Many forms of behaviour require our attention and conscious thinking. However, we all have our habits; things we have gotten used to and which are performed on 'auto-pilot'. Once we have gotten accustomed to certain patterns of behaviour, our conscious brain is no longer needed, and it can be 'used' for other purposes. It is quite peculiar that habituation helps us to 'relieve' us from conscious control, which is why neurologists from MIT set out to discover what actually happens in our brain.
In order to simulate the human situation of acquiring a habit, the researchers let a group of rats run through a maze. By giving them rewards, the rats quickly learned to find their way through the maze, something that was soon turned into a habit: they always choose the same way, regardless of the presence of a reward. This was shown by switching the reward to chocolate milk mixed with a substance known to cause nausea: the rats still took the same route through the maze, but they did no longer consume the reward at the end.
Breaking the habit
In order to assess whether the 'conscious' brain is involved with conducting habitual behaviour, a specific area of the prefrontal cortex was shut off. This particular brain area, known as the infralimbic cortex, is involved with instituting habits, but it was previously thought that it releases control once a particular form of behaviour becomes a habit. The MIT researchers sought to test this hypothesis by analyzing the effect on the rats' maze navigation behaviour once this particular brain area was no longer active.
As soon as the infralimbic cortex was shut down, the scientists noted that the rats no longer took the same old route through the maze. Apparently, this particular brain area not only helps by creating habits, but also keeps them alive. According to the researchers, shutting down the infralimbic cortex stops the reflexive patterns associated with habitual behaviour, thereby enabling the brain to adopt a new habit. This is also what the MIT scientists noted: after turning the infralimbic cortex off, the rats soon adopted a new habit of running through the maze. Again, this could be stopped by issuing another blockade in the infralimbic cortex.
This study shows that there is a brain part that functions as a control center when performing habitual behaviour. Because it is part of the brain area that governs conscious behaviour in humans, it means habits are not pure muscle memory. There is a form of residual control that also ensures that old habits do not quickly disappear.