A study published in Neuron, a prominent neuroscience journal, shows a promising connection between habit formation and the endocannabinoid system (ECS). The research was led by Christina Gremel, an assistant professor of physiology at the University of California San Diego.
The study showed that endocannabinoids, which are neurochemicals in our body that are similar to cannabinoids found in cannabis, allow us to form habits—meaning, our bodies switch over from what was once a goal-directed, or brand new, action to a habit, an automatic routine or practice performed many times, such as brushing our teeth. It was already known that the ECS plays a role in many parts of our bodies’ inner workings, but this study shows a new breakthrough in how important the endocannabinoid system is to our overall body function.
The Orbital Frontal Cortex’s Role in Habitual vs. Goal-Directed Actions
Earlier research by Gremel focused on the orbital frontal cortex (OFC), which is the part of the brain involved in the cognitive processing of decision-making and is important for relaying information related to goal-directed actions. When researchers increased the number of output neurons in the OFC using optogenetics—flashes of light that turn receptors on and off in the brain, they found that goal-directed action increased. When they decreased neuron outputs, the OFC was subdued and habit took over.
This previous research served as a base for the understanding of how the OFC is connected to habit formation and goal-directed actions. And it proved to be an important component in the more recent study that shows the connection between the ECS and habit formation.
Endocannabinoids May Allow Habits to Form
The study related to the ECS was conducted using trained mice, which pushed a lever for a food reward. Researchers placed the mice in two different environments, one that involved goal-directed action and the other that involved a habitual activity.
The mice were able to switch between the two environments with relative ease, much like a human can switch between habitual action and a new task they set out to do—for example, the difference between the habit of getting home or the goal-directed action of navigating to a new location not previously known.
The researchers hypothesized that cannabinoids—known to reduce neuron activity in general—may be responsible for quieting the OFC, therefore, allowing habit to take over in the brain.
To test this hypothesis, researchers deleted the CB1 receptor in the orbital frontal cortex-to-striatum pathway. Mice missing the CB1 receptors weren't able to form habits, showing the critical connection between the ECS and the neurochemicals that travel along the pathway. It can be concluded from this study that without the ECS stimulated by internal cannabinoids, the repercussions could be great, because the ability to form habits is then blocked.
“We need a balance between habitual and goal-directed actions. For everyday function, we need to be able to make routine actions quickly and efficiently, and habits serve this purpose,” said lead researcher Gremel. “However, we also encounter changing circumstances, and need the capacity to ‘break habits’ and perform a goal-directed action based on updated information. When we can’t, there can be devastating consequences.”
This study could prompt exploration into a new therapeutic use for marijuana for people with obsessive compulsive disorder (OCD) or addiction problems. If the endocannabinoid system is deeply rooted in habit forming, it could aid in decreasing the over-reliance on a particular habit. The body's own endocannabinoid system may need to be treated in some way to restore the ability to shift from habits to goal-directed action.
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