Brain Waves

Special Series: Brain Waves

Waves of Sleep

By David Kattenburg

Sleep is critical for human health. Poor sleep can have dire consequences. A good night’s shut-eye definitely helps us function better during the day. But why exactly? Only now are researchers beginning to connect the dots between brain plasticity and the healing powers of sleep.


Insomniacs are more than just lonely. Their brains are less flexible. A good night’s sleep re-wires grey matter and sheds chemical waste, boosting healthy brain activity in the day. For sleep to happen, night has to be dark and day bright. Patrice Bourgin studies the role of light in sleep regulation at the University of Strasbourg, in France.

Patrice Bourgin

Patrice Bourgin

“The role of light in sleep is very well known, to entrain the sleep-wake rhythm,” says Bourgin. “You will develop some synaptic plasticity; so, some new connections between neurons. And you can eventually erase neural circuits that you are not using so much.”

Sleep-wake cycling is controlled by a brain structure called the hypothalamus – with light input from the retina – and by the tiny pineal gland, which secretes the neurochemical melatonin. Together, they synchronize a host of clocks throughout the body.

Bourgin: “Food, for example; there is a food clock, and we’d be hungry at a certain time, and less at other times. And melatonin is going to act also on this clock.”

Brian Murray

Brian Murray

People who have trouble sleeping may visit a sleep disorder clinic. Brian Murray is director of the Department of Neurology & Sleep Medicine and Sleep Disorder Clinic at Sunnybrook Health Sciences Centre, in Toronto. “Eating too close to bedtime; not having a dark, quiet room; so light activates the retinal-hypothalamic tract in the brain, so if you’re looking at a light source or computer screen up close, it’s sending a signal to your brain to wake up! The opposite of what you want.”

Insomnia associated with bad “sleep hygiene” — or underlying physiological problems — is no fun. Everyone knows that wasted feeling, the day after a sleepless night of tossing and turning. Researchers are only beginning to understand the extent of the damage insomnia can cause. Fragmented sleep may amplify the effect of the Alzheimer’s gene, for example.

Dana Jewell

Dana Jewell, Sleep Disorder Clinic, Sunnybrook Hospital, Toronto

On the other hand, by promoting natural brain plasticity, solid sleep may stave off dementia, epilepsy and neurodegenerative disease. An average of eight hours of sleep each night is more than just restorative. It’s crucial for healthy brain function – especially as you grow old.