For release: Wednesday, May 4, 2005
A new study sheds light on how people quickly learn associations such as “stop at red” or “go at green”. This study challenges the current view of how specific brain areas help us learn rules and behave accordingly. The findings help to reveal how the brain organizes and orders its functions and processes, systems that may be disrupted in disorders such as schizophrenia and autism.
The research, led by Earl Miller, Ph.D., associate director of the Picower Center for Learning and Memory at MIT in Cambridge, Massachusetts, suggests that the jobs of the brain’s prefrontal cortex and basal ganglia in learning may be different than previously speculated. Until now, many researchers believed that the prefrontal cortex, which is highly developed in humans and primates, is the “higher order” thinking part of the brain that learns first. After the prefrontal cortex solves the problem, “primitive” structures like the subcortical basal ganglia take over to consolidate familiar routines into automatic habits. Dr. Miller and his lab have found the opposite. In their research with monkeys, signs of learning appeared sooner and more rapidly in the input to basal ganglia than the prefrontal cortex. These results suggest that the basal ganglia firsts identifies the rule, and then instructs the prefrontal cortex, which absorbs the lesson more slowly. This study was published in Nature* and was funded in part by the National Institute of Neurological Disorders and Stroke (NINDS).
“These findings suggest that new learning isn’t simply the ‘smarter’ prefrontal cortex figuring things out,” says Dr. Miller. “Surprisingly, primitive brain structures might be the engine driving even our most advanced high-level, intelligent learning abilities.”
The study measured the learning process of monkeys by recording signals from nerve cells in the prefrontal cortex and basal ganglia as the animals performed conditional visual-motor tasks, tests that required them to associate visual cues with eye movements. One of two cues was briefly presented at the center of a computer screen, followed by a delay and then presentation of two target spots on the right and left. The monkeys learned that ‘object A’ means look left while ‘object B’ means look right, concrete rules that are similar to the human rules of ‘stop at red’ or ‘go at green.’ Later, the monkeys had to learn the opposite response for each cue. This allowed the researchers to monitor the learning process and examine the brain areas involved. Improvements in behavior followed the slower changes in the prefrontal cortex rather than fast changes in the input of the basal ganglia. This suggests that rewarded associations are first identified by the basal ganglia, which then guides learning in the prefrontal cortex. Dr. Miller and his colleagues now plan to determine if this pathway of rule learning applies to other learning tasks and to other parts of the basal ganglia.
Patients with schizophrenia have demonstrated impairments in learning when performing novel association or pairing tasks, while children with autism have difficulty with learning of new organizational and social rules. The prefrontal cortex and basal ganglia are both involved in learning rules that are automatic enough for us to follow without much deliberation, and now the specific role of each is more clearly defined. The results suggest that maintaining a balance between the advanced cortex and more primitive brain structures is an important part of normal brain processing.
“This research showed us that new learning can be thought of as a series of interactions between the prefrontal cortex and basal ganglia areas, with a balance occurring between the two areas,” says Dr. Miller. “Certain disorders like autism and schizophrenia could result from an imbalance between these two areas. This research is a new way to think about learning, which leads to a new way of thinking about conditions that have impairments in learning.”
The NINDS is a component of the National Institutes of Health within the Department of Health and Human Services and is the nation’s primary supporter of biomedical research on the brain and nervous system.
*Pasupathy A, Miller EK. “Different time courses of learning-related activity in the prefrontal cortex and striatum.” Nature, February 24, 2005, Vol. 433, pp. 873-876.
-By Michelle D. Jones-London, Ph.D.
Last Modified January 31, 2007