Pattern Reversal Stimuli Research Articles

Pattern-reversal visual evoked potentials in prosthetic vision and simulated visual reduction

ObjectiveTo quantitatively evaluate visual evoked potentials (VEPs) in prosthetic vision and simulated visual reduction.Methods and analysisFour blind patients implanted with the Argus II retinal prosthesis and seven sighted controls participated....

Poster Session II: Attentional modulation of the achromatic and chromatic reversal VEP.

Previous literature has consistently revealed attentional modulation of the Visual Evoked Potential (VEP) response to achromatic pattern reversal stimuli but little to no attentional modulation of the VEP response to chromatic pattern onsets. Magnetic Resonance Imaging (MRI) research, however, has reported modulation of the responses to both achromatic and chromatic pattern reversal stimuli. Numerous methodological differences including mode of presentation, stimulus contrast, and attentional demand, make comparison of these results difficult. In this study, we report the results of experiments using comparable perceptual contrasts, pattern reversals, and a coextensive and highly-demanding, multiple object tracking (MOT) task. Our findings support prior VEP results indicating that although achromatic VEPs are modulated by attention, chromatic VEPs are more robust to attentional modulation, even for highly demanding distractor tasks. We also found that when compared to a non-attentional condition, the attenuation of the VEP when attending to the MOT task was greater in magnitude than the enhancement of the VEP when attending to the VEP stimulus. This supports prior conclusions, that while avoiding active distraction is likely important, insuring an "attentive state" is not always necessary when recording VEPs. Further experiments are underway to investigate why attentional modulation of chromatic signals in early visual cortex are observed in MRI but not VEP recordings.

Assessment of Visual Evoked Potential to Detect Visual Pathway Dysfunction in Gestational Diabetes Mellitus: A Longitudinal Case-Control Study With Postpartum Follow-up.

The increasing prevalence of gestational diabetes mellitus (GDM) during pregnancy has opened the opportunity to study its short- and long-term effects on maternal ophthalmic health. Visual evoked potential (VEP) is a non-invasive electrophysiological test that detects functional disturbances along the visual pathway before the physical signs of diabetic retinopathy (DR) can set in.This longitudinal study is aimed at the assessment of changes in VEP in GDM during different stages of pregnancy and 6-12 weeks after parturition by comparing it with normoglycemic controls. Diagnosed cases of GDM were recruited along with normoglycemic controls at 24-28 weeks of gestation.Each participant was required to attend two follow-up appointments at 32-38 weeks of gestation and 6-12 weeks after parturition. A blood sample was taken in a fasting state to record biochemical parameters. VEP was recorded using Neuropack S1 MEB-9400 electrodiagnostic equipment (Nihon Kohden, Tokyo, Japan) in a dark room by providing pattern reversal stimuli to each eye. A total of 29 participants (15 in the control group and 14 in the GDM group) completed the entire study procedure.The observed mean P100 latency of both eyes in the GDM group was recorded longer as compared to that in the control group at baseline and during late pregnancy. Although the mean P100 latency saw a significant decline in postpartum visits as compared to that in late pregnancy, the values were higher than in the control group. P100 latency at baseline correlated significantly to serum advanced glycated end products' (AGE'S) levels in the GDM group. Our study findings reflect that the diagnosis of GDM is associated with significant changes in VEP during and after pregnancy as compared to that of healthy pregnant women.

Reduced Visual Evoked Potential Amplitude in Autistic Children with Co-Occurring Features of Attention-Deficit/Hyperactivity Disorder.

Provided the significant overlap in features of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD), there is a critical need to identify transdiagnostic markers that could meaningfully stratify subgroups. The objective of this study was to compare the visual evoked potential (VEP) between 30 autistic children, 17 autistic children with co-occurring ADHD presentation (ASD + ADHD), and 21 neurotypical children (NTC). Electroencephalography was recorded while children passively viewed a pattern-reversal stimulus. Mean amplitude of the P1 event-related potential was extracted from a midline occipital channel and compared between groups. P1 mean amplitude was reduced in the ASD + ADHD group compared to the ASD and NTC groups, indicating a distinct pattern of brain activity in autistic children with co-occurring ADHD features.

