Cortical thickness relates to working memory performance after non-invasive brain stimulation

Abstract Objective We investigated whether baseline cortical brain thickness of regions of interest (ROIs) was associated with working memory (WM) performance after non-invasive brain stimulation (NIBS) probing the dorsolateral prefrontal cortex (DLPFC). Method Structural Magnetic Resonance Imaging data were analyzed from 22 healthy subjects who received transcranial direct current stimulation (tDCS), intermittent theta-burst stimulation (iTBS) and placebo. Bifrontal tDCS was placed over the neuronavigated left and right DLPFC (20 minutes/2mA). iTBS targeted the neuronavigated left DLPFC applying 1620 pulses. A 2-back task was conducted after the end of NIBS sessions. Selected ROIs were the bilateral DLPFC, medial PFC and posterior cingulate cortex (PCC). Results Findings revealed an inverse association between cortical thickness of the DLPFC and reaction time for both tDCS (left: p = 0.02; right: p = 0.007) and iTBS (left: p = 0.02) compared to placebo. Moreover, thickness of the right mPFC and the left PCC were inversely and directly associated with reaction time after iTBS, respectively (p = 0.046 and p = 0.03). No association was found for accuracy. Conclusion Our findings provide the first evidence that individual cortical thickness of healthy subjects might be associated with WM performance.