Motion-onset Visual Evoked Potentials Research Articles

Optic nerve involvement in patients with Lyme neuroborreliosis: an electrophysiological study.

The aim of this neurophysiological study was to retrospectively analyze visual evoked potentials (VEPs) acquired during an examination for diagnosing optic nerve involvement in patients with Lyme neuroborreliosis (LNB). Attention was focused on LNB patients with peripheral facial palsy (PFP) and optic nerve involvement. A total of 241 Czech patients were classified as having probable/definite LNB (193/48); of these, 57 were younger than 40 years, with a median age of 26.3 years, and 184 were older than 40 years, with a median age of 58.8 years. All patients underwent pattern-reversal (PVEP) and motion-onset (MVEP) VEP examinations. Abnormal VEP results were observed in 150/241 patients and were noted more often in patients over 40 years (p = 0.008). Muscle/joint problems and paresthesia were observed to be significantly more common in patients older than 40 years (p = 0.002, p = 0.030), in contrast to headache and decreased visual acuity, which were seen more often in patients younger than 40 years (p = 0.001, p = 0.033). Peripheral facial palsy was diagnosed in 26/241 LNB patients. Among patients with PFP, VEP peak times above the laboratory limit was observed in 22 (84.6%) individuals. Monitoring of patients with PFP and pathological VEP showed that the adjustment of visual system function occurred in half of the patients in one to more years, in contrast to faster recovery from peripheral facial palsy within months in most patients. In LNB patients, VEP helps to increase sensitivity of an early diagnostic process.

Effects of motion type on motion-onset and steady-state visual evoked potentials: rotation vs. flicker.

The underlying mechanisms of information processing for two basic motion types, rotation and flicker, are not fully understood. Rotational and flickering animations at four speeds - 7 frames per second (fps), 8 fps, 11 fps, and 12 fps, respectively - are presented as visual stimuli. The motion-onset visual evoked potentials (VEPs) and steady-state VEPs (SSVEP) elicited by these motion stimuli were compared between the rotation and flicker motion types at time windows of 0-500 ms and 1000-5000 ms post-stimulus, respectively. The standardized low-resolution electromagnetic tomography (sLORETA) source localization was investigated as well. Four motion speeds had no effect on the whole VEP waveform in either the rotation or the flicker groups. Significant differences in motion-onset VEPs and sLORETA source localization were found between the rotation and the flicker motion types at time windows of 200-500 ms post-stimulus. For the time windows of 1000-5000 ms post-stimulus, both the rotation and flicker groups all demonstrated the characteristics of SSVEP, with the peak spectral topographies showing at the four different frequencies, which correspond to the four motion speeds. Additionally, a higher power of spectral topography at each of the four motion speeds was found in the rotation relative to the flicker stimulation. The perceptual and cognitive processes are distinct for two types of motion: rotation and flicker. In terms of motion-onset VEPs and the characteristics of SSVEP, rotating visual stimulation is superior to flicker stimulation and may be more appropriate for clinical and engineering applications.

Effect of Dioptric Blur on Pattern-Reversal and Motion-Onset VEPs as Used in Clinical Research.

To describe the effect of dioptric blur on visual evoked potentials (VEPs) induced by motion onset (MO-VEPs). The effect of dioptric blur up to 4 D on MO-VEPs was tested on 12 subjects using central, peripheral, and full-field stimulation with a low-contrast structure of concentric circles with spatial frequency <1 c/°. The results were compared to VEPs evoked by 15' and 60' checkerboard pattern-reversal (PR-VEPs). The relationship between peak time and interpeak amplitude of the dominant components was related to the level of dioptric blur using linear regression. The MO-VEPs did not show a significant peak prolongation (P > 0.28) or amplitude attenuation (P > 0.14) with the blur, whereas for the PR-VEPs we observed a significant decrease in amplitude (P < 0.001) and increase in peak time (P < 0.001) for both checkerboard sizes. For MO-VEPs induced by radial motion of low contrast and low spatial frequency pattern, the change in retinal blur does not affect the peak time or the interpeak amplitude of the dominant N2 component. The resistance to retinal blur that we demonstrated for MO-VEP provides a diagnostic opportunity to test the integrity of the visual system and reveal a retrobulbar impairment even in uncorrected refractive errors.

