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Purpose: Diffusion tensor imaging (DTI) is commonly used to evaluate white matter integrity in multiple sclerosis (MS), but the relationship between DTI measures and functional changes during disease remains ambiguous. Using a mouse model of MS, we tested the hypothesis that DTI measures would correlate to the visual evoked potential (VEPs) dynamically at different disease stages. Methods: In vivo DTI, gadolinium-enhanced T1WI (Gd-T1WI) and VEPs were performed in 5 control and 25 mice after 2-12 weeks of experimental autoimmune encephalomyelitis (EAE). DTI indices, including fractional anisotropy (FA), axial and radial diffusivities (AD and RD), and Gd-T1WI enhancement, were measured in the optic nerve and tract (ON and OT), which were compared with measured VEPs. Results: Gd-T1WI showed a 3- to 4-fold enhancement over controls beginning after 2 weeks of EAE. Across the time course, we found progressive reductions in FA and increases in RD with increases in VEP latency and reductions in amplitude. Significant correlations between DTI (FA and RD) and VEP evolved; in control/early asymptomatic EAE mice, both FA and RD were highly correlated with VEP latency (but not amplitude), while in late EAE, both DTI indices were highly correlated with VEP amplitude (but not latency). Conclusion: DTI measures FA and RD are associated to VEP latency in early stages of EAE but associated to VEP amplitude in later stages, suggesting that the patterns of DTI related to the functional decline may depend on the stage of disease progression. [ABSTRACT FROM AUTHOR]

Optic neuritis is often the initial manifestation in multiple sclerosis (15%). There is a significant percent of patients affected by clinically definite multiple sclerosis that report no ocular symptoms. Some of this patients complain of poor vision despite the 6/6 visual acuity with Snellen test. Subclinical visual abnormalities may be revealed by more sensitive measures of visual function. Alteration of visual evoked potential latencies associated with brain MRI lesion burden, standard achromatic perimetry and low-contrast letter acuity, may detect subclinical visual manifestations. In this study we compare the efficiency of electrophysiological test (visual evoked potential) and subjective tests (contrast sensitivity and standard achromatic perimetry) in detection of visual impairment in a population of asymptomatic patients with clinically definite multiple sclerosis. Purpose. The detecting of subclinical impairment of visual function in a population of visual asymptomatic patients affected by clinically definite multiple sclerosis (MS) by using visual evoked potentials (VEPs), contrast sensitivity (CS), standard achromatic perimetry (SAP), magnetic resonance imaging (MRI), color vision test Ishihara, best corrected visual acuity (BCVA). Methods. Eighteen eyes of nine patients affected by clinically definite MS, without visual disturbances and optic neuritis history. All the patients were recruited at the Department of Neurology of Emergency University Hospital of Bucharest. Of the nine patients, 3 were male and 6 female. In all the cases the disease was in remission. The tests used to detect the involvement of visual pathway were: • VEPs (a P100 latency >115 ms) • CS • SAP (abnormal MD or PD) • MRI (at least one demyelinating plaque along visual pathway) • Color test Ishihara • Best corrected visual acuity (BCVA) • Biomicroscopy • Ocular fundus examination after pupil dilatation Results. From the 9 patients in the 29-47 year age group, VEPs was abnormal in 8 cases (88,8%), CS was abnormal in 8 cases (88,8%), SAP in 44,4%, color vision test Ishihara evidenced colour desaturation at 100% cases. Best corrected visual acuity, biomicroscopy and ocular fundus examination were normal in 55,5% cases. Conclusions. In patients affected by MS with no history of optic neuritis and no visual symptoms, there is large prevalence of visual pathway involvement that can be detected by performing multiple tests. Only a combination of CS, VEPs and SAP can detect most cases of visual dysfunction associated with MS.

Idiopathic intracranial hypertension – IIH (synonymous old terms: benign intracranial hypertension - BIH, pseudotumor-cerebri - PTC) it’s a syndrome, related to elevated intracranial pressure, of unknown cause, sometimes cerebral emergency, occuring in all age groups, especially in children and young obese womans, in the absence of an underlying expansive intracranial lesion, despite extensive investigations. Although initial symptoms can resolve, IIH displays a high risk of recurrence several months or years later, even if initial symptoms resolved. Results: A 20-year-old male, obese since two years (body mass index 30, 9), was admitted for three months intense headache, vomiting, diplopia, progressive visual acuity loss. Neurologic examination confirmed diplopia by left abducens nerve palsy, papilledema right > left. At admission, cerebral CT scan and cerebral MRI with angio MRI 3DTOF and 2D venous TOF was normal. Despite treatment with acetazolamide (Diamox), corticosteroid, antidepressants (Amitriptyline), anticonvulsivants (Topiramate) three weeks later headache, diplopia persist and vision become worse, confirmed by visual field assessment, visual evoked potential (VEP). A cerebral arteriography demonstrate filling defect of the superior sagittal sinus in the 1/3 proximal part and very week filling of the transverse right sinus on venous time. Trombophylic profile has revealed a heterozygote V factor Leyden mutation, a homozygote MTHFR and PAI mutation justifying an anticoagulant treatment initiated to the patient. The MRI showed a superior sagittal sinus, right transverse and sigmoid sinus thrombosis, dilatation and buckling of the optic nerve sheaths with increased perineural fluid especially retrobulbar, discrete flattening of the posterior segment of the eyeballs, spinal MRI showed posterior epidural space with dilated venous branches, with mass effect on the spinal cord, that occurs pushed anterior on sagittal T1/T2 sequences cervical and thoracic. The opening pression of lumbar puncture, done with the patient in the lateral decubitus position, was 60 cm H2O, the cytochemical CSF study were normal. The patient was operated: a lombo-peritoneal with a variable pressure valve was inserted. Two months after the patient general condition improved: he was without headache, abducens palsy and the visual field assessment, ocular motility examination, ophthalmoscopy were normal. Conclusion: IHH is rare, variable in evolution, and in many cases it disappears on its own within 6 months without affecting life expectancy. Weight loss, fluid or salt restriction, in conjunction with medical treatment, angioplasty and venous stenting across the sinus stenosis under general anesthesia and surgical treatment (shunting, optic nerve sheath decompression and fenestration, gastric by-pass surgery) are treatment alternatives. Such disorder should be closed monitored because 10 to 25% of cases could be affected by recurrencies or by permanent vision loss to those patients with resistant papilledema despite treatment.

