Comparison of isolated-check visual evoked potential and standard automated perimetry in early glaucoma and high-risk ocular hypertension

AIM：To compare the diagnostic performance of isolatedcheck visual evoked potential（ic VEP） and standard automated perimetry（SAP）,for evaluating the application values of ic VEP in the detection of early glaucoma.METHODS：Totally 144 subjects（288 eyes） were enrolled in this study.ic VEP testing was performed with the Neucodia visual electrophysiological diagnostic system.A 15% positive-contrast（bright） condition pattern was used in this device to differentiate between glaucoma patients and healthy control subjects.Signal-to-noise ratios（SNR） were derived based on a multivariate statistic.The eyes were judged as abnormal if the test yielded an SNR≤1.SAP testing was performed with the Humphrey Field Analyzer II.The visual fields were deemed as abnormality if the glaucoma hemifield test results outside normal limits;or the pattern standard deviation with P〈0.05;or the cluster of three or more non-edge points on the pattern deviation plot in a single hemifield with P〈0.05,one of which must have a P〈0.01.Disc photographs were graded as either glaucomatous optic neuropathy or normal by two experts who were masked to all other patient information.Moorfields regression analysis（MRA） used as a separate diagnostic classification was performed by Heidelberg retina tomograph（HRT）.RESULTS：When the disc photograph grader was used as diagnostic standard,the sensitivity for SAP and ic VEP was 32.3% and 38.5% respectively and specificity was 82.3% and 77.8% respectively.When the MRA Classifier was used as the diagnostic standard,the sensitivity for SAP and ic VEP was 48.6% and 51.4% respectively and specificity was 84.1% and 78.0% respectively.When the combined structural assessment was used as the diagnostic standard,the sensitivity for SAP and ic VEP was 59.2%and 53.1% respectively and specificity was 84.2% and 84.6% respectivlely.There was no statistical significance between the sensitivity or specificity of SAP and ic VEP,regardless of which diagnostic standard was based on.CONCLUSION：The diagnostic performance of ic VEP is not better than that of SAP in the detection of early glaucoma.

Short-duration transient visual evoked potentials and color reflectivity discretization analysis in glaucoma patients and suspects

AIM： To evaluate the use of short-duration transient visual evoked potentials（VEP） and color reflectivity discretization analysis（CORDA） in glaucomatous eyes,eyes suspected of having glaucoma,and healthy eyes.METHODS： The study included 136 eyes from 136 subjects： 49 eyes with glaucoma,45 glaucoma suspect eyes,and 42 healthy eyes.Subjects underwent Humphrey visual field（VF） testing,VEP testing,as well as peripapillary retinal nerve fiber layer optical coherence tomography imaging studies with post-acquisition CORDA applied.Statistical analysis was performed using means and ranges,ANOVA,post-hoc comparisons using Turkey＇s adjustment,Fisher＇s Exact test,area under the curve,and Spearman correlation coefficients.RESULTS： Parameters from VEP and CORDA correlated significantly with VF mean deviation（MD）（P〈0.05）.In distinguishing glaucomatous eyes from controls,VEP demonstrated area under the curve（AUC） values of 0.64-0.75 for amplitude and 0.67-0.81 for latency.The CORDA HR1 parameter was highly discriminative for glaucomatous eyes vs controls（AUC=0.94）.CONCLUSION： Significant correlations are found between MD and parameters of short-duration transient VEP and CORDA,diagnostic modalities which warrant further consideration in identifying glaucoma characteristics.

