Published in the journal Scientific Reports, the study helps build a case for the use of sleep therapeutics following trauma exposure.
"Basically, our study has found that if you can improve sleep, you can improve function," said study author William Vanderheyden from the Washington State University (WSU) in the US.
In a study, the research team examined the links between poor sleep and post-traumatic stress disorder (PTSD)--a psychiatric condition that affects an estimated egiht million Americans each year.
Their study used methods reviewed and approved by WSU's Institutional Animal Care and Use Committee, which oversees all university animal research procedures to ensure animals' humane treatment throughout their lifecycle.
This included a commonly used PTSD rodent model in combination with optogenetics, a technique that uses light-sensitive proteins to control the activity of brain cells.
After going through the PTSD protocol, rats were assigned to two groups.
In one group, the researchers used optogenetic stimulation to activate melanin-concentrating hormone (MCH)--a sleep-promoting brain cell type--over a period of seven days. Animals in the second group served as controls.
Comparing the two groups, the researchers found that optogenetic stimulation increased the duration of rapid eye movement (REM) sleep--the sleep phase thought to be important for learning and memory--across the rats' rest and active phases.
The researchers then assessed the rats' behaviour on a three-day classical conditioning experiment involving a memory task.
On day one, rats learned to associate an audible tone with the mildly unpleasant experience of receiving a small foot shock immediately after hearing the tone.
After several occurrences, rats would freeze after hearing the tone, anticipating the foot shock.
On day two, they heard the tone 30 times without receiving the shock, allowing them to gradually extinguish that memory.
On the third day, the researchers played the tone 10 times to test to what extent the previous day's memory extinction had stuck.
They found that rats that had received optogenetic stimulation to increase their sleep time had more successfully extinguished the memory, freezing less than control rats.
"This highlights that there is a time-sensitive window when--if you intervene to improve sleep--you could potentially stave off the negative effects of trauma," Vanderheyden said.