Fragmented sleep can affect memory formation

"Sleep continuity is one of the main factors affected in various pathological conditions that impact memory including Alzheimer`s disease and other age-related cognitive deficits," said Dr Luis de Lecea, who led a team at Stanford University which carried out the study.
 
Researchers have, in fact, based their findings on an analysis of laboratory rodents, the findings of which are published in the latest edition of the `Proceedings of the National Academy of Science` journal.
 
In their study, the researchers found disrupting sleep made it harder for the animals to recognise familiar objects. This study looked at sleep that was fragmented, but not shorter or less intense than normal for the mice. It used a technique called optogenetics, where specific cells are
genetically engineered so they can be controlled by light.
 
The researchers targeted a type of brain cell that plays a key role in switching between the states of being asleep and being awake. They then sent light pulses directly into the brains of mice while they slept.
 
This meant they could disrupt their sleep without affecting total sleep time or the quality or composition of sleep. The animals were then placed in a box with two objects, one of which they had encountered before.
 
Mice would naturally spend more time examining the newer object, and those who had been allowed uninterrupted sleep did just that. But those whose sleep had been disrupted were equally interested in both objects, suggesting their memories had been affected.

Broken sleep also affects people addicted to alcohol, and those with sleep apnoea - a condition in which the throat repeatedly narrows or closes during sleep, restricting oxygen and causing the patient to wake up.
 
The researchers add there is no evidence of a causal link between sleep disruption and any of these conditions.
 
But they added: "We conclude that regardless of the total amount of sleep or sleep intensity, a minimal unit of uninterrupted sleep is crucial for memory consolidation."
 
An expert, Dr Neil Stanley, a former chairman of the British Sleep Society, was quoted by the `BBC` as saying, "During the day, we accumulate all these memories. At some point we have to sort through what`s happened during the day.
 
"There are some things that we need to `lock down` as a permanent hard memory. That process occurs in deep sleep. So anything that affects sleep will have an effect on that process to a greater or a lesser extent."
 
He added that people with Alzheimer`s often had trouble sleeping, but said: "There is something there. But whether it`s the degeneration of the brain that causes poor sleep, or poor sleep that aids the degeneration of the brain has not been determined."