What’s New in Psychology?

Do Humans and Animals Have Control Over Dopamine Impulses?

Jim Windell

          Dopamine is the neurotransmitter that mediates pleasure in the brain. It is released during pleasurable situations – for instance, when you are eating a chocolate fudge sundae on a hot summer day or during sex – and motivates us to continue to seek out those activities we enjoy.

           Known as the brain's “feel good” chemical, dopamine has been extensively studied – often in terms of reward and pleasure.  

           However, University of California San Diego researchers set out to investigate less understood aspects related to spontaneous impulses of dopamine. The results of their investigation was recently published in the journal Current Biology.

           Conrad Foo, a UC San Diego graduate student, led the research that found that the neocortex in mice is flooded with unpredictable impulses of dopamine that occur approximately once per minute. But, Foo and his colleagues at UC San Diego Department of Physics and Section of Neurobiology and the Icahn School of Medicine at Mount Sinai in New York, asked a question: Are mice in fact aware that these dopamine impulses are actually occurring?

          The researchers already had documented in the lab through molecular and optical imaging techniques the ubiquitous nature of dopamine impulses. So, Foo and his associates devised a feedback scheme in which mice on a treadmill received a reward if they showed they were able to control the impromptu dopamine signals.

          Data from the study revealed that not only were mice aware of these dopamine impulses, but the mice could learn to anticipate and volitionally act upon a portion of them. In other words, it was found that mice could willfully manipulate these random dopamine pulses.

          The researchers note in their article that “Critically, mice learned to reliably elicit (dopamine) impulses prior to receiving a reward…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 researchers say the study opens a new dimension in the study of dopamine and brain dynamics. They now intend to extend this research to explore if and how unpredictable dopamine events drive foraging, which is an essential aspect of seeking sustenance, finding a mate and as a social behavior in colonizing new home bases. They added that, “We further conjecture that an animal's sense of spontaneous dopamine impulses may motivate it to search and forage in the absence of known reward-predictive stimuli.”

          In their efforts to control dopamine, the researchers explained that dopamine appears to invigorate, rather than initiate, motor behavior.

        “This started as a serendipitous finding by a talented, and curious, graduate student with intellectual support from a wonderful group of colleagues,” said study senior co-author David Kleinfeld, a professor in the Department of Physics (Division of Physical Sciences) and Section of Neurobiology (Division of Biological Sciences). “As an unanticipated result, we spent many long days expanding on the original study and of course performing control experiments to verify the claims. These led to the current conclusions.”

         Although it is too soon to say what the impact of this finding might have on humans and their ability to manipulate dopamine impulses, it may suggest that we might be able to regulate dopamine secretions to a larger extent than ever before realized.

         To read the original article, find it with this reference:

 Foo, C., Lozada, A., Aljadeff, J., Li, Y., Wang, J.W., Slesinger, P.A. & Kleinfeld, D. (2021).  Reinforcement learning links spontaneous cortical dopamine impulses to reward. Current Biology; DOI: 10.1016/j.cub.2021.06.069