Enhancing Human Cortical Plasticity: Visual Psychophysics and fMRI

Massachusetts General Hospital, Boston MA

Investigators

Abstract

With National Science Foundation support, Dr. Poldrack will conduct a year long investigation of a new approach to enhancing brain plasticity and increasing the speed of learning in adult humans. It has long been known that the brain changes extensively early in life, and that these changes are dependent upon particular experiences in the child's environment. However, more recent research has discovered that the brain continues to change throughout adulthood in response to experience. This ability to change is called plasticity, and is thought to underlie many forms of learning. Dr. Poldrack's project will explore an approach based upon results from studies of experimental animals, which have shown that plasticity in the cerebral cortex can be greatly enhanced by increasing the levels of the neurotransmitter acetylcholine. New drugs, known as cholinesterase inhibitors, that safely and effectively increase acetylcholine levels in humans have recently been developed and FDA-approved. The specific drug that Dr. Poldrack will use is galanthamine hydrobromide (tradename Reminyl). The effect of the drug on cortical plasticity will be assessed using both visual behavioral testing and functional magnetic resonance imaging, which is a non-invasive method for measuring the brain activity that occurs as a person performs a cognitive or perceptual task. The behavioral measure will be the rate at which the subjects learn to more accurately perform a simple visual perceptual learning task: learning to discriminate the orientation of a grating. The hypothesis to be tested is that learning of the visual task that takes place under the influence of the drug will proceed more quickly than learning that is paired with a placebo. Functional magnetic resonance imaging will be used to assess the effect of the drug on cortical plasticity, by comparing the pre-training versus post-training brain activation changes that are caused by learning the visual task while on the drug against those caused by learning the task on placebo. If this new method of enhancing plasticity should turn out to be successful, it will provide fundamentally important and novel knowledge about the nature of plasticity in the adult human brain, and could also lead to a wide range of potential clinical and practical applications. Understanding how brain plasticity works in adult humans is of critical importance, because recent research suggests that plasticity can be capitalized upon in order to remediate neurological problems, such as movement disorders resulting from stroke or from repetitive strain injury, and reading and language disorders.