OSCILLATORY POTENTIALS IN THE VISUAL SYSTEM

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In the previously funded period, I have succeeded in achieving stimulation and recording conditions which allow for the repeated and reliable recording of light evoked high frequency wavelets ("oscillatory potentials"), which are obtained from the occipital scalp in man. The specific aims of this project are directed toward further understanding of the characteristics and origins of light evoked electrophysiological activity of the human visual system, and toward the application of these measures to the diagnosis of visual system anomalies and disease. The following plan is proposed to achieve these aims: Phase I: Investigation of the development of VEP wavelets in newborns and infants. Included in Phase I will be a comparison of the developmental sequence of occipital VEP wavelets and slow waves; an analysis of the functions of wavelet and slow wave amplitude and implicit time as related to stimulus flash intensity; and an analysis in terms of the possible progression from subcortical to cortical visual mechanisms in the developing infant. Phase II: Investigation of specific properties and relationships of wavelets recorded at the eye (ERG) and at the scalp (VEP). Included in Phase II will be the determination of specific relationships between the various VEP wavelets and the temporally preceding electroretinogram (ERG) wavelets; investigation of the effects of different electrical reference sites upon the scalp distribution of VEP wavelets; investigation of the differences in spatial frequency tuning as reflected in the amplitude of wavelets and slow waves. Phase III: Investigation of the use of VEP wavelets for the diagnosis of visual system anomalies and disease. Included in Phase III will be inter-ocular comparisons of VEP wavelets in normal subjects; the determination of the changes in VEP wavelets in afferent optic nerve transmission deficits; and the determination of the changes in VEP wavelets in diabetic retinopathy. ERG and VEP signals will be recorded and computer analyzed, using newly-developed digital filtering techniques. Light stimuli will be carefully calibrated and controlled. The recording of high frequency VEP wavelets appears to represent significant advantages over the traditional recording of slower (lower frequency) waves from occipital scalp, chief among which is the relatively greater precision of measurement of peak latencies.