A high-density EEG study was conducted to investigate evoked and oscillatory brain activity in response to high speeds of simulated forward motion. Participants were shown an optic flow pattern consisting of a virtual road with moving poles at either side of it, simulating structured forward motion at different driving speeds (25, 50, and 75 km/h) with a static control condition between each motion condition. Significant differences in N2 latencies and peak amplitudes between the three speeds of visual motion were found in parietal channels of interest P3 and P4. As motion speed increased, peak latency increased while peak amplitude decreased which might indicate that higher driving speeds are perceived as more demanding resulting in longer latencies, and as fewer neurons in the motion sensitive areas of the adult brain appear to be attuned to such high visual speeds this could explain the observed inverse relationship between speed and amplitude. In addition, significant differences between alpha de-synchronizations for forward motion and alpha synchronizations in the static condition were found in the parietal midline (PM) source. It was suggested that the alpha de-synchronizations reflect an activated state related to the visual processing of simulated forward motion, whereas the alpha synchronizations in response to the static condition reflect a deactivated resting period.

Visual stimulation is frequently employed in electroencephalographic (EEG) research. However, despite its widespread use, no studies have thoroughly evaluated how the morphology of the visual event-related potentials (ERPs) varies according to the spatial location of stimuli. Hence, the purpose of this study was to perform a detailed retinotopic mapping of visual ERPs. We recorded EEG activity while participants were visually stimulated with 60 pattern-reversing checkerboards placed at different polar angles and eccentricities. Our results show five pattern-reversal ERP components. C1 and C2 components inverted polarity between the upper and lower hemifields. P1 and N1 showed higher amplitudes and shorter latencies to stimuli located in the contralateral lower quadrant. In contrast, P2 amplitude was enhanced and its latency was reduced by stimuli presented in the periphery of the upper hemifield. The retinotopic maps presented here could serve as a guide for selecting optimal visuo-spatial locations in future ERP studies. [ABSTRACT FROM AUTHOR]

Background: The goal of a brain-computer interface (BCI) is to enable communication by pure brain activity without neural and muscle control. However, the practical use of BCIs is limited by low information transfer rate. Recently, code modulation visual evoked potential (c-VEP) based BCIs have exhibited great potential in establishing high-rate communication between the brain and the external world.Objective: This study aims at exploring a more effective modulation code than the commonly used pseudorandom M sequence for c-VEP based BCIs (c-VEP BCIs) in order to increase the detection accuracy of stimulus targets and the resulting information transfer rate.Method: Golay complementary sequence pair is used for constructing the modulation code of c-VEP BCIs due to their superior autocorrelation property. The modulation code is created by concatenating a pair of Golay complementary sequences. Sixteen target stimuli are modulated by the Golay code and its time shift versions.Results: Through offline analysis on data recorded from seven subjects and online test on five subjects, the Golay code modulated BCI yielded higher detection accuracy and information transfer rate than those achieved by M sequence.Conclusion: The Golay code modulated BCI demonstrates a high performance compared with the M sequence modulated systems, and it is applicable to persons with motor disabilities. [ABSTRACT FROM AUTHOR]

Objects' borders are readily perceived despite absent contrast gradients, e.g. due to poor lighting or occlusion. In humans, a visual evoked potential (VEP) correlate of illusory contour (IC) sensitivity, the “IC effect”, has been identified with an onset at ~ 90 ms and generators within bilateral lateral occipital cortices (LOC). The IC effect is observed across a wide range of stimulus parameters, though until now it always involved high-contrast achromatic stimuli. Whether IC perception and its brain mechanisms differ as a function of the type of stimulus cue remains unknown. Resolving such will provide insights on whether there is a unique or multiple solutions to how the brain binds together spatially fractionated information into a cohesive perception. Here, participants discriminated IC from no-contour (NC) control stimuli that were either comprised of low-contrast achromatic stimuli or instead isoluminant chromatic contrast stimuli (presumably biasing processing to the magnocellular and parvocellular pathways, respectively) on separate blocks of trials. Behavioural analyses revealed that ICs were readily perceived independently of the stimulus cue—i.e. when defined by either chromatic or luminance contrast. VEPs were analysed within an electrical neuroimaging framework and revealed a generally similar timing of IC effects across both stimulus contrasts (i.e. at ~ 90 ms). Additionally, an overall phase shift of the VEP on the order of ~ 30 ms was consistently observed in response to chromatic vs. luminance contrast independently of the presence/absence of ICs. Critically, topographic differences in the IC effect were observed over the ~ 110–160 ms period; different configurations of intracranial sources contributed to IC sensitivity as a function of stimulus contrast. Distributed source estimations localized these differences to LOC as well as V1/V2. The present data expand current models by demonstrating the existence of multiple, cue-dependent circuits in the brain for generating perceptions of illusory contours. [ABSTRACT FROM AUTHOR]

In our previous study we found that it takes less time to detect colour change in a moving object compared to colour change in a stationary one (Kreegipuu et al., 2006, Vision Research 46(11), 1848-1855). Here, we replicated the experiment, but in addition to reaction times we measured visual evoked potentials, to see whether this effect of motion is revealed at the cortical level of information processing. We asked our subjects to detect colour changes in stationary (0º/s) and moving bars (4.4 and 17.6º/s). Psychophysical results replicate the findings from the previous study showing decreased reaction times to colour changes with increase of velocity of the colour changing stimulus. The effect of velocity on visual evoked potentials was opposite to the one found on reaction times. Except for component N1, the amplitudes of visual evoked potentials elicited by the colour change of faster moving objects were reduced than those elicited by the colour change of slower moving or stationary objects. The only significant effect of velocity on latency of peaks was found for P2 in frontal region. The results are discussed in the light of change-to-change interval and the two methods reflecting different processing mechanisms.