Optical coherence tomography and visual evoked potentials in evaluation of optic chiasm decompression

Chiasmal compression is a known cause of visual impairment, often leading to surgical decompression of the optic chiasm (OC). A prospective study was held at University Hospital in Hradec Králové to explore sensitivity of optical coherence tomography (OCT) and visual evoked potentials (VEPs) to OC compression and eventual changes after a decompression. 16 patients with OC compression, caused by different sellar pathologies, were included. The main inclusion criterion was the indication for decompressive surgery. Visual acuity (VA), visual field (VF), retinal nerve fibre layer (RNFL) and ganglion cell layer (GCL) thickness, and peak time and amplitude of pattern-reversal (P-VEPs) and motion-onset VEPs (M-VEPs) were measured pre- and postoperatively. The degree of OC compression was determined on preoperative magnetic resonance imaging. For M-VEPs, there was a significant postoperative shortening of the peak time (N160) (p < 0.05). P100 peak time and its amplitude did not change significantly. The M-VEPs N160 amplitude showed a close relationship to the VF improvement. Thinner preoperative RNFL does not present a statistically important limiting factor for better functional outcomes. The morphological status of the sellar region should be taken into consideration when one evaluates the chiasmal syndrome. M-VEPs enable detection of functional changes in the visual pathway better than P-VEPs.

Short- and Long-Term Stroboscopic Training Effects on Visuomotor Performance in Elite Youth Sports. Part 2: Brain-Behavior Mechanisms.

Stroboscopic training has repeatedly been shown to improve visuomotor abilities. However, although performance improvements were attributed to visual processes, information on the neurophysiological mechanisms is missing. Part 2 of this study investigated the effects of stroboscopic training on neural visual and motor functions and its contribution to training-induced changes in visuomotor reaction time. Forty-five young elite badminton athletes participated in this study, of which 32 (age, 13.7 yr) were included in the final data analysis. Participants were assigned to an intervention (stroboscopic vision) or control group (normal vision). Before and after a 10-wk training and after a 6-wk retention period, participants performed visual perception and reaction tasks in response to visual motion stimuli. The N2 and N2-r motion onset visual-evoked potentials, its linear combination (Vlc), and the BA6 negativity potential were determined using a 64-channel EEG. A significant TIME-GROUP effect was observed for the Vlc score (P = 0.019, ηp2 = 0.18), indicating a lower Vlc in the intervention group. However, post hoc tests did not reach significance. Within-subject correlation analyses revealed that changes in reaction speed were related to latency changes in N2 (r = 0.59, P < 0.001), N2-r (r = -0.64, P < 0.001), and the combined Vlc (r = 0.68, P < 0.001). Regression analyses across participants including multiple (N2/N2-r) or single (Vlc) predictors provided an explained variance of >60% (N2/N2-r, r2 = 0.62; Vlc, r2 = 0.64). No training effects or correlations were observed for the BA6 negativity. The results indicate that faster visuomotor reactions after stroboscopic training are accompanied by accelerated visual perception and processing, whereas motor processes seemed to be unaffected. Stroboscopic training may be promising to specifically address the visual system in visuomotor-demanding sports.

06-Diagnostic substantiation and current possibilities of VEPS examination

The aim of this introductory lecture is to point out that despite the intensive use of modern imagine techniques (MRI, OCT, etc.), the diagnostic applications of visual evoked potentials (VEPs) need not be obsolete, if not preferable in many cases. This objective, fully non-invasive, low-cost electrophysiological method can detect functional problems of the optic pathway and various brain cortical areas even before a development of the first displayable morphological changes. For the increased sensitivity of VEPs, it is necessary to use a larger spectrum of visual stimuli (activating quite selectively different subsystems of the visual pathway and visual cortex) compared to standards recommended by ISCEV or IFCN. It should include not only flash or pattern-related stimuli (pattern-reversal, pattern-on/off) but also motion-related (motion-onset VEPs) and cognitive visual stimulation. Then, not only the early diagnostics of a large spectrum of neuro-ophthalmological and neuro-psychiatric disorders is possible but also the physiological aging of visual information processing or a drug abuse is recognisable. For a better availability of VEPs examination and their long-term monitoring also in home conditions, we have just introduced a “Mobile (wearable), low-cost device for examination of visual evoked potentials (VEPs)”, the use of which will be demonstrated during the lecture. Acknowledgements: Supported by the project of Charles University “Progres Q40/07”.

