PITTSBURGH, May 22 -- Research at the University of Pittsburgh Medical Center (UPMC) and Carnegie Mellon University identifies regions of the brain that allow learning to take place without the person being consciously aware of it.
The process and the regions are described in today's issue of Science, and could change the way researchers view learning and may have implications for the treatment of certain disorders.
"Being able to learn and adapt to change subconsciously is an important function of the brain," says principal investigator Gregory S. Berns, M.D., Ph.D., resident in psychiatry at the UPMC's Western Psychiatric Institute and Clinic. "People base their behavior on consistency, whether it's driving to work every day or investing in the stock market. People who play the stock market for example, often develop a hunch on how a stock is going to move, without being able to say exactly why they feel that way," he explains. "They may do this because one part of their brain has formed expectations based on certain consistencies about the market while the other part is paying attention to what is actually happening moment to moment, both working on a subconscious level. These two parts of the brain share information and the investor forms a hunch."
"Most of us have experienced novelty without awareness when we learn a new skill," says co-investigator Jonathan D. Cohen, M.D., Ph.D., associate professor in Carnegie Mellon University's department of psychology. "For example, we may find ourselves humming a new tune that we may have heard, but haven't made a conscious effort to remember. In certain cases, we may not even be aware of the extent of our new knowledge and we certainly aren't aware of the learning process."
According to Drs. Berns and Cohen, two areas of the brain are at work in this process. The area of the brain they believe is responsible for learning consistencies and storing expectations is an area of the right prefrontal cortex, situated behind the forehead above the right eye.
Deep in the center of the brain, a part of the basal ganglia called the striatum seems to weigh what the cortex knows from experience against what is happening at that moment. If something in the environment changes, this system picks up on it and automatically, unconsciously, alters behavior accordingly.
"This is a fascinating concept," Dr. Berns adds. "This study shows the human brain is quite adept at learning subtleties, creating expectations and altering our behavior without us even knowing we're doing it."
In the study, the researchers had subjects perform simple reaction time tests in which a series of numbers or lights were flashed quickly on a screen. The participants did not know that the series actually followed a complex sequence. They were asked to hit a corresponding button each time they saw the flash. During the tests, the subjects' brains were scanned using positron emission tomography (PET) to identify the areas of the brain activated during each test.
"Without realizing it, they learned the sequences, even though they had no idea a pattern existed," Dr. Berns explains.
"Over the course of many trials, the study participants unconsciously learned to predict what light would flash next, and prepare for it," Dr. Cohen adds. "They were not only learning the sequences unconsciously, but were also keeping track of the previous flashes, subconsciously."
From a clinical perspective, Drs. Berns and Cohen may have identified a process that may help solve problems such as drug dependence and obsessive-compulsive disorder.
"Nearly all addictive substances -- nicotine, narcotics, alcohol -- cause changes in the part of the brain that we found responds to subconscious novelty. This may explain why people who are addicted have difficulty achieving and maintaining abstinence. They've lost some ability to respond to new events, which would then make it difficult to change their behavior.
"At the other end of the spectrum, studies show that people with obsessive-compulsive disorder have increased activity in that part of the brain," Dr. Berns continues. "Since we found that this structure responds to new information, this may actually give rise to the feelings of unease that people with OCD experience. They always feel that something's not quite right or is out of place. These feelings may cause them to repeat tasks like hand-washing over and over again."
"This research is only the tip of the iceberg," Dr. Cohen says. "We still need to discover what factors determine when such learning and knowledge become conscious, how much and what types of knowledge can be learned subconsciously and precisely what role key brain systems, such as the prefrontal cortex, play under such conditions."
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