Hillary R. Rodman - US grants

IBN: 9723178 PI: Rodman The primary visual cortex of the brain is known to be an important center for conscious visual perception, but there are other parts of the brain that also handle visual information in quite complex ways, though perhaps less "consciously." If the visual cortex is severely damaged, subjects are for most purposes considered blind. However, special tests can show that there is some kind of residual ability to detect visual targets and some properties about their location, movement and other features. This phenomenon is called "blindsight." It offers an unusual opportunity to study how visual activity in the brain can be separated from conscious visual perception. It is interesting that the degree of recovery from cortical loss is greater in early life, and may actually include some awareness of visual stimuli. This project utilizes testing of blindsight capabilities to understand differences between visual capabilities in early and in later life. Anatomical and physiological techniques will be used to see whether cells and their projections from a subcortical center called the thalamus still convey normal visual signals to remaining areas of visual cortex, and whether there are compensatory connections that develop between the thalamus and other brain regions. Results will be important to developmental neuroscience and cognitive psychology as well as to visual neuroscience, to enhance our knowledge of the organization and development of the visual system.

Damage to primary visual cortex (V1) is an important cause of blindness in both children and adults. However, far better recovery follows when the damage takes place early in life. The aim of this project was to examine the existence of a specific brain pathway in infant but not adult primates which could help account for the better recovery seen after early damage. Data collected this year do not support such a pathway, but point instead to a role for the pulvinar in the improved recovery. Moreover, the data suggest that the protein calbindin is important in the survival of cells in the visual system after damage to V1. of Prevent Blindness America

Humans with damage to primary visual cortex (V1) are for most purposes blind, although in some circumstances they can "guess" accurately about stimuli they do not consciously see (blindsight); if the damage occurs early in life recovery can be very good and include some awareness of stimuli. This project assesses the role of cells in the visual thalamus in the improved recovery via a monkey model. This year, subjects with V1 damage were prepared and assessed via MRI. Single-unit recording and anatomical studies of the thalamus will be performed in these subjects.