视觉皮层功能检测中旋转光栅作为刺激方式的临床研究

目的:观察旋转光栅刺激下皮层功能核磁共振的成像情况,探讨视皮层功能测定中有效便捷的视觉刺激方式。方法:以旋转光栅作为视觉刺激,采用组块设计方式,以1.5T磁共振成像系统采集17例视力正常者和9例弱视患者的视皮层BOLD-fMRI数据。观察分析不同任务/控制状态下对应皮层的成像部位。结果:旋转光栅含有多种视觉刺激成分,所有受检者均获得了与相应视觉刺激对应的视觉皮层反应脑图,且各组反应趋势基本一致。结论:旋转光栅是视皮层功能测定中良好便捷的视觉刺激方式。     

急性视神经炎的功能磁共振成像研究

目的应用功能磁共振成像技术探讨急性视神经炎的皮层功能变化。方法以1.5T磁共振成像系统采集14例单眼急性视神经炎、12例正常人视皮层BOLD-fMRI数据,比较正常组与视神经炎组两眼分别刺激时的视皮层激活像素数与激活信号平均强度,分析BOLD-fMRI数据与PVEPP100波潜时的相关性。结果正常组与视神经炎组枕叶视皮层、颞下回、后顶叶都有不同程度的兴奋,主要兴奋区位于枕叶距状裂周围。与对侧眼相比,视神经炎患眼刺激的皮层激活像素减少、激活信号平均强度降低。治疗4周后,患眼视力提高,皮层激活像素明显增多,屏状核、额前叶、丘脑亦有不同程度的兴奋。P100波潜时与皮层激活像素数呈负相关。结论功能磁共振成像技术可以反映视神经炎的皮层功能改变,为视神经炎的临床诊断和预后评估提供新的依据。     

视觉正常人简单图形视觉刺激的视皮层功能定位及定量研究

目的 利用功能磁共振成像的方法定位、定量研究视觉正常人简单图形视觉刺激时的视皮层反应模式,为视皮层假体的刺激位置和强度提供参考.方法 对3名视觉正常成年志愿者进行圆环形棋盘格视觉任务的功能磁共振成像实验,同一任务对每位志愿者重复3次,以SPM2脑功能专业分析软件包作后期处理,显示视皮层反应模式.结果 3名受试者均较好完成视觉任务,平均体素反应总数为5217.3±1110.6.反应最强点坐标 x值为(-4.3±8.7)mm,y值为(-83.3±3.7)mm,z值为(-4.0±4.7)mm.平均最大反应强度为15.99±1.58,最大反应脑区为双侧的Brodmann 18区即初级视皮层V2区.解剖上的舌回附近.结论 利用功能磁共振成像的方法可以定位、定量的研究视皮层反应模式,这些反应模式信息可以为视皮层假体的刺激位置、强度等参数提供参考.     

功能磁共振成像在视神经病变的应用研究

近年来功能磁共振成像技术不断发展,已逐步应用到视觉领域,使研究视中枢功能改变成为可能.功能磁共振能反映视神经炎,青光眼等视神经病变患者视觉皮层反应的异常,以及中枢皮层的适应性功能重建,有助于人们加深对视神经病变的认识,并可能研发出新的诊断技术和治疗方法.     

