Single neurons throughout human memory regions phase-lock to hippocampal theta

• Published in: bioRxiv
• Main Authors: Schonhaut, Daniel R, Ramayya, Ashwin G, Solomon, Ethan A, Herweg, Nora A, Fried, Itzhak, Kahana, Michael J
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 30.07.2020
• Subjects: Amygdala; Frequency dependence; Hippocampus; Neurons; Neurosurgery; Theta rhythms
• DOI: 10.1101/2020.06.30.180174

Functional interactions between the hippocampus and cortex are critical for episodic memory. Neural oscillations are believed to coordinate these interactions, and in rodents, prefrontal neurons phase-lock to hippocampal theta oscillations during memory-guided behavior. We assessed inter-regional phase-locking to hippocampal oscillations in humans by recording 1,233 cortical and amygdala neurons and simultaneous hippocampal local field potentials in 18 neurosurgical patients. We identified 362 neurons (29.4%) from multiple regions that phase-locked to rhythmic hippocampal activity, predominantly at theta (2-8Hz) frequencies. Compared to baseline spiking, strong theta phase-locking coincided with regionally-specific increases in hippocampal theta power, local and hippocampal high frequency activity, and cross-frequency power correlations between the hippocampus and a phase-locked neuron's local region. These results reveal that spike-time synchrony with hippocampal theta is a defining feature of cortico-hippocampal functional connections in humans. We propose that theta phase-locking could mediate flexible inter-regional communication to shape the content and quality of episodic memories. Competing Interest Statement The authors have declared no competing interest. Footnotes * http://memory.psych.upenn.edu/Electrophysiological_Data