Effect of infusion pressure during cataract surgery on ganglion cells measured using isolated-check visual evoked potential

AIM： To detect the relationship between infusion pressure and postoperative ganglion cells function.METHODS： This prospective observational cohort study included sixty-one eyes that underwent uncomplicated cataract surgery. Patients were divided into two groups according to infusion time（IT） recorded using surgery equipment [Group A： IT〉IT_（mean）（27 eyes）; Group B： IT

Visual acuity evaluation in children with hydrocephalus:An electrophysiological study with sweep visual evoked potential

The objective was to measure the visual acuity (VA) of children with the diagnosis of hydrocephalus with or without peritoneal-ventricular shunt (PVS). A total of 55 children were included in the study (34 Female), with an age range of 0 to 291 weeks. The VA was measured by the sweep visual evoked potential technique. Of those with a PVS, in 31 the ventricular valve was inserted before 15 days after the diagnosis whereas in 14 the ventricular valve was inserted after 15 days. The sweep VEP was performed in all children, 95 exams (94%) were abnormal and only 6 were normal. There was a statistical difference in the VA between children with a PVS inserted before 15 days of the diagnosis and children with a PVS after 15 days (p = 0.038) or those without a shunt (p = 0.031). Children with no complications of the PVS had a better VA as compared to those with shunt complications (p < 0.001). In the group of children with complications, again those who had a shunt inserted be-fore 15 days had better VA results in com- parison to those in whom the shunt was inserted after 15 days (p = 0.029). No statistical difference in the VA was found between children without the PVS and with those in which the shunt was inserted after 15 days of the di-agnosis of hydrocephalus (p = 0.699). We conclude that the delayed insertion of the PVS may compromise the visual development of these children.

Functional near-infrared spectroscopy can detect low-frequency hemodynamic oscillations in the prefrontal cortex during steady-state visual evoked potentialinducing periodic facial expression stimuli presentation

Brain oscillations are vital to cognitive functions,while disrupted oscillatory activity is linked to various brain disorders.Although high-frequency neural oscillations(>1 Hz)have been extensively studied in cognition,the neural mechanisms underlying low-frequency hemodynamic oscillations(LFHO)<1 Hz have not yet been fully explored.One way to examine oscillatory neural dynamics is to use a facial expression(FE)paradigm to induce steady-state visual evoked potentials(SSVEPs),which has been used in electroencephalography studies of high-frequency brain oscillation activity.In this study,LFHO during SSVEP-inducing periodic flickering stimuli presentation were inspected using functional near-infrared spectroscopy(fNIRS),in which hemodynamic responses in the prefrontal cortex were recorded while participants were passively viewing dynamic FEs flickering at 0.2 Hz.The fast Fourier analysis results demonstrated that the power exhibited monochronic peaks at 0.2 Hz across all channels,indicating that the periodic events successfully elicited LFHO in the prefrontal cortex.More importantly,measurement of LFHO can effectively distinguish the brain activation difference between different cognitive conditions,with happy FE presentation showing greater LFHO power than neutral FE presentation.These results demonstrate that stimuli flashing at a given frequency can induce LFHO in the prefrontal cortex,which provides new insights into the cognitive mechanisms involved in slow oscillation.

Normal values of flash visual evoked potentials in rabbits: Differences between the sexes and the eyes

