Yitzhak Norman’s goal is to uncover the mechanisms underlying our ability to encode, retrieve and reenact a personal experience in our minds. During his PhD in Neurobiology at Weizmann Institute of Science, he worked with patients undergoing invasive epilepsy monitoring, who are implanted with electrodes as part of a rare clinical procedure to locate their epileptic focus and surgically remove it. During the monitoring period, in between clinical sessions, patients often volunteer to participate in studies, providing a rare opportunity to obtain electrophysiological signals directly from their brains while they can relate, in real time, their conscious thoughts.
For his research, Dr. Norman worked with experts on intracranial EEG recordings and high-field fMRI at Weizmann Institute of Science, Stanford Medical Center, and at hospitals in Paris, Tel Aviv, and New York.
Patients were shown pictures, given a short distraction task, and then asked to freely recall and describe them. Dr. Norman found that 1-2 seconds before the patients recalled a picture, there was a significant increase in Sharp Wave Ripples, massive neuronal activity bursts occurring in the hippocampus. The ripples played a major role in recollection, coordinating re-activation of content in the cerebral cortex as well as in other areas related to memory.
Currently in the Department of Neurological Surgery at the University of California, San Francisco, Dr. Norman examines how we encode and recall a specific conversation in our memory. Such a question can only be explored in humans, not animal models. Using a combination of non-invasive brain imaging techniques (high-field fMRI) and intracranial recordings, Dr. Norman investigates the functional organization of language representations in the cortex and their interplay with memory centers in the brain. His research could reveal the neuronal mechanisms responsible for spontaneous verbal thoughts, and substantially advance our understanding of language and memory impairments that accompany neurodegenerative diseases such as Alzheimer’s and dementia, as well as speech problems caused by epilepsy and stroke.