Neurons activated by visual stimuli become more active during subsequent sleep, studies show

It’s easy to imagine that the brain shuts down when you fall asleep, but a University of Michigan study shows that a group of neurons activated during pre-learning continue to hum and put memory into the brain. ..

UM researchers are studying how memories associated with specific sensory events are formed and stored in mice.In a recently published study conducted before the coronavirus pandemic Nature CommunicationsResearchers have investigated how terrifying memories were formed in connection with specific visual stimuli.

They found that not only did neurons activated by visual stimuli remain more active during subsequent sleep, but sleep was essential for their ability to connect fear memory to sensory events.

Previous studies have shown that areas of the brain that are very active during intensive learning tend to exhibit more activity during subsequent sleep. But what was unclear was whether this “reactivation” of sleep memory would need to occur in order to completely preserve the memory of the newly learned material.

“Part of what we wanted to understand is the communication between the parts of the brain that mediate the memory of fear and the specific neurons that mediate the memory of the senses to which fear is associated. Whether they talked and what they have to do is sleeping? What is facilitating the process of making new associations, such as a particular set of neurons or a particular sleep stage. I really want to know, “says Saraaton, senior author of the study and UM professor. Department of Molecular, Cellular and Developmental Biology. “But for the longest time, there really wasn’t a way to test this ly.”

Currently, researchers have the tools to genetically tag cells that are activated by experience in a particular time frame. Focusing on a specific set of neurons in the primary visual cortex, Aton and graduate student Brittany Clawson, the lead author of the study, created a visual memory test. They showed a neutral image to a group of mice and expressed the gene in the image-activated visual cortex neurons.

To ensure that these neurons registered a neutral image, Aton and her team could stimulate the memory of the image stimulus by selectively activating the neurons without displaying the image. I tested. When they activated neurons and combined that activation with mild foot shock, they then discovered that subjects were afraid of visual stimuli that resembled the images encoded by those cells. They realized that the opposite was also true. After combining visual stimuli with foot shock, subjects responded for fear of neuronal reactivation.

“Basically, the lessons of visual stimuli and the lessons of this completely artificial activation of neurons produced the same response,” Aton said.

Researchers found that there was no fear associated with visual stimuli when sleep was interrupted after showing the subject an image and giving a slight foot shock. People with unmanipulated sleep have learned to be afraid of certain visual stimuli that have been paired with foot shock.

“We found that these mice were actually afraid of all the visual stimuli we showed,” Aton said. “Since I went to the room where the visual stimulus was presented, they seem to know that there is a reason to be scared, but they don’t know exactly what they are afraid of.”

This probably indicates that they must have a sleep-related reactivation of the neurons that code for that stimulus in the sensory cortex in order to make an accurate fear association with the visual stimulus, Aton says. I will. This allows you to generate memories that are unique to that visual clue. At the same time, researchers believe that the sensory cortex region needs to communicate with other brain structures in order to connect the sensory aspects of memory with the emotional aspects.

Aton says their findings can affect how anxiety and post-traumatic stress disorders are understood.

“For me, this is a kind of clue. When you associate fear with certain events during sleep, sleep disorders can affect this process. In the absence of sleep, the brain is the fact that you are. He seems to be in control of the process. I’m afraid, but I may not be able to tie it to something that I should be afraid of. ” “The specification process may not work with PTSD or generalized anxiety disorder.”