Automatic detection of violations of statistical regularities in the periphery is affected by the focus of spatial attention: A visual mismatch negativity study

We investigated the effect of spatial attention on an event‐related potential signature of automatic detection of violations of statistical regularities, namely, the visual mismatch negativity (vMMN). To vary the task‐field and the location of vMMN‐related stimulation, in the attentional field the stimuli of a tracking task with a steady and a moving (target) bar were presented. The target stimuli of the task appeared either relatively close or far from a passive (task‐irrelevant) oddball or equiprobable sequence at the lower part of the screen. Stimuli of the oddball sequence were shapes tilted either 45° (standard, p = 0.8) or 135° (deviant, p = 0.2), while the equiprobable sequence consisted of additional three shapes with identical number of lines to the oddball stimuli. Deviant stimuli in close proximity to a continuously attended field elicited larger vMMN than similar stimuli farther away from the stimulus field. In the condition with a smaller distance between the field of the tracking task and the vMMN‐related field, the deviant stimuli and the vMMN was followed by a posterior positivity. According to these results, spatial attention modulates vMMN and is capable of initiating further processing of the deviant stimuli.     

Visual and auditory evoked potentials in the early diagnosis and follow-up of neurosarcoidosis

Visual and brainstem auditory evoked potentials (VEPs, BAEPs) were recorded in 23 patients with neurosarcoidosis. Eight patients (35%) had abnormal BAEPs, and 10 (43%) had abnormal VEPs. Four of the 8 patients with abnormal BAEPs had facial paresis, one had impaired memory and only 3 had symptoms and signs compatible with brainstem lesion. Seven of the patients with abnormal VEPs had no visual symptoms. These findings suggest that BAEP and VEP can reveal subclinical nervous system involvement in sarcoidosis and can also help in the early diagnosis of neurosarcoidosis. Successive recordings of 5 patients showed that BAEP and VEP were useful in the follow-up of these patients.     

Somatosensory and visual evoked potentials in children with cerebral palsy: Correlations and discrepancies with MRI findings and clinical picture

Purpose: To determine if there is any association between the findings of visual evoked potentials (VEPs), somatosensory evoked potentials (SEPs), and magnetic resonance imaging (MRI) findings with the neurodevelopment and severity in children with cerebral palsy (CP). Methods: The present study included 15 children with spastic diplegic CP and five children with spastic hemiplegic CP and 42 healthy children as controls. The number of the controls was two-times greater than the study group to increase statistical power of this study. VEPs and SEPs were recorded in the CP children and compared with healthy controls. All MR scans were obtained using a 1.5 T MR scanner. Results: A significant difference was found in the latencies P100 (VEP) between the CP and controls. No correlations between increased P100 latencies and asphyxia, prematurity, the CP severity, MRI findings and mental retardation were noted. A significant difference in N13–N20 conductions (SEPs) between the subjects with CP and the control group was found. SEPs were positively correlated with mental retardation in CP children. The brain lesions in MRI showed a significant correlation with the CP severity scores and mental retardation. Conclusion: The differences in VEPs and SEPs were determined between CP children and healthy children. The MRI findings were positively correlated with the CP severity and mental retardation.     

Luminance and chromatic visual evoked potentials in type I and type II diabetes: relationships with peripheral neuropathy

Abstract The objective of the study was to investigate the subclinical visual deficit in type I and II diabetes, and its relationship with peripheral neuropathy. Thirty-two healthy volunteers, 20 patients with type I diabetes and 30 patients with type II diabetes were studied in a clinical neurophysiology setting. Luminance (VEPs) and chromatic visual evoked potentials (CVEPs) were recorded, with white-black, grey-black, red-green and blue-yellow sinusoidal gratings. The peak latencies of the VEP positive wave and CVEP negative wave were recorded. Ten patients with type I and 8 with type II diabetes had peripheral neuropathy. VEPs were slower in patients with type II diabetes and CVEPs were slower in patients with type I and type II diabetes than in controls. Blue-yellow CVEPs were slower in type II than in type I diabetes. VEPs and red-green CVEPs were slower in patients with diabetes with neuropathy than in those without. In conclusion, we found that visual system impairment differs in diabetes with and without peripheral neuropathy.     