Visual but not motor processes predict simple visuomotor reaction time of badminton players

The athlete’s brain exhibits significant functional adaptations that facilitate visuomotor reaction performance. However, it is currently unclear if the same neurophysiological processes that differentiate athletes from non-athletes also determine performance within a homogeneous group of athletes. This information can provide valuable help for athletes and coaches aiming to optimize existing training regimes. Therefore, this study aimed to identify the neurophysiological correlates of visuomotor reaction performance in a group of skilled athletes. In 36 skilled badminton athletes, electroencephalography (EEG) was used to investigate pattern reversal and motion onset visual-evoked potentials (VEPs) as well as visuomotor reaction time (VMRT) during a simple reaction task. Stimulus-locked and response-locked event-related potentials (ERPs) in visual and motor regions as well as the onset of muscle activation (EMG onset) were determined. Correlation and multiple regression analyses identified the neurophysiological parameters predicting EMG onset and VMRT. For pattern reversal stimuli, the P100 latency and age best predicted EMG onset (r = 0.43; p = .003) and VMRT (r = 0.62; p = .001). In the motion onset experiment, EMG onset (r = 0.80; p < .001) and VMRT (r = 0.78; p < .001) were predicted by N2 latency and age. In both conditions, cortical potentials in motor regions were not correlated with EMG onset or VMRT. It is concluded that previously identified neurophysiological parameters differentiating athletes from non-athletes do not necessarily determine performance within a homogeneous group of athletes. Specifically, the speed of visual perception/processing predicts EMG onset and VMRT in skilled badminton players while motor-related processes, although differentiating athletes from non-athletes, are not associated simple with visuomotor reaction performance.

Pattern- and motion-related visual evoked potentials in HIV-infected adults.

The goal of the current study was to explore visual function in virally suppressed HIV patients undergoing combined antiretroviral therapy (cART) by using pattern-reversal and motion-onset visual evoked potentials (VEPs). The pattern-reversal and motion-onset VEPs were recorded in 20 adult HIV+ patients with a mean age of 38years and CD4 cell counts ≥230×106 cells/L of blood. Nine out of 20 patients displayed VEP abnormalities. Pattern-reversal VEPs pathology was observed in 20% of subjects, and 45% HIV patients had impaired motion-onset VEPs. Five out of 16 neurologically asymptomatic HIV patients had prolonged motion-onset VEP latencies in both eyes. Four neurologically symptomatic patients displayed simultaneously abnormal motion-onset and pattern-reversal VEP latencies: monocular involvement was observed in two patients with Lyme and cytomegalovirus unilateral optic neuritis. Binocular involvement was noted in two patients with cognitive deficits. Correlation analysis between disease duration, CD4 cell count, HIV copies in plasma, MoCA and electrophysiological parameters did not show any significant relationships. The functional changes of the visual system in neurologically asymptomatic virally suppressed HIV patients displayed higher motion-onset VEP sensitivity than in standard pattern-reversal VEP examinations. This promising marker, however, has no significant association with clinical conditions. Further exploration is warranted.

Comparison of visual information processing in school-age dyslexics and normal readers via motion-onset visual evoked potentials

Standard pattern-reversal visual evoked potentials (VEPs) and motion-onset VEPs (M-VEPs) were tested in 19 dyslexics and 19 normal readers aged 7–13years in order to evaluate the feasibility of M-VEPs for the objective diagnostics of a visual subtype of dyslexia, in which a dysfunction of the magnocellular subsystem/dorsal stream of the visual pathway is suspected. The set of VEPs consisted of the pattern-reversal VEPs with check sizes of 20’, two types of translational motion (with low and high contrast) and two types of radial motion (in the full field or the periphery). While the P100 peak parameters in pattern-reversal VEPs did not differ between the group of dyslexics and controls, the group of dyslexics displayed significantly longer N2 latencies in all types of M-VEPs. Abnormal N2 latencies were found in 35–56% of dyslexics in different types of M-VEPs, with translational motion with high contrast being the most sensitive stimulation. A receiver operating characteristic analysis showed that the latencies of M-VEPs displayed higher discrimination potential than M-VEPs amplitudes. The study confirms a “magnocellular pathway/dorsal stream deficit” in approximately half of dyslexics.

