Rethinking traffic flow in the brain

Adela Talbot // Western News

Bruce Morton of Western’s Brain and Mind Institute, along with colleague Matthew Hutchison, has published a study showing the brain is not as hardwired as previously thought when performing learned tasks and solving familiar problems.

Think of a city road map. All the places you could possibly want to go – your home, your office, maybe the local coffee shop – are connected by roads. If you take the same road every time from, say, your home to the office, your actions would be in line with how neuroscientists generally regard human brain functions.

In other words, conventional thought has long maintained the human brain is ‘hardwired’ to perform particular tasks, accessing a fixed network of tools to solve problems, or enact certain behaviours, in a way that is largely the same among all individuals.

But Bruce Morton has disrupted this conventionality.

The Psychology professor and researcher at the Brain & Mind Institute, along with Western graduate Matthew Hutchison (now at Harvard University), recently published a study in the Journal of Neuroscience showing the brain is not hardwired. Instead, it is fluid in how it carries out everyday tasks.

Neuroscientists are interested in what areas of the brain are connected when you’re asked to perform Task X, Morton said.

“We like to think of it in terms of a metaphor – the brain as a city. Just like there are a bunch of destinations connected by roads, in the brain, there are a bunch of different areas connected by white matter fibre tracks. Just like traffic flows along the roads of the city to facilitate interactions between different locations, activity flows along these white matter fibre tracks when you (do Task X),” he explained.

Neuroscientists have long viewed these patterns of connectivity as fixed, meaning every time you do Task X, your brain accesses the same regions, in the same pattern, to carry out the action.

“Going back to the road metaphor, what was traditionally done (to study connectivity) is to lay down a rubber hose across the road, as it were, and over the course of, say, 48 hours, count how many cars run over that hose, along that road that connects one spot to another,” Morton continued.

This method generated an aggregate count of the number of messages sent along this particular pathway in the brain, and if that value exceeded a certain threshold, then neuroscientists concluded the two areas of the brain, connected by the road with the hose, are connected in the context of doing Task X.

“But (in this model), you’re getting a general, average picture of traffic flow, along a particular pathway, over time,” Morton noted.

Along with Hutchinson, Morton tested 51 individuals, ranging from 9-34 years of age, by asking them to complete tasks while scanning their brains in a functional magnetic resonance imaging (fMRI) scanner. After analyzing the scans, he found parts of the brain working to complete the tasks were constantly shifting and not simply ‘on’ or ‘off.’

“What we did instead (of the hose) is we set up a ‘video camera’ at the side of the road. We were able, not just to count the cars that passed, but we could also look at how the traffic flow changed over time,” he went on.

“If you were to imagine a camera by the roadside, you would see traffic in the morning flowing from the suburbs into the inner parts of the city. In the afternoon, traffic would be flowing in the opposite direction. During certain weather conditions, traffic would be flowing more slowly than on a sunny clear day, and on the weekends, the flow might be lighter than on weekdays,” Morton explained.

In case you aren’t following the metaphor anymore, his findings say traffic flow is as variable on city roads as the activity in human brains. The flow of traffic (or information) varies depending on the time of day or the road conditions – or, let’s say, the age and functionality of the brain.

“Traffic flow isn’t a static thing. Neither is information flow in the brain. If you study it the way we have, that allows for characterizing the changes of information flow,” Moron added.

“All of a sudden, the picture of the brain as somehow fixed or hardwired in terms of its functional configuration, is displaced by an idea that the flow of information in the brain is highly dynamic, and it changes in a principled way as a function of what it is the person is doing.”

Morton’s study raises new and counterintuitive questions, for instance, asking what is happening in a child’s brain as it develops.

“It turns the standard of understanding developmental change on its head. The idea, to this point, has been over the course of experience and repeated learning, the brain converges on a particular way of doing a problem. So, as you get older, the idea is, these patterns of connectivity will become increasingly hardwired, or burned into the circuitry of our mind,” he explained.

This means you would expect children to show more variability, as compared to adults. But what Morton and Hutchinson found was the opposite. The patterns of information flow in children were much more fixed. So, as the individual learns and the brain develops, the brain access increasingly different regions in performing the same task or solving the same problem.

“This (approach) is relatively new and ours is among the highest impact papers that have adapted this approach. We’re excited about it; it’s really new, from a developmental standpoint,” Morton said.