Coordinated ‘ripples’ of brain activity signal successful memory retrieval



Memory is one of our most important cognitive abilities, yet exactly how the human brain forms and retrieves memories is still relatively unknown. Brain recordings from animals have suggested that fast fluctuations in neural signals, known as ripples, may be related to the ability to form memories and to consolidate memories during sleep. However, no direct evidence existed that ripples of neural activity mediate our ability to recall a memory.


Using neural recordings captured directly from the brains of patients who were being monitored for epilepsy, a team of NIH and Duke University researchers led by IRP investigator Kareem Zaghloul, M.D., Ph.D., discovered that ripples of neural activity in the brain’s temporal lobe increase immediately before individuals remember words. These ripples were coordinated across two different brain regions: the medial temporal lobe, which had been previously implicated in memory formation, and the lateral temporal cortex, which is responsible for encoding the meanings of words that we are trying to remember. The observed ripples triggered a pattern of neural activity in the brain that represented the specific word being remembered. These results provide the first evidence in humans that ripples of neural activity are directly involved in our ability to recall memories.


Memory disorders represent a significant health burden for affected individuals, their families, and society at large. Despite significant efforts, our ability to treat these disorders has been limited. This study provides important insights into how the human brain is able to recall individual memories, potentially providing an important target for therapeutic interventions designed to help address memory disorders.


Vaz AP, Inati SK, Brunel N, Zaghloul KA. (2019). Coupled ripple oscillations between the medial temporal lobe and neocortex retrieve human memory. Science. Mar 1;363(6430):975-978.

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This page was last updated on Friday, June 9, 2023