基于多显示技术的多焦视诱发反应图像系统的研究

多焦视网膜电图是一种客观的、无创的视功能检查方法，可以同时反映视网膜多个微小区域的视功能，在眼底疾病的早期诊断上有独特的优势。介绍了基于多显示技术的多焦视诱发反应图像系统的原理与设计，利用Windows98以上的微软操作系统特有的多显示技术，控制图形刺激器对视网膜的各个区域分别进行刺激。然后用特制的电极把由视网膜多个区域产生的混合叠加信号提取出来。经放大、A/D转换后送入计算机。计算机利用快速M变换对混合信号进行分离，从而得到视网膜各个区域的反应信号。该系统具有控制简单，检测效果好，成本低等优点，在临床上有广泛的应用前景。     

多焦技术及其在mERG中的应用

多焦技术是目前信号处理的一项先进技术,它在视觉电生理系统中的主要应用为多焦视网膜电图(multifocal electroretinogram,mERG)及多焦视诱发电位(multifocal visual evoked potential,mVEP)检测.其中,mERG可以同时刺激视网膜上多个小区域,在较短时间内反映各个小区域对应的ERG特性,从而精确快速敏感的测量视功能.本文主要从互相关函数、m-序列等入手介绍了多焦技术的原理,并对其在视网膜电图上的应用--多焦视网膜电图进行了描述,阐明了在多焦视网膜电图中如何对每个小区域的生理电响应信号进行分离.     

172例多焦ERG检测分析

目的对172例患者行多焦视网膜电图检测。方法应用德国罗兰电生理仪检测,采用103个六边形刺激图形,记录172例患者多焦ERG的b波振幅密度值在六环的表现。结果多焦ERG表明各类眼底病变对视网膜损伤程度和范围是不相同的。结论多焦ERG检查具有局部定位和定量功能的诊断和分类,以及为眼底病变的早期诊断治疗提供依据具有重要意义。     

一种通过六边间隙式阵列的天线相位调制所产生的加热模式

本文介绍一种采用六边形阵列的微波天线所产生的热治疗癌症的方法。其目的是通过对六边形阵列的每一天线上的信号进行相位调制,既可产生均匀的,又可产生非均匀的可控的加热模式而作用于生物组织。该阵列包括位于六边形的角上,两根天线对角线的距离是4cm。在阵列内通过热传导模拟的方法可计算出每单位体积吸收的功率以及所转换的热量。本文还提出了有关吸收率和温度关系的模型,包括     

基于手指的触觉替代视觉系统的设计与实现

目的:设计与实现触觉替代视觉系统(TVSS),该系统尝试通过电极阵列刺激皮肤产生触觉感受,并利用触点的二维分布,为盲人开辟一条重获视觉信息的新途径.方法:系统由三个模块组成:多通道电触觉阵列,电极驱动电路以及嵌入式控制图像处理模块.其中256通道的电触觉阵列通过将球形镍电极焊接到印刷电路板上的方式制作而成.采用多路分时技术为多通道提供高压电脉冲刺激信号,通过光电隔离电路实现强弱电信号之间的隔离与控制.使用DM642开发板来实现图像的获取、处理以及传输功能.结果:手指尖电脉冲刺激的阈值在130V左右.结论:不同的刺激脉冲宽度,会引起刺激阈值以及刺激效果的变化,150 V以上的电脉冲会在指尖产生一个局部的舒适的电触觉感受.     

多焦视网膜电图多位点振幅概率图研究

多焦视网膜电图是用于检测视网膜后极部多个位点尤其是黄斑部功能的一种客观的眼电生理检查技术.本文记录并分析120位不同性别、不同年龄正常人的mfERG的103个刺激位点一阶反应振幅密度,按年龄、眼别统计出振幅密度正常值,自动画出异常概率图,并经过6例临床病人的mfERG数据验证,结果证实所得概率图与眼科医生的分析判断一致.     

