Sleep Loss And Poor Memory
Anecdotal evidence abounds on the effect that sleep deprivation has on memory function, but it is good to get some hard data to back these up. Stanford University researchers have used a new technique which utilizes light to control the cells of the brain. From this they have teased out the finding that sleep which is broken up tends to lead to memory impairment in mice. The new method is called optogenetics, and it allows researchers to manipulate a single aspect of sleep. The study was head by Luis de Lecea, PhD, an associate professor of psychiatry and behavioral sciences at Stanford University, and H. Craig Heller, PhD, professor of biology.
What the study indicated that even if the mice got the same quantity of sleep, that a minimal amount of continuous sleep was essential for memory to consolidate.
Experts have long thought that sleep is essential to memory retention, but it has been very hard to actually study these effects in isolation, as to disturb an animals sleep also tends to lead to stressing of the animal which can cause the results to be potentially due to this. Stress itself has been shown to affect memory also. As well as this fact is the malleability of memory when other factors of sleep are changed including quality and composition (e.g. amount of time spent in each different phase of sleep).
In humans memory impairment is shown most clearly with people suffering from certain conditions such as alcoholism and sleep apnea. With optogenetics the researchers were able to genetically engineer specific cells such that they are then controlled by pulse of light. This was specifically targeted at the neurons which play an important part in going from waking to sleeping. With a 10 second burst of light, they were able to successfully fragment the sleep of the target organism, from their observations it looked like their total sleep, quality and composition of sleep was not changed.
How the memory was tested
The memory of the mice was tested by making them do a task, this involved putting them in a box with 2 objects, one new object and one which they had seen before. The rodent will tend to be more interested in the new object, so if they on average spend more time with the new object then, this suggests that they remember the other object. As expected the mice who had their sleep disrupted did not explore the novel object more, which the ones who had an uninterrupted sleep did explore the novel object.
Summary
This study suggest that it is important to not only get enough sleep, but also to ensure that the sleep is uninterrupted, to have good memory retention. This study probably has most implications for people who are suffering from sleep apnea because this can be very disrupted to a nights sleep.