Uncovering the impact of neurological disorders on cognitive function
How do we learn? How is memory formed? And how are they affected by neurological disorders such as Alzheimer's and Parkinson's? Digging deep into those topics is Mark Gluck, Professor of Neuroscience at the Center for Molecular and Behavioral Neuroscience.
For more than 25 years, Gluck has been unlocking the doors of the hippocampus to gain a better understanding of how it interacts with different parts of the brain to support learning and memory. With Rutgers co-researcher Catherine E. Meyers, he has developed sophisticated computational models to show how the hippocampus cooperates with other brain regions to determine how new information should be encoded and stored throughout the brain. Like a clearing house, the hippocampus determines where to send different information for further processing and encoding. Through those models and other tools, Gluck also is helping to provide new insight into memory, learning and behavioral disorders associated with Alzheimer's, Parkinson's, epilepsy and other forms of brain injury.
As part of that research, he and Myers have developed a novel feedback-learning test that is helping to uncover how Parkinson's disease, and potentially other neurological disorders, alters people's ability to learn about the consequences of the choices they make. As reported in the journal Brain (Sept. 2009), Gluck and co-researchers Nikoletta Bódi and Szabolcs Kéri, of Semmelweis University in Hungary found that non-medicated patients in the early stages of Parkinson's experienced a marked decrease in their ability to learn from reward.
Using the feedback-learning test developed by Gluck and Myers, recently diagnosed patients who had yet to be medicated were shown to be impaired in their ability to learn from positive outcomes while their sensitivity to learning from negative outcomes remained normal. According to Gluck, the selective deficit in learning from reward is not surprising given that scientists have long known that dopamine is used to carry reward information throughout the brain. In Parkinson's patients, most of the dopamine-producing cells are lost by the time they are first diagnosed. The decrease in their ability to process rewarding outcomes could be one reason why many of those with Parkinson's experience depression, says Gluck. "It's not just that they have an awful disease, but they have lost the ability to process the rewarding aspects of life."
That reward-learning deficit is in direct contrast to what was found in Parkinson's patients once they began treatment with dopamine agonists, a standard therapy for treating the disease's motor symptoms. On dopamine agonists, a patient's ability to learn from positive outcomes improved to normal levels but their ability to learn from negative outcomes became impaired. Those findings could explain why some Parkinson patients treated with dopamine agonists develop impulse-control behaviors such as pathological gambling, alcoholism, and compulsive eating and shopping disorders. All those behaviors can be understood as reward-seeking behaviors that fail to recognize negative consequences.
The ability to test feedback learning, along with the computational models Gluck's lab has developed, represents an important new avenue for designing better treatment methods for neurological disorders.
In related research, Gluck is working with Palestinian and Israel doctors, as part of a joint Rutgers and Israeli-Palestinian brain research project, to study cognitive deficits in Israeli and Palestinian patients suffering from Parkinson's disease and depression. He also has launched an African-American Alzheimer's Disease Health Literacy Program to promote memory health and a better understanding of Alzheimer's among minority and economically disadvantaged seniors, who have a greater risk of developing the disease.
Mark Gluck is co-director of the Rutgers Memory Disorders Project, and publisher of the public health newsletter, Memory Loss and the Brain. He is the co-author of Gateway to Memory: An Introduction to Neural Network Models of the Hippocampus and Memory (MIT Press, 2001), and an undergraduate textbook, Learning and Memory: From Brain to Behavior (Worth Publishers, 2007). He has edited several other books and has published over 60 scientific journal articles. His awards include the Distinguished Scientific Award for Early Career Contributions from the American Psychological Society and the Young Investigator Award for Cognitive and Neural Sciences from the Office of Naval Research. In 1996, he was awarded a National Science Foundation Presidential Early Career Award for Scientists and Engineers by President Bill Clinton.