Idiopathic intracranial hypertension - IIH (synonymous old terms: benign intracranial hypertension - BIH, pseudotumor-cerebri - PTC) it's a syndrome, related to elevated intracranial pressure, of unknown cause, sometimes cerebral emergency, occuring in all age groups, especially in children and young obese womans, in the absence of an underlying expansive intracranial lesion, despite extensive investigations. Although initial symptoms can resolve, IIH displays a high risk of recurrence several months or years later, even if initial symptoms resolved. Results: A 20-year-old male, obese since two years (body mass index 30, 9), was admitted for three months intense headache, vomiting, diplopia, progressive visual acuity loss. Neurologic examination confirmed diplopia by left abducens nerve palsy, papilledema right > left. At admission, cerebral CT scan and cerebral MRI with angio MRI 3DTOF and 2D venous TOF was normal. Despite treatment with acetazolamide (Diamox), corticosteroid, antidepressants (Amitriptyline), anticonvulsivants (Topiramate) three weeks later headache, diplopia persist and vision become worse, confirmed by visual field assessment, visual evoked potential (VEP). A cerebral arteriography demonstrate filling defect of the superior sagittal sinus in the 1/3 proximal part and very week filling of the transverse right sinus on venous time. Trombophylic profile has revealed a heterozygote V factor Leyden mutation, a homozygote MTHFR and PAI mutation justifying an anticoagulant treatment initiated to the patient. The MRI showed a superior sagittal sinus, right transverse and sigmoid sinus thrombosis, dilatation and buckling of the optic nerve sheaths with increased perineural fluid especially retrobulbar, discrete flattening of the posterior segment of the eyeballs, spinal MRI showed posterior epidural space with dilated venous branches, with mass effect on the spinal cord, that occurs pushed anterior on sagittal T1/T2 sequences cervical and thoracic. The opening pression of lumbar puncture, done with the patient in the lateral decubitus position, was 60 cm H2O, the cytochemical CSF study were normal. The patient was operated: a lombo-peritoneal with a variable pressure valve was inserted. Two months after the patient general condition improved: he was without headache, abducens palsy and the visual field assessment, ocular motility examination, ophthalmoscopy were normal. Conclusion: IHH is rare, variable in evolution, and in many cases it disappears on its own within 6 months without affecting life expectancy. Weight loss, fluid or salt restriction, in conjunction with medical treatment, angioplasty and venous stenting across the sinus stenosis under general anesthesia and surgical treatment (shunting, optic nerve sheath decompression and fenestration, gastric by-pass surgery) are treatment alternatives. Such disorder should be closed monitored because 10 to 25% of cases could be affected by recurrencies or by permanent vision loss to those patients with resistant papilledema despite treatment. [ABSTRACT FROM AUTHOR]

A high-density EEG study was conducted to investigate evoked and oscillatory brain activity in response to high speeds of simulated forward motion. Participants were shown an optic flow pattern consisting of a virtual road with moving poles at either side of it, simulating structured forward motion at different driving speeds (25, 50, and 75 km/h) with a static control condition between each motion condition. Significant differences in N2 latencies and peak amplitudes between the three speeds of visual motion were found in parietal channels of interest P3 and P4. As motion speed increased, peak latency increased while peak amplitude decreased which might indicate that higher driving speeds are perceived as more demanding resulting in longer latencies, and as fewer neurons in the motion sensitive areas of the adult brain appear to be attuned to such high visual speeds this could explain the observed inverse relationship between speed and amplitude. In addition, significant differences between alpha de-synchronizations for forward motion and alpha synchronizations in the static condition were found in the parietal midline (PM) source. It was suggested that the alpha de-synchronizations reflect an activated state related to the visual processing of simulated forward motion, whereas the alpha synchronizations in response to the static condition reflect a deactivated resting period. [ABSTRACT FROM AUTHOR]

The chronological process of eye accommodation used when viewing objects was analysed to predict the size of viewed objects. Viewer's visual evoked potentials (VEP), eye movements and pupil oscillations were measured while six sizes of Landolt circles were presented for 1s each. The significant features of the metrics were extracted to illustrate the perception process and the resulting sizes of visual stimuli. The stimulus sizes affect P1 and N1 delay times of VEP, means of eye movement lengths and pupil diameters and oscillations during the second 500 milliseconds of observation. The feasibility of prediction of stimulus sizes viewed was confirmed using the features of eye behaviour and support vector machines. Both indices of eye movements and pupil diameters were determined to be significant features for making predictions. The influences of the combination of features and viewer's individual factors were also confirmed. This result suggests that features of oculo-motor indices reflect the size of objects being viewed and that these viewing sizes can be predicted using the features. [ABSTRACT FROM AUTHOR]

IntroductionAlzheimer‘s disease is a long term progressive neurodegenerative disease and might affect the retinal nerve fibre layer thickness of the eye. There is increasing evidence that visual evoked potentials, which are an objective way to indicate visual field loss, might be affected by the disease as well.Material and Methods22 patients (mean age: 75.9 ± 6.1 years; 14 women) with mild-to-moderate Alzheimer‘s disease and 22 sex-matched healthy patients were examined. We compared the use of visual evoked potentials and retinal nerve fibre layer thickness using latest high-resolution spectral domain optical coherence tomography with eye-tracking capabilities for optimised peripapillary scan centring for the first time in Alzheimer‘s disease patients.ResultsThe mean MMSE score was 22.59 ± 5.47 in the Alzheimer‘s disease group, and did not significantly correlate with the visual evoked potentials latencies. We found no significant difference between the visual evoked potentials latencies of the Alzheimer‘s disease patients and those of the control patients. No peripapillary sector of the retina had a retinal nerve fibre layer thickness significantly correlated with the visual evoked potentials latencies.DiscussionWe demonstrated that pattern visual evoked potentials did not show any significant correlation despite subtle loss in retinal nerve fibre layer thickness. It remains open whether additional flash visual evoked potentials combined with retinal nerve fibre layer thickness analysis may be useful in diagnosing Alzheimer‘s disease, particularly for mild-to-moderate stages of the disease.

In adult readers, letters and words are rapidly identified within visual networks to allow for efficient reading abilities. Neuroimaging studies of orthography have mostly used words and letter strings that recruit many hierarchical levels in reading. Understanding how single letters are processed could provide further insight into orthographic processing. The present study investigated orthographic processing using single letters and pseudoletters when adults were encouraged to pay attention to or away from orthographic features. We measured evoked potentials (EPs) to single letters and pseudoletters from adults while they performed an orthographic-discrimination task (letters vs. pseudoletters), a colour-discrimination task (red vs. blue), and a target-detection task (respond to #1 and #2). Larger and later peaking N1 responses (~170ms) and larger P2 responses (~250 ms) occurred to pseudoletters as compared to letters. This reflected greater visual processing for pseudoletters. Dipole analyses localized this effect to bilateral fusiform and inferior temporal cortices. Moreover, this letter-pseudoletter difference was not modulated by task and thus indicates that directing attention to or away from orthographic features didn’t affect early visual processing of single letters or pseudoletters within extrastriate regions. Paying attention to orthography or colour as compared to disregarding the stimuli (target-detection task) elicited selection negativities at about 175 ms, which were followed by a classical N2-P3 complexes. This indicated that the tasks sufficiently drew participant’s attention to and away from the stimuli. Together these findings revealed that visual processing of single letters and pseudoletters, in adults, appeared to be sensory-contingent and independent of paying attention to stimulus features (e.g., orthography or colour).