BACKGROUND: The wave form, latency and wave amplitude of visual evoked potentials (VEP) are obviously affected by the stimulative parameters, physiological status of the subjects and anesthetics, thus there are greater normal variations and individual differences. The features of flash VEP (F-VEP) are to be observed. OBJECTIVE: To observe and compare the differences of F-VEP latencies and wave amplitudes between eyes in rabbits, and investigate the correlation with sex and the side of eyes. DESIGN: A comparative animal experiment. SETTING: Department of Neurosurgery, General Hospital of Chinese PLA. MATERIALS: The experiment was carried out in the neurophysiological laboratory of the Institute of Neurosciences, General Hospital of Chinese PLA from September 2004 to February 2005. Thirty big-ear rabbits of clean degree, 15 males and 15 females, weighing 2.0-2.5 kg, were provided by the animal center of the General Hospital of Chinese PLA. METHODS: Viking-IV perioperative monitor and flash stimulator for special use were applied. The rabbits were anesthetized with intramuscular injection of compound ketamine. The recording electrode was placed at 3 mm anterior to exoccipital tuberosity (onion, Oz), and the reference electrode was placed at the ear edge of the same side. The stimulative frequency was 1.9 Hz, and the amplifier was 50 μV; The range of wave filter was 5 Hz for high pass and 100 Hz for low pass; The average overlapping was 200 times, and the analytical time was 250 ms. MAIN OUTCOME MEASURES: Comparison of F-VEP wave forms; F-VEP latencies and wave amplitudes. RESULTS: All the 30 rabbits were involved in the analysis of results. ① Comparison of F-VEP wave forms in rabbits: The F-VEP waves mainly manifested as positive-negative-positive (PNP). The F-VEP manifestations to light stimulations were extremely similar between left and right eyes, and the wave amplitudes of both eyes were obviously increased. ② Determinations of F-VEP latencies and wave amplitudes: There were no significant differences in the latencies and wave amplitudes of F-VEP between the two groups (P > 0.05), the latencies of P1, N1 and P2 waves of left eye were (32.59±2.01), (43.85±4.35) and (66.20±8.13) ms, respectively, and the wave amplitudes of P1, N1 and P2 waves of left eye were (16.45±10.22), (7.93±3.56) and (17.62±8.18) μV. F-VEP latencies were stable with small changes, whereas amplitudes had greater changes. CONCLUSION: ① The latency and wave amplitudes F-VEP were stable with good repetition. ② The latencies and wave amplitudes had no significant differences between males and females, as well as between left and right eyes. Further investigation should be undertaken on the animal and clinical field.

Effect of Wei’s triple nine needling therapy on flash visual evoked potentials in rats with traumatic optic neuropathy

Objective:To investigate the effect of Wei’s triple nine needling therapy on the N2-P2 wave of the flash visual evoked potential(FVEP)in rats of the of the transverse directional pulling model.Methods:Thirty-six Wistar rats were randomly grouped,nine were in normal control group without any treatment,and the remaining 27 were surgically modelled in the right eyes.Eighteen of these rats were randomly divided into a Wei’s triple nine needling therapy group and a model group of nine rats each after the TON model was made using the transverse quantitative retraction method.The other 9 rats were sham-operated,and only the optic nerve was exposed without retraction.On the next day of modelling,the Wei’s triple nine needling therapy group was treated with Wei’s triple nine needling therapy for 20 minutes/1 time/1 day for 14 days.The model group,sham-operated group and normal control group were not intervened.Wei's triple nine acupoints were represented as follows:1st link:"Jingming"(BL1)and"Chengqi"(ST1);2nd link:"Sizhukong"(SJ23)penetrating"Taiyang"(EX-HN5);and the third:"Fengchi"(GB 20)and"Taichong"(LV3).The FVEP of each group was observed on 1d,7d and 14d.The FVEP of each group was observed on 1d,7d and 14d.Results:Compared with the model group,the N2 wave latency and P2 wave latency were shortened in the Wei’s triple nine needling therapy on 1d(P<0.05,P<0.01);on 7d,their N2 wave latency was shortened(P<0.01)and the N2-P2 wave amplitude was increased compared with the model group(P<0.05);on 14d,their P2 wave latency was shortened(P<0.05)and the N2-P2 wave amplitude was increased.There was no statistical difference in N2 wave latency,P2 wave latency and N2-P2 wave amplitude in the sham-operated group on 1d,7d and 14d(P>0.05).The delayed N2 and P2 wave latencies in the model group did not improve from 1d to 14d(P>0.05)and the amplitude decreased throughout,showing a significant difference on 14d compared to 1d(P<0.05).In contrast,the N2 wave latency in Wei’s triple nine needling therapy group was not significantly different until 7d to 14d(P<0.05);its P2 wave latency,although significantly delayed from 1d to 7d(P<0.05),recovered on 14d and reached a level that was not statistically different from 1d and 7d(P>0.05).There was also no significant decrease in N2-P2 wave amplitude between 1d and 14d in Wei’s triple nine needling therapy group(P>0.05).Conclusion:In this experiment,the TON rat model was successfully established by the transverse quantitative retraction method,and the treatment of TON rats with Wei’s triple nine needling therapy reduced the P2 wave delay of the FVEP electrophysiological signal and increased the N2-P2 amplitude,which had a certain positive effect on the repair of optic nerve injury,probably related to its effect of improving the conduction function of the optic nerve and protecting the retinal ganglion cells that had not been degenerated and necrosed.