视路疾病患者脑功能性磁共振成像初步观察

目的 观察视路疾病患者视网膜拓扑投射的分布及脑功能性磁共振成像(fMRI)与视野检查结果的关系.方法 3例经病理检查确诊为垂体瘤和颅咽管瘤的鞍区占位患者(患者组)6只眼以及年龄24～30岁的3名健康志愿者纳入研究.患者组6只眼最佳矫正视力无光感～1.0;健康志愿者矫正视力1.0,除近视外无其他眼疾.受检者均无fMRI检查禁忌.常规行最佳矫正视力、直接和(或)间接检眼镜眼底检查,Octopus101电脑全自动视野计32程序策略趋势导向检查法行中心静态视野检查.fMRI检查采用GE signa VH/I 3.0T扫描机.视觉刺激占据12°视角,采用对比度接近100%的黑白棋盘格,背景为棋盘格的平均亮度,包括周期性扩张或收缩的环形刺激和顺时针或逆时针旋转的楔形刺激两种模式.功能图像采用梯度回波的平面同波序列的血氧水平依赖扫描序列,垂直于距状裂冠状位扫描,三维采集方式的扰相梯度回波序列矢状位采集高分辨率解剖结构数据.数据分析采用AFNI软件,并且应用Freesurfer进行皮层的分割、膨胀处理.结果 6只患眼中,视野颢侧缺损3只眼,颞上方缺损2只眼,不能完成检查1只眼.环形刺激的功能图像显示,枕叶视觉皮层产生了时相对应的激活图像,枕叶后极沿距状裂向前迁移对应黄斑中心区向周边视野的迁移.楔形刺激的功能图像显示,初级视觉皮层的极角拓扑投射的空间序列与视野相反.距状裂下方的视皮层主要对应对侧上方视野,距状裂上方主要对应对侧下方视野.刺激患眼不能诱导出与相应视野缺损相关的初级视觉皮层的激活,存在相应视觉皮层反应的减少.结论 fMRI检查结果与常规视野计检查的结果有很好的对应关系,可以反映视路疾病患者的视野缺损对应的皮层反应.     

视觉刺激功能磁共振成像在枕叶病变患者中的初步应用

目的 观察枕叶病变患者患侧与健侧的功能磁共振成像（fMRI）特点，评价fMRI在视觉中枢功能性病变检查、枕叶肿瘤定位、手术入路选择以及切除范围方面的临床应用价值。设计 病例系列。研究对象 伴有同侧偏盲的视觉中枢功能性病变及单侧枕叶肿瘤患者各1例。方法 对上述2例患者应用自行设计的双眼棋盘格刺激（5Hz）行脑fMRI检查。所得数据应用SPM软件处理（P〈0．01），与Goldmann视野计检查结果相比较，验证视野损害与其大脑皮层投影改变的一致性。主要指标 统计参数图，脑激活图，激活脑区信号变化的时间曲线，与标准化T1像叠加的脑激活图。结果 在视觉刺激on时，枕叶视功能区激活；off时无信号；2例患者fMRI检查右侧视功能区激活明确，左侧视功能区无信号与视野检查双眼右半视野缺损相一致。结论 视觉刺激程序能够很好地引出视觉中枢fMRI；fMRI的检查结果与视野结果一致性较好；fMRI在视觉中枢功能性检查、枕叶肿瘤范围定位的确定方面有良好的临床应用前景。     

屈光参差性弱视儿童色觉中枢激活范围的BOLD-fMRI初步研究

目的：利用血氧水平依赖性功能磁共振成像(blood oxygen level dependence-functional magnetic resonance imaging,BOLD-fMRI)及SPM8软件研究分析经过系统治疗后屈光参差性弱视儿童色觉中枢激活区域的恢复情况。

方法：自身前后对照研究。利用3.0T超导磁共振采集13例屈光参差性弱视儿童色觉中枢激活区域的试验数据,采用组块设计方案,以三原色作为刺激源获取色觉皮层激活区功能核磁共振数据,应用基于MATLAB软件下的运行的SPM8对数据进行预处理及分析,对比初诊、治疗1,2,4wk后色觉中枢激活区域的变化。

结果：弱视初诊患儿接受三原色刺激后,BA17,BA18,BA19,BA37均有不同范围的激活(P<0.01)。经过4wk治疗后,弱视患儿接受红色刺激后,视觉皮层激活范围无扩大; 接受绿色刺激后,视觉皮层左侧BA37、左侧BA19、左侧BA20激活范围均有不同程度扩大,平均t值分别为3.5210,3.2716,3.1534(P<0.01); 接受蓝色刺激后,视觉皮层右侧BA19、右侧BA18激活范围有不同程度扩大,平均t值分别为3.7345,3.2701(P<0.01)。