Amplitude and latency of visual evoked potential are un-correlated variables: A revelation from normative laboratory database of eastern India

To establish normative database andinvestigate whether VEP amplitude and latency have any correlation between them. Institution based cross-sectional observational study done in Electrophysiology of Vision Laboratory at a tertiary centre in Eastern India. 126 subjects of age group between 20 and 59 years of either sex with best corrected visual acuity 6/6 in both eyes and no other eye ailments (except error of refraction) on examination with informed consent were included. PVEP with pattern reversal stimulus with check element size 1° (60') was recorded with Retimax “Advanced” machine (manufactured by CSO s.r.l., (Firenze) Italy) and standard silver-silver chloride disc electrodes. The test parameters were customized in the machine by the manufacturer and designated to measure the N75-P100 amplitude and P100 latency.Normative values were established for our laboratory. Only the most reliable parameters for clinically significant alterations of visual pathway i.e. N75-P100 amplitude and P100 latency were included in the analysis. Results of uniocular, age group-wise and gender-wise values were obtained by descriptive statistics as per ISCEV guidelines. No linear co-relationship (ascertained by Spearman's rho Correlation Coefficient) was found between N75-P100 amplitude and P100 latency, in either of the eyes. PVEP amplitude and latency are uncorrelated variables. To the best of our knowledge, our study was the first study in literature on correlation between amplitude and latency of PVEP.

Is the prolongation latency of visual evoked potentials a pathological sign in children with Down’s syndrome without ocular abnormalities? Case–control study of children with Down’s syndrome

ObjectiveTo evaluate retino-cortical function in children with Down’s syndrome (DS) and no evident ocular abnormalities beyond mild refractive error, by recording visual evoked potentials (VEP) in response to pattern-reversal stimuli...

Altered brain connectivity during visual stimulation in schizophrenia.

Schizophrenia (SCZ) can be described as a functional dysconnectivity syndrome that affects brain connectivity and circuitry. However, little is known about how sensory stimulation modulates network parameters in schizophrenia, such as their small-worldness (SW) during visual processing. To address this question, we applied graph theory algorithms to multi-electrode EEG recordings obtained during visual stimulation with a checkerboard pattern-reversal stimulus. Twenty-six volunteers participated in the study, 13 diagnosed with schizophrenia (SCZ; mean age = 38.3years; SD = 9.61years) and 13 healthy controls (HC; mean age = 28.92years; SD = 12.92years). The visually evoked potential (VEP) showed a global amplitude decrease (p < 0.05) for SCZ patients as opposed to HC but no differences in latency (p > 0.05). As a signature of functional connectivity, graph measures were obtained from the Magnitude-Squared Coherence between signals from pairs of occipital electrodes, separately for the alpha (8-13Hz) and low-gamma (36-55Hz) bands. For the alpha band, there was a significant effect of the visual stimulus on all measures (p < 0.05) but no group interaction between SCZ and HZ (p > 0.05). For the low-gamma spectrum, both groups showed a decrease of Characteristic Path Length (L) during visual stimulation (p < 0.05), but, contrary to the HC group, only SCZ significantly lowered their small-world (SW) connectivity index during visual stimulation (SCZ p < 0.05; HC p > 0.05). This indicates dysconnectivity of the functional network in the low-gamma band of SCZ during stimulation, which might indirectly reflect an altered ability to react to new sensory input in patients. These results provide novel evidence about a possible electrophysiological signature of the global deficits revealed by the application of graph theory onto electroencephalography in schizophrenia.

Novel hybrid visual stimuli incorporating periodic motions into conventional flickering or pattern-reversal visual stimuli for steady-state visual evoked potential-based brain-computer interfaces.

In this study, we proposed a new type of hybrid visual stimuli for steady-state visual evoked potential (SSVEP)-based brain-computer interfaces (BCIs), which incorporate various periodic motions into conventional flickering stimuli (FS) or pattern reversal stimuli (PRS). Furthermore, we investigated optimal periodic motions for each FS and PRS to enhance the performance of SSVEP-based BCIs. Periodic motions were implemented by changing the size of the stimulus according to four different temporal functions denoted by none, square, triangular, and sine, yielding a total of eight hybrid visual stimuli. Additionally, we developed the extended version of filter bank canonical correlation analysis (FBCCA), which is a state-of-the-art training-free classification algorithm for SSVEP-based BCIs, to enhance the classification accuracy for PRS-based hybrid visual stimuli. Twenty healthy individuals participated in the SSVEP-based BCI experiment to discriminate four visual stimuli with different frequencies. An average classification accuracy and information transfer rate (ITR) were evaluated to compare the performances of SSVEP-based BCIs for different hybrid visual stimuli. Additionally, the user's visual fatigue for each of the hybrid visual stimuli was also evaluated. As the result, for FS, the highest performances were reported when the periodic motion of the sine waveform was incorporated for all window sizes except for 3 s. For PRS, the periodic motion of the square waveform showed the highest classification accuracies for all tested window sizes. A significant statistical difference in the performance between the two best stimuli was not observed. The averaged fatigue scores were reported to be 5.3 ± 2.05 and 4.05 ± 1.28 for FS with sine-wave periodic motion and PRS with square-wave periodic motion, respectively. Consequently, our results demonstrated that FS with sine-wave periodic motion and PRS with square-wave periodic motion could effectively improve the BCI performances compared to conventional FS and PRS. In addition, thanks to its low visual fatigue, PRS with square-wave periodic motion can be regarded as the most appropriate visual stimulus for the long-term use of SSVEP-based BCIs, particularly for window sizes equal to or larger than 2 s.

