Sleep is vital to the relationship between emotion and memory

Sleep is vital to the relationship between emotion and memory.  Nature·Communication: Sleep is vital to the relationship between emotion and memory

[Article on February 23, 2021 on the US “Science Daily” website] Title: Sleep is vital to the relationship between emotion and memory.

A recent study published by the University of Michigan in Nature Communications showed that the research team is committed to studying how memories related to specific sensory events are formed and stored in mice, and to verify how fear memories related to specific visual stimuli are formed . Studies have found that neurons activated by visual stimuli are not only more active during subsequent sleep, but sleep is also critical to its ability to associate fear memories with sensory events.

Previous studies have shown that in the process of intensive learning, highly active brain regions tend to be more active in subsequent sleep, but it is currently unknown whether it is necessary to “reactivate” memory during sleep to fully store newly acquired memories.

Sara Aton, a senior author of the study and a professor in the Department of Molecular, Cellular and Developmental Biology at the University of Michigan, said that one of the goals of the study is whether there is communication between the part of the brain that regulates fear memory and specific neurons that regulate fear-related sensory memory. Communication, and whether it is necessary to communicate while sleeping. We are eager to know what promotes the new connection process, such as a specific set of neurons or a specific sleep stage, but we have not been able to verify it through experiments for a long time.

Now, researchers have designed tools that can genetically label cells that are activated within a specific period of time, and create a visual memory test around a set of specific neurons in the primary visual cortex. The researchers showed a neutral image (image without sensory stimuli) to a group of mice, and then expressed genes in neurons of the mouse visual cortex that were activated by the image.

In order to verify whether these neurons recorded neutral images, Aton and his team tested whether they can stimulate their memory of image stimuli by selectively activating neurons without showing them images. When neurons were activated and this activation was paired with a slight electric shock to the foot, the subjects were then afraid of visual stimuli that looked similar to the images encoded by these cells. The opposite is also true. After the visual stimulus is paired with the foot shock, the subject will then have a fear response to reactivating the neuron. The visual stimulus and the fully artificially activated neuron basically have the same response.

The study also found that after the subjects were shown images and given a slight foot shock, the subjects’ sleep was disturbed, and the fear related to visual stimulation disappeared. Those with irregular sleep learned to be afraid of the foot shock. Specific visual stimuli.

Aton said these mice actually started to fear every visual stimulus we showed. From entering the room with visual stimulation, the mouse seemed to know that it would be frightened for some reason, but did not know the specific reason. This may indicate that in order to accurately link fear to visual stimuli, they must reactivate the neurons encoding the stimulus in the sensory cortex during sleep, which allows the generation of memories specific to visual cues. Researchers believe that at the same time, the sensory cortex must communicate with other brain structures in order to combine the sensory and emotional aspects of memory.

The findings of the study may shed light on how to understand anxiety and post-traumatic stress disorder, suggesting that if fear is associated with certain specific events in sleep, sleep interruption may affect this process. In the absence of sleep, the brain seems to process the facts you are afraid of, but you may not be able to connect them with the specific things you should be afraid of. In terms of post-traumatic stress disorder (PTSD) or generalized anxiety disorder, this normative process can be problematic.

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