Multi-tasking keeps the brain young

It may not come as too much of a surprise, but multi-tasking, or doing more than one thing at a time, takes more effort as we get older. More encouragingly, however, engaging in such multi-tasking, especially a combination of physical and mental activities, may help to ward off the cognitive declines associated with old age.

These are the conclusions of a study conducted by US and Japanese researchers led by Hironori Ohsugi at Seirei Christopher University in Shizuoka and published in BMC Neuroscience. Ohsugi and his team used NIR spectroscopy to monitor oxygenated haemoglobin levels, as a measure of brain activity, in the prefrontal cortex of 20 young people (aged 21‒25) and 15 elderly people (aged over 65) as they performed a physical and mental task, either in isolation or at the same time. The physical task involved stepping in place with each foot, while the mental task involved counting back from 100 in sevens.

The prefrontal cortex is associated with memory, attention and many higher cognitive functions, and is the area of the brain first affected by age-related changes, explaining why memory and attention are some of the first cognitive functions to decline as we age. Ohsugi found that oxygenated haemoglobin levels were similar in both young and elderly people when performing each task on its own, with the levels only rising when performing the mental task. When performing both tasks at the same time, however, the levels were higher in the elderly people and persisted for a longer period of time than in the young people.

This suggests that the elderly people found it more difficult than the younger people to perform both tasks at the same time, requiring more brain activity. 'From our observations during the dual task it seems that the older people turn their attention to the calculation at the expense of the physical task, while younger people are able to maintain concentration on both,' says Ohsugi. 'Since our subjects were all healthy it seems that this requirement for increased activation of the prefrontal cortex is part of normal decrease in brain function associated with aging.'

Although the finding that we find certain mental activities more difficult as we get older is rather depressing, there is a silver lining. Previous research has shown that increased activity in the pre-frontal cortex can help to prevent age-related changes in the brain. So the trick seems to be to keep on multi-tasking, particularly once it starts to become more difficult.