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BOLD fMRI response of early visual areas to perceived contrast in human amblyopia

JOURNAL OF NEUROPHYSIOLOGY 2000年第4期84卷 1907-1913页

作者： Goodyear, BG Nicolle, DA Humphrey, GK Menon, RS John P Robarts Res Inst Lab Funct Magnet Resonance Res London ON N6A 5K8 Canada Univ Western Ontario Dept Med Biophys London ON N6A 5C1 Canada London Hlth Sci Ctr Dept Ophthalmol London ON N6A 5A5 Canada Univ Western Ontario Dept Psychol London ON N6A 5C2 Canada Univ Western Ontario Dept Diagnost Radiol & Nucl Med London ON N6A 5A5 Canada

In this study, we used a temporal two-alternative forced choice psychophysical procedure to measure the observer's perception of a 22% physical contrast grating for each eye as a function of spatial frequency in four subjects with unilateral amblyopia and in six subjects with normal vision. Contrast thresholds were also measured using a standard staircase method. Additionally, blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) was used to measure the neuronal response within early visual cortical areas to monocular presentations of the same 22% physical contrast gratings as a function of spatial frequency. For all six subjects with normal vision and for three subjects with amblyopia, the psychophysically measured perception of 22% contrast as a function of spatial frequency was the same for both eyes. Threshold contrast, however, was elevated for the amblyopic eye for all subjects, as expected. The magnitude of the fMRI response to 22% physical contrast within "activated" voxels was the same for each eye as a function of spatial frequency, regardless of the presence of amblyopia. However, there were always fewer "activated" fMRI voxels during amblyopic stimulation than during normal eye stimulation. These results are consistent with the hypotheses that contrast thresholds are elevated in amblyopia because fewer neurons are responsive during amblyopic stimulation, and that the average firing rate of the responsive neurons, which reflects the perception of contrast, is unaffected in amblyopia.

关键词：弱视/病理生理学对比敏感度/生理学磁共振成像神经元/生理学氧/血液光刺激/方法心理物理学/方法参考值感觉阈空间知觉视皮质/血液供给视皮质/病理生理学视知觉/生理学成年人女(雌)性人类男(雄)性中年人

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Cerebral mechanisms involved in word reading in dyslexic children: A magnetic source imaging approach

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CEREBRAL CORTEX 2000年第8期10卷 809-816页

作者： Simos, PG Breier, JI Fletcher, JM Bergman, E Papanicolaou, AC Univ Texas Sch Med Dept Neurosurg Vivian L Smith Ctr Neurol Res Houston TX 77030 USA Univ Texas Sch Med Dept Pediat Houston TX 77030 USA Texas Reading Inst Houston TX USA

The purpose of the present investigation was to describe spatiotemporal brain activation profiles during word reading using magnetic source imaging (NISI). Ten right-handed dyslexic children with severe phonological decoding problems and eight age-matched non-impaired readers were tested in two recognition tasks, one involving spoken and the other printed words. Dyslexic children's activation profiles during the printed word recognition task consistently featured activation of the left basal temporal cortices followed by activation of the right temporoparietal areas (including the angular gyrus). Non-impaired readers showed predominant activation of left basal followed by left temporoparietal activation. In addition, we were able to rule out the hypothesis that hypoactivation of left temporoparietal areas in dyslexics was doe to a more general cerebral dysfunction in these areas. Rather. it seems likely that reading difficulties in developmental dyslexia are associated with an aberrant pattern of functional connectivity between brain areas normally involved in reading, namely ventral visual association cortex and temporoparietal areas in the left hemisphere. The interindividual consistency of activation profiles characteristic of children with dyslexia underlines the potential utility of this technique for examining neurophysiological changes in response to specific educational intervention approaches.

