Researchers at MIT have found a neural circuit that helps us build long-lasting memories. This neural circuit works best when the brain is paying attention to what we are seeing, a new study found.The basis of the study, published Sept 24 in the journal Proceedings of the National Academy of Sciences, shows that a type of under-appreciated brain cell known as the astrocyte seems to play a key role in processing sensory information and building memory.
Astrocytes are star-shaped brain cells previously thought to only play a supporting role in the nervous system. Studies have recently shown these cells also communicate with neurons, and modify sending and receiving signals, and probably have a bigger role.
The researchers wanted to find what happens to astrocytes when brain is stimulated into paying attention to what it is seeing. A structure deep in the brain called the nucleus basalis releases a neurotransmitter called acetylcholine when we are paying close attention to something. Some of the acetylcholine targets the astrocytes in the part of the brain that processes visual information.
The researchers watched how active the astrocytes in this visual centre were when mice were given different patterns to see. While seeing one of the patterns, the nucleus basalis was stimulated in order to release acetylcholine, which increased astrocyte activity.
Mice were shown the same patterns a few minutes later, to see how well they remembered them. The pattern they saw while being stimulated incited a stronger neural response in the visual cortex, meaning they remembered it better.
Astrocytes in action
The experiment was repeated on mice without working astrocytes, and the researchers didn’t see this increased remembering: Removing astrocytes prevented the stimulation from having any effects and thereby prevented a long lasting memory from being recorded.
“If you are paying attention to something, which causes this release of acetylcholine, that leads to a long-lasting memory of that stimulus. If you remove the astrocytes, that doesn’t happen,” study researcher Mriganka Sur, of MIT, said in a statement from the university.
When brain is attentive the astrocytes play an important role by sending messages to the visual cortex that they should respond strongly to whatever they are seeing. The moral of the story? When you command your brain to pay attention, you’ll remember whatever you are looking at better.
Previous research has found that acetylcholine drops in Alzheimer’s patients. A follow-up study on how astrocytes are affected by this chemical in Alzheimer’s patients may reveal new treatments for the disease.
“You cannot understand brain disorders without understanding the basic mechanisms of cortical brain function,” Sur said. “These cell types — astrocytes, inhibitory neurons — are emerging as major players in brain disorders, in unexpected ways.”
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