Rationale. Visual impairment is one of the most common clinical manifestations of multiple sclerosis (MS). Some multiple sclerosis patients complain of poor vision although the Snellen visual acuity is 20/20. This study reveals that sensitive measurements like visual evoked potential (VEP) and optical coherence tomography (OCT) can evidence subclinical disturbances of visual pathway. These methods examine the relation between the visual function (VEP) and retinal nerve fiber layer (RNFL) thickness, as a structural biomarker for axonal loss in patients with multiple sclerosis (MS). The findings in this study indicate the utility of combining structural and functional testing in clinical research on patients with MS. Purpose. To detect visual impairment in a population of visually asymptomatic patients affected by clinically definite multiple sclerosis (MS) and to compare the utility of optical coherence tomography (OCT) versus visual evoked potentials (VEP). Material and methods. Fourteen patients (28 eyes) affected by clinically definite MS, without a history of optic neuritis and asymptomatic for visual disturbances, were initially fully examined (visual acuity, ocular fundus, biomicroscopy) from an ophthalmic point of view and then measured by OCT (RNFL thickness) and VEP. Patients with a history of glaucoma or other retinal or optic nerve disease were excluded. Results. Of fourteen patients (28 eyes), VEP was abnormal in 11 cases (78,57%) and OCT (RNFL thickness) was abnormal in 5 cases (35,71%), while 3 patients had no abnormalities on neither tests. Conclusions. Optical coherence tomography (OCT) is less sensitive than visual evoked potentials (VEPs) in detecting visual subclinical impairment in patients with multiple sclerosis (MS). VEP remains the preferred test for the detection of clinical and subclinical optic neuritis. OCT may provide complementary information to VEP in cases with clinical definite MS and represent a valuable research instrument for the study of optic nerve disease in populations. The findings in this study reveal the utility of combining structural and functional testing in clinical research on patients with MS. [ABSTRACT FROM AUTHOR]

We often face the challenge of simultaneously attending to multiple non-contiguous regions of space. There is ongoing debate as to how spatial attention is divided under these situations. Whereas, for several years, the predominant view was that humans could divide the attentional spotlight, several recent studies argue in favor of a unitary spotlight that rhythmically samples relevant locations. Here, this issue was addressed by the use of high-density electrophysiology in concert with the multifocal m-sequence technique to examine visual evoked responses to multiple simultaneous streams of stimulation. Concurrently, we assayed the topographic distribution of alpha-band oscillatory mechanisms, a measure of attentional suppression. Participants performed a difficult detection task that required simultaneous attention to two stimuli in contiguous (undivided) or non-contiguous parts of space. In the undivided condition, the classic pattern of attentional modulation was observed, with increased amplitude of the early visual evoked response and increased alpha amplitude ipsilateral to the attended hemifield. For the divided condition, early visual responses to attended stimuli were also enhanced, and the observed multifocal topographic distribution of alpha suppression was in line with the divided attention hypothesis. These results support the existence of divided attentional spotlights, providing evidence that the corresponding modulation occurs during initial sensory processing time-frames in hierarchically early visual regions, and that suppressive mechanisms of visual attention selectively target distracter locations during divided spatial attention. [ABSTRACT FROM AUTHOR]

Abstract: Pallido-pyramidal syndromes combine dystonia with or without parkinsonism and spasticity as part of a mixed neurodegenerative disorder. Several causative genes have been shown to lead to pallido-pyramidal syndromes, including FBXO7, ATP13A2, PLA2G6, PRKN and SPG11. Among these, ATP13A2 and PLA2G6 are inconsistently associated with brain iron deposition. Using homozygosity mapping and direct sequencing in a multiplex consanguineous Saudi Arabian family with a pallido-pyramidal syndrome, iron deposition and cerebellar atrophy, we identified a homozygous p.G53R mutation in C19orf12. Our findings add to the phenotypic spectrum associated with C19orf12 mutations. [Copyright &y& Elsevier]

Abstract: Oculocutaneous albinism (OCA) is characterized by hypopigmentation of the skin, hair and eye, and by ophthalmologic abnormalities caused by a deficiency in melanin biosynthesis. OCA type II (OCA2) is one of the four commonly-recognized forms of albinism, and is determined by mutation in the OCA2 gene. In the present study, we investigated the molecular basis of OCA2 in two siblings and one unrelated patient. The mutational screening of the OCA2 gene identified two hitherto-unknown putative splicing mutations. The first one (c.1503+5G>A), identified in an Italian proband and her affected sibling, lies in the consensus sequence of the donor splice site of OCA2 intron 14 (IVS14+5G>A), in compound heterozygosity with a frameshift mutation, c.1450_1451insCTGCCCTGACA, which is predicted to determine the premature termination of the polypeptide chain (p.I484Tfs*19). In-silico prediction of the effect of the IVS14+5G>A mutation on splicing showed a score reduction for the mutant splice site and indicated the possible activation of a newly-created deep-intronic acceptor splice site. The second mutation is a synonymous transition (c.2139G>A, p.K713K) involving the last nucleotide of exon 20. This mutation was found in a young African albino patient in compound heterozygosity with a previously-reported OCA2 missense mutation (p.T404M). In-silico analysis predicted that the mutant c.2139G>A allele would result in the abolition of the splice donor site. The effects on splicing of these two novel mutations were investigated using an in-vitro hybrid-minigene approach that led to the demonstration of the causal role of the two mutations and to the identification of aberrant transcript variants. [Copyright &y& Elsevier]

Abstract: Many clinical and animal studies demonstrate the importance of long-chain polyunsaturated fatty acids (LCPUFA) in neural development and neurodegeneration. This review will focus on involvement of LCPUFA from genesis to senescence. The LCPUFA docosahexaenoic acid and arachidonic acid are important components of neuronal membranes, while eicosapentaenoic acid, docosahexaenoic acid, and arachidonic acid also affect cardiovascular health and inflammation. In neural development, LCPUFA deficiency can lead to severe disorders like schizophrenia and attention deficit hyperactivity disorder. Perinatal LCPUFA supplementation demonstrated beneficial effects in neural development in humans and rodents resulting in improved cognition and sensorimotor integration. In normal aging, the effect of LCPUFA on prevention of cognitive impairment will be discussed. LCPUFA are important for neuronal membrane integrity and function, and also contribute in prevention of brain hypoperfusion. Cerebral perfusion can be compromised as result of obesity, cerebrovascular disease, hypertension, or diabetes mellitus type 2. Last, we will focus on the role of LCPUFA in most common neurodegenerative diseases like Alzheimer’s disease and Parkinson’s disease. These disorders are characterized by impaired cognition and connectivity and both clinical and animal supplementation studies have shown the potential of LCPUFA to decrease neurodegeneration and inflammation. This review shows that LCPUFA are essential throughout life. [Copyright &y& Elsevier]

