The team also discovered a link between the ripples and the neural firing patterns seen during learning and recall. Later, the participants were shown one of the words, such as “cake,” and asked to recall the paired word, “fox.” A very similar firing pattern replayed in their brains just milliseconds before they correctly recalled the paired word. The researchers observed unique firing patterns of individual neurons when learning each new word pairing. In a recent study, the team found that ripples emerge in the brain fractions of a second before recalling a memory. They also analyzed “ripples”-high-frequency brain activity when many neurons are activated at once. The scientists focused on activity in the anterior temporal lobe, a brain language center, and the medial temporal lobe, an area linked to memory recall in rodents. Individual neurons are represented by different colors. Our brains may store memories in specific neuronal firing patterns, visualized here, that are replayed fractions of a second before remembering. Participants sat in front of a screen and were asked to learn unrelated word pairs such as “cake” and “fox.” Six participants were given memory tests while researchers monitored the electrical activity of thousands of individual neurons. This allowed the scientists to also investigate how memories are stored and retrieved. As part of the trial, the patients were temporarily living with electrodes surgically implanted in their brains to monitor neural activity. The team was conducting a study of patients with epilepsy whose seizures couldn’t be controlled with drugs. Results appeared in Science on March 6, 2020. The study was supported by NINDS, along with NIH’s National Institute of General Medical Sciences (NIGMS). Kareem Zaghloul of NIH’s National Institute of Neurological Disorders and Stroke (NINDS) set out to determine whether similar brain activity takes place in people when recalling memories. These patterns are replayed when the memory is retrieved. Studies in rodents have suggested that memories are stored as unique firing patterns of brain cells, or neurons. Scientists are working to understand how the brain stores and retrieves these memories of our past experiences.

metamorworks / iStock / Getty Images PlusĪ familiar scent or the chorus of an old song can trigger a memory.

Memories and their recall involve coordinated activity throughout the human brain.

Neurons firing in the brain