dorsolateral prefrontal cortex (dlPFC) on executive function task performance, and (2) determine which factors are associated with individual differences in cTBS responsivity. Data from 76 healthy young adult female participants aged 19-26 (M = 20.6; SD = 1.6) were included in the analyses. Significant attenuations in executive function task performance from baseline were observed following active cTBS. However, these effects were not totally universal in that cTBS-induced attenuation of executive functions was observed in 61.8% of participants (i.e., responders). In addition, baseline task performance was a significant predictor of the magnitude of the cTBS-induced change in task performance in that cTBS effect was larger for individuals with higher baseline executive control abilities than those with lower abilities. Together, these data provide a quantitative estimate of the degree to which healthy participants may vary in the responsiveness to prefrontal cTBS, and potential moderating factors.