Cortical configuration by stimulus onset visual evoked potentials (SO-VEPs) predicts performance on a motion direction discrimination task

The slowing of information processing, a hallmark of cognitive aging, has several origins. Previously we reported that in a motion direction discrimination task, older as compared to younger participants showed prolonged non-decision time, an index of an early perceptual stage, while in motion onset visual evoked potentials (MO-VEPs) the P1 component was enhanced and N2 was diminished. We did not find any significant correlations between behavioral and MO-VEP measures. Here, we investigated the role of age in encoding and perceptual processing of stimulus onset visually evoked potentials (SO-VEPs). Twelve healthy adults (age<55years) and 19 elderly (age>55years) performed a motion direction discrimination task during EEG recording. Prior to motion, the stimulus consisted of a static cloud of white dots on a black background. As expected, SO-VEPs evoked well defined P1, N1, and P2 components. Elderly participants as compared to young participants showed increased P1 amplitude while their P2 amplitude was reduced. In addition elderly participants showed increased latencies for P1 and N1 components. Contrary to the findings with MO-VEPs, SO-VEP parameters were significant predictors of average response times and diffusion model parameters. Our electrophysiological results support the notion that slowing of information processing in older adults starts at the very beginning of encoding in visual cortical processing, most likely in striate and extrastriate visual cortices. More importantly, the earliest SO-VEP components, possibly reflecting configuration of visual cortices and encoding processes, predict subsequent prolonging and tardiness of perceptual and higher-level cognitive processes.

37. Difficulties of motion-onset VEP examination in children

Introduction In our previous papers (for review see Kuba et al., Vision Res., 2007, 47, 189–202) we have shown that in adults the motion-onset visual evoked potentials (M-VEPs) represent a useful diagnostic tool in neuro-opthalmology because they enable to test quite selectively the magnocellular system/dorsal stream function. In adults robust M-VEPs with low variability and typical shape with dominant negative N160 peak can be acquired easily, however, it is difficult to record and evaluate this type of VEPs in children. The M-VEPs go through very long maturation (up to 18 years of age) accompanied by gradual shortening of main negative peak latencies and also by age dependent shape development (Langrova et al., Vision Res., 2006, 46, 536–544). Moreover, they are unidentifiable to standard moving stimuli in some children. To understand better this problem, we tested 30 normal children aged 7–12 years. Methods We performed the set of standard stimuli used in our lab (https://www.lfhk.cuni.cz/elf) for examination of adults – low contrast translation motion (TM) and expansion/contraction motion (EXCOM). Results Reliable VEPs were detected in 77% of children to TM and in 83% of children to EXCOM. The dominant peak of the VEPs was negative in all TM VEPs and in 80% of EXCOM VEPs (positive in 20%). In both VEP types there was large inter-individual latency variability (in the range of 176–268 ms in TM and 176–290 ms in EXCOM). When a high contrast TM stimulus (non-optimal “magno” stimulus) was used, the M-VEP latencies shortened and amplitudes increased in majority of subjects. In contrast to adults, M-VEPs to peripheral stimulation (outside central 20°) were detectable only in 43% of children. Conclusions Our findings show that maturation of motion perception in children is rather inter-individually variable, which makes a diagnostic use of M-VEPs in children quite complicated. Acknowledgement Supported by the project PRVOUK - P37/07.