Visual evoked potential (VEP) is commonly used to evaluate visual acuity in both clinical and basic studies. Subdermal needle electrodes or skull pre-implanted screw electrodes are usually used to record VEP in rodents. However, the VEP amplitudes recorded by the former are small while the latter may damage the brain. In this study, we established a new invasive procedure for VEP recording, and made a series of comparisons of VEP parameters recorded from different electrode locations, different times of day (day and night) and bilateral eyes, to evaluate the influence of these factors on VEP in mice. Our data reveal that our invasive method is reliable and can record VEP with good waveforms and large amplitudes. The comparison data show that VEP is greatly influenced by active electrode locations and difference between day and night. In C57 or CD1 ONC (optic nerve crush) models and Brn3b AP/AP mice, which are featured by loss of retinal ganglion cells (RGCs), amplitudes of VEP N1 and P1 waves are drastically reduced. The newly established VEP procedure is very reliable and stable, and is particularly useful for detecting losses of RGC quantities, functions or connections to the brain. Our analyses of various recording conditions also provide useful references for future studies. • We successfully established a sensitive and reliable procedure to record visual evoked potential (VEP). • VEP is significantly affected by electrode locations and circadian rhythm. • First VEP recording of Brn3b AP/AP mice demonstrated a dramatical loss of visual function in the mutant mice. [ABSTRACT FROM AUTHOR]

Highlights: [•] Spectral power analysis of VEPs in response to flash visual stimuli showed distinct spatiotemporal characteristics recorded from visual cortices in epilepsy surgery patients with intracranial recordings. [•] High γ (60–150Hz) evoked oscillations (EOs) predominantly belonged to the electrodes with simple form visual responses, whereas low γ (30–60Hz) and lower frequency (LF) <30Hz EOs were observed from those with intermediate form and LF EOs with complex form responses. [•] Phase-locked EOs in these frequency bands may have special neuroanatomical and functional organization during early visual processing in human. [Copyright &y& Elsevier]

Objectives: Children with Bipolar Mood Disorder (BMD) and those with Attention Deficit Hyperactivity Disorder (ADHD) share many clinical signs and symptoms; therefore, achieving an accurate diagnosis is still a challenge, especially in the first interview session. The main focus of this paper is to quantitatively classify the ADHD and BMD patients using their Visual Evoke Potential (VEP) features elicited from their Electroencephalogram (EEG) signals. Methods and materials: In this study, 36 subjects were participated including 12 healthy ones, 12 patients with ADHD and 12 ones with BMD. The age of ADHD patients was 16.92 ± 6.29 and for the BMD ones was 17.85 ± 3.68. Their scalp EEG signals in the presence of visual stimulus were recorded using 22 silver electrodes located according to the 10-20 international recording protocol. To extract their VEP, first a preprocessing step was executed to remove the power line and movement artifacts. Afterward, the wavelet denoising and synchronous averaging were applied to the preprocessed trials in order to elicit the P100 component. To obtain interpretable features from the evoked patterns, amplitude and latency were extracted and applied to the 1-Nearest Neighbor (1NN) classifier due to the locally scattered distribution of the VEP features. Results: The evaluation was performed according to leave-one(subject)-out method and the experimental results were led to 92.85% classification accuracy which is a fairly promising achievement to distinguish the BMD, ADHD, and healthy subjects from each other. Conclusion: From the physiological point of view, this result point out to the existence of significant difference in the neural activities of their visual system in the ADHD, BMD, and healthy subjects in response to a periodic optical stimulus. [ABSTRACT FROM AUTHOR]

Optic neuritis is often the initial manifestation in multiple sclerosis (15%). There is a significant percent of patients affected by clinically definite multiple sclerosis that report no ocular symptoms. Some of this patients complain of poor vision despite the 6/6 visual acuity with Snellen test. Subclinical visual abnormalities may be revealed by more sensitive measures of visual function. Alteration of visual evoked potential latencies associated with brain MRI lesion burden, standard achromatic perimetry and low-contrast letter acuity, may detect subclinical visual manifestations. In this study we compare the efficiency of electrophysiological test (visual evoked potential) and subjective tests (contrast sensitivity and standard achromatic perimetry) in detection of visual impairment in a population of asymptomatic patients with clinically definite multiple sclerosis. Purpose. The detecting of subclinical impairment of visual function in a population of visual asymptomatic patients affected by clinically definite multiple sclerosis (MS) by using visual evoked potentials (VEPs), contrast sensitivity (CS), standard achromatic perimetry (SAP), magnetic resonance imaging (MRI), color vision test Ishihara, best corrected visual acuity (BCVA). Methods. Eighteen eyes of nine patients affected by clinically definite MS, without visual disturbances and optic neuritis history. All the patients were recruited at the Department of Neurology of Emergency Universitary Hospital of Bucharest. Of the nine patients, 3 were male and 6 female. In all the cases the disease was in remission. The tests used to detect the involvement of visual pathway were: • VEPs (a P100 latency >115 ms) • CS • SAP (abnormal MD or PD) • MRI (at least one demyelinating plaque along visual pathway) • Color test Ishihara • Best corrected visual acuity (BCVA) • Biomicroscopy • Ocular fundus examination after pupil dilatation Results. From the 9 patients in the 29-47 year age group, VEPs was abnormal in 8 cases (88,8%), CS was abnormal in 8 cases (88,8%), SAP in 44,4%, color vision test Ishihara evidenced colour desaturation at 100% cases. Best corrected visual acuity, biomicroscopy and ocular fundus examination were normal in 55,5% cases. Conclusions. In patients affected by MS with no history of optic neuritis and no visual symptoms, there is large prevalence of visual pathway involvement that can be detected by performing multiple tests. Only a combination of CS, VEPs and SAP can detect most cases of visual dysfunction associated with MS. [ABSTRACT FROM AUTHOR]