视觉诱发电位,视网膜电图及眼电图的临床应用进展

现代科学研究表明至少有70％的外界信息是通过视觉系统被接受、分析和处理的。在视觉信息的处理和加工过程研究中占重要地位的是神经电活动。目前视觉电生理研究已拓展为神经生物学中取得长足进展的领域。视网膜是神经系统的外周感受器中了解得最清楚的区域之一;而对视皮层细胞结构和功能的研究远较大脑其它区域更为深入和清楚。随着视觉电生理的不断发展,越来越多的研究方法逐渐应用于眼科临床。如视觉诱发电位(Visual Evoked Potential,VEP)、视网膜电图(Electroretinograph,ERG)、眼电图(Electrooculargram,     

视觉诱发电位检测对视神经炎的诊断价值

视觉诱发电位(visual evoked potential,VEP)为检测视神经上行通路皮质下结构(包括视神经、视交叉、视束、外侧膝状体和视放射)的神经电生理检查方法之一,主要反映视网膜视锥细胞的电活动情况,从而检测视觉通路神经的功能.Halliday等[1]最先将棋盘格翻转视觉诱发电位(PS-VEP)用于临床并获得肯定结果,其后VEP被广泛应用,已成为神经眼科学重要的辅助诊断手段之一.     

基于稳态视觉诱发电位的脑-机接口无线智能家居系统研究

脑-机接口(BCI)系统是通过脑电(EEG)信号实现人和计算机等设备之间的交流和控制的系统。本文阐述了基于BCI技术的无线智能家居系统的工作原理,利用单片机、LED灯组成视觉刺激器诱发得到稳态视觉诱发电位(SSVEP),再利用在LabVIEW平台上的功率谱变换方法实时处理不同频率刺激下产生的EEG信号,将其转化为不同的指令,由无线射频设备收发控制命令,实现家居设备的实时智能控制。实验结果表明,10名受试者的正确率均达到100%,单个设备的平均控制时间为4s,实现了家居设备的智能控制。     

心房活动电生理信号特征提取

为从12导联体表心电图中有效地提取反映心房活动的电生理信号,构造一种稀疏表示下的独立成分分析模型。首先,对采集到的12导联体表心电信号进行预处理,然后通过小波变换,实现心电信号小波域的稀疏表示形式,对变换后的心电信号进行独立成分分析,并通过频谱分析确定出反映心房活动的电生理信号源。讨论了平均房颤周长的这一测量指标在房颤患者中的具体应用。实验表明,该方法可以有效提取心房活动的电生理信号,将对心房活动电生理的深入研究产生积极影响。     

Quantitative anatomy, synaptic connectivity and physiology of amacrine cells with glucagon-like immunoreactivity in the turtle retina

Summary Although a wide variety of neuropeptides have been localized in vertebrate retinas, many questions remain about the function of these peptides and the amacrine cells that contain them. This is because many of these peptidergic amacrine cells have been studied using only immunocytochemical techniques. To address this limitation, the present study used a combination of quantitative anatomy, biochemistry and electrophysiology to examine amacrine cells in the turtle retina that contain the neuropeptide glucagon. In the turtle retina, there is a small population of 2500 glucagonergic amacrine cells, which probably represents <1% of the total number of amacrine cells. Circular distribution statistics indicated that many of these tristratified amacrine cells had asymmetric dendritic arborizations that were radially oriented toward the retinal periphery. The cells were found to have similar dendritic coverage factors, to be distributed in a non-random arrangement in all regions of the retina, and to peak in density in the visual streak region. Electron microscopic studies indicated that glucagonergic amacrine cells made synaptic contacts primarily with other amacrine cells, and small numbers of bipolar cells. The synaptic inputs and outputs were balanced in the inner strata of the inner plexiform layer, and were biased toward synaptic outputs in the outer strate of the inner plexiform layer. These contacts involved small unlabelled synaptic vesicles, and not the large labelled dense core vesicles also found in these neurons. The biochemical studies indicated that glucagon could be released from the retina in a calcium dependent manner by high potassium stimulation. The electrophysiology found no color opponency, and the glucagonergic amacrine cells gave sustained hyperpolarizing responses to small stimulation spots and had antagonistic surrounds. The results of these studies suggest that there are significant regional specializations of glucagonergic amacrine cells, and that they may provide OFF-modulation in interactions between the ON- and OFF centre visual pathways in the turtle retina.     

