Our UHN programs and services are among the most advanced in the world. We have grouped our physicians, staff, services and resources into 10 medical programs to meet the needs of our patients and help us make the most of our resources.
University Health Network is a health care and medical research organization in Toronto, Ontario, Canada. The scope of research and complexity of cases at UHN has made us a national and international source for discovery, education and patient care.
Our 10 medical programs are spread across eight hospital sites – Princess Margaret, Toronto General, Toronto Rehab’s five sites, Toronto Western – as well as our education programs through the Michener Institute of Education at UHN. Learn more about the services, programs and amenities offered at each location.
Maps & Directions
Find out how to get to and around our nine locations — floor plans, parking, public transit, accessibility services, and shuttle information.
Ways You Can Help
Being touched by illness affects us in different ways. Many people want to give back to the community and help others. At UHN, we welcome your contribution and offer different ways you can help so you can find one that suits you.
The Newsroom is the source for media looking for information about UHN or trying to connect with one of our experts for an interview. It’s also the place to find UHN media policies and catch up on our news stories, videos, media releases, podcasts and more.
Deep brain stimulation (DBS) is being explored as a treatment for individuals with Alzheimer's disease.
Researchers have previously shown that stimulation applied to the fornix – a memory-related structure located deep in the brain – can cause vivid flashbacks of old memories and events in some, but not all, individuals with Alzheimer's disease. The occurrence of flashbacks suggests that the stimulation is activating brain circuits involved in memory recall.
"It is a mystery why only certain individuals experience these flashbacks – especially considering that the fornix is stimulated in everyone who undergoes the procedure," says Krembil Senior Scientist Dr. Andres Lozano, who led a recent study that has shed new light on how DBS causes flashbacks.
DBS involves the use of surgically implanted electrodes to stimulate specific regions of the brain. DBS has been successfully used to reduce the symptoms of certain neurological conditions, including tremors in Parkinson's disease.
In this study of DBS for Alzheimer's disease, DBS electrodes are implanted to stimulate the fornix.
Although the fornix is the main target in this type of DBS, other brain structures are likely activated at the same time due to the placement of the electrodes. Lozano's team suspected that this effect, which would vary between patients, may be the key to why only certain patients experience flashbacks.
The researchers examined scans from 39 individuals with mild Alzheimer's disease who previously participated in a clinical trial of fornix DBS to reduce memory impairment. Using computer modeling of the connections between different brain regions, the team identified three structures involved in flashbacks. They found that flashbacks were associated with stimulation of the fornix, the anterior commissure (a collection of nerve fibres that connects the two halves of the brain), and the bed nucleus of the stria terminalis (a part of the brain's emotion and memory circuits).
Patients were more likely to experience flashbacks when electrodes were placed in such a way that they stimulated these three regions. This finding provides further evidence that these deep brain structures make up an important memory-related circuit.
"Our findings reveal the areas of the brain where electrical stimulation produces DBS-induced memory recall, in approximately half the patients," says Dr. Lozano. "By demonstrating the importance of stimulating different, yet connected brain regions with DBS, these results improve our understanding of the brain circuits involved in memory.
"This information will help us to refine the DBS procedure so it has the greatest therapeutic impact for people with Alzheimer's disease, and perhaps other forms of dementia."
This work was supported by the Canadian Institutes of Health Research, the German Research Foundation and the Toronto General & Western Hospital Foundation. A Lozano is the RR Tasker Chair in Functional Neurosurgery.
Read more about the study