To compare the visual evoked potential (VEP) responses of amblyopic eyes with VEP responses of sound eyes in amblyopic children. A study of 65 amblyopic children with pattern-reversal VEPs elicited by checkerboard stimuli with large, medium and small checks. The children were classified into three groups: Group A, 22 children with anisometropic amblyopia; Group B, 16 children with exotropic strabismic amblyopia; and Group C, 27 children with esotropic strabismic amblyopia. Visual acuity (VA) was significantly worse in the amblyopic eye as compared to the sound eye. However, no statistically significant difference was found between the amblyopic and sound eye of amblyopic children in the three groups for VEP P1 amplitude and latencies for any check sizes. VEP is a very important tool in understanding the complex amblyopic mechanism. Although the sound eye has superior VA, the absence of differences in VEP P1 amplitudes and latencies demonstrate the functional abnormality of the eye considered 'good'. More studies are necessary to explain why the sound eye in amblyopic children cannot be considered completely normal. Special attention should therefore be paid to amblyopic treatment, as patching can have a negative effect on the sound eye. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To observe the impacts of acupuncture on brainstem evoked potentials in the patients with primary depression. Methods: Forty cases of primary depression were treated by acupuncture at Bâihuì (▪ GV 20), Yìntáng (▪ GV 29), Dàzhuī (▪ GV 14), bilateral Shénmén (▪ HT 7), bilateral Tàichōng (▪ LR 3), bilateral Nèiguān (▪ PC 6) and Sānyïnjiéo (▪ SP 6). The needles were retained for 30 min. Acupuncture treatment was given once every two days, three treatments a week. The brainstem auditory evoked potential (BAEP) and visual evoked potential (VEP) were observed in 6 weeks of treatment. The change in Hamilton depression scale (HAMD) score was observed before and after treatment in the depression group. Results: After treatment, VEP wave latency was shortened significantly in patients of depression (P<0.05), BAEPIII wave latency was shortened significantly (P<0.05). The score of HAMD was decreased apparently in the depression group (P<0.05). Conclusions: The stressability of visual and auditory stimuli in the central nervous system was decreased in the patients of depression. Acupuncture shortens remarkably the brainstem evoked potentials latency in the patients of depression and achieves the effective results in the treatment of primary depression. [Copyright &y& Elsevier]

A key feature of early visual cortical regions is that they contain discretely organized retinotopic maps. Titration of these maps must occur through experience, and the fidelity of their spatial tuning will depend on the consistency and accuracy of the eye movement system. Anomalies in fixation patterns and the ballistics of eye movements are well documented in autism spectrum disorder ( ASD), with off-center fixations a hallmark of the phenotype. We hypothesized that these atypicalities might affect the development of visuo-spatial maps and specifically that peripheral inputs might receive altered processing in ASD. Using high-density recordings of visual evoked potentials ( VEPs) and a novel system-identification approach known as VESPA (visual evoked spread spectrum analysis), we assessed sensory responses to centrally and peripherally presented stimuli. Additionally, input luminance was varied to bias responsiveness to the magnocellular system, given previous suggestions of magnocellular-specific deficits in ASD. Participants were 22 ASD children (7-17 years of age) and 31 age- and performance- IQ-matched neurotypical controls. Both VEP and VESPA responses to central presentations were indistinguishable between groups. In contrast, peripheral presentations resulted in significantly greater early VEP and VESPA amplitudes in the ASD cohort. We found no evidence that anomalous enhancement was restricted to magnocellular-biased responses. The extent of peripheral response enhancement was related to the severity of stereotyped behaviors and restricted interests, cardinal symptoms of ASD. The current results point to differential visuo-spatial cortical mapping in ASD, shedding light on the consequences of peculiarities in gaze and stereotyped visual behaviors often reported by clinicians working with this population. [ABSTRACT FROM AUTHOR]

In adult readers, letters, and words are rapidly identified within visual networks to allow for efficient reading abilities. Neuroimaging studies of orthography have mostly used words and letter strings that recruit many hierarchical levels in reading. Understanding how single letters are processed could provide further insight into orthographic processing. The present study investigated orthographic processing using single letters and pseudoletters when adults were encouraged to pay attention to or away from orthographic features. We measured evoked potentials (EPs) to single letters and pseudoletters from adults while they performed an orthographic-discrimination task (letters vs. pseudoletters), a color-discrimination task (red vs. blue), and a target-detection task (respond to #1 and #2). Larger and later peaking N1 responses (~170ms) and larger P2 responses (~250 ms) occurred to pseudoletters as compared to letters. This reflected greater visual processing for pseudoletters. Dipole analyses localized this effect to bilateral fusiform and inferior temporal cortices. Moreover, this letter-pseudoletter difference was not modulated by task and thus indicates that directing attention to or away from orthographic features did not affect early visual processing of single letters or pseudoletters within extrastriate regions. Paying attention to orthography or color as compared to disregarding the stimuli (target-detection task) elicited selection negativities at about 175 ms, which were followed by a classical N2-P3 complex. This indicated that the tasks sufficiently drew participant's attention to and away from the stimuli. Together these findings revealed that visual processing of single letters and pseudoletters, in adults, appeared to be sensory-contingent and independent of paying attention to stimulus features (e.g., orthography or color). [ABSTRACT FROM AUTHOR]

Alcohol addiction often compromises vision by impairing the visual pathway, particularly the retina and optic nerve. Vision decline in alcoholics consists of a sequential transition from reversible functional deterioration of the visual pathway to irreversible clinical vision degeneration or vision loss. Thus, the control of alcoholic vision decline should focus on prevention before permanent damage occurs. Visual electrophysiology is a promising method for early detection of retinal dysfunction and optic neuropathy, including full-field electroretinography (ffERG) and pattern-reversal visual evoked potential (PR-VEP). So far, however, research studying the electrophysiological characteristics in the preclinical stage of vision decline caused by alcohol addiction is still lacking. Here we conducted a retrospective study with 11 alcoholics and 14 matched control individuals to address this need. We had performed comprehensive visual electrophysiological tests, including ffERG and PR-VEP. We next analyzed all electrophysiological parameters using multivariate statistical analyses and discovered some highly sensitive alterations to alcohol addiction. We found severely reduced amplitudes in scotopic ffERG oscillatory potentials (OPs) in alcohol addicts. These changes indicate the alcohol-induced disturbances of amacrine cells and retinal circulation. In subjects with alcohol addiction, the amplitudes of b-waves diminish significantly in scotopic but not photopic ffERG, implying the impaired function of the retinal rod system and the dysfunction of the inner retina. PR-VEPs elicited by checkerboard stimuli with large 1 degree (°) checks mainly reflect the state of the optic nerve and ganglion cells, and PR-VEPs provoked by small 0.25° checks mainly reflect the function of the macular. We performed both measurements and observed a robust amplitude reduction in all three peaks (N75-P100, P100-N135) and a significant peak time extension in P100. Our research provides an affordable and non-invasive tool to accurately evaluate visual pathway conditions in alcohol addicts and help clinicians take targeted treatment., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Xie, Feng, Wang, Zhang, Hong and Zhang.)