结论：经过4wk的系统治疗后屈光参差性弱视儿童色觉中枢激活范围较初诊时增大但幅度较低,经短期治疗弱视患儿色觉中枢有一定程度的恢复但不明显。     

DIT与BOLD-fMRI技术对屈光不正性弱视皮层损害机制的研究

目的基于大脑各皮层区的功能动力学特征受到皮层间及皮层外解剖结构连接制约的观点,探讨屈光不正性弱视视觉皮层功能损害与胼胝体、视辐射发育不良的关系。方法利用弥散张量成像(DTI)及纤维跟踪技术(DTT)比较30例屈光不正性弱视患者与30例正常人胼胝体、视辐射各向异性分数(FA)值和平均弥散系数(DCavg)值,及神经纤维投射方式;并对屈光不正性弱视组和正常组各10例行血氧水平依赖的功能性磁共振成像(BOLD-fMRI),分别在平面与立体图刺激下比较视皮层激活水平。结果与正常组比较,屈光不正性弱视组背侧视皮层区域激活范围与强度显著低于正常组,胼胝体体部DCavg值显著高于正常组,视辐射FA值显著低于正常组,连接枕叶与顶枕联合皮层的胼胝体纤维数与视辐射纤维数明显减少。结论胼胝体后部和视辐射发育不良,视皮层神经元活动减少或神经元同步化活动减少可能是弱视视皮层功能损害的主要机制。     

功能性磁共振成像在视觉科学研究中的应用进展

磁共振成像是目前较为普及的影像学检查手段之一,传统的磁共振成像及增强成像在眼科临床诊疗中已得到广泛应用.功能性磁共振成像技术包括血氧水平依赖的功能磁共振成像、磁共振波谱成像和弥散张量成像在内,在视觉皮层定位、视神经炎、弱视、青光眼、眼眶肿瘤以及视觉中枢白质纤维重建研究中显示了独特的价值.本文就功能性磁共振成像技术在上述方面的研究进展作一综述.     

弱视患者的皮层视觉运动觉

目的采用功能磁共振成像技术对弱视的视觉运动功能进行研究。方法采用组块设计方式，对9例弱视患者与8例健康志愿者分别进行两侧单眼的旋转光栅刺激、1．5T磁共振扫描和sPM软件离线处理。分别比较弱视组及对照组两单眼间不同的反应水平。结果弱视患者弱视眼的反应体素数目及反应强度均较正常眼低（tAN=3．47，P〈0．05；tAT=2．57，P〈0．05）；正常人双眼间差异无显著性（tAN=1．28，P〉0．1；tNT=-0．02，P〉0．5）。结论弱视患者视皮层视觉运动觉功能下降。     

Mechanism of Neurophysiological Treatment of Amblyopia Using Functional Magnetic Resonance Imaging

Introduction Human amblyopia is a common eye disease, which results from insufficient activation during the critical period of visual development, and there exists deficit in the visual cortex of the brain. Neurophysiological treatment, initiated by Campbell et al[1, 2], as a convenient and effective clinical therapy for amblyopia, has been used for many years. It directly activates the visual cortex of the amblyopia eye with rotating grating, and im- proves the eyesight. In addition, the gra…     

Visual areas and spatial summation in human visual cortex

Functional MRI measurements can securely partition the human posterior occipital lobe into retinotopically organized visual areas (V1, V2 and V3) with experiments that last only 30 min. Methods for identifying functional areas in the dorsal and ventral aspect of the human occipital cortex, however, have not achieved this level of precision; in fact, different laboratories have produced inconsistent reports concerning the visual areas in dorsal and ventral occipital lobe. We report four findings concerning the visual representation in dorsal regions of occipital cortex. First, cortex near area V3A contains a central field representation that is distinct from the foveal representation at the confluence of areas V1, V2 and V3. Second, adjacent to V3A there is a second visual area, V3B, which represents both the upper and lower quadrants. The central representation in V3B appears to merge with that of V3A, much as the central representations of V1/2/3 come together on the lateral margin of the posterior pole. Third, there is yet another dorsal representation of the central visual field. This representation falls in area V7, which includes a representation of both the upper and lower quadrants of the visual field. Fourth, based on visual field and spatial summation measurements, it appears that the receptive field properties of neurons in area V7 differ from those in areas V3A and V3B.     

Principal components analysis for source localization of VEPs in man

This study defines and compares the topologies of the visual evoked potentials to various stimuli such as pattern onset/offset, pattern reversal, pattern motion and high frequency luminance flicker. The responses recorded from 24 occipital derivations were examined using a three sphere conductance model to represent the head, with the assumption that activity from an underlying cortical source is equivalent to a single dipole. Principal components analysis was used to find the dimensionality of the data space. From this analysis could be concluded that all stimuli evoked reponses in the primary visual cortex. Only pattern onset, and to a lesser degree pattern offset and pattern reversal, yielded activity in higher visual areas. In particular it has been shown that the CI, CII interval of the pattern onset response has its origins in two different cortical regions. A fast positive (CI)—negative (part of the CII) component arises from area 18 (or 19), a slower negative (initial part of CII) component comes from area 17.     

