Theses Doctoral

Temporal coordination of neuronal activity underlies human memory and learning

Gedankien, Tamara

Memory-related disorders, such as Alzheimer’s disease and dementia, are devastating and often irreparable given our limited knowledge of how to effectively treat them. Animal studies have made significant advances in identifying neural correlates of memory, but in order to develop better interventions for memory loss, we need a deeper understanding of the neural basis of memory in the human brain. The main focus of my research is examining large-scale electrophysiological correlates of memory and learning in humans. In my studies, I recorded local field potential (LFP) data directly from the brains of neurosurgical patients performing memory tasks.

First, in Chapter 2, I investigated the prevalence of sharp-wave ripples—synchronous high-frequency bursts of LFP activity—in the human hippocampus and cortex. I found that spectral characteristics of detected ripples closely matched those of other previously described high-frequency patterns in the human brain, thus raising important considerations for the detection and definition of ripple-like activity in humans. For my second study, in Chapter 3, I examined the impact of scopolamine, a cholinergic blocker, in the human hippocampal area during episodic memory. I found that the memory impairment caused by scopolamine was coupled to disruptions of both the amplitude and phase alignment of theta oscillations (2-10 Hz) during encoding. These findings suggest that cholinergic circuits support memory by coordinating the temporal dynamics of theta oscillations. Finally, in Chapter 4, I explored how brain oscillations in the medial temporal lobe (MTL) support learning. I found that subjects’ accuracy in a spatial memory task improved significantly within and across sessions, and that these short- and long-term learning effects were predicted by greater theta synchrony.

My research translates important memory- and learning-related signals from animal studies, and extends those findings by revealing spectral patterns that are specifically relevant to humans. Together, my studies point to a key electrophysiological phenomenon underlying memory and learning in humans: the synchrony of neuronal activity in the brain. In particular, my results suggest that the temporal coordination of neuronal activity offered by brain oscillations, especially those in the theta frequency band, is vital for successful memory and learning. These findings expand our mechanistic understanding of the neurophysiology of human memory and learning, and suggest that improving the temporal coordination of neuronal activity in the MTL may provide a novel route to treating memory- and learning-related disorders.


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More About This Work

Academic Units
Biomedical Engineering
Thesis Advisors
Jacobs, Joshua
Ph.D., Columbia University
Published Here
July 12, 2023