Rod-cone independence for sensitizing interaction in the human retina

1. Illumination of a retinal area adjoining a tested area can cause either desensitization or sensitization through lateral interaction, depending on whether the distance separating the illuminated and tested areas is small or large. This interaction occurs both in the rod and the cone mechanisms of the retina when each is tested separately by selection of appropriate adapting and testing stimuli.2. In the mixed rod/cone region of the near periphery of the human retina the spatial parameters of interaction within the rod and cone systems were different when mapped out by using only one kind of adapting stimulus and sampling the excitatory state of the rod and cone systems by different probing stimuli.3. Sensitizing interaction signals generated by the rod system are incapable of causing sensitization of the cone system.     

Identification of appropriate primitive polynomials to avoid cross-contamination in multifocal electroretinogram responses

The basis of the multifocal/electroretinogram is the use of a decimated m-sequence for simultaneous and independent stimulation of many areas of the visual pathway. The purpose of this study was to investigate the effects of cross-contamination from higher orders of the response. A series of primitive polynomials were found by construction of finite fields. The first-order ERG response was formed by cross-correlation of m-sequence with the physiological response. A second-order response was formed by investigation of particular flash sequences of the stimulation sequence and cross-correlation of a second-order m-sequence with the physiological response. Zech logarithms were used to identify cross-contamination between the various first and second-order sequences. Tables of good and bad primitive polynomials were constructed for degrees 12–16, and the effects of window length and decimation length were examined. When the sequence was decimated into 128 areas, and a window of length 16 was examined, cross-contamination occurred in all sequences generated from primitive polynomials of degree less than or equal to 12, but in only 26% of degree 14, and 5.6% of degree 16. A photodiode (artificial eye) was used in an experiment to construct trace arrays showing responses from 61 individual areas. Additional waveforms were present on the trace array when the experiment was carried out with a bad primitive polynomial. The use of finite field theory to generate primitive polynomials and Zech logarithm analysis allowed prediction of which primitive polynomials were suitable for m-sequence generation for multifocal electroretinography. Practical investigations supported the theoretical analysis. This has important implications for developers of multifocal electrophysiology systems.     

Large-scale remapping of visual cortex is absent in adult humans with macular degeneration

The occipital lobe contains retinotopic representations of the visual field. The representation of the central retina in early visual areas (V1-3) is found at the occipital pole. When the central retina is lesioned in both eyes by macular degeneration, this region of visual cortex at the occipital pole is accordingly deprived of input. However, even when such lesions occur in adulthood, some visually driven activity in and around the occipital pole can be observed. It has been suggested that this activity is a result of remapping of this area so that it now responds to inputs from intact, peripheral retina. We evaluated whether or not remapping of visual cortex underlies this activity. Our functional magnetic resonance imaging results provide no evidence of remapping, questioning the contemporary view that early visual areas of the adult human brain have the capacity to reorganize extensively.     

Mechanism of visual perception of movement

We here present a logical mathematical model for the visual perception of movement in man; it is based on the treatment of signals in the retina in relation to time and distance and on the statistical theory of the separation of signal from noise in the visual system. It shows good agreement with experimental results and has made it possible to determine the comparative level of internal noise of the visual system, the mean rate of spread of excitation from the photoreceptors along the surface of the retina, and many other characteristics.Translated from Izvestiya Akademii Nauk SSSR, Seriya Biologicheskaya. No. 5. pp. 701–712, September–October, 1975.     