关键词：发音障碍/并发症发音障碍/病理生理学脑图大脑皮质/病理生理学阅读障碍/并发症阅读障碍/诊断阅读障碍/病理生理学功能偏侧化脑磁图描记术顶叶/病理生理学反应时间阅读颞叶/病理生理学视皮质/病理生理学青少年儿童女(雌)性人类男(雄)性

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EVIDENCE THAT MONOAMINES INFLUENCE HUMAN EVOKED-POTENTIALS

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BRAIN RESEARCH 1975年第1期99卷 49-58页

作者： SCHAFER, EWP MCKEAN, CM UNIV CALIF SONOMA STATE HOSPLANGLEY PORTER NEUROPSYCHIAT INSTBRAIN BEHAV RES CTRELDRIDGECA 95431

We have measured latency and flash/pattern differentials of the visual evoked potential (VEP) from phenylketonuric humans, while systematically manipulating rates of amine synthesis in the central nervous system using two techniques. We have observed that stimulation of monoaminergic activity in the visual processing system, either by lowering inhibitory levels of phenylalanine through dietary restriction or by a properly balanced administration of indole and catecholamine precursors, shortened VEP latencies and permitted the development of a discriminative brain response to patterned stimuli. The close temporal relationship between these electrophysiological changes and the neurochemical manipulations following treatment initiation of discontinuation argue that monoamines play a significant role in the mediation of human sensory evoked potentials.

关键词： 5-羟色氨酸生物胺类/生理学二羟苯丙氨酸/治疗应用诱发电位苯丙氨酸/代谢苯丙酮尿症/病理生理学反应时间酪氨酸/治疗应用视皮质/生理学视皮质/病理生理学视知觉/生理学青少年女(雌)性人类男(雄)性

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Lack of cortical contrast gain control in human photosensitive epilepsy

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NATURE NEUROSCIENCE 2000年第3期3卷 259-263页

作者： Porciatti, V Bonanni, P Fiorentini, A Guerrini, R CNR Inst Neurophysiol Area Ric I-56100 Pisa Italy Univ Pisa Inst Dev Neurol & Psychiat I-56018 Pisa Italy IRCCS Stella Maris Med Res Inst I-56018 Pisa Italy Kings Coll Hosp London Div Neurosci London SE5 9RS England

Television and video games may be powerful triggers for visually induced epileptic seizures. To better understand the triggering elements of visual stimuli and cortical mechanisms of hyperexcitability, we examined eleven patients with idiopathic photosensitive epilepsy by recording visually evoked potentials (VEPs) in response to temporally modulated patterns of different contrast. For stimuli of low-medium, but not high, temporal frequency, the contrast dependence of VEP amplitude and latency is remarkably abnormal for luminance contrast (black-white), but not so for chromatic contrast (equiluminant red-green) stimuli. We conclude that cortical mechanisms of contrast gain control for pattern stimuli of relatively low temporal frequency and high luminance contrast are lacking or severely impaired in photosensitive subjects.

关键词：方差分析色对比敏感度/生理学脑电描记术癫痫反射性/病理生理学诱发电位视觉/生理学光光刺激发作/病理生理学时间因素视皮质/病理生理学青少年成年人女(雌)性人类男(雄)性

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Magnetoencephalographic fields from patients with spontaneous and induced migraine aura

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ANNALS OF NEUROLOGY 2001年第5期50卷 582-587页

作者： Bowyer, SM Aurora, SK Moran, JE Tepley, N Welch, KMA Henry Ford Hosp Henry Ford Hlth Syst Dept Neurol Neuromagnetism Lab CFP 78 79 Detroit MI 48202 USA Oakland Univ Dept Phys Rochester MI USA Univ Kansas Sch Med Kansas City KS USA

We investigate and characterize the magnetoencephalographic waveforms from patients during spontaneous and visually induced migraine aura. Direct current neuromagnetic fields were measured during spontaneous onset of migraine auras in 4 migraine patients, and compared with recordings from 8 migraine-with-aura patients and 6 normal controls during visual stimulation of the occipital cortex. Complex direct current magnetoencephalographic shifts, similar in waveform, were observed in spontaneous and visually induced migraine patients;but not in controls. Two-dimensional inverse imaging showed multiple cortical areas activated in spontaneous and visually induced migraine aura patients. In normal subjects, activation was. only observed in the primary visual cortex. Results support a spreading, depression-like neuroelectric event occurring during migraine aura that can arise spontaneously or be visually triggered in widespread regions of hyperexcitable occipital cortex.

