Amplitude Of Visual Evoked Response Research Articles

Visual-Evoked-Response-Supported Outcome of Intravitreal Erythropoietin in Management of Indirect Traumatic Optic Neuropathy.

Purpose Investigating the efficacy of intravitreal injection of erythropoietin (EPO) in managing indirect traumatic optic neuropathy (ITON) of different durations. Methods A case series that included two groups of ITON patients: recent ITON group (<3 months trauma duration; 7 eyes) and old duration ITON group (3–36 months; 7 eyes). Diagnostic computerized tomography (CT) and baseline flash visual evoked response (VER) were performed at the presentation time. At the initial visit and each follow-up, all patients had undergone assessment of best-corrected visual acuity (BCVA), pupil reaction, and anterior and posterior segments. VER was repeated 1 and 3 months after injection. All patients received an intravitreal injection of 2000 IU EPO in 0.2 ml of commercially available sterile EPREX 4000 solution, Jansen Cilag, Zug, Switzerland. Five patients had received a second injection 3 months later. Results Significant improvement was found in BCVA, VER amplitude, and latency (P < 0.0001, 0.0154, and 0.0291, respectively). Initial values of BCVA, VER amplitude, and latency correlated significantly to the final values. Differences between recent and old trauma groups were insignificant in the three parameters. In patients who received second injection, further clinical but statistically insignificant improvement was noted in BCVA in 60% of patients, VER amplitude in 50% of patients, and in VER latency in 100% of patients. No complications were recorded. Conclusion Intravitreal injection of EPO may be effective and safe in treatment of recent and old indirect traumatic optic neuropathy.

Steroids versus No Steroids in Nonarteritic Anterior Ischemic Optic Neuropathy: A Randomized Controlled Trial

To examine the role of oral steroid therapy in the treatment of nondiabetic cases of acute nonarteritic anterior ischemic optic neuropathy (NAAION). Randomized double-blind clinical trial. Thirty-eight patients with acute nondiabetic NAAION divided into 2 arms of 19 patients each. One arm constituted the cases and the other constituted the controls. Cases received oral steroid therapy and were designated the steroid group, whereas controls received placebo and were designated the nonsteroid group. Best-corrected visual acuity (BCVA), visual evoked response (VER), and OCT were performed at baseline, 1 month, 3 months, and 6 months after recruitment into thetrial. Best-corrected visual acuity, VER, and retinal nerve fiber layer changes on OCT. Both groups showed significant improvement in BCVA, VER latency, and resolution of disc edema on OCT parameters over 6 months. Final outcome showed no statistically significant difference with regard to visual acuity, although VER was better in the steroid group (P= 0.011). Best-corrected visual acuity, VER amplitude, and VER latency (P= 0.02, P= 0.02, and P= 0.04, respectively) showed a greater percentage improvement in the steroid group, which also saw a faster resolution of disc edema on OCT (1-month follow-up). Oral steroids in acute NAAION did not improve the visual acuity significantly at 6 months. However, they improved resolution of disc edema significantly and enabled a greater improvement in VER parameters. This subtle benefit of oral steroids in NAAION is clinically unimportant and does not provide support for its use.

Optimization of retinotopy constrained source estimation constrained by prior

Studying how the timing and amplitude of visual evoked responses (VERs) vary between visual areas is important for understanding visual processing but is complicated by difficulties in reliably estimating VERs in individual visual areas using noninvasive brain measurements. Retinotopy constrained source estimation (RCSE) addresses this challenge by using multiple, retinotopically mapped stimulus locations to simultaneously constrain estimates of VERs in visual areas V1, V2, and V3, taking advantage of the spatial precision of fMRI retinotopy and the temporal resolution of magnetoencephalography (MEG) or electroencephalography (EEG). Nonlinear optimization of dipole locations, guided by a group-constrained RCSE solution as a prior, improved the robustness of RCSE. This approach facilitated the analysis of differences in timing and amplitude of VERs between V1, V2, and V3, elicited by stimuli with varying luminance contrast in a sample of eight adult humans. The V1 peak response was 37% larger than that of V2 and 74% larger than that of V3, and also ~10-20 ms earlier. Normalized contrast response functions were nearly identical for the three areas. Results without dipole optimization, or with other nonlinear methods not constrained by prior estimates were similar but suffered from greater between-subject variability. The increased reliability of estimates offered by this approach may be particularly valuable when using a smaller number of stimulus locations, enabling a greater variety of stimulus and task manipulations.

