Causal Connectivity Maps Derived from Single-Pulse Interleaved TMS/fMRI

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neuromodulation

Background:

• Understanding brain circuit function is crucial for developing effective neuromodulation therapies.
• Previous methods lacked causal evidence for TMS-induced network engagement.
• Personalized targeting approaches are needed to optimize TMS efficacy.

Purpose of the Study:

• To generate causal activation maps using interleaved single-pulse transcranial magnetic stimulation with functional MRI (spTMS/fMRI).
• To investigate TMS-evoked brain responses in the left hemisphere using personalized connectivity targeting.
• To validate image-guided TMS for causally engaging distributed brain regions and networks.

Main Methods:

• Employed interleaved spTMS/fMRI in over 80 participants.
• Utilized personalized resting-state connectivity targeting approaches.
• Quantified TMS-evoked BOLD responses using voxelwise event-related fMRI, controlling for confounds.

Main Results:

• Stimulation of frontal and ventrolateral targets induced specific BOLD responses in targeted and distributed regions.
• Subgenual anterior cingulate cortex (sgACC) and amygdala stimulation modulated widespread cortical and subcortical networks.
• No significant group differences in evoked responses were found between depressed and healthy control participants.

Conclusions:

• Image-guided TMS can causally engage distributed brain networks, validating its utility for circuit-based neuromodulation.
• The generated causal connectivity maps can guide future research linking brain circuits with outcomes.
• This approach offers a powerful tool for understanding and modulating brain function.