The area centralis of the retina in the cat and other mammals: focal point for function and development of the visual system

In many mammals, particularly species with frontalised eyes, a small region o retina is strongly specialised for high resolution, binocular vision. The region is typically located near the centre of the retina, a few millimetres temporal to the optic disc, and is termed the "area centralis" or, in some primates in which the specialisation is particularly well developed, the "fovea centralis". Where the specialisation is well developed, the area or fovea centralis dominates the organisation of the adult visual system. Studies of the histogenesis of the retina of the cat indicate that the process of retinal maturation is centred on the area centralis, which thus seems to be an organising focus in the ontogeny as well as the adult function of the visual system.     

Nonlinearity of spatial summation in simple cells of areas 17 and 18 of cat visual cortex.

1. Nonlinearity of spatial summation in areas 17 and 18 of cat visual cortex was compared with the type of spatial nonlinearity that differentiates X and Y cells in the lateral geniculate nucleus (LGN) and retina. The comparisons were made to examine to what extent the information from X and Y cells may remain separated in higher visual centers. 2. Responses of simple cells in areas 17 and 18 were recorded while stationary, optimally oriented sinewave gratings were sinusoidally modulated within the receptive field of the cell. Both the spatial frequency and spatial phase of the stimulus were varied. 3. Y cells in the retina and LGN are defined by the presence of a specific form of spatial nonlinearity. When tested with contrast-modulated sinewave gratings of spatial frequencies about three-fold greater than the optimal, their responses are dominated by a frequency-doubled component. The amplitude of the frequency-doubled component is not dependent on the spatial phase of the stimulus. 4. Many simple cells in the cortex showed a form of spatial nonlinearity similar to the defining nonlinearity found in retinal and geniculate Y cells. A frequency-doubled response dominated at spatial frequencies more than threefold greater than the optimal spatial frequency. When this response was present, it was phase independent. 5. More than 50% of the simple cells in area 18 showed the Y-like spatial nonlinearity. Fewer than 10% of the simple cells in area 17 showed the Y-like spatial nonlinearity. 6. The virtual absence of Y-like nonlinearity in area 17 and its relative abundance in area 18 suggest that the functional separation between the parallel X and Y pathways remains distinct within areas 17 and 18 of cat visual cortex.     

Interhemispheric influences on area 19 of the cat

Summary Anatomical studies have shown an extensive network of homotopic and heterotopic interhemispheric connections in area 19 of the cat visual cortex (Segraves and Rosenquist 1982a; 1982b). We have investigated their functional organization by recording visual responses in area 19 of cats following a midsagittal section of the optic chiasm. This operation interrupts all crossed optic fibers coming both from the nasal and the temporal retinae; as a result, each hemisphere receives optic fibers only from the lateral hemiretina of the ipsilateral eye which conveys information from the contralateral visual field. Visual information transmitted to the same hemisphere from the contralateral retina and the ipsilateral visual field must be attributed to an indirect, interhemispheric pathway. We found that a rather high proportion of neurons (31.8%) in area 19 of seven split-chiasm cats responded to visual stimuli presented to the contralateral eye. 1 — All neurons receiving this interhemispheric activation were also driven by the ipsilateral eye via an intrahemispheric pathway. 2 — The property of binocularity was significantly related to the visuotopic map in that both receptive fields of each binocular neuron adjoined or were in the immediate vicinity of the vertical meridian. 3 — Due to the small size of receptive fields in area 19, the contribution of the interhemispheric pathway to the representation of the visual field is rather limited and it is certainly less extensive than that predicted by anatomical studies. The representation of the ipsilateral visual field in area 19 of intact cats, as assessed electrophy-siologically, was comparable to that found in split-chiasm cats. Recordings in areas 17–18 of split-chiasm cats showed that the visual field represented through the corpus callosum in these visual areas is certainly not less and probably more, extensive than that found in area 19. The results support the conclusion that the relation to the vertical meridian and the receptive field size can explain the organization of the interhemispheric connections in the visual areas studied so far.