9. Visual stimulation for long-term monitoring of brain functions via evoked potentials evaluation

Introduction At present, predominantly stationary visual stimulators are used for diagnostic examination of visual evoked potentials (VEPs). They cover significantly the central visual field of the tested subject and such examination does not allow any other parallel activity during the stimulation. Therefore, it cannot be used e.g. for a long-term monitoring and evaluation of functional changes of CNS functions – for continual assessment of visual perception. Methods We have introduced a visual stimulator (Czech Republic patent No. 303192 pending), the principle of which is that the source of light stimuli is in periphery of the visual field – a row of light emitting diodes (LEDs) is placed on the head of a stimulated subject on a standard peak (a part of a baseball cap). A control unit switches individual LEDs (flash or motion stimuli are generated) and synchronizes VEPs evaluation. The set of LEDs is located about 20° from the center of the stimulus field. There are several variants of stimulation available because of significant inter-individual differences in reactivity of subjects to particular stimuli. The motion stimuli have similar parameters as stimulations used for clinical diagnostic purposes (see Kuba, M., Kubova, Z., Kremlacek, J., et al. Motion-onset VEPs: Characteristics, methods, and diagnostic use. Vision Res., 2007, vol. 47, p. 189–202 – http://dx.doi.org/10.1016/j.visres.2006.09.020 ). Recording of VEPs (with the use of built-in amplifiers) and on-line evaluation of their parameter changes can be done via “blue-tooth” transmission to a standard computer or in a built-in microprocessor (in preparation). Results Since using of this kind of VEPs examination does not interfere with common human activities, it is possible to use it not only for standard diagnostic purposes in neuro-ophthalmological diseases but also for monitoring of CNS function changes or level of vigilance/fatigue, e.g. in drivers or some other professions. Supported by EU project CZ.1.05/3.1.00/13.0284 and by Charles University project PRVOUK P37/07.

39. Electrophysiological diagnosis of early cns involvement in HIV-1 infection – Pilot study

Introduction The aim of our study was to verify the possibility of early identification of HIV-related neural injury using visual evoked potentials (VEPs) in neurologically asymptomatic HIV seropositives. In the CART (combination antiretroviral therapy) era, the prevalence of neurocognitive impairment remains high, up to 50%, and HIV-associated neurocognitive disorder (HAND) has shifted towards a milder clinical presentation. Such a mild clinical presentation can escape detection [1]. Methods The examination consisted of the Montreal Cognitive Assessment (MoCA) [2], and VEPs to pattern-reversal, motion-onset stimulation (radial movement), and of visual ERPs recorded during an odd-ball test (http://www.lfhk.cuni.cz/elf). Subjects: 9 homosexual men and 3 heterosexually infected women were examined in this study. All patients had ⩾350×106 CD4 cells/l blood at inclusion. The duration of the HIV infection was 0.5 – 7years, and mean age of the patients was 35 (24–50) years. Results P100 potential was recorded with no alteration in the VEP amplitude or latency. However, in 5 patients with CD4 counts 350–750×106cells/l, there was prolonged latency of the N160 peak compared to the reference values obtained in our laboratory, which suggests a dysfunction of the motion-processing (magnocellular system or the dorsal cortical stream) [3]. P300 latencies and MoCA results were within the normal range in all HIV patients. Conclusions Our data suggest that motion-onset VEPs may be a sensitive measure of subclinical visual pathway dysfunction in early HIV-1 infection, however, we did not reveal any cognitive decline in this pilot group. Subsequently, the patients will be investigated using VEPs and visual ERPs at six-month intervals to evaluate the long-term development of the visual pathway involvement in HIV patients.

Difficulties of motion-onset VEP interpretation in school-age children

In adults, motion-onset visual evoked potentials (M-VEPs) with a dominant N2 peak represent a useful diagnostic tool. However, it is difficult to use this type of VEP in children because of the long maturation (up to 18 years) of M-VEPs, which is characterised by a gradual decrease in N2 peak latency and shape development. Moreover, in some children, M-VEPs are difficult to identify with standard stimuli. We tested features of M-VEPs in 30 children (7-12 years) with the following set of standard stimuli used in our lab for examining adults ( https://web.lfhk.cuni.cz/elf ): low-contrast translation motion (TM) and expansion/contraction motion (ExCoM) in full field and in periphery (with central 20° masked). In 16 children, a high-contrast TM was also tested. With standard (low-contrast) stimuli, a common M-VEP to TM and to ExCoM was detected in 77 and 83 % of children, respectively. The M-VEPs to ExCoM in the periphery were detected in only 43 % of children. An abnormal dominant P1 peak was found in 9 % of VEPs to TM, 12 % of VEPs to full-field ExCoM and 14 % of VEPs to peripheral ExCoM. The M-VEPs to all low-contrast stimuli displayed large inter-individual latency variability (N2 peak latency differed for more than 100 ms). High contrast (more suitable for the non-mature magnocellular pathway) shortened M-VEP latencies and improved amplitudes. Our findings show that the maturation of motion perception in children is inter-individually variable, which limits the diagnostic use of M-VEPs.

