Neuroscientists from the University of California San Diego investigated the less understood aspects of dopamine impulses. They found that mice can willfully manipulate this "feel-good" brain chemical for reward.
Lead author, UCSD graduate student Conrad Foo found that the neocortex of mice is flooded with unpredicted dopamine impulses that occur once per minute instead of only occurring when presented with a reward, which is pleasurable.
Mice Learned to Elicit Dopamine Impulses Before Receiving A Reward
Working with colleagues from the university's Department of Physics and Section of Neurobiology and the Icahn School of Medicine at Mount Sinai in New York, Foo investigated whether mice are aware of dopamine impulses in their neocortex.
According to UC San Diego News Center, the team developed a feedback scheme that mice on a treadmill receive a reward to control the impromptu dopamine signals. The data revealed that mice are aware of these dopamine impulses and confirm that they also learn to anticipate and willingly act upon them.
"Critically, mice learned to reliably elicit (dopamine) impulses prior to receiving a reward," the researchers wrote in the paper. "These effects reversed when the reward was removed. We posit that spontaneous dopamine impulses may serve as a salient cognitive event in behavioral planning."
The team noted that the animal's spontaneous dopamine impulses could motivate or invigorate motor behavior, such as looking for food without reward-predictive stimuli.
The scientists said that their study opens a new door to study dopamine and how the brain works. They plan to extend their study to see how unpredictable dopamine could affect their foraging behavior, finding a mate, and social behavior in colonizing new home areas.
This study was a product of serendipitous findings that led to many long days on expanding the original research and performing controlled experiments to verify hypotheses that eventually led them to their current conclusions.
They published their study, titled "Reinforcement learning links spontaneous cortical dopamine impulses to reward," in Current Biology.
Dopamine: The Feel-Good Brain Chemical
Dopamine is a neurotransmitter that the nervous system uses to send messages between neurons, according to WebMD. Sometimes, it is also called the chemical messenger that plays a significant role in how humans feel pleasure. It is one of the unique traits of the human body's ability to think and plan to help them strive, focus, and look for things that interest them.
Dopamine is made in the brain by first changing the amino acid tyrosine to dopa and then transforming it into dopamine. It mainly affects behavior and physical functions, such as learning, motivation, heart rate, kidney function, sleep, mood, attention, pain, movement, and many more.
It is sent through four major pathways in the brain. But like most other bodily systems, it cannot be noticed until there is a problem. Too much or too little dopamine could signal problems in health. Some are serious, such as Parkinson's disease, while others are much less dire.
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