Low Contrast Visual Evoked Potentials for Early Detection of Optic Neuritis

Optic neuritis (ON) detection is important for the early diagnosis and management of multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD). However, the conventional high-contrast visual evoked potential (VEP) used for ON detection lacks sensitivity for identifying ON presenting as mild or unremarkable visual disturbance, which is common in first-episode ON. Therefore, this study aimed to investigate whether a change in contrast or check size improves the sensitivity of VEP to first-ever ON. In total, 60 patients with the demyelinating disease (29 MS and 31 idiopathic patients with ON) without ON or with first-ever ON at least 6 months prior and 32 healthy controls underwent neuro-ophthalmic evaluations. VEPs were induced using three pattern-reversal checkerboard stimuli having, respectively, 10% contrast with a check size of 32' (LC32 VEP), 100% contrast with a check size of 32' (HC32 VEP; conventional VEP), and 100% contrast with a check size of 16' (HC16 VEP). The receiver operating characteristic (ROC) curve analysis and area under the curve (AUC) were calculated to determine the most appropriate VEP method for detecting optic nerve involvement. The optimal cut-off point was determined using the Youden index (J-index). The McNemar test was used to determine whether dichotomous proportions were equivalent. In comparison with first-ever ON eyes (n = 39) and healthy eyes (n = 64), LC32 VEP showed the highest AUC for discriminating ON (0.750, p < 0.001; 0.730 for HC32 VEP, p < 0.001; 0.702 for HC16 VEP, p = 0.001). In the first-ever ON group, LC32 VEP and conventional HC32 VEP were abnormal in 76.9 and 43.6%, respectively (McNemar, p < 0.001), and combining these tests did not improve sensitivity. These indicate that LC32 VEP is the most sensitive method for detecting first-ever ON. Visual evoked potential with 10% contrast stimuli was superior to conventional VEP for detecting first-ever ON. Thus, adding these LC stimuli might be helpful in identifying optic nerve involvement in ON with mild or unremarkable visual impairment.

Longitudinal assessment of the relationship between visual evoked potentials and cognitive performance in multiple sclerosis

ObjectiveVisual evoked potentials (VEPs) can provide insight into disease activity in people with multiple sclerosis (PwMS). However, few studies have tracked concurrent changes in VEPs and cognitive functioning over time in MS. To address this, we examined the longitudinal relationship between VEP and cognitive performance in PwMS over a two-year period. MethodsAt baseline (T1) and follow-up (T2, 2.14 years after baseline, on average), P100 peak latency and inter-ocular latency (IOL) between eyes were calculated from the VEP elicited for checkerboard pattern-reversal stimuli. Cognitive performance was assessed for seven different domains (NeuroTrax battery). The potential for VEP variables to predict the T1-to-T2 change in cognitive performance was assessed in a series of multiple linear regression models. ResultsBaseline IOL and VEP latency were significantly associated with T1-to-T2 change in information processing speed. Post-hoc analyses indicated that PwMS that had both prolonged VEP latency and elevated IOL at baseline tended to exhibit greater information processing speed decline. Increase in VEP latency from T1-to-T2 was also associated with decline in psychomotor function over time. ConclusionsThese findings provide evidence that VEP measures can serve as valuable prognostic indicators of longitudinal cognitive change in PwMS. SignificanceVisual system neurophysiology corresponds with changes in speeded cognitive performance in MS.

