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Age-related hearing loss (ARHL) is associated with cognitive decline as well as structural and functional brain changes. However, the mechanisms underlying neurocognitive deficits in ARHL are poorly understood and it is unclear whether clinical treatment with hearing aids may modify neurocognitive outcomes. To address these topics, cortical visual evoked potentials (CVEPs), cognitive function, and speech perception abilities were measured in 28 adults with untreated, mild-moderate ARHL and 13 age-matched normal hearing (NH) controls. The group of adults with ARHL were then fit with bilateral hearing aids and re-evaluated after 6 months of amplification use. At baseline, the ARHL group exhibited more extensive recruitment of auditory, frontal, and pre-frontal cortices during a visual motion processing task, providing evidence of cross-modal re-organization and compensatory cortical neuroplasticity. Further, more extensive cross-modal recruitment of the right auditory cortex was associated with greater degree of hearing loss, poorer speech perception in noise, and worse cognitive function. Following clinical treatment with hearing aids, a reversal in cross-modal re-organization of auditory cortex by vision was observed in the ARHL group, coinciding with gains in speech perception and cognitive performance. Thus, beyond the known benefits of hearing aid use on communication, outcomes from this study provide evidence that clinical intervention with well-fit amplification may promote more typical cortical organization and functioning and provide cognitive benefit.

Multiple sclerosis (MS) is a complex disease of the central nervous system (CNS), characterized by inflammation, demyelination, neuro-axonal loss, and gliosis. Inflammatory demyelinating lesions are a hallmark of the disease. Spontaneous remyelination, however, is often incomplete and strategies that promote remyelination are needed. As a result, accurate and sensitive in vivo measures of remyelination are necessary. The visual pathway provides a unique opportunity for in vivo assessment of myelin damage and repair in the MS-affected brain since it is highly susceptible to damage in MS and is a very frequent site of MS lesions. The visually evoked potential (VEP), an event-related potential generated by the striate cortex in response to visual stimulation, is uniquely placed to serve as a biomarker of the myelination along the visual pathway. The multifocal VEP (mfVEP) represents a most recent addition to the array of VEP stimulations. This article provides a current view on the role of mfVEP as a biomarker of demyelination, spontaneous remyelination, and myelin repair in MS.

Introduction Pseudoisochromatic stimuli are widely used in psychophysical color vision testing and the features of the luminance noise present on these stimuli have been reported modifying the psychophysical chromatic discrimination. Objective The present study investigated how modifications in the luminance noise features (luminance contrast and number of luminance values) affect chromatic visual evoked cortical potentials (VECP) elicited by pseudoisochromatic gratings, aiming to evaluate the influence of luminance contrast and the number of luminance values in the pseudoisochromatic stimulus on the chromatic VECP. Methods The sample consisted of seven young trichromatic participants. The waveforms of the visual evoked cortical potentials (VECP) were analyzed, focusing on the P1, N1, and P2 components across all stimulus conditions. The luminance noise contrast in the pseudoisochromatic stimulus had distinct effects on the amplitudes of the VECP components. Significant effects were observed for the amplitudes of the P1 ( p = 0.01) and P2 ( p = 0.04) components, while no significant effect was found on the amplitude of the N1 component ( p = 0.3). Results There was no significant effect of the luminance noise range on the latency of the VECP components (P1 VECP component, p = 0.54; N1 VECP component, p = 0.79; P2 VECP component, p = 0.49). The number of luminance values in the noise had no significant effect on VECP components amplitude and latency. Different manipulations of luminance noise influenced P1 and P2 VECP components and no modification of the luminance noise had influence on the main chromatic VECP component, N1 component. Conclusion Manipulations in features of the luminance noise in pseudoisocrhomatic stimulus impacted in putative luminance components, but not chromatic components, of visual evoked potentials. The present findings may have potential applications in clinical neuro-ophthalmology, particularly for assessing congenital and acquired color blindness.