Age-related changes in the dynamics of human albino visual pathways

A deficiency of melanin in the retinal pigment epithelium, which regulates the development of neural retina, leads to chiasmal misrouting such that the uncrossed pathway (to the ipsilateral hemisphere) is reduced relative to the crossed pathway (to the contralateral hemisphere). This study examines age-related changes in the flash and pattern appearance visual evoked potentials (VEP) of human albinos. Scalp recorded cortical VEPs to flash (FVEP) and pattern appearance stimulation were recorded in 58 albino (8 months to 60 years) and 34 normal subjects (4-55 years). VEPs were analysed by amplitude and latency. The contralateral hemisphere FVEP amplitude decreased with age in albino subjects, as in both hemispheres in normals. However, the ipsilateral hemisphere FVEP amplitude was significantly lower in young albino subjects, initially giving a marked interhemispheric asymmetry, but this normalized with age. Significant interhemispheric FVEP latency asymmetries were not observed. The contralateral pattern appearance VEP latency in albino subjects decreased with age, as in both hemispheres in normals; the ipsilateral latency increased significantly with age. Significant interhemispheric pattern appearance VEP amplitude asymmetries were not observed. These novel and unexpected observations indicate significant age-related changes in the retinocortical pathways of the human albino. These changes have implications for our understanding of development and plasticity of the central visual pathways.     

Study of visual evoked potentials in diabetics without retinopathy: correlations with clinical findings and polyneuropathy

To evaluate central optic pathways' involvement in diabetics, visual evoked potentials (VEP), in particular the latency of positive peak (LP100), were studied in 35 patients without retinopathy (4 insulin-dependent, 31 non-insulin-dependent) and 35 normal controls using reversal pattern stimulation. LP100 was significantly delayed in diabetics at both binocular and monocular stimulation. Furthermore, the delay in LP100 was significantly longer in the diabetics with polyneuropathy than in those without, particularly after binocular stimulation. A positive correlation was found between latencies of VEP and HbA1, duration of disease, and neurologic score. VEP measurement seems a simple and sensitive method for detecting early alterations in central optic pathways in diabetics.     

Event-related potential activity in the basal ganglia differentiates rewards from nonrewards: temporospatial principal components analysis and source localization of the feedback negativity

Event-related potential studies of reward processing have consistently identified the feedback negativity (FN), an early neural response that differentiates feedback indicating unfavorable versus favorable outcomes. Several important questions remain, however, about the nature of this response. In this study, the FN was recorded in response to monetary gains and losses during a laboratory gambling task, and temporospatial principal components analysis was used to separate the FN from overlapping responses. The FN was identified as a positive deflection at frontocentral recording sites that was enhanced for rewards compared with nonrewards. Furthermore, source localization techniques identified the striatum as a likely neural generator. These data indicate that this apparent FN reflects increased striatal activation in response to favorable outcomes that is reduced or absent for unfavorable outcomes, thereby providing unique information about the timing and nature of basal ganglia activity related to reward processing.     

Hemifield pattern-reversal visual evoked potentials (VEPs) in retrochiasmal lesions with homonymous visual field defect

This study was designed to examine the clinical significance and the reliability of hemifield pattern reversal VEPs in the assessment of homonymous visual field defects due to retrochiasmal lesions.13 patients with traumatic, neoplastic or ischemic lesions of the cerebral parenchyma, and 18 normal subjects were studied.The results show that amplitude asymmetries over 4 V (between responses evoked by right and left hemifield stimulation, recorded ipsilaterally to the stimulated hemifield) are clinically relevant for hemianopic visual field defect.Significant correlations were found between the VEP features and the site of the damage: lesions of the occipital cortex were generally found to cause more pronounced bioelectrical abnormalities than those due to lesions affecting the visual pathways, with cortical sparing.

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Sommario Viene discussa la utilità clinica dello studio dei PVE da pattern-reversal nella diagnosi dei difetti campimetrici emianopsici omonimi da lesioni retrochiasmatiche (documentate dalla TAC).Sono stati studiati 13 pazienti affetti da lesioni cerebrali di natura traumatica, neoplastica o ischemica, e 18 soggetti normali.Dai risultati si deduce che asimmetrie di ampiezza superiori a 4 V, tra le risposte evocate per stimolazione dei singoli emicampi destro e sinistro (registrate da elettrodi posti omolateralmente all'emicampo stimolato), sono clinicamente suggestive della presenza di emianopsia omonima.Sono emerse, inoltre, correlazioni tra quadro bioelettrico ed anatomo-lesionale: le lesioni della corteccia occipitale provocano, generalmente, anomalie bioelettriche più evidenti rispetto a quelle dovute a lesioni interessanti le vie ottiche con risparmio della corteccia stessa.

