- MIT researchers identify brain region that controls habitual behaviours
- They find old habits never go away, but can be replaced with new ones
- However, the potential to switch back to the old behaviour remains
By Damien Gayle
PUBLISHED: 07:23 EST, 2 November 2012 | UPDATED: 07:23 EST, 2 November 2012
Old habits die hard, so the saying goes – but they may be overridden, suggests a new study which raises hopes for the treatment of obsessive behaviours.
Scientists have identified a brain region which can switch us between new and old habits, raising questions about how automatic habitual behaviours really are.
Habits are wired so deeply in our brains that we perform them automatically, such as getting to work each day. This frees up the brain to think of other things – like what to have for dinner.
But MIT scientists say that the brain does not completely relinquish control of habitual behaviour. A small region of the prefrontal cortex, where most thought and planning occurs, is responsible for moment-by-moment control of which habits are switched on at a given time.
‘We’ve always thought – and I still do – that the value of a habit is you don’t have to think about it. It frees up your brain to do other things,’ said Professor Ann Graybiel of MIT’s McGovern Institute for Brain Research.
‘However, it doesn’t free up all of it. There’s some piece of your cortex that’s still devoted to that control.’
The research suggests that bad habits, however deeply ingrained, could be overidden by the brain’s planning centres. This could lead to possible intervention in those suffering from conditions such as obsessive compulsive disorder.
Dr Kyle Smith carried out on tests on rats in which the rodents were placed in a T-shaped maze. As the rats approached the decision point, they heard a tone indicating whether they should turn left or right.
When they chose correctly, they received a reward — chocolate milk for turning left or sugar water for turning right.
Even when researchers removed the rewards the rats eventually responded to the tones in the same way, showing the behaviours had become fully ingrained.
And when the reward for turning left correctly was spiked with a substance that made the rats sick, they would still turn left when cued to do so – but simply not consume the fluid.
The team then altered part of the prefrontal cortex known as the infralimbic (IL) cortex, which is needed for habitual behaviour to develop.
THE MICE WITH WINDOWS STITCHED INTO THEIR BELLIES
If you think giving rats a drink to make them sick to investigate habits is a little cruel, spare a thought for these unfortunate rodents.
Scientists investigating the spread of cancer cells surgically implanted windows into the bellies of live mice.
The glass portholes stitched directly into the rodents’ abdominal walls are intended to help researchers track how cancer cells spread to form secondary tumours.
Dutch researchers surgically removed a section of a mouse’s abdominal wall altogether and replaced it with a tiny glass pane about half an inch wide surrounded by a biocompatible titanium ring.
‘It’s just like a window in a ship or a plane,’ Dr Jacco van Rheenen of the Hubrecht Institute for Developmental Biology and Stem Cell Research in the Netherlands told New Scientist.
Tightly stitched to the skin and abdominal wall, the windows reportedly did not impair the rodents’ movements and they caused no signs of infection and inflammation.
However, in just over one in 50 cases the glass panes did break, with presumably grisly consequences.
Where this did not occur, the windows remained in place for an average of five weeks before the stitches loosened, giving the Hubrecht Institute team plenty of time to record their findings.
Using optogenetics, a technique that allows researchers to inhibit specific cells with light, they turned off IL cortex activity for several seconds as the rats approached the point in the maze where they had to decide which way to turn.
Almost instantly, the rats dropped the habit of running to the left, the side with the now nauseating reward.
This suggests that turning off the IL cortex switches the rats’ brains from an ‘automatic, reflexive mode to a mode that’s more cognitive or engaged in the goal – processing what exactly it is that they’re running for,’ Dr Smith said.
Once broken of the habit of running left, the rats soon formed a new habit, running to the right side every time, even when cued to run left.
The researchers showed that they could break this new habit by once again inhibiting the IL cortex with light.
To their surprise, they found that these rats immediately regained their original habit of running left when cued to do so.
‘This habit was never really forgotten,’ Dr Smith said. ‘It’s lurking there somewhere, and we’ve unmasked it by turning off the new one that had been overwritten.’
Professor Graybiel said that the findings showed the IL cortex is responsible for determining, moment-by-moment, which habitual behaviours will be expressed.
She said: ‘To us, what’s really stunning is that habit representation still must be totally intact and retrievable in an instant, and there’s an online monitoring system controlling that.’
Jane Taylor, a professor of psychiatry and psychology at Yale University, who was not part of the research team, said the study also raises interesting ideas concerning how automatic habitual behaviours really are.
‘We’ve always thought of habits as being inflexible, but this suggests you can have flexible habits, in some sense,’ she added.
Professor Graybiel said it would be too invasive to use the same techniques to break habits in humans but the technology could one day evolve to a point where it could be used to treat compulsive or addictive behaviour.
The teams findings were reported in the journal Proceedings of the National Academy of Science.
Read more: http://www.dailymail.co.uk/sciencetech/article-2226848/Old-habits-die-hard–overwritten-New-study-raises-hopes-treatment-obsessive-behaviours.html#ixzz2B8H8H9r1