A study by the University of Groningen found that memory loss caused by sleep deprivation can be restored using medications for asthma, lung diseases and erectile dysfunction.
Dr. Robert Havex noted that lack of sleep can significantly affect memory processes in the human brain. His early work helped shed light on some of the molecular mechanisms underlying this type of memory loss.
It is known that lack of sleep affects the brain, including memory, but research is beginning to show that these memories are not lost, but are simply “hidden” in the brain and difficult to retrieve.
The new study shows that access to these hidden memories can be restored in mice using a drug currently used to treat asthma and chronic obstructive pulmonary disease.
The team of researchers also showed that another drug currently used to treat erectile dysfunction can restore access to spatial memories.
The researchers say that these spatial memories in mice are similar to, for example, humans remembering where they put their keys the night before, while social memories can be compared to remembering a new person you have met.
“Since I started my PhD many years ago, I have been amazed to see that even a single period of sleep deprivation can have such a profound effect on memory processes and the brain as a whole,” said lead researcher Dr Robert Haavikes of the University of Groningen in the Netherlands. “Early work published years ago helped us identify some of the molecular mechanisms that mediate memory loss. By specifically manipulating these pathways in the hippocampus, we were able to make memory processes resilient to the negative effects of sleep deprivation. In our new studies, we investigated whether we could reverse memory loss even days after the initial learning event and the period of sleep deprivation.”
“We can do this by activating the original memory and then using drugs,” Dr. Hafikis said.
During the experiments, the researchers gave the mice the opportunity to choose between interacting with a mouse they had never met or a familiar mouse. Typically, the mice preferred to spend time with a new mouse rather than one they knew.
When subjected to the same choice the next day, the mice reacted to a similar extent to both the familiar mouse and the mouse they had met the day before, since both mice were considered familiar to them.
However, if mice are sleep deprived after their first encounter, the next day they will still prefer to interact with the new mouse as if they had never met it before.
These results suggest that the mice simply were unable to remember their previous encounter.
The team found they were able to permanently recover these hidden social memories, using a technique called optical engram technology. The technique allows them to identify neurons in the brain that together form a memory known as a memory engram (a unit of cognitive information within the brain) for a particular experience and change those neurons so they can be reactivated by light.
Researchers can then use light to reactivate this specific group of neurons, leading to the recollection of a particular experience (in this case, social memory).
They were also able to restore social memories in mice by treating them with roflumilast, a type of anti-inflammatory drug used to treat chronic obstructive pulmonary disease.
This finding is particularly interesting because it provides a starting point for studies of sleep deprivation and memory in humans, says Dr. Havicks, and he is now collaborating with another research group that is embarking on human studies.
Similarly, the researchers treated spatial memory loss with another drug, vardenafil, which is currently used to treat erectile dysfunction. These findings, according to the press release, provide a starting point for studies to move to human trials.