title: Pattern-reversal visual evoked potentials and retinal eccentricity.
abstract: The effect of stimulation of discrete areas of the retina on visual evoked potentials (VEP) was studied in 16 normal volunteers. The stimulus consisted of a constant luminance 2 degrees 18' field containing checks of 34'30' reversing at a frequency of 500 msec. The amplitude of the VEP was highest at the fixation point and inside the 2 degrees isopter. Rapid amplitude decrement was noted with stimuli located within the 2-4 degrees isopters. No identifiable response was obtained outside the 4 degrees or 6 degrees isopter with a 2 degrees 18' stimulus. VEP could, however, be elicited by increasing the size of the stimulus. The smallest size of a field required to evoke a detectable response also varied in relations to retinal eccentricity. Stimulation at 0 degree, 8 degrees and 14 degrees horizontal eccentricities with fields of a size estimated to activate an equivalent amount visual cortex produced VEPs of similar amplitude.
mesh_terms: D004569:Electroencephalography; D005074:Evoked Potentials, Visual; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012160:Retina / Q000502:physiology*; D014792:Visual Acuity; D014794:Visual Fields