Observing the steady-state visual evoked potentials with a compact quad-channel spin exchange relaxation-free magnetometer

We observed the steady-state visually evoked potential(SSVEP) from a healthy subject using a compact quad-channel potassium spin exchange relaxation-free(SERF) optically pumped magnetometer(OPM). To this end, 30 s of data were collected, and SSVEP-related magnetic responses with signal intensity ranging from 150 fT to 300 f T were observed for all four channels. The corresponding signal to noise ratio(SNR) was in the range of 3.5–5.5. We then used different channels to operate the sensor as a gradiometer. In the specific case of detecting SSVEP, we noticed that the short channel separation distance led to a strongly diminished gradiometer signal. Although not optimal for the case of SSVEP detection, this set-up can prove to be highly useful for other magnetoencephalography(MEG) paradigms that require good noise cancellation.Considering its compactness, low cost, and good performance, the K-SERF sensor has great potential for biomagnetic field measurements and brain-computer interfaces(BCI).

Characteristics of Pattern Visual Evoked Potential in Two Eyes with Varying Visual Acuity in One Eye and Forensic Application

In this study, we aimed to study the pattern visual evoked potentials （P-VEPs） in two eyes with varying visual acuity in one eye and to provide an objective estimation of visual acuity by comparing P-VEPs in one and two eyes. Thirty subjects were chosen, who had one eye with an acuity of 5.0, 4.85, 4.6, 4.0, or scieropia and obstructed vision and the other eye with an acuity of 5.0, respectively. P-VEPs were detected under the large grating stimuli at 3x4 spatial frequency, moderate grating stimuli （12× 16 spatial frequency） and small grating stimuli （48×64 spatial frequency）. Under large grating stimuli, there was no significant difference in P100 peak latency between the groups, nor was there a significant difference between the amplitude of two eyes and the amplitude of one normal-vision eye. Under moderate and small grating stimuli, there was a significant difference in P100 peak latency between the group with both eyes having an acuity of 5.0 and the group with visual acuity below 4.0 in one eye. There was a significant difference in P100 amplitude between the group with visual acuity of 5.0 in both eyes and the group with one normal-vision eye. There was no significant difference in the amplitude of two eyes and the amplitude of one normal-vision eye between any other two groups. In forensic identification, characteristics and variability of P-VEPs in one and two eyes can be used to identify malingering or decline in visual acuity.

Effect of sodium tungstate on visual evoked potentials in diabetic rats

AIM： To evaluate the effect of sodium tungstate on visual evoked potentials（VEPs） in diabetic rats.· METHODS： Wistar rats were randomly divided into three groups as normal control, diabetic control and diabetic rats treated with sodium tungstate. Diabetes was induced by single intraperitoneal injection of streptozotocin（50 mg/kg）. Sodium tungstate [40 mg/（kg·d）]was administered for 12 wk and then VEPs were recorded.Additionally, thiobarbituric acid reactive substance（TBARS） levels were measured in brain tissues.·RESULTS： The latencies of P1, N1, P2, N2 and P3 waves were significantly prolonged in diabetic rats compared with control group. Diabetes mellitus caused an increase in the lipid peroxidation process that was accompanied by changes in VEPs. However, prolonged latencies of VEPs for all components returned to control levels in sodium tungstate-treated group. The treatment of sodium tungstate significantly decreased brain TBARS levels and depleted the prolonged latencies of VEP components compared with diabetic control group.· CONCLUSION： Sodium tungstate shows protective effects on visual pathway in diabetic rats, and it can be worthy of further study for potential use.