VEP evidence of significant differences in motion perception in children

AbstractPurpose In adults the motion‐onset visual evoked potentials (M‐VEPs) represent a useful diagnostic tool in neuro‐opthalmology (Kuba et al.,Vision Res., 2007, 47, 189‐202) since they test quite selectively the magnocellular system/dorsal stream function. Whilst in adults robust M‐VEPs with low variability can be acquired easily, it is difficult to record and evaluate them in children. They not only display very long maturation and age dependent shape development (Langrova et al., Vision Res., 2006, 46, 536‐544) but in some children they are unidentifiable to standard stimuli.Methods To understand better this problem we tested 30 normal children aged 7 ‐ 12 years. Two types of motion stimuli were used – translation motion (TM) and expansion/contraction motion (EXCOM).Results Reliable VEPs were detected in 77% of children to TM and in 83% of children to EXCOM. The dominant peak of the VEPs was negative in all TM VEPs and in 80 % of EXCOM VEPs (positive in 20%). In both VEP variants the latency of the negative peak did not shorten significantly in the tested age range and there was large interindividual latency variability (176 ms – 268 ms). High contrast stimuli (non‐optimal “magno” stimulus) shortened the M‐VEPs latencies and enlarged amplitudes in majority of subjects. M‐VEPs to peripheral stimulation (outside central 20°) were in contrast to adults detectable only in 43 % of children.Conclusion These findings show distinct differences in maturation of motion perception in children, which makes a diagnostic use of M‐VEPs in children quite complicated. Acknowledgement: Supported by the project PRVOUK ‐ P37/07.

Motion‐onset visual evoked potentials ‐ Important tool in vision and eye research

AbstractPurpose Despite quite a long history of visual evoked potentials (VEPs), their use has been limited so far almost exclusively to flash or pattern related responses of the primary visual cortex (mediated mainly via activation of the parvocellular system of the visual pathway. It is surprising that efforts to extend it to more complex testing including an examination of the motion processing system (magnocellular system and dorsal stream) are quite rare (e.g. Kuba and Kubová, Doc Ophthalmol, 1992, 80, 83‐89; Kubová et al., 1995, Vision Res, 35, 197‐205.Methods Early or selective involvement of the motion processing system is suspected in many CNS disorders and we suggest that motion‐onset VEPs may recognize functional problems of this kind better than imagine techniques (Kuba et al., Vision Res, 2007, 47, 189‐202.Results Motion‐onset VEPs display latency shortening up to the age of about 18 years representing very slow individually different maturation of the motion processing system (Langrova et al., Vision Res., 2006, 46, 536‐544. In early adulthood they start accelerated latency prolongation when compared to pattern‐reversal, which might be a good indicator of individual biological ageing (Kuba et al., Vision Res, 2012, 62, 9‐16.Conclusion Since about 30% of pathological findings in our parallel pattern‐reversal and motion‐onset VEPs examinations in neuro‐ophthalmological patients display exclusively the motion‐onset VEPs pathology, we strongly recommend using them both in the theoretical vision research and ophthalmological diagnostics. Acknowledgement: Supported by the project PRVOUK ‐ P37/07.

Aging effects on visual evoked potentials (VEPs) for motion direction discrimination

Age-related declines in motion perception have been well documented. We investigated the impact of age on electrophysiological correlates of motion perception, namely the P1 and N2 components of motion onset visual evoked potentials (MO-VEPs). Additionally, we used a model of response times based on the diffusion model to pinpoint the cognitive processes affected by aging. Twelve healthy adults (age <55years) and 19 elderly (age >55years) performed a motion direction discrimination task during EEG recording. Behaviorally, younger and older participants had similar, high accuracy rates — 98% correct, but older adults exhibited 85ms longer response times. Fitting behavioral results with a diffusion model revealed differences between young adults and elderly in non-decision time, which we argue reflects an early perceptual stage. Electrophysiologically, aging effects were present at MO-VEPs P1 and N2 components at the posterior sites. For the P1 component, older as compared to younger adults showed greater topographical voltage distribution. For the N2 component of elderly as compared to young adults we found delayed onsets and diminished amplitudes. We did not find any significant correlations between behavioral and MO-VEP measures. However, regression analysis showed that N2 amplitude and latency were significant age predictors. Overall, our results indicate that in motion perception, age-related changes occur in early stages of visual processing, most likely in striate and extrastriate visual cortices.

