Does intermittent theta burst stimulation improve working memory capacity? A randomized controlled cross-over...

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neuromodulation

Background:

• Intermittent theta burst stimulation (iTBS) is hypothesized to enhance memory by inducing long-term potentiation (LTP)-like plasticity in the dorsolateral prefrontal cortex (DLPFC).
• The hemispheric differences in iTBS effects on working memory in healthy adults remain under-investigated.

Purpose of the Study:

• To investigate the effects of iTBS on the left (LDLPFC) and right (RDLPFC) dorsolateral prefrontal cortex on working memory performance in healthy adults.
• To determine if unilateral iTBS over the DLPFC yields memory-enhancing effects.

Main Methods:

• A randomized, cross-over design was employed with 31 healthy, right-hand dominant adults.
• Participants received single sessions of iTBS to the LDLPFC, RDLPFC, and sham stimulation across three visits, separated by one-week intervals.
• Working memory capacity was assessed using 2-back and 3-back tasks before and immediately after each stimulation session.

Main Results:

• Significant time effects were observed for overall accuracy in both 2-back (p=0.013) and 3-back tasks (p=0.027), and for reaction time in the 3-back task (p=0.021).
• An increase in correction rejections was noted for the 2-back task (p=0.009).
• No significant time-by-group interaction effects were found, indicating no differential impact of iTBS location.

Conclusions:

• A single session of iTBS applied to either the RDLPFC or LDLPFC did not produce additional memory-enhancing effects in healthy adults.
• Observed improvements in working memory performance were attributable to practice effects rather than iTBS intervention.