Quantitative Fiber Tracking of the Optic Radiation Is Correlated with Visual-Evoked Potential Amplitude in Preterm Infants

Children born preterm are at risk for adverse outcome, including visual impairment. We examined the relationship between neonatal DTI and sVEP in children born preterm to determine whether visual outcomes are related to early measurements of brain microstructure. Subjects were born at <34 weeks gestation and imaged before term-equivalent age. DTI fiber tracking was used to delineate the optic radiations and measure tract-specific average FA, D(av), and parallel and transverse diffusivity. Visual-evoked response amplitudes were measured as a function of spatial frequency, contrast, and vernier offset size with sVEP at 6-20 months after birth. The association between DTI and sVEP was assessed by using the Spearman correlation coefficient and linear regression for repeated measures. Nine children with 15 scans were included. The peak response amplitudes for spatial frequency sweeps were associated with increasing FA and decreasing D(av) and transverse diffusivity (P ≤ .006) but not with parallel diffusivity (P = 1). There was only modest association with the swept contrast condition and no detectable association with the vernier offset sweeps. Microstructure of the optic radiations measured shortly after birth is associated with quantitatively measured responses elicited by moderate-to-high contrast spatiotemporal gratings in infancy. These findings are in keeping with studies showing a relationship between brain microstructure and function. While the clinical impact is not known, quantitative neuroimaging of white matter may ultimately be important for predicting outcome in preterm neonates.

Neonatal and fetal response decrement of evoked responses: A MEG study

Objective To investigate the response decrements of visual evoked responses (VER) in newborns and assess the applicability of this paradigm to fetuses in magnetoencephalographic (MEG) recordings. Methods Twelve newborns with no known risks or complications participated at chronological ages between 6 and 22 days. They constituted the follow-up group to a prenatal study conducted on a sample of 25 fetuses whose gestational age (GA) varied between 29 and 37 weeks at the time of recording. Trains of four light flashes with an interstimulus interval of 2 s followed by 10 s without stimulation were delivered to record VER. Results Nine of the 12 newborns responded to the stimulation and showed response decrements in amplitude from the first to the last light flash. Furthermore, the response latency increased significantly from the first to the last stimulus. The remaining three recordings were discontinued early. Even though the prenatal visual evoked response rate was only 29%, the fetuses exhibited a response decrement after the first stimulus. Conclusions The amplitude of VERs can be used to elicit a response decrement in newborns and, with limitations, even in fetuses. This paradigm might be a useful tool for a direct non-invasive assessment of neonatal and prenatal brain development and CNS functioning. Significance The proposed method might be a first step towards an early detection of developmental deficits in newborns and fetuses.

Recording pattern reversal visual evoked response with the scanning laser ophthalmoscope.

We recorded visual evoked responses (VERs) to alternating, checkerboard pattern stimuli using the scanning laser ophthalmoscope (SLO). Retinal position and focus of checkerboard stimuli were monitored on the SLO video monitor throughout testing. Checkerboard size, check size, and retinal positions were varied. Consistent with other, well-established pattern reversal techniques, the SLO method produced: 1) reliable VERs with amplitudes of 2 to 10 microvolts, 2) maximum amplitudes at an intermediate check size for a fixed overall pattern size, and 3) variations in VER amplitude depending on stimulus retinal position relative to the fovea. Hence, the SLO-VER technique would be useful for clinical VER measurements when precise retinal stimulus position and focus are desired.

Objective evaluation of binocular function with pattern reversal VER. IV. Effect of spatial and temporal frequency.

