Modulation of Fronto-Striatal Functional Connectivity Using Transcranial Magnetic Stimulation

Area of Science:

• Neuroscience
• Neuroimaging
• Brain Stimulation

Background:

• The fronto-striatal network is crucial for motor, cognitive, and emotional functions.
• Intermittent theta burst transcranial magnetic stimulation (iTBS) modulates brain network connectivity.
• Optimal stimulation intensity for transcranial magnetic stimulation (TMS) therapy remains under-explored.

Purpose of the Study:

• To investigate the effects of different iTBS intensities on fronto-striatal connectivity.
• To compare sub-threshold versus supra-threshold stimulation effects on brain networks.
• To analyze resting-state functional magnetic resonance imaging (rsfMRI) changes pre- and post-iTBS.

Main Methods:

• Sixteen healthy subjects received iTBS over the left dorsolateral prefrontal cortex (DLPFC) at 90% and 120% of resting motor threshold (rMT) on separate days.
• rsfMRI scans were acquired before and after iTBS.
• Seed-to-seed functional connectivity was calculated for fronto-striatal and amygdala regions using DPABI.

Main Results:

• Sub-threshold iTBS (90% rMT) significantly increased functional connectivity between the left DLPFC and bilateral caudate.
• Supra-threshold iTBS (120% rMT) did not alter fronto-striatal connectivity.
• Supra-threshold iTBS increased functional connectivity between the right amygdala and right caudate.

Conclusions:

• Sub-threshold iTBS is sufficient and potentially more effective for enhancing fronto-striatal connectivity.
• Higher stimulation intensities may induce network homeostatic effects, counteracting desired connectivity changes.
• This suggests intensity modulation is critical for optimizing TMS protocols.