Canadian researchers have built what they called "the world's largest simulation of a functioning brain," which may help scientists better understand how the brain works.

The researchers from the University of Waterloo published their findings in this week's issue of Science journal.

The model, called Spaun, runs in computers. It consists of 2.5 million simulated neurons and captures biological details of each neuron, including which neurotransmitters are used, how voltages are generated in the cell, and how they communicate, the researchers said.

Spaun uses this network of neurons to process visual images, and then uses a physically modeled arm to show answers in eight perceptual, cognitive and motor tasks, they said.

For example, when Spaun is presented the image of a numeral, it can reproduce the visual features of the number from memory and repeat a series of numbers back in order. It can also perform reinforcement learning, in which it changes its behavior based on probabilistic rewards from the environment.

"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 behavior," said Professor Chris Eliasmith, director of the Center for Theoretical Neuroscience at Waterloo.

The researchers hope that Spaun can also be used to understand how changes to the brain affect changes to behavior.

"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," he added.