During slumber, certain neural signals get restored or reinitialized.
During slumber, the brain's capacity to absorb and store fresh memories is revitalized thanks to a particular method, as revealed by a group of researchers from Cornell University. Their findings, published in the journal "Science," indicate that specific parts of the hippocampus become dormant during deep sleep. This inactivity allows neurons to undergo a reset, which could potentially enable the brain to recycle the same resources and neurons for new learning opportunities the following day, stated neurobiologist Azahara Oliva in a university statement.
The hippocampus, a seahorse-shaped structure inside the brain, is responsible for transitioning consciously learned memory content from short-term to long-term memory, predominantly during sleep. The researchers were puzzled as to how individuals could continue learning new things throughout their lives without depleting all of their neurons.
Addressing the role of the midregion
The hippocampus is segmented into three areas, known as C1, C2, and C3. Although C1 and C3 have been extensively studied and found to significantly impact memory processing in terms of time and space, the function of C2 was unknown. The research team led by Oliva seems to have addressed this gap with their current study.
In order to conduct their research, electrodes were implanted into the hippocamps of mice, allowing the researchers to observe neuronal activity in the animals' brains during learning and sleeping periods. "We identified other sleep states within the hippocampus where everything is silent," said Oliva. "The previously highly active regions CA1 and CA3 suddenly became calm. It's a reset of memories. This state is generated by the middle region, CA2."
The role of pyramidal neurons
Pyramidal neurons are believed to be the actively functioning neurons essential for tasks such as learning. In contrast, interneurons, which have various subtypes, were thought to regulate different neural pathways. The researchers discovered that there are parallel circuits in the brain that are manipulated by two types of interneurons - one that administers memory retention, and the other that facilitates memory resets.
These new findings allow for a better understanding of human and animal sleep's importance, as well as the dynamic nature of memory, according to Oliva. The research team is optimistic that these results could potentially aid in memory enhancement, such as for individuals with Alzheimer's, and may even hold the key to erasing traumatic memories in individuals suffering from post-traumatic stress disorder.
The study reveals that the midregion of the hippocampus, specifically CA2, plays a crucial role in generating a memory reset state during deep sleep, causing the previously active regions CA1 and CA3 to become calm. This process could potentially explain how individuals can continue learning new things without depleting their neurons, as the brain recycles resources and neurons for new learning opportunities.
The researchers also found that there are parallel circuits in the brain manipulated by two types of interneurons - one promoting memory retention and the other facilitating memory resets. These discoveries could lead to potential advancements in memory enhancement for individuals with conditions like Alzheimer's and may even help in erasing traumatic memories in those suffering from post-traumatic stress disorder. The disease, in reference to these conditions, could benefit from the findings associated with memory enhancement and neural reprocessing during sleep.