The effects of changing spatial and temporal frequencies on the amplitude of pattern reversal monocular and binocular visual evoked response (VER) were investigated. The pattern reversal VER and the degree of binocular summation (binocular VER amplitude/monocular VER amplitude) were lowest at the spatial frequency (check size) of 0.3 cycles per degree (CPD) and highest at the spatial frequency of 4.0 CPD. The largest VER amplitudes were observed at 1.2 CPD under both the binocular and monocular recording conditions. Regarding the effects of changing temporal frequency (alteration or reversal rate) on the pattern reversal VER, the transient condition (1.5 to 3.0 Hz) did not produce significant binocular summation. At the higher temporal frequencies (6 to 12 Hz), significant binocular summation was produced compared with the transient stimulus condition. At very high temporal frequencies, the degree of the binocular summation showed a decrease. From these results, we selected a pattern with an element around 1.2 CPD with a relatively swift temporal frequency for evaluating binocular function with the pattern reversal VER.

Visual function and pattern visual evoked response in optic neuritis.

The disparity between clinical visual function and pattern visual evoked response (VER) was studied in 53 patients who had suffered an attack of optic neuritis (ON) more than six months before. The visual functions tested included Snellen visual acuity, colour vision, visual field, and contrast sensitivity. The effect of pattern presentation, check size, and luminance was tested by recording VERs with several stimulus configurations. VER amplitudes were found to be associated with the outcome of all four clinical tests, independently of check size, luminance, or the presentation method used. On the other hand VER latencies were hardly ever related to the results of any of the four clinical visual tests. These findings support the idea that VER amplitude provides information about visual spatial perception, while VER latency is more related to the extent of demyelination.

Objective evaluation of binocular function using the pattern reversal visual evoked response. II. Effect of mean luminosity.

The effect of mean luminosity change on pattern reversal visual evoked response (VER), especially monocular VER, binocular VER and binocular summation, was studied. The mean luminosity level was changed with the use of neutral density filters. When mean luminosity level was decreased binocularly, binocular and monocular VER amplitudes decreased and binocular summation increased, reaching its peak at a luminosity of -0.3 log foot-lambert. When mean luminosity was changed monocularly and the interocular luminosity difference was larger than 0.6 log unit, the binocular VER became almost equal to or smaller than the monocular VER. In dim luminosity, the binocular system functioned better than the monocular system. Even a slight luminosity difference between the two eyes could disturb the binocular system.

Steady-State Visual Evoked Response Amplitudes and Concurrent Electroencephalographic Activity

Among the possible causes of steady-state visual evoked response (VER) amplitude variability are: concurrent electroencephalographic (EEG) activity occurring at frequencies other than that of the VER (alpha rhythms, etc.), and EEG activity occurring at the same frequency as the VER (Noise). To evaluate these two factors, 10 steady-state VER's (7.8 Hz pattern reversal rate) and 10 samples of resting EEG activity were obtained from each of 20 normal subjects. The correlations between VER and concurrent EEG activity at other frequencies were calculated from simultaneous determinations of Fourier-derived VER and EEG amplitudes. No significant correlations were found. Because EEG Noise occurring at the same frequency and time as the VER cannot easily be separated from the VER by Fourier transformation, two indirect techniques for assessing the amplitude of this Noise were evaluated: measurement of simultaneously recorded activity at frequencies directly adjacent to the 15.6 Hz VER frequency and measurement of EEG activity at 15.6 Hz obtained just before the VER measurements. Neither of these procedures could predict trial-by-trial variations in the amplitude of the Noise at 15.6 Hz. However, across subjects both procedures provided good estimates of the mean EEG Noise underlying the VER.

Stimulus deprivation amblyopia. Simultaneous recording of local macular electroretinogram and visual evoked response.

Local macular electroretinogram (ERG) and visual evoked response (VER) were recorded simultaneously in ten adult patients with stimulus deprivation amblyopia. The fundus was monitored by an infrared television fundus camera. The location of the stimulus spot and eccentric fixating point were also monitored during recording. Responses in amblyopic eyes were compared with those in the normal fellow eyes in terms of the size of the stimulus spot, location of the eccentric fixating point in response to the stimulus spot, and visual acuity. The amplitude of VER in the amblyopic eye showed enhancement when the stimulus spot centering around the fovea involved the eccentric fixating point. The amplitude and peak time of the ERG in the amblyopic eye was essentially normal regardless of the degree of eccentricity of the fixating point and visual acuity.

