Research Profiles: Biology

Have you ever wondered how the learning process occurs or how memory works? What exactly goes on in the brain that helps us do these things?

The brain is one of the most intriguing structures of the human anatomy. However, very little is known about it. Jay McClelland, the Walter Van Dyke Bingham Professor of Psychology and Cognitive Neuroscience at Carnegie Mellon, is currently trying to address a few cognitive neuroscience issues in learning, memory, and language at an abstract neurocomputational level.

Language learning is often very difficult. Learning and actively practicing vocabulary, grammar, and sentence formations are critical. Have you ever wondered why you did not have to go through this tedious routine to learn your mother tongue or native language? You just “knew it.”

McClelland’s lab is involved in a project that tries to learn the development of language and the sensitive period in which language learning is accomplished. He also attempts to understand why people fail to distinguish between sounds that are not used in their spoken language. For example, Japanese adults are often incapable of distinguishing between the l and r sounds. Some approaches suggest this inability is caused by a simple switching-off of learning about speech sounds as a function of age or puberty. McClelland’s view is that the switching-off is the result of learning. As the child develops in his or her native language environment, the unused sounds cause certain neurons to be incapable of firing. On the other hand, as a particular sound is used frequently, the connections between the neurons become stronger.

As McClelland put it, “As an individual grows, the production and processing of new sounds becomes difficult. But my students and I continue to hope that we can find new ways to rewire the necessary connections.”

Other aspects of McClelland’s research include trying to understand the processing of memory and the ability of individuals to differentiate between objects.For example, what constitutes a person’s ability to distinguish between a cat and a tiger? Experiments are currently being done on patients whose ability to make a distinction between different objects is lost. Such patients suffer from semantic dementia, a degenerative disease seen in people over the age of 50.

These patients are made to take a “pyramids and palm trees” test where they are asked to distinguish between 400 different pictures. Since this process of inability to distinguish is a gradual one, the ability to tell the difference between similar objects is first lost. For example, patients first lose the ability to distinguish between two birds and, as the disease progresses, they could even fail to tell an elephant apart from a dog.

In the lab, there is a computerized simulation of the brain which attempts to understand the cause of this disorder by temporal lobe atrophy. This is not due to impaired vision. When the patients are asked to copy objects that represent animals, they copy them just fine. If the object is taken away, however, they are unable to draw a picture which resembles the animal. This disease is different from Alzheimer’s disease in that it is a “presentation of the knowledge” that is impaired.

So where does all this research lead us? “We are trying to establish a useful framework for understanding developmental processes,” said McClelland. His lab is trying to develop a “conceptual representation” of the brain that may be useful in addressing other questions regarding its structural functions. “My own role in this research will be to try to understand better how different parts of the brain work together when we think and learn,” said McClelland. This will be useful in helping people with other disorders and diseases such as autism.