Contributed Session II: Attentional Modulation of Early Cortical Chromatic Responses

Prior research demonstrates that attention can modulate the amplitude of achromatic (black and white) pattern reversal stimuli. Similarly, MRI research has shown attentional modulation of BOLD responses to both chromatic and achromatic stimuli. However, prior research has also demonstrated that the chromatic onset visual evoked potential (VEP) is robust to attentional modulation (e.g., Highsmith & Crognale, 2010; Wang & Wade, 2011) with either spatially contiguous or spatially disparate manipulations. It is possible that more demanding attentional tasks than those that have been used previously, may reveal attentional modulation of the chromatic VEP. Here we report the results of experiments in which we recorded chromatic and achromatic VEPs while subjects performed multiple object tracking (MOT) tasks with several levels of difficulty. Steady-state onset responses were recorded at 3hz for stimuli modulated along the chromatic and achromatic axes. Our preliminary results suggest that the increased attentional demand provided by MOT can reveal a clear, but idiosyncratic modulation of chromatic VEP responses. The question remains whether or not chromatic and achromatic mechanisms share similar attentional gain processes as reflected in the VEP. We are currently characterizing the nature of these attentional gain mechanisms.

Improved spatio-temporal measurements of visually evoked fields using optically-pumped magnetometers

Recent developments in performance and practicality of optically-pumped magnetometers (OPMs) have enabled new capabilities in non-invasive brain function mapping through magnetoencephalography. In particular, the lack of cryogenic operating conditions allows for more flexible placement of sensor heads closer to the brain, leading to improved spatial resolution and source localisation capabilities. Through recording visually evoked brain fields (VEFs), we demonstrate that the closer sensor proximity can be exploited to improve temporal resolution. We use OPMs, and superconducting quantum interference devices (SQUIDs) for reference, to measure brain responses to flash and pattern reversal stimuli. We find highly reproducible signals with consistency across multiple participants, stimulus paradigms and sensor modalities. The temporal resolution advantage of OPMs is manifest in a twofold improvement, compared to SQUIDs. The capability for improved spatio-temporal signal tracing is illustrated by simultaneous vector recordings of VEFs in the primary and associative visual cortex, where a time lag on the order of 10–20 ms is consistently found. This paves the way for further spatio-temporal studies of neurophysiological signal tracking in visual stimulus processing, and other brain responses, with potentially far-reaching consequences for time-critical mapping of functionality in healthy and pathological brains.

Portable Diagnostic System for Age-Related Macular Degeneration Screening Using Visual Evoked Potentials.

BackgroundDelayed Dark-Adapted vision Recovery (DAR) is a biomarker for Age-related Macular Degeneration (AMD), however its measurement is burdensome for patients and examiners.MethodsIn this study, we developed a portable, wireless and user-friendly system that employs a headset with a smartphone to deliver controlled photo-bleach and monocular pattern reversal stimuli, while using custom electroencephalography (EEG) electrodes and electronics in order to measure Dark-Adapted Visual Evoked Potentials (DAVEP) objectively and separately at the peripheral and central visual field. This is achieved in one comfortable 20-minute session, without requiring subject reporting. DAVEP responses post photo-bleach for up to 15 minutes were measured concurrently from both eyes in 12 AMD-patients, 1 degenerative myopia patient, and 8 controls who had no diagnosed macular vision loss.ResultsRobust positive polarity DAVEP responses were observed at 200–500 ms from stimulus onset to scotopic stimuli that have been seldom reported and analyzed previously. The amplitude recovery of the DAVEP response was significantly delayed in AMD patients as compared to controls. We developed DAVEP1 scores, a simple metric for DAR, which classified 90% of subject eyes correctly, indicating the presence of AMD in at least one eye of all pre-confirmed subjects with this diagnosis.ConclusionWe developed a user-friendly, portable VEP system and DAVEP1 metric, which show a high potential to identify DAR-deficits in AMD-patients. This novel technology could aid in early diagnosis of AMD.

Cortical Contrast Processing in Retinitis Pigmentosa: Evidence of PVEPs Spatial Functions.

