http://www.sciencedaily.com/releases/2016/01/160121130015.htm

In organismal relations — precedence matters. Whatever comes first has a distinct advantage in getting sustained… especially under unnatural or stressful circumstances.

“The researchers then compared the brains of mice that had formed a habit to the ones that didn’t. In particular, the team studied electrical activity in the basal ganglia, a complex network of brain areas that controls motor actions and compulsive behaviors, including drug addiction.

In the basal ganglia, two main types of paths carry opposing messages: One carries a ‘go’ signal which spurs an action, the other a ‘stop’ signal.

Experiments by Duke neurobiology graduate student Justin O’Hare found that the stop and go pathways were both more active in the sugar-habit mice. O’Hare said he didn’t expect to see the stop signal equally ramped up in the habit brains, because it has been traditionally viewed as the factor that helps prevent a behavior.

The team also discovered a change in the timing of activation in the two pathways. In mice that had formed a habit, the go pathway turned on before the stop pathway. In non-habit brains, the stop signal preceded the go.

These changes in the brain circuitry were so long-lasting and obvious that it was possible for the group to predict which mice had formed a habit just by looking at isolated pieces of their brains in a petri dish.”