Efficacy of nerve growth factor on the treatment of optic nerve contusion Evaluation with visual evoked potential

BACKGROUND： Pattern- visual evoked potential （PVEP） can reflect the functional status of retinal ganglial cells （RGC） and visual cortex, and is an objective examination for visual pathway function. It is a unique method for objectively examining the optic nerve function of optic ganglion cells. OBJECTIVE： To observe the effects of nerve growth factor （NGF） on PVEF in the treatment of optic nerve contusion, evaluate the clinical efficacy of NGF, and make an efficacy comparison with vitamin B12. DESIGN： A randomly grouping, controlled observation. SETTING： Department of Ophthalmology, Tangshan Gongren Hospital Affiliated to Hebei Medical University. PARTICIPANTS： Forty patients with optic nerve contusion caused by eye trauma, who received the treatment in the Tangshan Worker Hospital Affiliated to Hebei Medical University between January 2006 and June 2007, were recruited in this study. The involved 40 patients, including 34 males and 6 females, were aged 14-59 years. They were confirmed to have optic nerve contusion by ophthalmologic consultation combined with history of disease and orbital CT examination. Informed consents of treatments and detected items were obtained from all the patients. The patients were randomly divided into 2 groups with 20 in each： NGF group and vitamin B12 group. METHODS： Conservative treatment was used in the two groups. In addition, patients in the NGF group were intramuscularly injected with NGF solution 18 μg /time, once a day. Those in the vitamin B12 group were injected by the same method with common vitamin B12 of 500 μg combined with vitamin B1 of 100 mg, once a day. MAIN OUTCOME MEASURES： PVEP examination was conducted in all the patients before, one and two weeks after treatment, and latency and amplitude at P100 were detected. RESULTS： Forty patients with optic nerve contusion participated in the final analysis. Before treatment, significant differences in the latency and amplitude at P100 were not found in patients between two groups （P 〉 0.05）. For each patient in the NGF group, the latency of PVEP at P100 was significantly shortened, and the amplitude was significantly increased one and two weeks after treatment as compared with vitamin B12 group（t =2.06-2.34, P 〈 0.05）. CONCLUSION： NGF treatment can obviously improve the visual function of patients with optic nerve contusion. The curative effect of NGF is superior to vitamin B12.

Specificity and sensitivity of visual evoked potentials P100 latency to different events exercise

Visual evoked potentials (VEPs) are a series of signals about visual occipital cortex in response to visual stimuli and can be used as one of ob-jective non-invasive neuro-physiological pa-rameters to reflect the visual organs and central visual pathway’s functional integrity. Previous studies have shown that acute and chronic ex-ercise could affect VEPs independent from body temperature and other physiological parameters. VEPs may well be used as neuro-physiological criteria in defining the performances of the ath-letes. Different sports training have different effects on VEPs, but the results are not consis-tent. P100 latency is the representative compo-nent of VEPs and it is of high, steady amplitude and of slight intra- and inter-individual variabil-ity so that the index is most commonly used. The purpose of this study was to investigate the specificity and sensitivity of P100 latency to dif-ferent physical activities. The neural electricity device of NDI-200 was used to measure the pattern reversal VEPs of all subjects, including the values of the resting state before and after different events exercise. Different events exer-cise contained an aerobic cycloergometric ex-ercise (7 subjects were conducted to a Bruce Graded Exercise Test on the Monark Ergomedic 839E cycloergometer, THR (target heart rate) = 85% HRmax, 3 times/week, about 10 minutes once time, 6 weeks), tennis training (16 volun-teers, 2 hours/day, 3 days/week, 8 weeks), aerobic Latin exercise (7 subjects, 1 hour/day, 3 days/week, 6 weeks) and the Baduanjin of Health Qigong training (6 subjects, 1 hour/day, 3 days/week, 6 weeks). The VEPs recordings of the control groups obtained synchronized with the experimental groups. SPSS 11.5 for win-dows was used for statistical analysis. A level of P﹤0.05 was accepted as statistically significant. The VEPs P100 latency of post-exercise of all experimental groups except Baduanjin group became shorter significantly compared with those of pre-exercise (P﹤0.05). No significant difference was found between pre-and post- exercise for the control groups. This study showed that exercise could shorten the P100 la-tency significantly. Moreover, it also indicated that VEPs were sensitive to exercise to a certain extent. We concluded that VEPs might well be used as neuro-physiological criteria in defining the performances of the athletes. It was found that the VEPs P100 latency became shorter after most training programs;furthermore, it demon-strated that P100 latency of VEPs had little specificity to different events.