Objective: To study the effect of check width size of the stimuli on the amplitude and latency of the P100 component of visual evoked potentials recorded in patients with retinitis pigmentosa (RP). Methods: Pattern reversal visual evoked potentials (PVEPs) were recorded in 16 RP patients and 20 visually normal subjects. Pattern reversal stimuli with five different check widths and 100% of contrast were projected in the right eye of both patients and control subjects. PVEPs induced by stimuli with 78%, 16%, and 6% of contrast were also recorded in 10 of the control subjects. Results: In RP patients, the amplitude of P100 was smaller than controls in all check sized used and the peak P100 amplitude was obtained with a larger check width than in controls. P100 was also delayed in RP patients in all check sizes studied. The P100 amplitude- and latency-check size functions of RP patients were like those found in control subjects with low contrast stimuli of 16% and 6%. Conclusion: The PVEPs spatial functions of RP patients show quantitative and qualitative changes, suggesting disease induced alteration in the neural processing of stimulus contrast.

Steady-State Visually Evoked Potentials Elicited by Multifrequency Pattern-Reversal Stimulation.

PurposeIt has been shown that multifrequency stimulation with multifocal electroretinography can reduce recording time without a loss in signal-to-noise ratio. Here, we studied the applicability of multifrequency stimulations for steady-state visually evoked potential (VEP) recordings.MethodsMultifrequency VEPs were recorded monocularly from 10 healthy subjects using pattern-reversal stimuli. The reversal frequency varied between 5 and 30 Hz. Pattern-reversal checkerboard stimuli were generated using four square arrays, each containing 100 light-emitting diodes (LEDs), positioned in four quadrants. Each array had a temporal frequency that differed slightly from the nominal frequency. The long duration of the data acquisition ensured that the slightly different stimulus frequencies in the four LED arrays can be resolved and that the responses to the stimulus in each array can be distinguished (e.g., with a frequency resolution: 0.011 Hz at 12 Hz). The best response from the four recording electrode configuration, defined as the recording with the maximal signal-to-noise ratio, was used for further analysis. Algorithmic latencies were calculated from the ratio of phase data and frequencies in a range of 4 and 20 Hz.ResultsQuadrant-VEPs with simultaneous pattern-reversal stimulation yielded a significant dependency on temporal frequency and stimulus location. The frequency range leading to the maximal response amplitude was between 10 and 12 Hz. Response phases decreased approximately linearly, with increasing temporal frequency suggesting a mean algorithmic latency between 112 and 126 ms.ConclusionsMultifrequency stimulation using LED arrays is an efficient method for recording pattern-reversal VEPs while all stimuli are presented at the same time.Translational RelevanceSimultaneously recorded VEPs as performed by the multi-frequency method can be used for objective measurements of visual field defects.

F105. The influence of myopia on visual evoked potential

Introduction To investigate the influence of myopia on outcomes of visual evoked potential. Methods Twenty subjects (40 eyes), whose visual acuity was around 0.1 before correction and more than 0.8 after correction, were chosen from our hospital refraction center starting from October, 2015 to February 2016. After receiving the LASIK (laser-assisted in situ keratomileusis), all of them were given the VEP examination with electromyography & evoke potential equipment (MED-9200K, Japan). The PRVEP setup is in accordance with International 10–20 system standard (reference electrodes at Fz, record electrode at O1,Oz,O2, ground electrode at FPz) and the subjects sit in front of pattern reversal stimulator with a horizontal distance of 75 cm from their eyes to screen, received full field stimuli. When conducting examination, the subjects were asked to stare at the visual marker in the screen center and avoid the frequent eye blinking and movement, while the pattern reversal stimuli was set to rotate 2 turns per second. Before and after the visual correction, every naked eye was checked 2 times at least with an interval of 3 min and an increment of 100 times. Then two similar results were overlaid to assess the consistency of waveform in hope of enhancing the precision of outcomes. After recording, the comparison between unaided and corrected visual acuity was performed to evaluate their corresponding P100 difference of latent period. Results The latent value of wave N75, P100, N145 of unaided eyes of 20 subjects (40 eyes) were improved significantly compared with those after visual correction. Conclusion P100, with minor variation and reliability, can be recorded in all healthy subjects and has been taken as the unique and dependable wave component for analysis of PRVEP. Additionally, P100 peak latency is less susceptible to the degree of attention and visual acuity and consequently become the crucial indicator of clinical assessment. The P100 latency of unaided eyes was considerably longer than that of corrected eyes, which relatively approximate to normal value. Conclusively, our data has shown that visual acuity can exert a substantial influence on P100 latency and the subjects with myopia are advised to correct their visual acuity more than 0.8 when receiving VEP, otherwise this will contribute to false positive results and negatively affect clinical diagnosis.

