Neural and behavioral effects of theta burst stimulation priming on processing of affective and neutral information in working memory

Abstract Theta-burst stimulation (TBS) has been increasingly used to target prefrontal brain regions, such as the dorsolateral prefrontal cortex (DLPFC), to improve neurocognitive and emotional functioning. However, despite the promising outcomes, there is still a lot of variability in responses and the clinical efficacy remains rather modest. Interestingly, fundamental research targeting the motor cortex has suggested the use of priming techniques to enhance TBS-related changes in cortical excitability. Hence, TBS priming - using a prime TBS protocol to enhance the effects of a subsequent test TBS protocol - can yield improved TBS efficacy when applied over the prefrontal cortex. Moreover, recent developments in the field indicate that stimulation priming can be highly efficacious in reducing depressive symptoms. In this within-subjects, sham-controlled study, we investigated how different TBS priming protocols over the left DLPFC affect cognitive performance and task-related brain activity in a sample of fifty healthy adults. Participants performed a verbal working memory task, consisting of affective and neutral word stimuli, during functional magnetic resonance imaging (fMRI) after receiving one of four TBS priming combinations (i.e., a prime followed by a test protocol); (1) sham TBS + sham TBS, (2) sham TBS + intermittent TBS, (3) intermittent TBS + intermittent TBS, (4) continuous TBS + intermittent TBS. Each prime and test protocol was separated by a 15-minute break and there was one week in between each experimental session. Task performance and participants’ activation patterns elicited by the task following the different TBS priming conditions were assessed. During this talk, the behavioral and neural findings will be presented. Moreover, implications of the study findings for further studies evaluating the neurobehavioral effects of TBS priming on emotional working memory, in healthy and neuropsychiatric samples, will be discussed. Keywords: Theta Burst Stimulation (TBS), functional magnetic resonance imaging (fMRI), Stimulation Priming, Working Memory