Functional magnetic resonance imaging of visual cortex in a patient with cerebrovascular insufficiency

We compare the findings of functional magnetic resonance imaging (MRI) of the visual cortex in a patient with moyamoya disease with other neuro-imaging techniques. Automated static perimetry demonstrated a slight depression of the left visual field in both eyes. MRI of the brain showed diffuse atrophy of the right cerebral hemisphere, sparing the occipital lobe. Single-photon emission computed tomography showed relatively preserved perfusion to the right occipital lobe. Functional MRI during visual stimulation, however, demonstrated an apparent lack of activation of the right primary visual cortex, which did not correlate with the known retinotopic map of the visual cortex. The patient seems to have had a lack of reserved ability to respond to visual stimuli with maximal autoregulatory vasodilatation in the visual cortex, even though apparent morphologic change and dense visual field defects had not been observed.     

Cerebral correlates of impaired grating perception in individual, psychophysically assessed human amblyopes

We investigated neuronal correlates of amblyopic deficits resulting from early onset strabismus or anisometropia by monitoring individual responses in retinotopically mapped cortical visual areas with functional magnetic resonance imaging (fMRI) in eight psychophysically assessed adult amblyopes. In lower visual areas (V1/V2), grating stimuli presented to the normal and the amblyopic eye evoked strong cortical responses, while responses to the amblyopic eye were progressively reduced in higher areas on the central visual pathway (V3a/VP; V4/V8; lateral occipital complex, LOC). Selective reduction for high spatial frequency gratings was especially obvious in LOC. This suggests that transmission of activity from the amblyopic eye is increasingly impaired while it is relayed towards higher processing levels. Elevated responses in parts of areas V1 and V2 to monocular stimulation of the amblyopic eye might be related to the spatial and temporal distortions experienced by some amblyopic subjects.     

Regional cerebral blood flow response to visual stimulation measured quantitatively with PET

Objectives: Regional cerebral blood flow (rCBF) was measured by positron emission tomography with bolus injections of 15 O-labeled water in order to learn the normal pattern of response of the occipital rCBF to flicker and video stimulation. Materials and methods: Six normal volunteers and a patient with partial cortical blindness were studied. They underwent quantitative rCBF measurement in the eye closed resting condition, under full-field stimulation with flickering light, and during video movie viewing, which contains form, color, and movement visual information. Stimulation-minus-rest subtraction PET images were overlaid onto the MRI images resliced parallel to the midline. Results: In normal subjects, the rCBF response to flickering stimuli and to the video in the posterior part of primary visual cortex was +30.5 and +34.5% of whole brain mean value, respectively. The rCBF increase in the association visual cortex was more pronounced by the video movie viewing (+27.5% of whole brain mean value) than by the flickering light stimulation (+6.5% of whole brain mean value). Activated areas in the primary visual cortex corresponded well to the stimulated visual field according to retinotopic organization. Poor activation in primary and in association visual cortex were seen in the patient with cortical blindness. Conclusion: Flickering light and video movie induced different activation patterns. More complicated visual stimuli, which require more extensive neuronal integration, caused greater activation of the higher visual cortex.     

Topographical representation of binocular depth in the human visual cortex using fMRI

We used binocular stimuli to define how the visual location of stereoscopic depth structure maps topographically onto the human visual cortex. The main stimulus consisted of a circular disk of dots, most at zero-disparity, against which a single quadrant was defined with changing disparity ('correlated' disparity), and moved around the visual field. The second stimulus had exactly the same structure, except that the disparity in the quadrant was 'anticorrelated,' that is black dots in one eye were paired with white dots in the other. Unlike the correlated stimulus, this 'anticorrelated' stimulus did not lead to a perception of depth. The activation maps to these disparity stimuli are very similar to those produced using stimuli defined by luminance or motion. The lateral area of the occipital lobe showed the largest difference in response to correlated, as opposed to anticorrelated, disparity. This region included human MT/V5 and two areas, LO-1 and LO-2, recently defined as retinotopically distinct areas within area KO. All these areas, plus V3 and hV4, showed a significantly larger response to the correlated stimulus, compared to the anticorrelated stimulus. No other visual areas showed a significant difference in response. However, the responses to correlated disparity were significantly more reliable than those to anticorrelated in all areas, except V1. Although there are considerable differences in the experimental approach, our fMRI results are broadly consistent with primate neurophysiology showing responses to anticorrelated disparity in V1 neurons.     