     

Myoclonus and Seizures in a Patient with Parkinsonism: Induction by Levodopa and Its Confirmation on SEPs

Abstract: A 68-year-old woman with parkinsonism showed cortical myoclonus and seizures under antiparkinsonian medication. Myoclonus was induced and enhanced by L-dopa, developing into generalized seizures. EEG was abnormal and somatosensory-evoked potentials (SEPs) showed giant SEPs, transcortical reflex (C reflex) and jerk locked potentials. Myoclonus and seizures disappeared after discontinuation of L-dopa and the introduction of valproate sodium (VPA). We described the occurrence of L-dopa-induced myoclonus and seizures in a case of parkinsonism with its SEPs findings.     

Neurophysiological study in chronic GM2 gangliosidosis (hexosaminidase A and B deficiency), with motor neuron disease phenotype

We report the electrophysiological investigation of two adult cases with GM 2 gangliosidosis with hexosaminidase A and B deficiency. Superficial peroneal biopsy was obtained from one patient. The electrophysiological alterations of the peripheral nervous system were fasciculations, signs of collateral reinnervation and loss of motor units, decrease in sensory potential amplitude and increase in distal motor latency. Increase in N9-N13 interpeak latency of the somatosensory evoked potentials and an increase I–V interpeak latency of the brain-stem auditory potentials were evident in both cases. Visual evoked potentials were normal. Nerve biopsy showed a severe loss of myelinated fibers, especially of those with the largest diameter, with no signs of segmental demyelination, or remyelination. A tentative interpretation of our findings is given.

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Sommario Gli autori riportano lo studio neurofisiologico ed istologico di 2 soggetti adulti affetti da GM2 gangliosidosi da deficit di esosaminidasi A e B. Le alterazioni elettrofisiologiche del sistema nervoso periferico consistono in fascicolazioni, segni di reinnervazione collaterale e perdita di unità motorie, riduzione in ampiezza dei potenziali sensitivi e incremento delle latenze motorie distali. Sono presenti in ambedue i casi un incremento dell'interpicco N9-N13 dei potenziali evocati somatosensoriali e un aumento dell'interlatenza I–V di quelli uditivi. Normali sono i potenziali evocati visivi. La biopsia del nervo peroneo superficiale eseguita in un solo soggetto dimostra una severa perdita di fibre mieliniche soprattutto di più grosso calibro, senza segni di demielinizzazione segmentaria o rimielinizzazione. Viene infine proposta un 'interpretazione di tutti i dati.

     

Intracortical evoked potentials of cats elicited by punctate visual stimuli in receptive field peripheries

Intracortical visual evoked potentials, related to stimulus eccentricity from receptive field center, were investigated as a possible measure of interaction among adjacent populations of cortical neurons. Displacement of the stimuli from field center resulted in (1) a progressive decline in amplitude of the primary potential and (2) an enhancement or development of longer latency (60–100 ms) ‘secondary’ potentials often not apparent with field center stimulation.     

The effect of task‐irrelevant visual backgrounds on human transcranial magnetic stimulation‐evoked electroencephalography responses and cortical alpha activity

Brain responses evoked by transcranial magnetic stimulation (TMS) in task‐free experimental contexts are known to depend on psychophysiological states such as sleep, vegetative state and caffeine‐induced arousal. Much less is known about how TMS‐evoked responses depend on task‐irrelevant steady perceptual input. Here, we examined ongoing alpha activity and the mean amplitude of EEG potentials in response to occipitally applied TMS as a function of task‐irrelevant visual backgrounds. Responses to TMS were robustly modulated by photographs of natural scenes and man‐made environments. These effects began as early as during the N100 and continued for several hundred milliseconds after the stimulation. There was also a more general effect of background along with other stimuli, such as blank backgrounds, sinusoidal gratings and moving dot‐patterns. This effect was observable from ongoing alpha activity as well. Based on these results we conclude that different types of steady perceptual input modulate visual cortex reactivity and/or connectivity and it is possible to measure these modulations by combining TMS with electroencephalography.     