Applications of the isolated-check visual evoked potential in primary open angle glaucoma with or without high myopia

AIM:To explore the diagnostic performance of isolatedcheck visual evoked potential(ic VEP)for primary open angle glaucoma(POAG)in both highly myopic and nonhighly myopic populations and compare it with those of optical coherence tomography(OCT)and Heidelberg retinal tomography(HRT)parameters.METHODS:A total of 126 participants were recruited,including 31 highly myopic participants with POAG(HM-POAG),36 non-highly myopic participants with POAG(NHM-POAG),25 highly myopic participants without POAG(HM)and 34 controls without high myopia(Normal).All the participants underwent a complete ophthalmic examination.The signal-to-noise ratio(SNR)was used to assess the ic VEP.Both qualitative and quantitative diagnostic performances of OCT,HRT and the ic VEP were analyzed and compared.RESULTS:Based on the criterion of SNR≤1,the diagnostic performance of the ic VEP in highly myopic subjects[area under the receiver operating characteristic curve(AUC)=0.862]was better than that in non-highly myopic subjects(AUC=0.789),and the SNR had fairly good specificity.In distinguishing the HM-POAG and HM groups,the AUC of the SNR was not different from those of the OCT and HRT parameters(P>0.05)in either the qualitative or quantitative comparison.In the qualitative analysis,the ic VEP showed good consistency with damage to the central 10°of the visual field(kappa=0.695-0.747,P<0.001).CONCLUSION:The ic VEP has the potential to discriminate individuals with and without POAG,especially in populations with high myopia.

Appropriate stimulation in visual evoked potential to evaluate visual perception state of athletes

BACKGROUND： Several studies have demonstrated that visual evoked potentials can be influenced by sport events. To the best of our knowledge, there are no specific parameters for the most appropriate stimulation for evaluating the functional state of athletes. OBJECTIVE： To investigate the best stimulation in visual evoked potential to apply to functional evaluation of athletes. DESIGN, TIME AND SETTING： Ninety-five, healthy students from the Shandong Normal University took part in an observational, contrast study. PARTICIPANTS： All active participants were male. Sixty-five students majored in physical education, and had participated in exercise for the duration of （4.26 ± 3.08） years. An additional 30 students majored in other subjects. METHODS： The neural electricity tester, NDI-200, was adapted to examine and record visual evoked potential with varying probes using bipolar electrodes attached to the head of all the participants in a dark room. The visual evoked potential values were analyzed transversally. A chessboard pattern reversal method was applied with the following parameters： 2 Hz stimulation frequency, brightness of 90 cdp, 80% contrast, 1-100 Hz bandpass filters, and 10 μV sensitivity; 100 responses were averaged. MAIN OUTCOME MEASURES： latency, peak latencies, and inter-peak latencies were measured in N75, P100, N145 with varying probe stimulations. RESULTS： （1） Comparisons between the little check, middle check, and big check stimulation, demonstrated that the common tendencies in visual evoked potential indexes of the two groups of N75 latency were successively shorter and N145 were longer. P100-N145 peak latency was decreased and each inter-peak latency was longer. （2） Changes of N75, P100, and N145 with different check stimulations in the physical education student group： after compared with the middle check stimulation, N75 latency was significantly longer （P 〈 0.01）, and N75-P100 inter-peak latency （P 〈 0.05） and N75-N145 inter-peak latency were both shorter （P 〈 0.05）. N75-P100 inter-peak latency was shorter （P 〈 0.01） in the little check stimulation. When compared with the big check stimulation, N75 latency was significantly longer （P 〈 0.01） and N145 was shorter （P 〈 0.01）. Compared with the big check stimulation, N145 latency was significantly shorter （P 〈 0.05） （3） Changes of N75, P100, and N145 with different check stimulations in the normal students： when compared with the big check stimulation, N75 latency was significantly longer （P 〈 0.05） and N145 latency was shorter （P 〈 0.05）. Each inter-peak latency was shorter （P 〈 0.05） in the little check stimulation. When comparing the middle check stimulation, N75-N145 inter-peak latency was shorter （P 〈 0.05）. CONCLUSION： Large visual evoked potential differences were observed between students majoring in physical education and other subjects when medium probe stimulation was applied. These results suggest that the use of medium probe stimulation （25 mm×25 mm） should be adopted when evaluating the functional state of athletes.

