Intracranial neurofeedback of hippocampal theta oscillations enhances human memory formation

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

Vandana Prasad^1,2,3,6 (vandana.prasad@mail.utoronto.ca), Chaim N. Katz^1,3,5,7, Kramay Patel^1,3,4,7, Thomas M. Biba^1,10, Katherine Duncan¹⁰, Taufik A. Valiante^{1,2,3,6,7,8,9}; ¹Krembil Brain Institute, Toronto Western Hospital (TWH), Toronto, Ontario M5T 1M8, Canada;, ²Electrical and Computer Engineering, University of Toronto, Toronto, Ontario M5S 3G4, Canada;, ³Center for Advancing Neurotechnological Innovation to Application (CRANIA), Toronto, Ontario, M5G 2A2, Canada;, ⁴Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada;, ⁵Faculty of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada;, ⁶The KITE Research Institute, University Health Network, Toronto, Ontario M5G 2A2, Canada;, ⁷Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3G9, Canada;, ⁸Institute of Medical Sciences, University of Toronto, Toronto, ON M5S 1A8, Canada;, ⁹Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Ontario M5S 1A1, Canada., ¹⁰Department of Psychology, University of Toronto, Toronto, ON M5S 3G3, Canada

While hippocampal theta oscillations (3–8 Hz) have long been hypothesized to underlie memory formation, causal evidence in humans is limited. Neurofeedback is a technique that allows individuals to volitionally control their brain state by receiving task feedback based on their online neural activity. This approach uniquely enables the causal manipulation of brain states, tightly constrained by task demands. Thus, to test if causally increasing or decreasing hippocampal theta power benefited or diminished memory formation, we employed neurofeedback in individuals with epilepsy undergoing intracranial electroencephalographic (iEEG) recordings. The task involved object classification during the time of encoding, where subjects made one of two judgments about an object image following a color cue (Green: Size; Blue: In/Out). Neurofeedback was controlled via the brightness of the color cue: increased theta power yielded a brighter hue, whereas decreased theta power yielded a darker hue. Neurofeedback was performed before the presentation of each object image for up to two minutes until theta power reached a threshold, which triggered the presentation of the object image. Theta power used for neurofeedback was estimated after accounting for aperiodic components. Preliminary analysis revealed a significant increase in associative memory hit rate for up-regulated vs. down-regulated trials (n = 8, t(7) = 2.02, p <.05) for patients who received neurofeedback to the posterior hippocampus. To our knowledge, this provides the first evidence of hippocampal theta neurofeedback modulating associative memory formation, providing casual evidence for its role in human memory.

Topic Area: LONG-TERM MEMORY: Episodic