Identification of Cortical Targets for Modulating Function Supported by the Human Hippocampal Network

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neuroimaging

Background:

• Individualized transcranial magnetic stimulation (TMS) targeting via functional connectivity analysis of functional magnetic resonance imaging (fMRI) shows promise for inducing neuroplasticity.
• The precise application of this technique to modulate episodic memory, supported by the hippocampal network, requires further investigation.

Purpose of the Study:

• To identify individualized TMS targets within the hippocampal network for modulating episodic memory.
• To reveal cortical regions within the hippocampal network suitable for TMS intervention.

Main Methods:

• Utilized resting-state fMRI data from 1,133 individuals in the Human Connectome Project.
• Analyzed the hippocampal network using seed-based functional connectivity.
• Identified average centroids of individualized TMS targets at the medial prefrontal cortex (mPFC) and posterior parietal cortices (PPCs) using a weighted sum of cortical time series.

Main Results:

• Identified specific MNI coordinates for mPFC and PPC targets in both left and right hemispheres.
• Demonstrated high reproducibility of these functional connectivity centroids between sessions (average separations of ~2-4 mm).
• Confirmed reliable identification of these coordinates (>90% of individuals) using cortical "seedmaps," with significantly smaller deviations compared to average functional connectivity centroids and atlas coordinates.

Conclusions:

• The study suggests candidate TMS target coordinates within the mPFC and PPC for modulating hippocampal function.
• These findings provide a foundation for developing more precise, individualized TMS protocols to enhance episodic memory.
• The identified coordinates offer reliable targets for future research and clinical applications in memory modulation.