scholarly journals Abnormalities of coherent motion processing in strabismic amblyopia: Visual-evoked potential measurements

10.1167/8.4.2 ◽  
2008 ◽  
Vol 8 (4) ◽  
pp. 2 ◽  
Author(s):  
Chuan Hou ◽  
Mark W. Pettet ◽  
Anthony M. Norcia
Keyword(s):  
Visual Evoked Potential ◽  
Evoked Potential ◽  
Coherent Motion ◽  
Motion Processing ◽  
Strabismic Amblyopia ◽  
Visual Evoked

The sequential processing of visual motion in the human electroretinogram and visual evoked potential

2000 ◽  
Vol 17 (4) ◽  
pp. 631-646 ◽  
Author(s):  
MATTHIAS KORTH ◽  
RAINER RIX ◽  
OTTO SEMBRITZKI
Keyword(s):  
Spatial Frequency ◽  
Visual Evoked Potential ◽  
Evoked Potential ◽  
Stimulation Frequency ◽  
Motion Processing ◽  
Spatial Frequencies ◽  
Wide Range ◽  
The Brain ◽  
Moving Pattern ◽  
Visual Evoked

Mechanisms of motion vision in the human have been studied extensively by psychophysical methods but less frequently by electrophysiological techniques. It is the purpose of the present investigation to study electrical potentials of the eye (electroretinogram, ERG) and of the brain (visual evoked potential, VEP) in response to moving regular square-wave stripe patterns spanning a wide range of contrasts, spatial frequencies, and speeds. The results show that ERG amplitudes increase linearly with contrast while VEPs, in agreement with the literature, show an amplitude saturation at low contrast. Furthermore, retinal responses oscillate with the fundamental temporal stimulus frequency of the moving pattern while brain responses do not. In both the retina and the brain, the response amplitudes are tuned to certain speeds which is in agreement with the nonlinear correlation-type motion detector. Along the ascending slopes (which means increasing amplitudes) of the tuning functions, the ERG curves overlap at all spatial frequencies if plotted as a function of temporal stimulation frequency. The ascending slopes of the tuning functions of the VEP overlap if plotted as a function of speed. The descending slopes (which means decreasing amplitudes) of the tuning functions show little (ERG) or no (VEP) overlap and the waveforms at high speeds approach pattern-offset-onset responses. These observations suggest that in the retina motion processing along the ascending slopes of the tuning curves takes place by coding the temporal stimulation frequency which depends on the spatial frequency of the moving pattern. In the brain, however, motion processing is by speed independent of spatial frequency. Simple calculations show that the VEP information is decoded from the ERG signal into a speed signal.

Olfactory Modulation of Steady- State Visual Evoked Potential Topography in Comparison with Differences in Odor Sensitivity

2002 ◽  
Vol 16 (2) ◽  
pp. 71-81 ◽  
Author(s):  
Caroline M. Owen ◽  
John Patterson ◽  
Richard B. Silberstein
Keyword(s):  
Steady State ◽  
Visual Evoked Potential ◽  
Evoked Potential ◽  
Behavioral Responses ◽  
Simultaneous Recording ◽  
Odor Concentration ◽  
Odor Detection ◽  
Detection Response ◽  
Response Groups ◽  
Visual Evoked

Summary Research was undertaken to determine whether olfactory stimulation can alter steady-state visual evoked potential (SSVEP) topography. Odor-air and air-only stimuli were used to determine whether the SSVEP would be altered when odor was present. Comparisons were also made of the topographic activation associated with air and odor stimulation, with the view toward determining whether the revealed topographic activity would differentiate levels of olfactory sensitivity by clearly identifying supra- and subthreshold odor responses. Using a continuous respiration olfactometer (CRO) to precisely deliver an odor or air stimulus synchronously with the natural respiration, air or odor (n-butanol) was randomly delivered into the inspiratory airstream during the simultaneous recording of SSVEPs and subjective behavioral responses. Subjects were placed in groups based on subjective odor detection response: “yes” and “no” detection groups. In comparison to air, SSVEP topography revealed cortical changes in response to odor stimulation for both response groups, with topographic changes evident for those unable to perceive the odor, showing the presence of a subconscious physiological odor detection response. Differences in regional SSVEP topography were shown for those who reported smelling the odor compared with those who remained unaware of the odor. These changes revealed olfactory modulation of SSVEP topography related to odor awareness and sensitivity and therefore odor concentration relative to thresholds.

Visual Evoked potential signal processing and analysis for normal and galucomic eyes

2015 ◽  
Vol 8 (2) ◽  
pp. 2106-2121
Author(s):  
Hamed Ibrahem Abdelkader ◽  
Mona Abdelkader ◽  
Mohammed Kabeel ◽  
Malak Alya
Keyword(s):  
Evoked Potentials ◽  
Visual Evoked Potential ◽  
Evoked Potential ◽  
Optic Tract ◽  
Pattern Reversal ◽  
Blue Color ◽  
Check Size ◽  
Retinal Stimulation ◽  
Normal Individuals ◽  
Visual Evoked

Visual evoked potentials (VEPS) are obtained from optic tract by recording the evoked potentials generated by retinal stimulation. The flash VEP (FVEP) is used less frequently than pattern reversal VEP (PRVEP) because; it shows great variation in both latency and amplitude. The present study was undertaken to evaluate the effect of change of wavelength of flash and change of check size on the parameters of visual evoked potential (amplitude and latency) in normal individuals and glaucoma patients. The group of healthy subjects in the age of 20-45 years while the group of glaucoma subjects where  in the age of 25-50 years.  The two groups were exposed to flash VEP with white light and blue color and they also were exposed to checks subtending a visual angles of 15, 30,60 and 120 minutes of arc. The measured data were statistically analyzed and summarized by histograms. The interindividual and intraindividual in latencies and amplitudes for FVEP were assessed using  the coefficient of variation (COV). In conclusion, monochromatic flash VEP was preferred than white as there were minimal inter and intra individual variation of latencies and amplitudes. The most preferred check size in PRVEP was 120' for  the two groups.  

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