Bilateral occipital lobe stroke with inferior altitudinal defects.

BACKGROUND: Cerebrovascular disease is the most common cause of neurological disability in Western countries. Patients who survive cerebrovascular accidents exclusive to the occipital lobe often have no significant neurological deficits other than visual-field loss. Visual-field defects from occipital lobe stroke typically include congruous homonymous hemianopsias or quadranopsias, with or without macular sparing. CASE REPORT: A 61-year-old white man came to us with symptoms of sudden loss of vision and difficulty reading. Visual-field testing revealed a bilateral inferior altitudinal defect with normal optic nerve and fundus appearance in both eyes. On radiological examination, he was found to have had a bioccipital lobe cerebrovascular accident secondary to complete occlusion of the left vertebral artery. An embolic event causing the artery occlusion, in combination with bilaterally compromised cerebellar and posterior cerebral arteries, presumably caused the bilateral stroke. After appropriate medical and neurological consultation, optometric management consisted of maximizing the patient's remaining vision with a prismatic spectacle correction. DISCUSSION/CONCLUSION: Patients with infarction exclusive to the occipital lobe typically have no other neurological deficits except visual-field loss and are often easier to manage than patients with infarctions to other areas of the cerebral cortex or multiple infarctions. Visual-field loss from occipital lobe damage can be successfully managed with optical systems and/or visual rehabilitation. Factors related to management include location and extent of visual-field damage, functional visual needs, and both personal and health concerns of the patient. A discussion is presented on cerebrovascular disease, occipital lobe infarction, imaging techniques, and visual rehabilitation.     

儿童屈光参差性弱视立体视觉中枢区激活的fMRI研究

目的 利用血氧水平依赖性功能性磁共振成像(BOLD-fMRI)技术评价屈光参差性弱视儿童在规范弱视训练后,立体觉映射的脑皮层功能区的恢复情况.方法 自身前后对照研究.选择11例屈光参差性弱视初诊患儿,行任务态组块式(Blocks)设计的fMRI实验,在弱视治疗后1周、2周及4周时复查BOLD-fMRI.采用基于Matlab 7.12.0.635的SPM8软件包进行图像后处理,采用随机效应法分别获得各组脑皮层激活的矩阵数据,利用假设驱动法对各治疗阶段结果进行自身前后配对t 检验,获得治疗前后各组视皮层激活的差异数据.立体图像为计算机生成的随机点立体视觉检查图,通过配戴红蓝眼镜观察立体视图像,当识别立体视图像后迅速点按反馈键.结果 弱视训练至4周时,左侧枕叶(BA18)、枕中回(BA19)、边缘叶(BA19)及右侧枕叶舌回(BA17)和双侧顶上小叶(BA7)激活范围不同程度扩大,与治疗前的平均激活强度差异t值分别是1.636、1.902、1.727、1.350与1.777(P＜0.01),但增进幅度偏小,且与随机点立体视图的恢复不平行.结论 儿童屈光参差性弱视对立体觉映射的脑皮层功能损害严重、短期恢复困难.     

Occipital lobe dysfunction revealed by functional brain imaging in a patient with traumatic visual field loss

We report a patient with visual field loss due to closed head trauma who was imaged with anatomic and functional brain imaging. The findings of ophthalmologic examination were normal except for a complete homonymous hemianopia on the right, an incongruous homonymous hemianopia on the left, and right oculomotor palsy. The results of anatomic brain imaging, computed tomography, and magnetic resonance imaging (MRI) were unremarkable. However, single-photon emission computed tomography (SPECT) scan revealed marked hypoperfusion of the left occipital lobe and functional MRI showed a corresponding strikingly reduced response to visual stimuli in the left occipital lobe. Therefore, this patient is thought to have had dysfunction of the left occipital lobe. Functional brain imaging techniques, such as SPECT and functional MRI, can be helpful in the localization of the responsible lesions even when conventional neuro-imagings are nondiagnostic.