Multimodal evidence for hippocampal engagement and modulation by functional connectivity-guided parietal TMS

Area of Science:

• Neuroscience
• Cognitive Science
• Neuromodulation

Background:

• The hippocampus is crucial for memory and cognitive functions.
• Transcranial magnetic stimulation (TMS) guided by functional connectivity (FC) shows potential for memory improvement.
• Direct neural evidence for TMS modulating hippocampal activity is limited.

Purpose of the Study:

• To provide direct neural evidence of TMS engaging and modulating hippocampal activity.
• To investigate the causal relationship between parietal cortex stimulation and hippocampal responses.
• To explore personalized neuromodulation strategies for hippocampus-dependent functions.

Main Methods:

• Combined intracranial electroencephalography (iEEG) with TMS in neurosurgical patients.
• Utilized functional magnetic resonance imaging (fMRI) in healthy participants to map hippocampal FC.
• Applied single-pulse and repetitive TMS to the parietal cortex guided by individual hippocampal-FC.

Main Results:

• Single-pulse TMS evoked distinct temporal and spectral activity in the hippocampus.
• Variability in TMS-evoked hippocampal responses correlated with parietal-hippocampus FC strength.
• Repetitive TMS selectively suppressed hippocampal theta oscillations.

Conclusions:

• Multimodal data provide causal neural evidence for TMS modulating hippocampal activity.
• Findings offer mechanistic insights into TMS effects on the hippocampus.
• Supports the development of personalized neuromodulation for memory and cognitive enhancement.