THE ROLE OF PLASTICITY IN COGNITION: A TMS-EEG STUDY

Abstract

Past studies have implicated a relationship between the Dorsolateral Prefrontal Cortex (DLPFC), and working memory and cognitive flexibility performance as measured via the N back and Trail Making tasks. It stands to reason that inducing plastic change to increase excitability of the DLPFC should result in improved performance on these tasks. This study used a 2 x 2 within groups single-blinded design with fourteen healthy participants (19 to 29 years old) attending two sessions, receiving iTBS in one, and sham in the other, investigating whether intermittent theta burst stimulation (iTBS) increased excitability of the DLPFC, and improved task performance. Cortical excitability was measured with TMS-evoked potentials (TEPs). Wilcoxon tests were used to determine the effect of iTBS on TEPs and psychometric performance, and the relationships between dependent variables were investigated using correlational analyses. Results show nonsignificant mild increases in 2-Back and Trail Making A tasks following iTBS relative to sham, and moderate correlations between changes in task performance and iTBS induced TEP changes. These findings go against previous research that support the iTBS to modulate TEP amplitudes, but are consistent with literature only finding mild effects of rTMS on improving working memory and cognitive flexibility.