A recent study demonstrates how the brain converts motivation into action that is goal-oriented.

An animal's drive to successfully pursue a goal—finding and hunting for food—can be fueled by hunger.

Researchers from the University of Alabama at Birmingham and the National Institute of Mental Health, or NIMH, have published a highly innovative study in Current Biology that explains how two major neuronal subpopulations in the paraventricular nucleus, a region of the brain's thalamus, contribute to the dynamic regulation of goal pursuits. This study sheds light on the processes by which the brain monitors motivational moods to influence instrumental behavior.

In order to conduct the study, the mice had to be taught in a behavior similar to foraging utilizing a long, hallway-style enclosure with a reward zone located more than four feet from one end and a trigger zone at the other.

The mice were trained to wait two seconds in a trigger zone before beginning their behavioral activity, which was similar to foraging, when they heard a beep. After that, a mouse might go at its own speed to the reward zone where it would be given a tiny sip of Ensure with a strawberry flavor. The mice had to exit the reward zone and head back to the trigger region in order to wait for another beep in order to end the trial. Mice demonstrated rapid learning and high levels of engagement during training by finishing a significant number of trials.

The activity of two major neuronal subpopulations of the paraventricular nucleus, or PVT, was then continuously monitored by the researchers using optical photometry and the calcium sensor GCaMP during the reward approach from the trigger zone to the reward zone and during the trial termination from the reward zone back to the trigger zone following a taste of strawberry-flavored food. In order to quantify calcium release, an indication of neural activity, an optical fiber is inserted into the brain approximately at the point of visual threshold.

The paraventricular nucleus's two subpopulations, denoted as PVTD2(+) or PVTD2(–), respectively, are distinguished by the dopamine D2 receptor's presence or absence. A chemical called dopamine facilitates communication between neurons.

"We found that the execution and termination of goal-oriented actions are encoded by PVTD2(+) and PVTD2(–) neurons, respectively," co-corresponding author of the paper Sofia Beas, Ph.D., an assistant professor in the UAB Department of Neurobiology, remarked. "Furthermore, activity in the PVTD2(+) neuronal population mirrored motivation parameters such as vigor and satiety."