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James W. Pennebaker, Chair The University of Texas at Austin, SEA 4.212, Austin, TX 78712 • (512) 475-7596

What can we teach damaged adult visual systems to see? Insights from recovered vision in cortical blindness

Wed, March 5, 2014 • 3:00 PM - 4:00 PM • SEA Library, 4.244

Presented by

Krystel R. Huxlin, Ph.D.

Professor of Ophthalmology, Neurobiology & Anatomy

Brain & Cognitive Science, Center for Visual Science, and Flaum Eye Institute

University of Rochester Medical Center


Abstract:  What can we teach damaged adult visual systems to see? Insights from recovered vision in cortical blindness

  Cortical blindness, caused by stroke or other damage to the primary visual cortex, afflicts close to 1% of the non-institutionalized human population older than 49 years of age. While significant clinical efforts are expended to prevent the occurrence or progression of ocular blinding diseases, when it comes to cortical blindness, remarkably little effort is devoted to recover lost vision. This is partly due to the belief that the adult visual system lacks the kind of plasticity inherent in other cortical systems, and partly because of controversies surrounding the efficacy of commercial visual rehabilitation therapies. As a result, cortical blindness is still considered intractable by most clinical practitioners. Patients are either sent home or to low vision clinics, where they are encouraged to develop compensatory behaviors rather than to try and regain visual perceptual function.

Research in our laboratory over the last 10 years has studied this problem first using an animal model of visual cortical damage, and more recently, in affected humans.  We have used a multiplicity of technical approaches to show that visual learning can be induced in cortically blind fields, if the visual system is forced, through repeated practice, to perform visual discrimination tasks in blind regions of the visual field. Our ongoing work is exploring the extent of perceptual re-learning possible, the kind of vision that can be recovered, ways to increase the efficacy and generalizability of the training, and the brain mechanisms that underlie recovery of function. Our findings suggest that cortically blind subjects are able to relearn to discriminate a wider range of stimuli in their blind field than predicted by blindsight alone. However, only partial recovery was obtained on some visual functions, suggesting significant, residual inefficiencies in some aspects of visual processing. An important question is whether these inefficiencies can be overcome or whether the cortical areas damaged impose clear limits on the type and extent of visual recovery attainable in this patient population.

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