Chris Eliasmith, director of the Centre for Theoretical Neuroscience, Waterloo. Photo: University of Waterloo, Communications & Public Affairs
Researchers at the University of Waterloo have built the world’s largest simulation of a functioning brain. The model is named Spaun, which stands for Semantic Pointer Architecture Unified Network. A computer model made of 2.5 million simulated neurons, the brain can think, remember and interact with its environment.
In addition, Spaun can capture the biological details of each neuron, including which neurotransmitters are used, how voltages are generated in the cell, and how they communicate. Spaun uses the neural network to process visual images in order to control an arm that draws the brain’s answers to perceptual, cognitive and motor tasks.
What’s unique about the brain model is that it can perform several tasks. Researchers can present the brain with various patterns of digits and letters, through the model’s eye, and it will process the information and then write its response to any of eight tasks. Just like the human brain, Spaun shifts from task to task, recognizing an object one moment and memorizing a list of numbers the next. Because of its biological foundation, Spaun can also be used to understand how changes to the brain affect changes to behaviour.
The team’s research, published recently in the journal Science, can help scientists and other researchers understand how the complex activity of the brain is linked to complex behavior in humans and animals.
“This is the first model that begins to get at how our brains can perform a wide variety of tasks in a flexible manner—how the brain coordinates the flow of information between different areas to exhibit complex behaviour,” said professor Chris Eliasmith, director of the Centre for Theoretical Neuroscience at Waterloo. He is also Canada Research Chair in Theoretical Neuroscience, and a professor in Waterloo’s department of philosophy and department of systems design engineering.
“In related work, we have shown how the loss of neurons with aging leads to decreased performance on cognitive tests,” said Eliasmith. “More generally, we can test our hypotheses about how the brain works, resulting in a better understanding of the effects of drugs or damage to the brain.”
In addition, the model provides insight into the sorts of algorithms that might be useful for improving machine intelligence. For instance, it suggests new methods for controlling the flow of information through a large system attempting to solve challenging cognitive tasks.
Professor Eliasmith has written a book on the research. “How To Build A Brain” will be on shelves this winter. Videos on the project are at http://nengo.ca/build-a-brain/spaunvideos.
