Continuous theta-burst stimulation over the right dorsolateral prefrontal cortex impairs visuospatial working memory performance in medium load task

Previous studies have shown that visuospatial working memory (VSWM) plays a key role in the encoding and processing of visuospatial information. More importantly, there is evidence suggesting the role of frontal and parietal cortical areas in VSWM and especially, the influence of the frontal cortex in regulating goal-directed behavior. However, the functional role of the right dorsolateral prefrontal cortex (rDLPFC) in visuospatial working memory is still unclear. Here, we noninvasively modulated the rDLPFC activity using continuous theta-burst stimulation (cTBS), with the vertex as the control site. Our study aimed to investigate the effects of cTBS over rDLPFC on working memory task (2- and 4-back) performance. Working memory performance was assessed at the baseline and after stimulation. We observed that the working memory performance as measured by discriminability index was impaired after cTBS over rDLPFC in 2-back task, whereas 4-back task performance was not significantly affected. More so, there was no effect on performance after cTBS over the vertex, suggesting a functional role of rDLPFC in VSWM. Our findings demonstrate the involvement of the rDLPFC in VSWM as well as the load-dependent effect of working memory performance. Taken together, our work constitutes a useful addition to the literature and underscores the effectiveness and efficiency of noninvasive brain stimulation in modulating neuro-cognitive activity.