fMRI guided rTMS evidence for reduced left prefrontal involvement after task practice

Area of Science:

• Cognitive Neuroscience
• Neuroimaging

Background:

• Consistent mapping tasks show performance improvements with practice, linked to reduced brain activity in prefrontal and parietal regions.
• Repetitive transcranial magnetic stimulation (rTMS) can reduce processing efficacy, making it a tool to investigate brain region involvement.

Purpose of the Study:

• To investigate whether reduced brain activity after practice reflects reduced involvement or increased efficiency in prefrontal and parietal cortices.
• To examine the role of these brain regions in novel versus practiced cognitive tasks using fMRI-guided rTMS.

Main Methods:

• Subjects performed a Sternberg task with novel and practiced target-sets during fMRI to identify peak activity sites.
• Real and sham rTMS were applied to left prefrontal and parietal cortex outside the scanner to assess task performance changes.

Main Results:

• rTMS applied to prefrontal and parietal cortex significantly reduced accuracy for novel targets.
• Prefrontal rTMS interference was significantly lower for practiced targets compared to novel targets.
• rTMS did not impact non-target accuracy or reaction time.

Conclusions:

• Task practice in consistent environments reduces prefrontal cortex involvement.
• Findings suggest the prefrontal cortex is crucial for target maintenance and comparison.
• Practice may enable response selection without direct target comparison, supporting process switching and resource redistribution hypotheses.