Scientists Stimulate Dreaming Sleep

"We were able to specifically stimulate an area of the brain responsible for rapid eye movement (REM) sleep, and therefore selectively increase the amount of dreaming sleep," says Dr. Brian Murray, senior author of a new study and sleep specialist and neurologist at Sunnybrook Health Sciences Centre. "This finding is significant for patients as it confirms, in principle, that we can selectively adjust different stages of sleep and this may make a big difference to sleep quality as well as other affected neurological functions and brain health."

This finding also has implication for further brain sciences research, providing tools to study learning and memory, and may be important for conditions such as stroke recovery and depression.

Previous research in this lab showed that PGO (Ponto-Geniculo-Occipital waves, or P waves) are the earliest sign of dreaming sleep in humans. The P waves are detected even before an electroencephalogram (EEG) test shows anything. These waveforms were recorded in patients who had electrodes in the brain during surgery for severe Parkinson's disease.

Recently published in Annals of Neurology, the journal of the American Neurological Association, the follow-up study allowed researchers to look at ways to increase the amount of dreaming sleep by stimulating the electrodes post-surgery, in order to potentially improve neurological function. "After surgery, the electrodes can be stimulated by a programmed device, like a pacemaker for the brain," says Dr. Murray.

The study involved five patients with severe Parkinson's disease, who were undergoing a neurosurgical procedure to help relieve symptoms of their disease. MRI scans helped sleep researchers determine the area they wanted to investigate. Electrodes were implanted 1.5 millimetres apart, into a specific area deep in the brain, localized as close as possible to the human P-wave source, within an incredible 3 millimetre area.

The dream waves were detected in a small area at the base of the centre of the brain called the pons, during REM sleep and just before it. "It's a difficult spot to reach," says Dr. Lim, lead author on the study, and a sleep fellow at Harvard, who did the work while at Sunnybrook and the University of Toronto.

"This is a particularly important finding for sleep researchers," adds Dr. Murray, who is also an assistant professor in the Division of Neurology at the University of Toronto. "We think this is the start of a stream of highly sophisticated work using deep brain recordings and stimulation to understand sleep, cognition, and various neurodegenerative disorders".

"This area of the brain is difficult to study, as a similar study in a healthy subject is ethically impossible. This was an excellent opportunity to investigate the area while a patient was undergoing a neurosurgical procedure for another reason," says Dr. Lim. "The fact that we not only found the fundamental waveforms of dreaming sleep but also managed to adjust REM sleep means we can look at how this affects many brain conditions and processes."

Sleep is known to be important for cognition, brain functioning, and overall health. The amount and quality of dreaming sleep is associated with mood disorders such as depression, and neurological conditions such as dementia. "With this research, we have envisioned a futuristic prosthesis where we can improve sleep and other neurological functions," says Dr. Murray.

This University of Toronto Division of Neurology collaboration included Movement Disorder Scientists at Toronto Western Hospital. Dr. Lozano, a neurosurgeon internationally known for his deep brain stimulation work, performed the surgical procedure to treat the patient's symptoms of Parkinson's Disease, and Sunnybrook's sleep experts conducted the sleep research work. Other collaborators include Drs. Moro, Hamani, Hutchison, Dostrovsky, Lang and Wennberg.