MONDAY, 8 FEBRUARY 2016
Researchers in the groups of Associate Professors Nicole Calakos and Henry Yin trained mice to develop sugar habits by letting them pressing a lever which delivered tiny sweet pellets. The mice formed the habit to different extents, with addicted individuals continuing to press the lever even after the sweets stopped appearing.
Electrical activity in the brains of mice which had formed a habit was compared to that of mice which had not. The investigation focused in particular on the basal ganglia, an area of the brain responsible for controlling motor actions and compulsive behaviours. In this area, there are two neuronal pathways that transmit opposing ‘go’ and ‘stop’ signals which promote and prevent actions, respectively. New labelling strategies allowed the scientists to visualize the activity of dozens of neurons at the same time and so enabled the study of both pathways simultaneously.
Surprisingly, the experiments showed that both the ‘go’ and ‘stop’ pathways were activated strongly in the sugar-habit mice. Furthermore, in the non-habit mouse brains the ‘stop’ signal occurred first. In contrast, the neuronal circuitry of mice with habits was changed so that the ‘go’ signal was activated before the ‘stop’ message. Now the scientists are investigating whether this head start makes the animals more likely to engage in the habitual behaviour. They also demonstrated that the mice with relatively weaker ‘go’ pathways could unlearn the lever pressing behaviour more successfully.
The Duke University researchers hope that findings like these will one day lead to more effective medical treatments for conditions such as addiction or obsessive-compulsive disorder.
Written by Raghd Rostom