ラットの睡眠期および覚せい期の視覚誘発反応に及ぼす脳弓破壊の効果

The effects of fornix lesion on visual evoked responses (VERs) recorded from the occipital cortex (OCX) and the lateral geniculate body (LGB) were examined during wakefulness (W), slow wave sleep (SWS) and paradoxical sleep (PS) respectively, in freely moving rats (N=6). In intact animals, amplitudes of VERs changed with sleep-waking stages in a decreasing order of SWS, PS and W. After fornical lesion, mean amplitudes of VERs were significantly enhanced at OCX, but not at LGB. As to OCX, amplitudes of early components of VERs increased during all sleep-waking stages, and those of later components increased only during sleep. These results suggest that the fornix system exerts some modulatory (probably inhibitory) influence on OCX in close relations to sleep-waking stages in rats.

Binocular interaction in visual-evoked responses: summation, facilitation and inhibition in a clinical study of binocular vision.

Binocular visual-evoked responses (VER) were recorded in normal and strabismic subjects. The percent increase of binocular with respect to monocular response was correlated to the degree of binocular performance expressed by the values of stereopsis in the Titmus stereo test and TNO test. Summation, facilitation and inhibition of binocular responses were found. In no case was a clear relationship found between the degree of binocularity and the amplitude of binocular VER. This limits clinical application of binocular VER recordings in the diagnosis of binocular vision disturbances.

The contribution of the central retina to the laser speckle visual evoked response.

Laser speckle stimuli were used to examine the contribution of the central retina to the visual evoked response (VER). The foveally fixated test stimuli were either small circular spots or annular targets with dark centers. The speckle elements were shifted seven times per second. Reliable responses could be recorded for even the smallest (1 degree) target size. In addition, it was clearly evident that for spots up to 5 degree in diameter, VER amplitude increased linearly with stimulus area. However, data from annular targets revealed that this result was not strictly dependent upon stimulus area. In many instances, large annular stimuli evoked responses with smaller amplitude than spot stimuli with less area. This result may be due to a center-surround antagonistic interaction. These experiments suggest a potential value for laser speckle VER techniques in the assessment of discrete lesions of the macula.

Analysis of the effect of temporal frequency on the dichoptic visual-evoked response.

When observers with normal binocularity view reversing black and white checkerboard patterns, the amplitude of the resulting binocular visual-evoked response (VER) is significantly greater than the amplitude of either corresponding monocular response. When the same checkerboard pattern is dichoptically presented with an interocular luminance difference (1.3 to 2.0 log units), the amplitude of the dichoptic VER is significantly less than either monocular response. In a previous study, we attributed this effect to interference between the monocular components of the binocular response resulting from a phase shift induced by the interocular luminance difference. To test this hypothesis, dichoptic VER's were recorded for three temporal frequencies (1.88, 3.75, and 7.5 Hz). The results obtained support the phase shift interpretation.

The effect of retinal isomers on the VER and ERG of vitamin A deprived rats

Male weanling Long-Evans and Sprague-Dawley rats were administered a vitamin A deficient diet and the electroretinogram (ERG) and/or visual evoked response (VER) were recorded weekly. After 6–10 weeks, when the animal showed a greatly decreased VER and ERG, the animal was injected intraperitoneally with a retinal isomer. Following dark adaptation for 18 hr, the ERG and VER were recorded. The rat was then sacrificed and the retina dissected. The retina was used for either solubilizing the visual pigment in 2% Ammonyx LO or extracting the retinals in methylene chloride. The visual pigments were characterized by the absorbance spectra and the retinal isomers were identified by high pressure liquid Chromatography (HPLC). The physiologically occurring isomers of retinal (11- cis and all- trans) are incorporated in the retina of deprived animals and the VER and ERG amplitudes for a given light intensity, diminished as a result of vitamin A deprivation, are restored to their normal values. 9- cis retinal is also incorporated into the retina, as shown by extraction of the retina with organic solvent and identification of the isomers by HPLC; a pigment is formed which has a λ max blue-shifted from that of rhodopsin. The ERG and VER amplitudes of deprived rats injected with 9- cis retinal are restored to normal. No incorporation of 13- cis retinal into the retina is observed and the ERG and VER amplitudes are not significantly affected.