Sex differences in visual evoked potentials in school-age children: What is the evidence beyond the checkerboard?

Visual evoked potentials (VEPs) are known to be influenced by several biological variables, including sex. In adult populations studies using conventional high-contrast checkerboard have shown that females display larger amplitudes and shorter latencies than males. To date, few studies have been conducted in children; the available data suggests that girls display significantly larger amplitudes than boys but the effect on latency is absent or negligible. We investigated sex-related VEP differences in 149 school-age (11.3±0.6years) children from Northern Quebec using several VEP protocols: achromatic pattern-reversal VEPs at high (95%) and low contrast (30%, 12% and 4%), as well as motion-onset VEPs and isoluminant pattern-reversal VEPs. Girls showed significantly larger amplitudes in achromatic VEPs for most of the contrast levels as well as in N2 response to motion-onset. No significant difference was found regarding the amplitude of isoluminant VEPs. In addition, girls showed shorter latencies for the achromatic N75 and a trend (p<0.1) for the P100, regardless of the contrast level. Interestingly, this latency effect appeared mostly due to head size, not sex. No differences in latency were found for motion or isoluminant responses. Overall, these findings show that sex-related differences are present in children mostly in VEP amplitude not only for high contrast achromatic pattern-reversal but also for low contrast levels and motion-onset VEPs, suggesting that sex affects VEP responses in a general fashion.

Spared cognitive processing of visual oddballs despite delayed visual evoked potentials in patient with partial recovery of vision after 53 years of blindness

We examined the visual and cognitive functions of a 72-year-old subject, KP, who recovered his sight after 53years of visual deprivation. We used visual evoked potentials (VEPs) to pattern-reversal and motion-onset stimuli and cognitive responses (ERPs) during the oddball paradigm to assess the effect of long-term deprivation on a mature visual system. KP lost his sight at the age of 17years, and light projection onto his right retina was restored at 71years by a corneal implant. Nine months after sight recovery we recorded reproducible responses to all examined stimuli. The response to pattern reversal contained two P100-like peaks with the later peak being dominant and significantly delayed (260ms) when compared to the P100s of two control subjects, to whom the stimuli were adjusted in size and contrast to mimic KP’s vision. KP’s motion-onset VEPs to full-field and peripheral stimuli had a characteristic shape with a well-defined N2 peak; however, both peaks were significantly delayed (262 and 272ms) compared to control responses. Unlike the P100 and N2 peaks, which represent sensory detection, the P3b/P300 component of the ERP to a target event in the oddball paradigm was not further delayed. In spite of degraded vision and sensory deprivation lasting 53years, KP displayed reproducible responses to all reported stimuli. Long-term visual deprivation and retinal detachment degraded KP’s visual sensory processing, assessed by pattern-reversal and motion-onset VEPs, whereas the cognitive processing of appropriate visual stimuli was not compromised.

Motion and pattern cortical potentials in adults with high-functioning autism spectrum disorder

Autism spectrum disorder (ASD) is a condition in which visual perception to both static and moving stimuli is altered. The aim of this study was to investigate the early cortical responses of subjects with ASD to simple patterns and moving radial rings using visual evoked potentials (VEPs). Male ASD participants (n=9) and typically developing (TD) individuals (n=7) were matched for full, performance and verbal IQ (p>0.263). VEPs were recorded to the pattern reversing checks of 50' side length presented with Michelson contrasts of 98 and 10% and to the onset of motion-either expansion or contraction of low-contrast concentric rings (33.3% duty cycle at 10% contrast). There were no significant differences between groups in the VEPs elicited by pattern reversal checkerboards of high (98%) or low (10%) contrast. The ASD group had a significantly larger N160 peak (1.85 x) amplitude to motion onset VEPs elicited by the expansion of radial rings (p=0.001). No differences were evident in contraction VEP peak amplitudes nor in the latencies of the motion onset N160 peaks. There was no evidence of a response that could be associated with adaptation to the motion stimulus in the interstimulus interval following an expansion or contraction phase of the rings. These data support a difference in processing of motion onset stimuli in this adult high-functioning ASD group compared to the TD group.