Cross regional coordination of activity in the human brain during autobiographical self-referential processing

Poster Session C - Sunday, April 14, 2024, 5:00 – 7:00 pm EDT, Sheraton Hall ABC

James Stieger¹ (jstieger@stanford.edu), Josef Parvizi²; ¹Stanford University

For the human brain to operate, populations of neurons across remote anatomical structures must coordinate their activity. While neuroimaging studies have highlighted the presence of cross-regional interactions over slower time periods, our understanding of ultra-fast interactions at the sub-second time window has remained limited. Here, to address this gap of knowledge, we recorded directly from the hippocampus (HPC), posteromedial cortex (PMC), ventromedial/orbital prefrontal cortex (OFC), and anterior thalamus (ANT) – a set of structures within the default mode network (DMN) – during two experiments of autobiographical memory processing in 31 patients. We found that the presentation of memory retrieval cues elicited a significant increase of slow frequency (LF, < 6Hz) activity followed by cross-regional phase coherence of this LF-activity before select populations of neurons within each region showed increase of high-frequency (HF >70Hz) activity. The power of HF activity was modulated by memory content and its onset followed a specific temporal order of ANT->HPC/PMC->OFC. Further, we probed cross-regional causal effective interactions with repeated electrical pulses and found that HPC stimulations cause the greatest increase in LF-phase coherence across all regions whereas the stimulation of any region caused the greatest LF-phase coherence between that particular region and ANT. These observations support the role of ANT in gating, and the HPC in synchronizing, the activity of cortical midline structures when humans retrieve self-relevant memories of their past. Our findings offer a fresh perspective, with high temporal fidelity, about the dynamic signaling and underlying causal connections among DMN regions.

Topic Area: LONG-TERM MEMORY: Episodic