Human Visual Acuity Assessment through Linear Extrapolation to Threshold of Bar Grating VERs

Visual evoked responses (VERs) were obtained from seven normal eyes, using high contrast square-wave gratings of varying bar size on an 8 degrees or 24 degrees stimulus field. VER amplitude was plotted as a function of bar size. These plots, called square wave transfer functions (SWTFs), have one or more peaks when generated by a 24 degree field. In some individuals, the small bar size extreme of the function can be fitted well with a straight line for purposes of extrapolation to the visual acuity bar size. However, interindividual differences in the shape of the 24 degree field SWTF invalidates any a priori assumption of what bar sizes may be included in the extrapolation. Results from three subjects, using an 8 degree field, suggest that a more uniform single-peaked triangular SWTF with a peak near 5 min arc may be assumed for extrapolation purposes. The interindividual SWTF differences obtained with the 24 degree field were not random, the subjects falling into one of two groups on the basis of SWTF shape. This SWTF shape dichotomy may be correlated with the presence or absence of strabismus.

ラットの逆説睡眠期における視覚誘発反応

Visual evoked response (VER) to flash was averaged at the occipital cortex during paradoxical sleep (PS) in rats. The peak-to-peak amplitude with about 30 to 80 msec latency decreased as rapid eye movement (REM) rates during PS increased. Theta frequency increased with REM rates but there was no clear relationship between VER amplitude and theta frequency when no REM occurred. Further, after the medial septal lesions which abolished hippocampal theta activity, the relationship between the VER amplitude and REM rates remained while the VER amplitude, as a whole, was enhanced. Thus cortical VER may be assumed to be controlled by two inhibitory systems associated with (a) REM and (b) hippocampal theta activity. Usually they are highly related but may function independently at least in rats.

Effects of aging on visual evoked responses.

The effects of aging of visual evoked responses (VER) and critical frequency of photic driving (CFPD) was studied in 74 volunteers aged 18 to 79. The amplitude of VER to pattern reversal stimulation did not vary with sex or age. The latencies of the first major negative and of the first major positive defection of the VER were significantly delayed (P less than .001) with advancing age. This increase of latency probably reflects a slowing of conduction velocity in the optic nerve or optic pathways or both. CFPD, defined as the highest frequency of photic driving response expressed in flashes per second, showed an inverse correlation, decreasing with age in older subjects. Critical frequency of photic driving is the electrophysiological counterpart of critical flicker fusion, which is known to decrease with advancing age. These data support the concept that aging influences the functions of specialized sensory systems.

Visual evoked potentials and reaction time in normal and dyslexic children.

ABSTRACTThis investigation compared the visual evoked responses (VERs) and reaction time (RT) performance of 24 dyslexic boys and 24 controls at four different age levels (7, 9, 11, and 13 yrs). Prescreening and matching techniques were used to eliminate differences due to social or educational deprivation, gross sensory‐motor handicaps, specific neurological deficiencies, or intellectual impairment. The VER was recorded from four scalp locations (O1, O2, P3, and P4) referenced to the vertex during a detection task in which subjects were required to respond to dim flashes occurring in a train of brighter flashes. An overall hemispheric asymmetry in VER amplitude (right &gt; left) was observed in both experimental and control subjects. Dyslexics exhibited an increased amplitude to unattended stimuli and a slower RT to attended stimuli. Normals exhibited significant correlations between RT and VER latency, dyslexics did not. There were no significant VER‐IQ correlations. The results are discussed in terms of an attentional deficit hypothesis.