The purpose of this study was to assess changes in the response profile of the pattern visual evoked potential (VEP) using three stimulus configurations simulating visual-field scotomas: central circular and central blank fields increasing incrementally in diameter from 1° to 15°, hemi-field, and quadrant patterns. Five visually normal adult subjects (ages 22-68 years) were tested binocularly at 1 m for each stimulus configuration on 5 separate days. A checkerboard test pattern (64 × 64 black-and-white checks, 85 % contrast, 64 cd/m luminance, 20 s of stimulus duration, 2-Hz temporal frequency) was used. The group mean VEP amplitude increased in a linear manner with increase in the central circular diameter ( y = 0.805 x + 2.00; r = 0.986) and decrease in central blank field diameter ( y = −0.769 x + 16.22; r = 0.987). There was no significant change in latency in nearly all cases. The group mean coefficient of variability results indicated that the VEP amplitude was repeatable for the different stimulus configurations. The finding of VEP response linearity for the circular stimulus fields, and repeatability for all stimulus configurations, suggests that the clinician may be able to use the VEP technique with the suggested test patterns as a rapid and simple tool for objective assessment for several types of visual-field defects for a range of abnormal visual conditions and special populations. [ABSTRACT FROM AUTHOR]

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Long-term potentiation (LTP) is a synaptic mechanism underlying learning and memory that has been studied extensively in laboratory animals. The study of LTP recently has been extended into humans with repetitive sensory stimulation to induce cortical LTP. In this review article, we will discuss past results from our group demonstrating that repetitive sensory stimulation (visual or auditory) induces LTP within the sensory cortex (visual/auditory, respectively) and can be measured noninvasively with electroencephalography or functional magnetic resonance imaging. We will discuss a number of studies that indicate that this form of LTP shares several characteristics with the synaptic LTP described in animals: it is frequency dependent, long-lasting (> 1 hour), input-specific, depotentiates with low-frequency stimulation, and is blocked by N-methyl-D-aspartate receptor blockers in rats. In this review, we also present new data with regard to the behavioral significance of human sensory LTP. These advances will permit enquiry into the functional significance of LTP that has been hindered by the absence of a human model. The ability to elicit LTP with a natural sensory stimulus noninvasively will provide a model system allowing the detailed examination of synaptic plasticity in normal subjects and might have future clinical applications in the diagnosis and assessment of neuropsychiatric and neurocognitive disorders. [Copyright &y& Elsevier]

Abstract: Early visual processing stages have been demonstrated to be impaired in schizophrenia patients and their first-degree relatives. The amplitude and topography of the P1 component of the visual evoked potential (VEP) are both affected; the latter of which indicates alterations in active brain networks between populations. At least two issues remain unresolved. First, the specificity of this deficit (and suitability as an endophenotype) has yet to be established, with evidence for impaired P1 responses in other clinical populations. Second, it remains unknown whether schizophrenia patients exhibit intact functional modulation of the P1 VEP component; an aspect that may assist in distinguishing effects specific to schizophrenia. We applied electrical neuroimaging analyses to VEPs from chronic schizophrenia patients and healthy controls in response to variation in the parafoveal spatial extent of stimuli. Healthy controls demonstrated robust modulation of the VEP strength and topography as a function of the spatial extent of stimuli during the P1 component. By contrast, no such modulations were evident at early latencies in the responses from patients with schizophrenia. Source estimations localized these deficits to the left precuneus and medial inferior parietal cortex. These findings provide insights on potential underlying low-level impairments in schizophrenia. [Copyright &y& Elsevier]

Abstract: Gamma Band Activity (GBA) is increasingly studied for its relation with attention, change detection, maintenance of working memory and the processing of sensory stimuli. Activity around the gamma range has also been linked with early visual processing, although the relationship between this activity and the low frequency visual evoked potential (VEP) remains unclear. This study examined the ability of blind and semi-blind source separation techniques to extract sources specifically related to the VEP and GBA in order to shed light on the relationship between them. Blind (Independent Component Analysis—ICA) and semi-Blind (Functional Source Separation—FSS) methods were applied to dense array EEG data recorded during checkerboard stimulation. FSS was performed with both temporal and spectral constraints to identify specifically the generators of the main peak of the VEP (P100) and of the GBA. Source localisation and time-frequency analyses were then used to investigate the properties and co-dependencies between VEP/P100 and GBA. Analysis of the VEP extracted using the different methods demonstrated very similar morphology and localisation of the generators. Single trial time frequency analysis showed higher GBA when a larger amplitude VEP/P100 occurred. Further examination indicated that the evoked (phase-locked) component of the GBA was more related to the P100, whilst the induced component correlated with the VEP as a whole. The results suggest that the VEP and GBA may be generated by the same neuronal populations, and implicate this relationship as a potential mediator of the correlation between the VEP and the Blood Oxygenation Level Dependent (BOLD) effect measured with fMRI. [Copyright &y& Elsevier]

Abstract: Multiple sclerosis (MS) patients may suffer from optic disturbances. Toxin-induced demyelinations have frequently been developed to investigate the cellular and structural aspects of demyelination and remyelination processes, separately. The present study describes functional consequence of lysolecithin (LPC)-induced lesion in the adult rat optic nerves and chiasm by recording the visual evoked potentials (VEPs) from the visual cortex and its correlation with myelin basic protein (MBP) expression in lesion site. Records of VEP were obtained at 2, 7, 14 and 28days post-injection. We observed that the VEPs generated by light stimuli progressively changed in both amplitude and latency after the lesion as well as in comparison with those generated in control animals. These observations were confirmed through measurement of mRNA expression level for MBP which is one of the important genes expressed in mature oligodendrocytes and Schwann cells. The level of MBP mRNAs in demyelinated chiasm and optic nerves decreased following lysolecithin injection with its least value on day 7, and then it increased to the control level 14days post-lesion. However, it continued to increase even after that and reached a maximum level 28days post lesion. Results of the present paper show that, LPC injection in the chiasm share functional and molecular alterations which are found in demyelinating disorders in both the optic nerves and chiasm and also these alterations were coming back to level of control animal on 28days post lesion, which is typically seen in myelin repair process. The present paper provides new insights into the experimental toxin-induced models that may be useful for evaluating the functional recovery of demyelinated optic nerves and chiasm following various repairing strategies. It also seems to be useful for studying the protective or remyelinating effects of different therapies in e.g. optic apparatus which is more affected by MS. [ABSTRACT FROM AUTHOR]

Abstract: EEG quality is a crucial issue when acquiring combined EEG-fMRI data, particularly when the focus is on using single trial (ST) variability to integrate the data sets. The most common method for improving EEG data quality following removal of gross MRI artefacts is independent component analysis (ICA), a completely blind source separation technique. In the current study, a different approach is proposed based on the functional source separation (FSS) algorithm. FSS is an extension of ICA that incorporates prior knowledge about the signal of interest into the data decomposition. Since in general the part of the EEG signal that will contain the most relevant information is known beforehand (i.e. evoked potential peaks, spectral bands), FSS separates the signal of interest by exploiting this prior knowledge without renouncing the advantages of using only information contained in the original signal waveforms. A reversing checkerboard stimulus was used to generate visual evoked potentials (VEPs) in healthy control subjects. Gradient and ballistocardiogram artefacts were removed with template subtraction techniques to form the raw data, which were then subjected to ICA denoising and FSS. The resulting EEG data sets were compared using several metrics derived from average and ST data and correlated with fMRI data. In all cases, ICA was an improvement on the raw data, but the most obvious improvement was provided by FSS, which consistently outperformed ICA. The results show the benefit of FSS for the recovery of good quality single trial evoked potentials during concurrent EEG-fMRI recordings. [Copyright &y& Elsevier]

