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About SickKids

April 19, 2007

Researchers find that neurons compete to become part of memory networks in the brain

TORONTO – Researchers at The Hospital for Sick Children (SickKids), Columbia University, UCLA, Harvard Medical School and University of California, Irvine have found that there is competition between brain cells during memory formation and that the expression of a particular protein is involved in the success of a brain cell becoming part of a given memory. This research is reported in the April 20 issue of Science.

Memories are thought to be created through the strengthening of connections between brain cells (neurons) to form a memory trace. Each memory is thought to be supported by a unique memory trace, involving different populations of neurons. Previous research showed that not all neurons in a given structure are needed to form or encode a given memory. In fact, these findings suggested that only a subset of neurons in a given structure were necessary to encode a particular memory.

“We wondered why one neuron, rather than its neighbour, seemed to be chosen for inclusion in a particular memory trace,” said Sheena Josselyn, SickKids scientist in Neurosciences & Mental Health, Canada Research Chair in Molecular and Cellular Cognition and assistant professor of Physiology at the University of Toronto. “Competition has previously been shown to be important during brain development, so we wondered whether competition occurred between neurons during memory formation in the adult brain.”

“Our findings show for the first time that competition between neurons occurs during memory formation. The ‘winner’ neurons form the memory trace whereas the ‘losers’ are excluded from the trace for that particular memory. Furthermore, we identified a particular protein, called CREB, which influence the outcome of this competition.”

The research team also found that increasing CREB function in roughly 20 per cent of neurons in a particular structure rescued the memory deficits in mice in which the CREB gene had been “knocked out”. Their next steps are to determine how many neurons are sufficient to encode a memory and to test other proteins that may also influence the outcome of neuronal competition during memory formation.

Over 30 million North Americans suffer from some type of clinically recognized learning or memory disorder, from inherited forms of mental retardation to the gradual weakening of memory with age or the ravages of Alzheimer’s disease. In order to develop new treatment or prevention strategies, the mechanisms underlying normal memory formation must be understood.

Members of the research team were Jin-Hee Han, Adelaide Yiu and Christy Cole from SickKids, Steven Kushner, Anna Matynia, Robert Brown and Alcino Sliva from UCLA, Rachael Neve of Harvard Medical School and John Guzowski of the University of California, Irvine.

This research was funded by the Canadian Institutes of Health Research, the National Institutes of Health and SickKids Foundation.

The Hospital for Sick Children (SickKids), affiliated with the University of Toronto, is Canada’s most research-intensive hospital and the largest centre dedicated to improving children’s health in the country. As innovators in child health, SickKids improves the health of children by integrating care, research and teaching. Our mission is to provide the best in complex and specialized care by creating scientific and clinical advancements, sharing our knowledge and expertise and championing the development of an accessible, comprehensive and sustainable child health system. For more information, please visit www.sickkids.ca. SickKids is committed to healthier children for a better world.

For more information, please contact:

Public Affairs
The Hospital for Sick Children
555 University Avenue
Suite 1742, Public Affairs, First floor Atrium
Toronto, ON
M5G 1X8
Phone: 416-813-5058
Fax: 416-813-5328