We’ve all had those sleepless nights filled with endless tossing and turning, no shuteye in sight. For 3 to 5 per cent of the population, insomnia is a nightly struggle that takes over their lives. Its causes and consequences remain elusive, but recent MRI scans suggest a connection between the sleeping disorder and abnormalities in brain communication networks.
In a recent study of insomniacs published online in Radiology, researchers from the Department of Medical Imaging at Guangdong No. 2 Provincial People’s Hospital in Guangzhou, China, found reduced white matter in the thalamus, which regulates consciousness, sleep, and alertness, and in the limbic system, which supports functions like emotion, behaviour, motivation, long-term memory, and olfaction.
“White matter tracts are bundles of axons — or long fibres of nerve cells — that connect one part of the brain to another,” said co-author Shumei Li in a press release. She added: “If white matter tracts are impaired, communication between brain regions is disrupted.”
Li and her colleagues recruited 23 primary insomnia patients — those whose sleeplessness is not attributable to a medical, psychiatric, or environmental cause — and 30 healthy controls. All the participants answered questionnaires about the quality of their sleep and their levels of anxiety and depression. They also underwent an MRI scan with a specialized technique called diffusion tensor imaging, which helps researchers analyse the pattern of water movement along white matter tracts to identify abnormalities in communication networks.
The findings revealed that insomnia patients had significantly reduced white matter integrity in several parts of the right brain, including the body corpus callosum — the largest white matter structure of the brain — and the right thalamus. Researchers linked the reduced activity of the body corpus callosum to more severe insomnia and depression scores in the patients.
“The involvement of the thalamus in the pathology of insomnia is particularly critical, since the thalamus houses important constituents of the body’s biological clock,” said Li.
The pineal body, which secretes the sleep hormone melatonin, controls the body’s biological clock. However, it takes its orders from the thalamus, so an abnormality in there disrupts melatonin release, keeping the brain constantly “on.”
Dr Lisa Fairweather, a psychiatrist in Colleyville, Texas, uses a car analogy to explain how the brain acts in patients who have difficulty sleeping.
“The brain is like a car with the engine of a Ferrari but the brakes of a bicycle. It performs extremely well switching gears and racing forward, but it suffers from an ability to slow down. This can be most obvious during bedtime,” she told Medical Daily.
Researchers suspect the underlying cause of the abnormal white matter connections may be loss of myelin, which protects the brain’s circuitry, shielding axons and speeding electrical impulses along nerve fibres. Sleep helps produce cells that make myelin, so sleepless insomniacs may be losing myelin.
Previous brain imaging studies have linked primary insomnia to brain abnormalities in young and middle-aged adults. A 2008 paper found that patients who have primary insomnia for more than six months showed a 30 per cent reduction in gamma-amino butyric acid, whose purpose is to decrease overall activity in many areas of the brain, helping to shut it down, especially when it’s time to sleep. This could be why insomniacs commonly complain that their minds keep racing and won’t quiet down at night.
This constant “on” state is one of hyper arousal, with unusually high levels of cortisol, metabolic activity, and sympathetic activity when insomniacs are both awake and asleep, according to Dr David Brown, a sleep psychologist at the Children’s Medical Center in Dallas.
Brown believes the biggest problem with insomnia is that it is not a single entity.
“There are many types of insomnia and many different causes. Insomnia severity may be short lived and acute, or chronic,” he told Medical Daily. “Some insomnias show difficulty falling to sleep, some have difficulty staying asleep, some wake too early and cannot get back to sleep.”
While the sleeping disorder continues to plague the general population, research to clarify the relationship between the brain and insomnia still remains in its infancy.
Source: Medical Daily