We present the 3-D EEG source images reconstructed by using the minimum norm least square (MNLS) method in combination with the functional magnetic resonance imaging (fMRI) statistical parametric mapping. For a group of five normal subjects, electroencephalogram (EEG) and fMRI signals responding to the full-view checkerboard pattern-reversal visual stimulation were recorded simultaneously and separately. The electrical activities in V1/V2 and VS were successfully imaged in the N75-P100-N145 and P100-N145 components, respectively. The present results demonstrate the merits of high-resolution spatiotemporal functional neuroimaging by integrating the simultaneously recorded fMRI and EEG data. [ABSTRACT FROM AUTHOR]

Pattern reversal evoked potentials (PVEPs) are a noninvasive procedure that are useful for detecting lesions of the visual pathways. This article reviews anatomy of the visual pathway and the testing protocols for full field and hemifield PVEP and flash (goggle) visual evoked potentials (FVEP). Criteria for evaluation of normal and abnormal responses and clinical correlates are discussed. We conclude with a brief discussion of recording visual evoked potentials (VEPs) from subdural or depth electrodes to localize primary, visual cortex in patients, with a parieto-occipital seizure focus, who are undergoing evaluation for epilepsy surgery. [ABSTRACT FROM AUTHOR]

Abstract: Recent research suggests that rapid visual stimulation can induce long-term potentiation-like effects non-invasively in humans. However, to date, this research has provided only limited evidence for input-specificity, a fundamental property of cellular long-term potentiation. In the present study we extend the evidence for input-specificity by investigating the effect of stimulus orientation. We use sine wave gratings of two different orientations to show that rapid visual stimulation can induce orientation-specific potentiation, as indexed by changes in the amplitude of a late phase of the N1 complex of the visual-evoked potential. This result suggests that discrete populations of orientation-tuned neurons can be selectively potentiated by rapid visual stimulation. Furthermore, our results support earlier studies that have suggested that the locus of potentiation induced by rapid visual stimulation is visual cortex. [Copyright &y& Elsevier]

Electroencephalogram (EEG) was used in 8-month-old infants and adults to study brain electrical activity as a function of perception of structured optic flow and random visual motion. A combination of visual evoked potential (VEP) analyses and analyses of temporal spectral evolution (TSE, time-dependent spectral power) was carried out. Significant differences were found for the N2 component of VEP for optic flow versus random visual motion within and between groups. Both adults and infants showed shorter latencies for structured optic flow than random visual motion, and infants showed longer latencies, particularly for random visual motion, and larger amplitudes than adults. Both groups also showed significant differences in induced activity when TSE of the two motion stimuli (optic flow and random visual motion) was compared with TSE of a static dot pattern. Infants showed an induced decrease in the amplitudes in theta-band frequency, while adults showed an induced increase in beta-band frequency. Differences in induced activity for the two motion stimuli could, however, not be observed. Brain activity related to motion stimuli is different for infants and adults and the differences are observed both in VEPs and in induced activity of the EEG. To investigate how changes in locomotor development are related to accompanying changes in brain activity associated with visual motion perception, more data of infants with different experiences in self-produced locomotion are required. [ABSTRACT FROM AUTHOR]

Purpose: To report a pediatric patient with bilateral chorioretinopathy and microcephaly who from birth to 2 years of age is reaching appropriate developmental milestones.Design: Retrospective case report with clinical findings and literature review. Main Outcome Measures: Clinical findings and visual acuity estimated by sweep visual evoked potentials (VEP), electroretinogram (ERG) and fundoscopic exam. Results: A microcephalic child with normal motor and cognitive development had improving sweep VEP despite atypical fundoscopic findings of bilateral chorioretinopathy, attenuated retinal vessels, and anomalous optic nerves. The etiology for these collective findings despite extensive workup, including prenatal TORCH titers and neuro-imaging, has remained unidentified. Conclusions: Most published cases of microcephaly with chorioretinopathy have described patients with mild to severe mental retardation. Patients with chorioretinopathy and microcephaly may, however, reach all developmental milestones with improvement in visual development as was seen in this case. The long-term cognitive and visual prognosis may be better than previously reported. [ABSTRACT FROM AUTHOR]

Abstract: Phosphenes (“light flashes”) have been reported by most astronauts on space missions and by healthy subjects whose eyes were exposed to ionizing radiation in early experiments in particle accelerators. The conditions of occurrence suggested retinal effects of heavy ions. To develop an in vivo animal model, we irradiated the eyes of anesthetized wild-type mice with repeated bursts of 12C ions delivered under controlled conditions in accelerator. 12C ions evoked electrophysiological retinal mass responses and activated the visual system as indicated by responses recorded from the visual cortex. No retinal immunohistological damage was detected. Mice proved a suitable animal model to study radiation-induced phosphenes in vivo and our findings are consistent with an origin of phosphenes in radiation activating the retina. [Copyright &y& Elsevier]

Abstract: The present study examined the neurophysiological aspects of discrimination of geometric figures with different eccentricities. In the behavioral experiment, a circle and 3 geometric polygons (square, hexagon, or octagon) were presented for 300 ms at quadrant locations. The eccentricity was changed from 2° to 16° at 2° intervals. The participants (10 adults) were instructed to fixate the center of the CRT and find the circle among the polygons. In the neurophysiological experiment, 4 identical stimuli (squares, hexagons, octagons, or circles) were presented at an eccentricity of 4°, 8°, or 12°. Discrimination performance in the periphery declined when the angularity of the polygons increased. ERP components at 80 ms (P1 with posterior positivity) and 140 ms (N1 with posterior negativity) were observed regardless of the eccentricity or shape of the stimuli. N1 lasted longer as eccentricity increased. P2 with posterior positivity at 200 ms became blurred in the periphery, except for squares. The topography of N1 and P2 changed, depending on the retinal stimulus location; it was influenced by the angularity of the geometric figures in the peripheral visual field. Cerebral processing concerned with N1 and P2 might play an important role in the perception and recognition of visual objects in the peripheral visual field. [Copyright &y& Elsevier]