Key brain area plays a crucial role in addiction

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New research finds that the cerebellum, a large part of the human brain that scientists thought was primarily involved in motor control, may play a key role in reward-seeking and social behaviors. The findings may help inform future therapies for treating addiction.

Recent research has hinted at the fact that, in addition to movement, the brain’s cerebellum may also help to control cognitive functions, such as language, learning, and attention.

Now, scientists at the Albert Einstein College of Medicine in Bronx, NY, suggest that this area could also regulate reward-processing and addiction.

Kamran Khodakhah, Ph.D., who is a professor and chair of the Dominick P. Purpura Department of Neuroscience at Einstein, led the new study. The scientists conducted the study in mice.

Prof. Khodakhah and his team published their results in the journal Science. Ilaria Carta, a doctoral researcher at Einstein, and Christopher Chen, Ph.D., are both first authors of the paper.

Why study the cerebellum?

Prof. Khodakhah and his colleagues were prompted in their research endeavor by more recent studies that have hinted at the cerebellum’s role in addiction and social interaction.

For instance, some studies have found that the cerebellum does not function properly in people with addictive behavior, autism spectrum disorder (ASD), cognitive affective syndrome, and schizophrenia.

Other MRI studies have shown that the cerebellum of people living with addiction is hyperactive in response to stimuli that their addiction relates to, such as an image of a syringe.

“The notion that the cerebellum did much beyond controlling movement was met with a lot of skepticism,” explains the study’s senior author, “and no one had any real clues as to how the cerebellum might affect dopamine release.”

Scientists have dubbed dopamine the “sex, drugs, and rock’n’roll” neurotransmitter due to its key role in reward-seeking behavior. When humans — or primates — receive a pleasurable reward, be it at the end of a learning process or for recreational purposes, their body releases the hormone.

Another brain area that scientists have implicated in reward processing is the so-called ventral tegmental area (VTA). So, in the current study, the scientists hypothesized that the neurons in the cerebellum would somehow communicate with the VTA neurons, which are responsible for releasing dopamine.

Using light to study neurons in mice

The scientists used optogenetics to test their hypothesis. Optogenetics is a technique in which scientists genetically modify neurons so that they respond to light.

By genetically inducing photosensitivity, the researchers could selectively activate the axons of the neurons in the cerebellum. By doing so, they wished to see how the neurons in the VTA would be affected.

A third of the VTA neurons fired in response to the stimulation of the axons, proving that the neurons in the cerebellum communicate with those in the VTA.

Next, the scientists wanted to see how, if at all, this interneuronal communication affected reward-seeking behavior. To examine this aspect, the researchers conducted a series of experiments in mice.

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