Effect of visual stimulus locations on pattern-reversal visual evoked potential An epidural electrocorticogram study

To explore the effect of the location of a visual stimulus on neural responses in the primary visual cortex （V1）, a micro-electromechanical system-based microelectrode array with nine channels was implanted on the cerebral dura mater of V1 in adult cats. 2 Hz pattern reversal checkerboard stimul were used to stimulate the four visual quadrants （i.e., upper left, upper right, lower left, and lower right fields）. The results showed that there was a N75 component of the visual evoked potential around 50-80 ms after the onset of a checkerboard stimulus, and the onset of these N75 peaks varied with different stimulus locations. The checkerboard stimuli Jnduced shorter latencJes in the contralateral V1 than in the ipsilateral V1, while the checkerboard stimulus in the upper half visual field induced shorter latencies for N75. These results suggested that the pattern-reversal stimuli induced neural activities in V1 that can be recorded with multichannel microelectrodes, and more detailed temporal and spatial properties can be measured.

Retinal Symmetry of Multifocal Visual Evoked Potential in Both Eyes of Normal Subjects

Purpose:.To analyze the retinal symmetry of multifocal visual evoked potential (mfVEP) in both eyes of normal subjects. Methods: The monocular mfVEP in both eyes of 36 normal subjects (72 eyes) were tested with VERIS Science 4.0. The stimulus was the pattern reversal dart array consisted of 60 sectors each including 16 black-white reverse patterns. The visual stimulation was controlled by a binary pseudo-random m-sequence and subtended 25 degrees of retinal region. Results: The mfVEP patterns between left and right eyes of each subject were similar, and P1 latency and amplitude in correspondent visual field quadrants between left and right eyes had no significant difference(P>0.05). The latency of superotemporal visual field quadrant in right eyes was shorter than that of superonasal visual field quadrant in left eyes,and the amplitude of superonasal visual field quadrant in right eyes was longer than that of superotemporal visual field quadrant in left eyes(P<0.05). The P1 latency and amplitude among four visual field quadrants of each eye had significant difference(P<0.05). The P1 latency between the superonasal visual field quadrant and inferotemporal visual field quadrant or between the superonasal visual field quadrant and inferonasal quadrant visual field had significant differences in right or left eyes(P<0.05). Conclusion: The mfVEP of normal subjects exists retinal symmetry.

Local Electroretinogram and Pattern Visual Evoked Potential in Maculopathies

Purposes: To observe the characteristics of local electroretinogram (LERG) in normal subjects and patients with maculopathies, and to evaluate the applied worth of LERG and pattern visual evoked potential (PVEP) in maculopathies. Methods: LERGs at 5° and 15° macular regions were recorded from 27 normal subjects (54 eyes). The factors of age, different eyes and stimulate areas for LERG influence were observed. Meanwhile, the LERG and PVEP were recorded from 25 patients (35 eyes) with maculopathies for making contrast study. Results: In normal subjects, there was no significant influence of age to LERG. As the stimulated areas increased, the a- and b-wave amplitudes of LERG increased. In the patients with maculopathies, the a- and b-wave amplitudes of LERG at 5°, 10°and 15° macular regions were significantly lowered and the mean values of P1 latency were prolonged and N1-P1 amplitudes of VEP were lowered, comparing with the control group. In the nearing stimulated area (5°LERG and 14. 9×19°PVEP.),