A-19. Visual evoked potentials: Basic technology and clinical applications

Visual information is processed simultaneously via multiple parallel channels and each channel constitutes a set of sequential processes. The visual evoked potentials (VEPs) are the evoked electrophysiological potential that can be extracted, using signal averaging, from the electroencephalographic activity recorded at the scalp. VEPs can provide important diagnostic information regarding the functional integrity of the visual pathways and the visual cortex. Commonly used visual stimuli are flashing lights or pattern reversal (checkerboards or gratings) on the TV monitor or video screen. Pattern reversal is the preferred technique for most clinical purposes. The results of pattern reversal stimuli are less variable in the waveform and the timing than the results elicited by other stimuli. The pattern onset/offset technique can be useful in the detection of malingering and in patients with nystagmus, and the flash VEP is particularly useful when optical factors or poor cooperation make the use of pattern stimulation inappropriate. In addition, pattern reversal VEP to full-field stimulation is best suited to evaluate anterior visual pathways while hemi-field VEP is most effective in the assessment of chiasmal and post-chiasmal functions. This article presents the basic technology and current standard for flash and pattern reversal VEP recording methods based on the major parallel pathways of the visual system from the retina to the primary visual cortex via lateral geniculate nucleus that receive visual input.

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.

Neural Correlates of Expert Visuomotor Performance in Badminton Players.

Elite/skilled athletes participating in sports that require the initiation of targeted movements in response to visual cues under critical time pressure typically outperform nonathletes in a visuomotor reaction task. However, the exact physiological mechanisms of this advantage remain unclear. Therefore, this study aimed to determine the neurophysiological processes contributing to superior visuomotor performance in athletes using visual evoked potential (VEP). Central and peripheral determinants of visuomotor reaction time were investigated in 15 skilled badminton players and 28 age-matched nonathletic controls. To determine the speed of visual signal perception in the cortex, chromatic and achromatic pattern reversal stimuli were presented, and VEP values were recorded with a 64-channel EEG system. Further, a simple visuomotor reaction task was performed to investigate the transformation of the visual into a motor signal in the brain as well as the timing of muscular activation. Amplitude and latency of VEP (N75, P100, and N145) revealed that the athletes did not significantly differ from the nonathletes. However, visuomotor reaction time was significantly reduced in the athletes compared with nonathletes (athletes = 234.9 ms, nonathletes = 260.3 ms, P = 0.015). This was accompanied by an earlier activation of the premotor and supplementary motor areas (athletes = 163.9 ms, nonathletes = 199.1 ms, P = 0.015) as well as an earlier EMG onset (athletes = 167.5 ms, nonathletes = 206.5 ms, P < 0.001). The latency of premotor and supplementary motor area activation was correlated with EMG onset (r = 0.41) and visuomotor reaction time (r = 0.43). The results of this study indicate that superior visuomotor performance in athletes originates from faster visuomotor transformation in the premotor and supplementary motor cortical regions rather than from earlier perception of visual signals in the visual cortex.

Objective Assessment of Eye Dominance Using the VEP: A Pilot Study.

To develop a clinical protocol for the determination of eye dominance using an objective method (i.e., the visual evoked potential [VEP]), and furthermore to determine the correlation of these objective findings with clinical subjective tests of eye dominance to provide guidance in clinical monovision refractive correction. The Diopsys NOVA-TR system was used to record the VEP amplitude and latency of 10 visually-normal, presbyopic, adult subjects aged 50 to 70 years ((Equation is included in full-text article.)=60, SEM=0.17 years). First, eye dominance was assessed in two ways: a sensory-based "sensitivity to blur task" and a motor-based "sighting task." Next, while monocularly defocused, subjects binocularly viewed a black-and-white checkerboard (20-min arc size), pattern-reversal stimulus under 7 different test conditions: (1) baseline, (2) dominant (DE) eye blurred +1 diopter (D), (3) nondominant (NDE) eye blurred +1 D, (4) DE +2 D, (5) NDE +2 D, (6) DE +3 D, and (7) NDE +3 D. Under nearly all conditions (22/24=92%), the amplitude and latency were significantly different from baseline with any amount of defocus (P<0.05). Monocular defocus decreased, and increased, the mean binocular VEP amplitude and latency, respectively. There were no significant differences in either the binocular VEP amplitude or latency values when comparing defocused dominant vs. nondominant eyes. Eye dominance type (i.e., sensory or motor) and status (i.e., DE or NDE) did not provide a differential effect with respect to the VEP findings. Thus, the VEP technique does not show promise as an objective adjunct in the fitting of monovision correction.