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Grantee: McMaster University, Hamilton, Ontario, Canada
Project Lead: Daphne Maurer, Ph.D.Co-PIs: Terri L. Lewis, Bruce McCandliss, Takao Hensch, Dennis Levi, and Donald Mitchell
Grant Title: In support of an international collaboration on recovery from amblyopia
Program Area: Bridging Brain, Mind & Behavior
Grant Type: Collaborative Activity Award
Year Awarded: 2006
Project Summary:
One of the most problematic concepts in neural and behavioral science is that of a "critical period." Hatchlings acquire this behavior, however, only if they observe the moving object during a critical period in development, which lasts from around 5 to 20 hours after hatching. This has suggested that for certain kinds of learning, experience is required during well-defined windows in development. Other prominent examples of critical period phenomena are first and second language learning and normal development of the human visual system.
Critical periods have become more significant to development science, since scientists have further assumed that critical period learning is permanent and irreversible. The current paradigm of a critical period effect is the development of the visual system, where Hubel and Wiesel showed that normal, binocular visual input is required during critical periods for the proper wiring of visual circuits in the brain. One of the results of abnormal visual experience early in life is amblyopia, which results in life-long vision damage. It is estimated that up to five percent of the population suffers from this impairment.
Because of strong views about the permanence and irreversibility of critical periods, clinicians have not treated amblyopics older than six years of age, assuming that any treatment would be ineffective. Recently however, clinical research groups have shown that some therapeutic interventions are effective for older patients, even adults. Given these results, the collaborative team believe it is time to examine such interventions systematically, as well as to revisit the purported implications of critical period limitations on learning and development. This collaborative will question received dogma both in basic neuroscience and clinical ophthalmology. They will use amblyopia as a model system to re-examine critical periods and developmental changes in brain plasticity.