Background Electrical potentials generated in the central nervous system in response to brief visual stimuli, flash visual evoked potentials (FVEPs), can be recorded non-invasively over the occipital cortex. FVEPs are used clinically in human medicine and also experimentally in a number of animal species, but the method has not yet been evaluated in the horse. The method would potentially allow the ophthalmologist and equine clinician to evaluate visual impairment caused by disorders affecting post-retinal visual pathways. The aim was to establish a method for recording of FVEPs in horses in a clinical setting and to evaluate the waveform morphology in the normal horse. Methods Ten horses were sedated with a continuous detomidine infusion. Responses were recorded from electrodes placed on the scalp. Several positions were evaluated to determine suitable electrode placement. Flash electroretinograms (FERGs) were recorded simultaneously. To evaluate potential contamination of the FVEP from retinal potentials, a retrobulbar nerve block was performed in two horses and transection of the optic nerve was performed in one horse as a terminal procedure. Results A series of positive (P) and negative (N) peaks in response to light stimuli was recorded in all horses. Reproducible wavelets with mean times-to-peaks of 26 (N1), 55 (P2), 141 (N2) and 216 ms (P4) were seen in all horses in all recordings. Reproducible results were obtained when the active electrode was placed in the midline rostral to the nuchal crest. Recording at lateral positions gave more variable results, possibly due to ear muscle artifacts. Averaging ≥100 responses reduced the impact of noise and artifacts. FVEPs were reproducible in the same horse during the same recording session and between sessions, but were more variable between horses. Retrobulbar nerve block caused a transient loss of the VEP whereas transection of the optic nerve caused an irreversible loss. Conclusions We describe the waveform of the equine FVEP and our results show that it is possible to record FVEPs in sedated horses in a clinical setting. The potentials recorded were shown to be of post-retinal origin. Further studies are needed to provide normative data and assess potential clinical use.

In 30 healthy men (age 19–25 years) with normal hearing and 30 men of the same age suffering from complete congenital deafness, we examined peculiarities of the cortical visual evoked potentials, VEPs (photostimulation of the right and left eye by LED flashes, recording from loci O1 and O2). It was found that subjects with auditory deprivation demonstrated significantly shorter (P < 0.05–0.001) peak latencies of the early VEP components (P1, N2, and P2), while peak latencies of the late waves (N2 and P3) were greater (P < 0.05) than the corresponding indices in the control group. Peak-to-peak amplitudes of all VEP components in deaf subjects were about two to three times lower than those in subjects with normal hearing (P < 0.05–0.001). The mean total duration of the VEPs in deaf persons was significantly greater than in the control group (P < 0.05). Therefore, loss of the auditory function in deaf subjects results, due to cross-modal transformations, in substantial modifications of the potentials reflecting perception of the visual signals.

Neurophysiologic monitoring during deep brain stimulation (DBS) interventions in the globus pallidus internum (Gpi) for the treatment of Parkinson's disease or primary dystonia is generally based upon microelectrode recordings (MER); moreover, MER request sophisticated technology and high level trained personnel for a reliable monitoring. Recordings of cortical visual evoked potentials (CVEPs) obtained after stimulation of the optic tract may be a potential option to MER; since optic tract lies just beneath the best target for Gpi DBS, changes in CVEPs during intraoperative exploration may drive a correct electrode positioning. Cortical VEPs from optic tract stimulation (OT C-CEPs) have been recorded in seven patients during GPi-DBS for the treatment of Parkinson's disease and primary dystonia under general sedation. OT C-VEPs were obtained after near-field monopolar stimulation of the optic tract; recording electrodes were at the scalp. Cortical responses after optic tract versus standard visual stimulation were compared. After intraoperative near-field OT stimulation a biphasic wave, named N40–P70, was detected in all cases. N40–P70 neither change in morphology nor in latency at different depths, but increased in amplitude approaching the optic tract. The electrode tip was positioned just 1 mm above the point where OT-CVEPs showed the larger amplitude. No MERs were obtained in these patients; OT CVEPs were the only method to detect the Gpi before positioning the electrodes. OT CVEPs seem to be as reliable as MER to detail the optimal target in Gpi surgery: in addition they are less expensive, faster to perform and easier to decode.

