In vivo human hippocampal cingulate connectivity: a corticocortical evoked potentials (CCEPs) study

Area of Science:

• Neuroscience
• Human Brain Networks
• Epilepsy Research

Background:

• The human limbic system's intricate network remains incompletely understood.
• Cortico-cortical evoked potential (CCEP) offers a method to investigate brain connectivity.

Purpose of the Study:

• To explore the functional connectivity within the human limbic system.
• To investigate the relationship between the hippocampus and the posterior cingulate gyrus using CCEP.

Main Methods:

• Stereoelectroencephalogram (SEEG) electrode implantation in five epilepsy patients.
• Delivery of electrical stimuli to the hippocampus and posterior cingulate gyrus.
• Averaging 60 stimuli to obtain CCEP responses for network analysis.

Main Results:

• Hippocampal stimulation evoked CCEP responses in the posterior cingulate gyrus (latencies 20-175 ms).
• CCEPs were also observed in the posterior parahippocampal gyrus, medial superior frontal gyrus (SFG), and orbitofrontal cortex.
• Posterior cingulate stimulation elicited CCEPs in the hippocampus (latencies 25-234 ms).

Conclusions:

• The hippocampus is interconnected with the posterior cingulate gyrus, posterior parahippocampal gyrus, medial SFG, and orbitofrontal cortex.
• A bidirectional network exists between the hippocampus and posterior cingulate gyrus via the cingulum.
• This study provides novel insights into the human limbic network's architecture.