关键词：脑图磁共振成像脑磁图描记术先兆偏头痛/诊断先兆偏头痛/病理生理学枕叶/病理生理学光刺激扩散性皮质抑制视皮质/病理生理学成年人女(雌)性人类男(雄)性中年人

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Visual function and brain organization in non-decussating retinal-fugal fibre syndrome

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CEREBRAL CORTEX 2000年第1期10卷 2-22页

作者： Victor, JD Apkarian, P Hirsch, J Conte, MM Packard, M Relkin, NR Kim, KHS Shapley, RM New York Presbyterian Hosp Dept Neurol & Neurosci New York NY 10021 USA Erasmus Univ Fac Med Dept Physiol NL-3000 DR Rotterdam Netherlands Mem Sloan Kettering Canc Ctr Dept Neurol New York NY 10021 USA NYU Ctr Neural Sci New York NY 10003 USA

Functional neuroimaging, psychophysical and electrophysiological investigations were performed in a patient with non-decussating retinal-fugal fibre syndrome, an inborn achiasmatic state in which the retinal projections of each eye map entirely to the ipsilateral primary visual cortex. Functional magnetic resonance imaging (fMRI) studies showed that for monocularly presented simple visual stimuli, only the ipsilateral striate cortex was activated. Within each hemisphere's striate cortex, the representation of the two hemifields overlapped extensively. Despite this gross miswiring, visual functions that require precise geometrical information (such as vernier acuity) were normal, and there was no evidence for the confounding of visual information between the overlapping ipsilateral and contralateral representations. Contrast sensitivity and velocity judgments were abnormal, but their dependence on the orientation and velocity of the targets suggests that this deficit was due to ocular instabilities, rather than the miswiring per se. There were no asymmetries in performance observed in visual search, visual naming or illusory contour perception, fMRI analysis of the latter two tasks under monocular viewing conditions indicated extensive bilateral activation of striate and prestriate areas. Thus, the remarkably normal visual behavior achieved by this patient is a result of both the plasticity of visual pathways, and efficient transfer of information between the hemispheres.

关键词：脑图对比敏感度/生理学脑电描记术功能偏侧化磁共振成像运动知觉/生理学神经元可塑性视交叉/畸形视神经疾病/诊断视神经疾病/病理生理学光刺激视网膜/病理生理学综合征双生二卵视皮质/病理学视皮质/病理生理学视通路/病理学视通路/病理生理学视知觉青少年女(雌)性人类婴儿

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Undercounting features and missing features: evidence for a high-level deficit in strabismic amblyopia

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NATURE NEUROSCIENCE 2000年第5期3卷 496-501页

作者： Sharma, V Levi, DM Klein, SA Univ Houston Coll Optometry Houston TX 77204 USA Univ Calif Berkeley Sch Optometry Berkeley CA 94720 USA

Abnormal visual development in strabismic amblyopia drastically affects visual perception and properties of neurons in primary visual cortex (V1). To test the notion that amblyopia also has consequences for higher visual areas, we asked humans with amblyopia to count briefly presented features. Using the amblyopic eye, strabismic amblyopes counted inaccurately, markedly underestimating the number of features. This inaccuracy was not due to low-level considerations (blur, visibility crowding, undersampling or topographical jitter), as they also underestimated the number of features missing from a uniform grid. Rather, counting deficits in strabismic amblyopes reflected a higher-level limitation in the number of features the amblyopic Visual system can individuate.