Background: Some histological investigations have reported anomalies in the primary visual pathways of individuals with dementia of the Alzheimer type (DAT), while others have suggested that these visual structures are spared by the disease process. Objectives: This study was conducted to address this issue of substantial controversy. We determined in vivo whether DAT alters the functioning of the primary visual pathways by evaluating pattern-reversal electroretinograms (ERGs) and cortical visual evoked potentials (VEPs). Methods: Twenty-seven individuals with mild to moderate DAT and 27 age- and sex-matched control subjects were included in the investigation. ERG and VEP recordings were obtained from all participants with the use of a clinical electrodiagnostic system. Stimulus conditions were biased towards a preferential response from the magnocellular and parvocellular subdivisions of the visual system. Results: Amplitude and latency of the ERG were not affected by DAT. The VEP amplitude was not attenuated in DAT individuals, but there was a delay in the latency of the VEPs arising from both magnocellular and parvocellular streams of visual processing. Conclusion: Our results indicate that while the inner retina appears to be spared by the disease process, the visual function is altered upstream in the retinocortical visual pathways of individuals with DAT.

Visual acuity after cataract surgery in patients with glaucoma cannot be predicted accurately. We studied preoperative recordings of pattern visual evoked cortical potentials (PVECPs) to evaluate postoperative vision in patients with glaucoma and cataract. Fifty patients with glaucoma and no cataract and 31 patients with glaucoma and cataract who underwent phacoemulsification were included in this study. Age and P100 component significantly correlated with postoperative visual acuity with multiple linear regression analysis. A significantly greater number of patients with glaucoma, cataract, and a P100 component preoperatively showed a visual acuity of 0.7 or better postoperatively, as compared to those without a P100 component. PVECP before cataract surgery was able to predict postoperative good visual acuity in patients with glaucoma and cataract.

The visual evoked cortical potential (VECP) is widely used to verify complaints of reduced visual performance and to identify the site of the disorder. In this study, we investigated the correlation between reduced visual acuity and VECP in volunteers with normal corrected visual acuity and in patients suffering from inherited macular degeneration or from age related macular degeneration (ARMD). Flash evoked VECP was not affected by the visual acuity in the cases of refractive error and in ARMD patients but was reduced in amplitude and delayed in implicit time in the patients suffering from inherited macular degeneration. The VECP elicited by pattern reversal checkerboard (PVECP) was not affected by the quality of the visual image in volunteers with uncorrected refractive error when checks of 60' or larger were used but were considerably reduced in size and prolonged in implicit time for checks smaller than 15'. In both groups of patients suffering from macular dysfunction, pattern reversal VECP was very subnormal and was characterized by prolonged implicit time compared to values expected from their visual acuity. These findings indicate that the PVECP does not directly correlate with visual acuity but rather with foveal function. Therefore, we suggest that recordings of PVECP can be used to differentiate between refractive error and macular disorders as causing reduction in visual acuity when other clinical signs are missing or not available.

Binocular interaction for a central field was studied with transient scalp visual evoked cortical potentials (VECPs) using two light-emitting-diodes. VECPs were obtained for binocular and monocular visions with dominant and non-dominant eyes, and arithmetical sums of monocular VECPs with dominant and non-dominant eyes were calculated. Amplitude and latency of remarkable initial three peaks were tested with the multivariate analysis of variance. Significant differences were noted among the four VECPs. Pairwise comparisons showed that (1) the amplitude of the first peak for the binocular VECPs was larger than that for the monocular VECPs but smaller than that for the sum-VECPs; the latency of the first peaks for the binocular VECPs were earlier than that for the monocular VECPs with the non-dominant eye; (2) the amplitude of the first negative peak for the sum-VECPs was larger than that for the binocular VECPs, and the peak latency for the sum-VECPs showed later than that for the binocular VECPs; (3) the amplitude of the second positive peak for the binocular VECPs and monocular VECPs with the dominant eye was larger than that with the non-dominant eye, but smaller for the binocular VECPS than that for the sum-VECPs; the latency for the binocular VECPs showed earlier than that for the monocular VECPs with the dominant eye and for the sum-VECPs. Binocular suppression was noted in amplitude for the three peaks and binocular facilitation was noted in latency for the latter two peaks.