Modulation of a brain-behavior relationship in verbal working memory by rTMS

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Brain Imaging

Background:

• The brain-behavior relationship (BBR) between regional cerebral blood flow (rCBF) and verbal working memory (WM) accuracy is not fully understood.
• Investigating how non-invasive brain stimulation techniques like repetitive transcranial magnetic stimulation (rTMS) can modulate this relationship is crucial for understanding cognitive function.

Purpose of the Study:

• To investigate if rTMS of the left or right middle frontal gyrus (MFG) modulates the BBR between rCBF and verbal WM accuracy.
• To explore the involvement of the prefrontal cortex in WM based on individual performance.

Main Methods:

• Fourteen participants underwent a 2-back WM task with letter stimuli.
• rTMS was applied to the left or right MFG while rCBF was measured using positron emission tomography (PET).
• Region-of-interest and whole-brain analyses were performed to correlate individual accuracy with rCBF.

Main Results:

• Without rTMS, a negative BBR was observed in the left MFG, suggesting increased effort with lower performance.
• Left MFG rTMS shifted the BBR towards the superior frontal gyrus (SFG), showing a positive BBR in anterior SFG.
• Right MFG rTMS resulted in a BBR shift to the left inferior frontal gyrus, located posteriorly and inferiorly.

Conclusions:

• rTMS can alter the BBR in verbal WM, demonstrating short-term neural plasticity.
• These findings provide insights into prefrontal cortex involvement in WM beyond traditional cognitive subtraction methods.
• The study highlights how temporary disruption of neural network modules by rTMS impacts cognitive performance and brain activity.