A recent study from Cornell University reveals that sleep not only consolidates memory but also resets neurons, allowing the brain to keep learning without depleting its resources. This discovery could have major implications for treating neurological disorders such as Alzheimer's disease or post-traumatic stress disorder.
When a person learns or experiences new things, neurons in the hippocampus, a key brain region for memory, become active. During sleep, these neurons replay the activity patterns observed during the day, a process essential for memory consolidation, with memories then stored in the cortex. However, scientists have questioned how the brain can continue acquiring new information throughout life without exhausting its neurons.
The study, published in
Science, shows that at certain moments during deep sleep, specific regions of the hippocampus "shut down," allowing neurons to reset. Azahara Oliva, assistant professor of neurobiology and lead author of the study, explains: "This mechanism might allow the brain to reuse the same neurons for new learning the next day."
The hippocampus is divided into three main regions: CA1, CA2, and CA3. The CA1 and CA3 regions, well-studied, are involved in encoding time-and-space-related memories. In contrast, the function of CA2 was less understood until now. This research demonstrated that CA2 is essential in causing the silencing of other hippocampal regions, thus facilitating memory "reset" during sleep.
Researchers implanted electrodes in the hippocampus of mice to record neural activity during learning and sleep. They observed that neurons in the CA1 and CA3 regions replay neural patterns developed during the day before being silenced by the influence of CA2. This suggests the brain has parallel circuits regulated by two types of neurons: pyramidal neurons, crucial for learning, and interneurons, which ensure memory resetting.
This discovery is pivotal in understanding why sleep is essential in all animals: it not only serves to consolidate memories but also to reset the brain for continued functionality during waking hours. Researchers hope this knowledge can be used to enhance memory and treat related disorders, like Alzheimer's, or to erase traumatic memories.
Article author: Cédric DEPOND