Multi-day rTMS exerts site-specific effects on functional connectivity but does not influence associative memory...

Area of Science:

• Neuroscience
• Cognitive Science
• Neuromodulation

Background:

• Repetitive transcranial magnetic stimulation (rTMS) can modulate brain networks and cognitive functions.
• Previous studies suggested long-lasting improvements in memory and connectivity with multi-day rTMS targeting specific networks.

Purpose of the Study:

• To evaluate the reproducibility and specificity of memory and connectivity enhancements after multi-day rTMS.
• To investigate effects of rTMS on parietal-hippocampal and pre-SMA-putamen networks.

Main Methods:

• Participants underwent four days of 20 Hz rTMS targeting either the left lateral parietal cortex or the pre-supplementary motor area (pre-SMA).
• Associative memory and resting-state functional connectivity were assessed before and after stimulation.
• Two stimulation sites were tested in separate weeks.

Main Results:

• No significant long-lasting enhancement in associative memory or targeted network connectivity was found after parietal or pre-SMA rTMS.
• Short-term (approx. 24h) site-specific modulations in functional connectivity were observed, including decreased within-network and increased between-network connectivity.
• Findings suggest complex interactions between rTMS protocols and brain network dynamics.

Conclusions:

• Multi-day rTMS to parietal or pre-SMA regions did not yield the expected long-lasting cognitive or connectivity benefits.
• Observed transient connectivity changes indicate a complex response to rTMS, necessitating further research.
• Developing reliable rTMS paradigms for cortical-subcortical network modulation requires further investigation.