The Brain Prepares Itself for New Memories at Night
A good night's sleep is crucial to helping people create new memories, according to a new study. Learning or experiencing something new activates neurons in the hippocampus, a region of the brain vital for memory.
Photo: Pixabay.com
Researchers reported in the journal Science that neurons that record new memories during the day are restored during sleep.
«This mechanism may allow the brain to reuse the same resources, the same neurons, for new learning the next day,» explains neuroscientist Azahara Oliva.
The new analysis has shown that at certain times during deep sleep, certain areas of the hippocampus are turned off, allowing these neurons to reboot.
This process occurs in the hippocampus, a region of the brain that is vital to a person’s ability to create memories. It is divided into three regions: CA1, CA2, and CA3. CA1 and CA3 are involved in encoding memories related to time and space and are well studied, but less is known about CA2, which causes the hippocampus to shut down and reboot during sleep.
The researchers implanted electrodes in the hippocampi of mice, allowing them to record neuronal activity during learning and sleep. They were able to observe that during sleep, neurons in the CA1 and CA3 regions reproduced the same neural patterns that had developed during learning during the day.
But the researchers wanted to know how the brain continues to learn every day without overloading or starving its neurons. Those same neurons later repeat the same pattern of activity while you sleep, transmitting the day’s memories to a larger region of the brain called the cerebral cortex.
“We realized that there are other states of the hippocampus that occur during sleep, when everything shuts down,” Oliva explained. “The CA1 and CA3 areas, which were very active, suddenly go quiet. It’s a memory reset, and this state is generated by the middle region, CA2.”
Cells called pyramidal neurons are thought to be active neurons that are important for functional purposes like learning. Another type of cell, called interneurons, has different subtypes. The researchers found that the brain has parallel circuits regulated by these two types of interneurons: one that regulates memory and one that allows memories to be retrieved.
This new understanding could help researchers develop tools to improve memory by altering the mechanisms by which memories are consolidated.
The researchers believe they now have tools to improve memory that could be used in memory disorders like Alzheimer’s disease. Importantly, the new study also provides data for studying ways to erase negative or traumatic memories, which could then help treat conditions like post-traumatic stress disorder.
“We’re showing that memory is a dynamic process,” Oliva concludes.