|Visual Evoked Potential|
Visual Evoked Potentials (VEP) are measurements of the brain's electrical activity in response to visual stimulation.
We proposed a model for the emergence of an intermediate frequency component in the VEP power spectrum that we found during binocular fusion at two dichoptically presented identical checkerboard patterns that differ in reversal rate. We showed that this intermediate frequency component remains constant independent of both monocular and binocular changes in stimulus contrast. We believe that this signal represents binocular fusion, a lower function than stereo vision.
Rapid sweep displays, in which subjects view a stimulus pattern which is counterphase modulated at a fixed temporal frequency of 5 to 25 Hz, while simultaneously undergoing spatial frequency or contrast modulations are used to estimate VEP sensory thresholds. We recorded VEP for 26 subjects viewing contrast modulated sinusoidal stimuli with spatial frequency sweeps of 12.5 to 0.2 cycles/degree. We showed that for large phase shifts, the signal to noise ratio was not diminished by modifying contrast reversal rate, direction of spatial frequency sweep or sweep time. We concluded that when using spatial frequency sweeps, phase-insensitive detection is superior to phase-sensitive, contrary to existing theory.
Peli E, McCormack G, Sokol S. (1988) Signal to noise ratio considerations in the analysis of sweep visual-evoked potentials. Applied Optics 27(6): 1094-1098. [PDF 455 KB]
Peli E, McCormack G, Sokol S. (1987) Comparison of synchronous detection methods for sweep stimulus VEP. Proceedings of the Ninth Annual Conference of the IEEE/ Engineering in Medicine and Biology Society, Boston MA, 597-599. PDF Coming Soon.
Katsumi O, Peli E, Oguchi Y, Kawara T. (1985) Effect of contrast on fusional visual evoked potential (VEP): A model and experimental results. Am J Optom Physiol Opt 62(4): 233-239. [PDF 457 KB]
Katsumi O, Oguchi Y, Peli E. (1984) Effects of stimulus contrast on binocular VER. Japanese Journal of Ophthalmology 28: 401-408 [PDF 343 KB]