A research team from the NIH (National Institutes of Health) from the United States managed to identify the neural circuits that are linked to the learning abilities and behavioral patterns of laboratory mice. Their study was recently published in the journal Nature Neuroscience; results showing that specific neural circuits in the forebrain are responsible for decision making and adaptive learning. According to the researchers, their findings provide better understanding of the processes of the brain that command and control the ability of mice to choose and adapt their behavior to certain situations. Furthermore, the research team believes that the results of the study might bring new insight on different compulsive behavior patterns, such as gambling, eating, drinking alcohol, and other obsessions.
Kenneth Warren, who is the main author of the study, and also the director of the NIAAA (National Institute on Alcohol Abuse and Alcoholism), explains that researchers need to understand much more information about the pathways that are involved in the learning of a behavioral response, versus the ability to switch the old behavioral with a new response that is better. He adds that the current study reveals novel information about the brain processes that take part in the behavioral response pathway and the way these processes can go off course.
Alcoholism, like other obsessions and addictions, is a disease in which patients progressively lose their behavioral control. This results in compulsive and other undesired actions. Researchers believe that the normal brain processes that are involved in the completion of daily activities become redirected towards the use and abuse of alcohol.
The research, which was conducted by the research team from the NIAAA, received support from the NIMH (National Institute of Mental Health) and from the University of Cambridge, from the United Kingdom. Researchers used a wide variety of techniques in order to better understand the processes behind choice. One of the techniques involved the use of a simple choice task. In order to perform this task, mice needed to touch specific images presented on a touchscreen computer display. If they touched the correct image, food would be awarded to them. Through the use of multiple imaging techniques, the research team visualized and recorded the neural activity of the tested mice. They learned that the consistency of choice was responsible for activating the dorsal striatum, which is a part of the forebrain. Thus, scientists believe that the dorsal striatum plays an important part in the neural pathways of decision-making, motivation, and reward.
Contrariwise, when the mice were taught to switch their image choice to a new one, in order to receive the food reward, the dorsal striatum stopped its activity. In response, other regions of the prefrontal cortex activated. In order to further investigate the results, the research team blocked a component of the NMDA receptor known as the GluN2B unit. This component is known to bind glutamate in two distinct areas of the brain: the frontal cortex and the striatum. Precedent studies revealed that the GluN2B unit plays a critical role in spatial reference, attention, and memory.
The research team discovered that if the GluN2B unit is inactivated in the dorsal striatal, the mice experienced slower learning capabilities. However, when inactivating the GluN2B unit in the prefrontal cortex, the mice were less able to re-learn the image required to receive the food reward, once the image was changed from the original one. According to the senior author of the study, professor Andrew Holmes, the information discovered in the study further adds data to the understanding of neural control, making the GluN2B unit a critical substrate for the processes of learning and behavioral flexibility.