The effect of congenital alternating esotropia on background EEG activity of children aged 5-12 as measured by power spectra
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Abstract
Experience can lead to anatomical and physiological changes in underlying neural substrates. These alterations in structure and function can result in modifications to subsequent behavior.
This concept has been examined extensively in the animal literature in relation to the effects of experimentally induced visual deprivation of functioning visual systems of cats and monkeys. The physiological and morphological data show that animals subjected to various types of anomalous visual experience demonstrate shifts in cortical connections which match the ocular experience. These studies also demonstrate that experience acts as a viable influence for. neural change during a developmentally vulnerable time.
The current project examined this relationship in children, using the condition of congenital alternating esotropia. It was hypothesized that atypical visual experience, during a postnatal period of cortical plasticity, would result in modifications to the substrate for visual processing. Related functional changes could be identified by differences in the organization and frequency content of the background EEG. This was investigated by the analysis of the EEG's of nine congenital esotropes, ages 5-12, and nine age and sex matched controls. Power spectra, representing samples from baseline and stimulus conditions, were analyzed for frequency content and organizational qualities. Measures of absolute power, relative power and spectral shape were evaluated for group differences using multiple regression analysis.
Several measures of spectral power differentiated the groups. The esotropic subjects had less absolute power within the 3-15 Hz frequency bands in baseline and stimulation conditions. Analysis of relative power values during stimulation indicated a shift in the esotropics' power concentration to slower frequencies in comparison to controls. These findings were confined topographically to the occipital lobes, indicating compromise to the visual processing substrates only.
These results indicate that congenital esotropes have electrophysiological differences that accompany their binocular processing deficits. This supports the original hypothesis, that early visual experience can initiate functional changes to the substrate that will be identified by differences in the background EEG.
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Dissertation (Ph.D.)--Boston University
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