关键词：弱视/病理生理学注意力/生理学提示模型神经学神经心理学测验光刺激斜视/病理生理学时间因素视觉单眼/生理学视皮质/病理生理学视知觉/生理学成年人人类

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NEUROPHYSIOLOGICAL ASPECTS OF PATTERN-SENSITIVE EPILEPSY

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BRAIN 1979年第MAR期102卷 1-25页

作者： WILKINS, AJ DARBY, CE BINNIE, CD INST EPILEPSIEBESTRIJDING HEEMSTEDENETHERLANDS RUNWELL HOSP DEPT CLIN NEUROPHYSIOLWICKFORDESSEXENGLAND

The capacity of striped patterns (square-wave gratings) to induce paroxysmal EEG activity in a group of pattern-sensitive epileptic patients is shown to depend on: 1. The spatial frequency of the pattern. The optimum spatial frequency lies between 1 and 4 cycles/degree in every patient tested. 2. The orientation of the pattern. Although, for the patient group as a whole, no one orientation is consistently more likely to induce paroxysmal activity than any other, the responses of individual patients can show marked orientation selectivity. 3. The brightness contrast of the pattern. The probability of paroxysmal EEG activity increases dramatically as contrast is increased from 0.2 to 0.4. Red/green gratings at isoluminance fail to induce paroxysmal activity. 4. The size of the pattern. There is considerable variation between patients in the subtense of a centrally-fixated circular pattern necessary to induce paroxysmal activity with a given probability. However, for every patient an increase in the probability of paroxysmal activity from near zero to near unity is effected by an increase in the angular subtense of the pattern by a factor of two. Patterns other than square-wave gratings are capable of inducing paroxysmal activity but, in general, patterns that stimulate more than one orientation system are less epileptogenic. The above findings are compatible with the hypothesis of a seizure trigger in the striate cortex and are incompatible with a trigger confined to the lateral geniculate nucleus of the thalamus. Further evidence against a geniculate trigger is obtained from an investigation of the response of a pattern-sensitive patient to a diffuse (unpatterned) flickering field in which it is shown that the effects of counter-phase interocular flicker implicate binocular mechanisms.

关键词：色觉/生理学半球优势大脑/生理学脑电描记术癫痫部分性/病理生理学癫痫/病理生理学闪光融合/生理学形状知觉/生理学模式识别视觉/生理学光刺激/副作用大小知觉/生理学视皮质/病理生理学视通路/病理生理学青少年成年人儿童女(雌)性人类男(雄)性

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With color in mind

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NATURE NEUROSCIENCE 1998年第3期1卷 171-173页

作者： Heywood, C Cowey, A Dept Expt Psychol Oxford OX1 3UD England

Which human brain area produces color blindness when damaged? High-resolution functional neuroimaging suggests that it is area V8, not the favorite candidate V4.

关键词：脑图色觉缺陷/病理生理学视皮质/病理生理学人类

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Functional activation of microgyric visual cortex in a human

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ANNALS OF NEUROLOGY 2001年第5期50卷 672-676页

作者： Innocenti, GM Maeder, P Knyazeva, MG Fornari, E Deonna, T Karolinska Inst Dept Neurosci Div Neuroanat & Brain Dev S-17177 Stockholm Sweden CHU Vaudois Dept Radiol CH-1011 Lausanne Switzerland CHU Vaudois Dept Pediat Neurol CH-1011 Lausanne Switzerland Univ Lausanne IBCM Lausanne Switzerland

We report on the case of a 20-year-old man with bilateral parasagittal parieto-occipital polymicrogyria and epilepsy. Functional magnetic resonance imaging responses to reversing checkerboard and interhemispheric electroencephalogram coherence changes to moving gratings were investigated. Results of both studies indicate that the polymicrogyric cortex was activated by visual stimuli, suggesting preserved function in the dysplastic area.

关键词：深度知觉脑电描记术癫痫/并发症癫痫/诊断癫痫/病理生理学磁共振成像运动知觉神经系统畸形/并发症神经系统畸形/诊断神经系统畸形/病理生理学顶叶/畸形顶叶/病理学顶叶/病理生理学光刺激/方法视皮质/畸形视皮质/病理学视皮质/病理生理学成年人人类男(雄)性

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