Optimizing Hippocampal-Cortical Network Modulation via Repetitive Transcranial Magnetic Stimulation: A Dose-Finding...

Area of Science:

• Neuroscience
• Neuromodulation
• Medical Imaging

Background:

• Repetitive transcranial magnetic stimulation (rTMS) shows potential for modifying brain functional connectivity (FC).
• The optimal number of rTMS sessions for therapeutic effect remains undetermined.
• Functional connectivity (FC) is a key biomarker for brain network function.

Purpose of the Study:

• To determine the minimum effective dose of rTMS for inducing significant changes in brain functional connectivity (FC).
• To apply a Bayesian adaptive method (continual reassessment method - CRM) for dose-finding in rTMS treatment.
• To investigate the relationship between rTMS session number and FC changes in a hippocampal network.

Main Methods:

• Utilized the continual reassessment method (CRM), a Bayesian adaptive procedure, for dose-finding.
• Administered daily rTMS to the left posterior parietal cortex in 15 subjects.
• Measured resting-state functional connectivity (FC) using fMRI in a predefined left hippocampal network.
• Defined a response criterion based on a 0.028 change in FC between the hippocampus and parietal cortex.

Main Results:

• A criterion change in FC was observed in 9 out of 15 participants.
• The CRM analysis indicated that more than four rTMS sessions are required for reliable FC changes.
• The study successfully adapted a Bayesian adaptive method for rTMS dose-finding.

Conclusions:

• The continual reassessment method (CRM) is a viable approach for optimizing rTMS dosing when reliable outcome measures like FC are available.
• The estimated minimum effective dose for achieving an 87.5% efficacy in altering hippocampal network FC is greater than four rTMS sessions.
• This research pioneers the use of Bayesian adaptive methods to explore rTMS parameters, paving the way for more personalized neuromodulation strategies.