A good night’s sleep resets memory
While everyone knows that a good night’s sleep restores a person’s energy, a new study finds it resets memory, another vital function, an American university says.
Learning or experiencing new things activates neurons in the hippocampus, a region of the brain vital for memory, Cornell University says on its website. Later, while we sleep, those same neurons repeat the same pattern of activity, which is how the brain consolidates those memories that are then stored in a large area called the cortex. But how is it that we can keep learning new things for a lifetime without using up all of our neurons? The study reports that at certain times during deep sleep, certain parts of the hippocampus go silent, allowing those neurons to reset.
“This mechanism could allow the brain to reuse the same resources, the same neurons, for new learning the next day,” says corresponding author Azahara Oliva.
The hippocampus 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 the current study found generates this silencing and resetting of the hippocampus during sleep.
The researchers implanted electrodes in the hippocampi of mice, which allowed them to record neuronal activity during learning and sleep. This way, they could observe that during sleep, the neurons in the CA1 and CA3 areas reproduce the same neuronal patterns that developed during learning in the day. But the researchers wanted to know how the brain continues learning each day without overloading or running out of neurons.
“We realised there are other hippocampal states that happen during sleep where everything is silenced,” says Oliva. “The CA1 and CA3 regions that had been very active were suddenly quiet. It’s a reset of memory, and this state is generated by the middle region, CA2.”
The researchers believe they now have the tools to boost memory, by tinkering with the mechanisms of memory consolidation, which could be applied when memory function falters, such as in Alzheimer’s disease. Importantly, they also have evidence for exploring ways to erase negative or traumatic memories, which may then help treat conditions such as post-traumatic stress disorder.
The findings are in the Science journal.
