Abstract

Electrophysiology provides a means for obtaining an objective measure of neural function, as well as an indicator of nervous system pathology. In the case of the visual system, noninvasive electrophysiology commonly utilizes recording the potentials evoked by visual stimuli from various points along the optic tract. Although the flash electroretinogram may be well over 150 microvolts in amplitude, the steady-state visual evoked potential (ssVEP), elicited from the visual cortex by counterphased, patterned stimuli, is usually much lower--on the order of 1 to 10 microvolts. In the clinic, the response recorded from patients may be of even lower amplitude due to the underlying disease process. In addition, the pathology may change the nature of the ambient noise, as well as making the patient less amenable to the recording process. All of these factors interfere with the use of the ssVEP in electrodiagnosis. Clearly, techniques which improve the analysis of evoked potential data will be welcomed by the clinical electrophysiologist. We have found that the generalized order statistic (GOS) filters can be used to analyze ssVEP data, reducing the length of recording time required to acquire the signal, and improving the signal to noise ratio by removing transient and impulsive noise from the biological data. The principles and practice for the use of generalized order statistic filters will be outlined below.

© 1991 Optical Society of America