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

Individualized transcranial magnetic stimulation (TMS) targeting using functional connectivity analysis of functional magnetic resonance imaging (fMRI) has been demonstrated to be advantageous in inducing neuroplasticity. However, how this approach can benefit modulating the episodic memory function supported by the hippocampal network remains elusive. We use the resting-state fMRI data from a large cohort to reveal tentative TMS targets at cortical regions within the hippocampal network. Functional MRI from 1,133 individuals in the Human Connectome Project was used to analyze the hippocampal network using seed-based functional connectivity. Using a weighted sum of time series at the cortex, we identified the average centroids of individualized targets at the medial prefrontal cortex (mPFC) and posterior parietal cortices (PPCs) at (-10, 49, 7) and (-40, -67, 30) in the left hemisphere, respectively. The mPFC and PPC coordinate at the right hemispheres are (11, 51, 6) and (48, -59, 24) in the right hemisphere, respectively. Centroids of the individualized functional connectivity at the mPFC and PPC were reproducible between sessions with separations in average about 2 and 4 mm, respectively. These separations were significantly smaller than the distance to average functional connectivity centroids (~10 mm) and atlas coordinate (~20 mm). These coordinates can be reliably identified (> 90% of individuals) using cortical "seedmaps." Our results suggest candidate TMS target coordinates to modulate the hippocampal function.