Many people like to think they can multitask, but they probably can’t – at least not effectively. As Cosmos has reported previously, neither gender is very good at it.
The reality is that despite the brain’s remarkable flexibility and billions of neurons, it struggles to do more than one thing at a time – and trying to make it do more can cause problems.
“Multitasking costs the global economy an estimated $450 billion annually in lost productivity and has also been estimated to triple error rates in busy environments, such as when busy doctors make medical decisions,” says psychologist Kelly Garner from Australia’s University of Queensland.
There is an upside, however. Garner and colleagues say they have discovered a missing piece in the brain’s efforts to multitask and showed that practice can mitigate its limitations.
The neural networks involved in multitasking were previously linked with the brain’s extensive outer layer – the neocortex – but Garner says there are lots of theoretical reasons to believe deeper brain structures such as the striatum are involved.
Her team tested this idea by investigating how “coupling” between the neocortex and striatum changes with multitasking and how it might improve with practice.
“Coupling can be thought of as how activity in one brain region affects the rate of change in the activity of its coupled brain region,” she explains. “We take this as a proxy of the extent to which two brain regions could be sharing information with each other.”
The researchers recruited 100 volunteers to familiarise them with computerised motor-sensory tasks which they then performed while being scanned with functional magnetic resonance imaging (fMRI) before and after a week of solid practice on 3000 trials.
Half were instructed to use their middle or index finger on one hand to press a button when they saw one of two shapes and from the other hand if they heard one of two tones, either separately (single task) or together (multitask). The rest performed a different, complex task not expected to require multitasking performance.
Then the researchers applied modelling to quantify how much coupling changes between brain regions within the neocortex or between the striatum and neocortex.
Multitasking consistently recruited connectivity between the outer and inner brain regions, specifically the putamen in the striatum, and the extra cost of doing this was reduced after practice.
The team suggests impaired performance on more than one task can be at least partly attributed to the speed at which the putamen can communicate with the relevant cortical areas, although Garner says this is just one piece of a bigger puzzle.
“[T]his is just an early snapshot on the consequences of long term learning,” she says, “and it is likely that there are many more brain changes to be observed as people practise a skill or task over months and years.”
The research is published in the journal eNeuro.
Natalie Parletta is a freelance science writer based in Adelaide and an adjunct senior research fellow with the University of South Australia.
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