Pattern-reversal visual evoked potentials in patients with newly diagnosed epilepsy

PURPOSE: The possible occurrence of evoked potential (EP) abnormalities in patients with newly diagnosed epilepsy has been little investigated. The main purpose of the present study was to investigate possible changes in pattern-reversal visual evoked potential (P-VEP) responses in newly diagnosed epilepsy patients. METHODS: By using P-VEPs, latency values of the N75 and P100 together with amplitude values of P100 were recorded in newly diagnosed idiopathic epilepsy patients. The patients comprised two groups; nonphotosensitive (non-PS), and photosensitive (PS) patients. RESULTS: Shortened N75 and normal P100 latencies of the P-VEP with higher than normal P100 amplitudes were detected in PS patients. In non-PS patients, N75 latencies of the P-VEPs were unaffected; however, P100 latencies were prolonged, and P100 amplitudes were unchanged. CONCLUSIONS: P-VEPs are different from those of controls in previously untreated idiopathic epilepsy patients. Results also indicate different P-VEP features in patients with and without photoparoxysmal responses. The changes might be the result of a disorder of one or more neurotransmitters or subtle morphologic damage such as microdysgenesis.     

MRI and visual-evoked potentials in partners of multiple sclerosis patients

Hawkes CH, Chawda S, Derakshani S, Muhammed N, Visentin E, Boniface D. MRI and visual‐evoked potentials in partners of multiple sclerosis patients.
Acta Neurol Scand: 2012: 125: 424–430.
© 2011 John Wiley & Sons A/S. Objective – Some epidemiological evidence, particularly concerning the role of Epstein Barr Virus implies that multiple sclerosis (MS) may be transmissible and if correct, this might be revealed by increased prevalence of MS in cohabiting partners. Methods – We addressed this problem by neurological assessment, visual‐evoked potentials (VEP) and magnetic resonance imaging (MRI) in 112 partners of patients with MS in comparison to a control group of 93 individuals with clinically non‐significant head or neck pain and in comparison to UK prevalence. Results – We found one instance of conjugal definite MS. Including this case, VEP were abnormal in five instances with either significant delay (n = 3) or increased interocular latency difference (IOLD) (n = 2) in partners of MS patients thus raising the possibility of subclinical optic nerve demyelination. The mean absolute value of IOLD in partners was greater than the value in controls (P = 0.033). There were no significant differences in MRI findings between the two groups. Conclusion – The finding of one conjugal pair and abnormal VEP in a further four MS partners could have several explanations. It is compatible with the concept of a transmissible agent, although our observations could be due to several biases as well as the play of chance alone.     

Comparative study of visual evoked potentials in spinocerebellar ataxias and multiple sclerosis

Visual evoked potentials (VEPs) were delayed in 11 out of 18 patients with Friedreich's ataxia, in 1 out of 8 patients with Strumpell's hereditary spastic ataxia, in 2 out of 5 cases with cerebellar atrophy and in 42 out of 50 patients with multiple sclerosis (MS). Responses were normal in 5 cases with Pierre Marie's disease. Amplitude and temporal dispersion were statistically analyzed in the above-mentioned groups of patients with respect to controls. An abnormal temporal dispersion, also considered as interpeak N1P2, was frequently found in MS but only occasionally in spinocerebellar ataxias. Amplitude was statistically reduced in Friedreich's ataxia group, where an inverse relationship between latency and amplitude was found. No relation was found between VEP delay and duration of the disease, in any group considered.     

Reduced platelet MAO activity in healthy male students with blood group O

The association between the two genetic markers of affective disorders, ABO blood group system and platelet MAO (monoamine oxidase) activity was studied in 70 healthy young males. The platelet MAO activity of subjects with blood type O was significantly lower than that of subjects with blood type A and with blood types A + B AB + B together. This finding could constitute a "bridge" between the two genetic approaches to affective disorders.     

