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Abstract
To better characterize the properties of chromatic VEPs to onset-offset of red-green
and blue-yellow equiluminant patterns, and establish normative values for a set of
stimuli able to elicit robust and reliable responses, suitable for the clinical application.
Chromatic VEPs have been recorded (Oz lead) from 28 normal subjects (age range 20-53
years) in response to monocular presentation of both red-green and blue-yellow equiluminant
sinusoidal gratings. Stimuli were generated by a Cambridge VSG/2 card and displayed
on a Barco CCID monitor (14x14 deg field size). Spatial frequency, chromaticity, contrast
and onset-offset duration were varied.
For both red-green and blue-yellow equiluminant stimuli, robust responses have been
obtained with gratings of 2 c/deg, presented in onset (300 ms) offset (700 ms) mode,
at contrasts ranging from 90 to 6%. In all observers, the VEP waveform consisted mainly
of a negative wave at stimulus onset, with a latency rapidly increasing with decreasing
contrast. For both red-green and blue-yellow stimuli, the VEP contrast threshold coincided
with the psychophysical threshold.
The results complement previous studies aimed at characterizing the properties of
chromatic VEPs. In addition, normative data are provided for a set of stimulus characteristics
suitable for the clinical routine.