Testing and surpassing limits of adaptation in visual cortex

The brain has a remarkable ability to modify its own function. In the visual system such neuroplasticity occurs routinely, for example when we move from indoors to outside. Changing environments affects visual input dramatically, and cortical neurons alter how they respond in order to keep us seeing well. This type of neuroplasticity, called visual adaptation, occurs readily in the adult brain. Its effects tend to be short-lasting, however, limiting its potential applications in education, training, and health. To understand and overcome this roadblock, Dr. Stephen Engel and colleagues at The University of Minnesota will test the limits of adaptation, by extending laboratory studies an order of magnitude in duration. Participants will adapt for up to a week continuously, by viewing the world through virtual reality goggles that display modified output of a head-mounted camera. The experiments will measure how long-lasting the effects of adaptation can become, and test several factors that could be limiting the growth of this type of neuroplasticity. These include competition between the parts of the brain that benefit from neuroplasticity and the parts that could be hurt by it, since they depend upon stability of the brain regions that provide their input. Understanding adaptation should allow it to produce beneficial neuroplasticity, which has many applications. It could become part of training visual experts such as baggage scanner operators or imagery analysts. It could become part of efforts to rewire the brains of patients suffering from visual diseases, such as amblyopia ('lazy eye'). The work will also test theories of neuroplasticity that are applicable in many domains. It will produce educational materials for teaching of cognitive neuroscience, and will directly support the training of a diverse set of graduate and undergraduate students in cutting edge methods.

Adult visual cortex can alter its function dramatically in response to changes in the environment, allowing it to function optimally, despite large changes in input. Critically, the longer vision experiences an environment, the stronger and longer lasting adaptation becomes. This suggests that long-term exposure to altered visual input may produce long-lasting changes in cortex. Technical issues have prevented the study of long adapting durations under controlled conditions, however leaving it unknown whether some factors 'put on the brakes', restricting its strength and durability. The PI developed methods to overcome this roadblock, and examined effects of a 4-days of continuous adaptation, revealing significant limits. The general goal of the grant is to understand the brakes producing those limits. For vision as a whole, adaptation can produce costs, as well as benefits, and this proposal will test whether observed limits are due to them. A first set of experiments will test whether costs limit adaptation in early visual areas, examining specific costs from the literature, removing them, and observing whether limits on adaptation remain present. A second set of experiments will examine longer-term adaptation. They will test the hypothesis that long-term adaptation can overcome limits, reducing costs by correcting for a 'coding catastrophe' in later visual areas. The work will distinguish between major theories of adaptation, using quantitative analysis of behavioral and functional MRI (fMRI) data. It also represents a major empirical step forward; dozens of studies have examined adaptation in visual cortex, but no previous work has measured or tested adaptation's limits. Results of this research could influence work in a diverse array of fields where visual plasticity is important, from education to the military to public health. Results of the work will be incorporated into educational materials (an introductory fMRI course and text) that will be freely distributed. The grant will also provide training opportunities for a diverse group of students.