The value of brain stem auditory, visual and somatosensory evoked potentials and blink reflexes in the diagnosis of multiple sclerosis

Cervical and cortical somatosensory evoked potentials (SEP) following electrical stimulation of the median nerve and blink reflexes (BR) following electrical stimulation of the supraorbital nerve were recorded in 30 normal subjects aged 20–49 years. Subjects aged 40–49 had longer SEP latencies than subjects aged 20–39 years.
A total of 29 slightly affected patients with multiple sclerosis (MS) aged 26–49 years, including four patients without clinical signs (suspected MS) and 19 patients with signs indicating only one lesion (possible MS) were examined by low-rate random-stimulated brain stem auditory (BAEP), checkerboard pattern-reversal visual evoked potentials (VEP), SEP and BR. Abnormal recordings by at least one of the examinations were found in all but three patients, and by all four tests in five patients.
In patients with definite or probable MS, demonstration of clinically recognized or subclinical lesions was of minor diagnostic value, in contrast to the importance such findings had in patients with suspected or possible MS. Silent lesions were shown by at least one of the tests in the four suspected and in 13 of the possible MS patients, so these 17 patients could be transferred to a more certain diagnostic category. This reclassification was most often due to the BAEP recording.
In patients with spinal signs, the combination of BAEP and VEP recording was sufficiently efficient. In patients with optic neuritis a combination of BAEP and SEP was preferred. No abnormal recordings were found in 15 normal subjects examined by all four tests.     

Morbidity risk for psychiatric disorders in families of probands with affective disorders divided according to levels of platelet MAO activity

In a series comprising 166 subjects with affective disorders, the lowest and highest quartiles in the male and female platelet monoamine oxidase (MAO) distribution, respectively, were included. The morbidity risk in the first-degree relatives (parents and siblings) of these low and high platelet MAO subjects was determined. First-degree relatives of low platelet MAO probands were found to have an increased morbidity risk for neurotic-reactive depressions and for alcoholism. The results seem to be in line with the biological high-risk paradigm, indicating that platelet MAO could be a biological marker for increased vulnerability. First-degree relatives of high platelet MAO probands were found to have an increased morbidity risk for bipolar affective disorders.     

Low B12 levels related to high activity of platelet MAO in patients with dementia disorders. A retrospective study

In 35 patients with Alzheimer's presenile disease (AD), 56 patients with senile dementia of the Alzheimer type (SDAT), 54 patients with vascular dementia (VD) and 10 patients with confusional states, age, vitamin B12 in serum, P-folate, B-folate and B-Hb were investigated. Platelet monoamine oxidase (MAO) and cerebrospinal fluid (CSF) levels of homovanillic acid (HVA), 5-hydroxyin-doleacetic acid and 3-methoxy-4-hydroxyphenylglycol were measured. Group differences showed that vitamin B12 levels were reduced in the group of patients with confusional states and SDAT. Five out of ten and 13 out of 56 (respectively) had vitamin B12 concentrations below the lower limit of the reference value (130 pmol/l). A negative correlation was found between B12 levels and platelet MAO activity. The findings indicate that there is a subgroup of patients with late-onset dementia that has low vitamin B12 blood concentrations. HVA levels in CSF, usually found to be reduced in AD patients, were normal in this subgroup.     

老年抑郁症患者面孔知觉早期加工的事件相关电位研究

目的 采用事件相关电位技术,探讨老年抑郁症患者面孔识别(区分面孔还是非面孔)和面孔结构信息早期加工的脑电生理机制.方法 被试者包括19例老年抑郁症患者(患者组)及17名健康老年人(对照组).要求被试者观看图片并计数蝴蝶(靶刺激)呈现次数,其他图片(包括面孔、非面孔)为非靶刺激.记录32导脑电波.结果 (1)患者组非靶刺激诱发的P＜,1＞[(3.9±0.8)μV]和N170波幅[(-10.1±1.1)μV]均低于对照组[P<,1>:(6.8±0.8)μV;N170:(-14.4±1.1)μV;P＜0.05～0.01];(2)患者组和对照组均产生显著的N170效应(Nd170)以及N170翻转效应(倒立面孔图像时的N170变化),但患者组右侧颢枕区的N170效应[(-5.8 4±0.9)μV]弱于对照组[(-8.8±0.9)μV,P＜0.05],翻转效应的组间差异则无统计学意义(P＞0.05);(3)患者组靶刺激的P＜,3＞潜伏期[(400 ±10)ms]长于对照组[(368±10)ms;P＜0.05].结论 老年抑郁症患者可能存在面孔基本水平(区分面孔还是非面孔)早期识别的损害,而对面孔结构信息的早期加工则保持相对完整.