Influence of stimuli color on steady-state visual evoked potentials based BCI wheelchair control

In recent years, Brain Computer Interface (BCI) systems based on Steady-State Visual Evoked Potential (SSVEP) have received much attention. This study tries to develop a SSVEP based BCI system that can control a wheelchair prototype in five different positions including stop position. In this study four different flickering frequencies in low frequency region were used to elicit the SSVEPs and were displayed on a Liquid Crystal Display (LCD) monitor using Lab-VIEW. Four stimuli colors, green, red, blue and violet were used to investigate the color influence in SSVEPs. The Electroencephalogram (EEG) signals recorded from the occipital region were segmented into 1 second window and features were extracted by using Fast Fourier Transform (FFT). One-Against-All (OAA), a popular strategy for multiclass SVM, is used to classify SSVEP signals. During stimuli color comparison SSVEP with violet color showed higher accuracy than that with green, red and blue stimuli.

The Changes of Pattern Reversal Visual Evoked Potentials in Normal Infants

Purpose:To study pattern reversal visual evoked potential(PVEPs)and deter-mine the developmental character and mature time of visual function in normal in-fants t different months of age.Methods:PVEPs were recorded from115normal infants at3,6,9,12moths age.P1latency for different checks(1°40′，25′，6′）was analyzed and compared to those of normal adults,Changes of N1,N2latency of PVEPs were also exam-ioned.Results:P1 latency for all checks(1°40′,25′，6′）was significantly longer at 3months than at 6months of age(P<0.05),but no significant differences can be seen after 6months of age for largen(1°40′）and intermediate(25′）checks(P>0.05).P1latency for larger checks(1°40′）reached adult level after 3months of age,but not for the intermediate check(25′）,while P1latency for small check(6′）presented the character of fluctuation.Conclusion:The visual system continued to develop after birth and appeared a certain regularity,Our results showed thatP1latency for larger check(1°40′）reached adult levels after 3months of age.ButP1latency for intermediate check still has not reached adult levels after 3months of age.To deterine the age at which adult levels are finally reached,infants of 12months and older must be tested.The reason why P1latency for smaller check(6′）presented the character of fluctuation should be the temporal tuning function developing much more slowly.Eye Science1995;11:161-164.

EXPERIMENTAL AND CLINICAL STUDY ON BILIRUBIN NEUROTOXICITY DETECTED BY VISUAL EVOKED POTENTIALS TO FLASH

Objective Evaluate the sensitivity and reliability of visual evoked potential to flash (F-VEP) in detecting bilirubin neurotoxicity and approach the risk parameters of bilirubin neurotoxicity in hyper-bilirubinemia newborns. Methods Based on the successful establishment of animal models for acute bilirubin encephalopathy by intraperitoneal infusion of bilirubin with a dosage of 100～200μg/g body weight to 1-week-old guinea pigs, the F-VEP was recorded in animal models and human neonates with hyperbilirubinemia, and the sensitivity and reliability of F-VEP in detecting bilirubin neurotoxicity were evaluated. Results F-VEP features and its P1 latency significantly correlated to brain adenosine triphosphate (ATP) level, neurobeha-vioral and neuropathological changes in experimental bilirubin encephalopathy; neonates with hyperbiliru-binemia showed significant F-VEP changes characterized by absence of P1 or P1 latency prolonged in 1～7-day-old newborns, especially when the jaundice was caused by immun oincompatibility and infectious diseases. Conclusion F-VEP would be a good discriminator for bilirubin neurotoxicity, and can become a promising technique in monitoring bilirubin encephalopathy.