共查询到20条相似文献，搜索用时 46 毫秒
1.
Ocular dominance column development: analysis and simulation 总被引：15，自引：0，他引：15
The visual cortex of many adult mammals has patches of cells that receive inputs driven by the right eye alternating with patches that receive inputs driven by the left eye. These ocular dominance patches (or "columns") form during early life as a consequence of competition between the activity patterns of the two eyes. A mathematical model of several biological mechanisms that can account for this development is presented. Analysis of this model reveals the conditions under which ocular dominance segregation will occur and determines the resulting patch width. Simulations of the model also exhibit other phenomena associated with early visual development, such as topographic refinement of cortical receptive fields, the confinement of input cell connections to patches, monocular deprivation plasticity including a critical period, and the effect of artificially induced strabismus. The model can be used to predict the results of proposed experiments and to discriminate among various mechanisms of plasticity. 相似文献
2.
The existence of spontaneous neural activity in mammalian retinal ganglion cells during prenatal life has long been suspected. This activity could play a key role in the refinement of retinal projections during development. Recordings in vivo from the retinas of rat fetuses between embryonic day 17 and 21 found action potentials in spontaneously active ganglion cells at all the ages studied. 相似文献
3.
Peretz B 《Science (New York, N.Y.)》1969,166(3909):1167-1172
In Aplysia periodic spontaneous gill movements are controlled by activity endogenous to the abdominal ganglion. These movements were still observed when only the ctenidio-genital nerve was left intact between the ganglion and the gill. One kind of spontaneous gill movement (one per 5 minutes at 15 degrees C) was correlated with the expression of activity of interneuron II; others were not. With reference to this kind of spontaneous gill movement, four types of central neurons in the ganglion send processes to the gill via the nerve. Two cell types (ii, iii) are inhibited and the other two (i, iv) are excited. Two types (i, ii) elicited gill movement-one type activating large gill areas elicited spontaneous gill movements, and the other activating specific gill regions did not participate in the spontaneous gill movements. The value of this preparation in studying the role of central neurons eliciting specific patterned movements and the temporal organization of their activity is shown. 相似文献
4.
In this paper we introduce the one-inflated bivariate Beta distribution as a new approach to analyze matching scores related to retinal image identification in lambs. These kind of data sets present many values equal to one, the perfect matching, and this justifies the introduction of one-inflation patterns. In addition, matching scores are correlated according to several bivariate patterns: left and right eye, 3 and 12 months of age, etc. Some examples of applications are given. 相似文献
5.
Ikegaya Y Aaron G Cossart R Aronov D Lampl I Ferster D Yuste R 《Science (New York, N.Y.)》2004,304(5670):559-564
How can neural activity propagate through cortical networks built with weak, stochastic synapses? We find precise repetitions of spontaneous patterns of synaptic inputs in neocortical neurons in vivo and in vitro. These patterns repeat after minutes, maintaining millisecond accuracy. Calcium imaging of slices reveals reactivation of sequences of cells during the occurrence of repeated intracellular synaptic patterns. The spontaneous activity drifts with time, engaging different cells. Sequences of active neurons have distinct spatial structures and are repeated in the same order over tens of seconds, revealing modular temporal dynamics. Higher order sequences are replayed with compressed timing. 相似文献
6.
Neuronal controls of a behavioral response mediated by the abdominal ganglion of Aplysia 总被引：8，自引：0，他引：8
Tactile stimulation of the siphon and mantle shelf in Aplysia causes a characteristic withdrawal response of the external organs of the mantle cavity. A similar response also occurs spontaneously. Both responses are mediated by the abdominal ganglion and therefore provide an opportunity for correlating cellular functioning and behavior in a relatively simple and well-studied neuronal system. The withdrawal responses are controlled by five identified motor cells which receive two types of synaptic inputs. One set of excitatory connections, activated by tactile stimulation of the siphon and mantle shelf, mediates the defensive withdrawal reflex. A second set of connections is activated by a spontaneous burst of activity in a group of closely coupled interneurons which are excitatory to some of the motor cells and inhibitory to the others. This second set of connections mediates the spontaneous withdrawal response. These two inputs can therefore switch the same population of motor cells from a simple reflex to a more complex, internally organized response. 相似文献
7.
Synchronous bursts of action potentials in ganglion cells of the developing mammalian retina 总被引：37，自引：0，他引：37
The development of orderly connections in the mammalian visual system depends on action potentials in the optic nerve fibers, even before the retina receives visual input. In particular, it has been suggested that correlated firing of retinal ganglion cells in the same eye directs the segregation of their synaptic terminals into eye-specific layers within the lateral geniculate nucleus. Such correlations in electrical activity were found by simultaneous recording of the extracellular action potentials of up to 100 ganglion cells in the isolated retina of the newborn ferret and the fetal cat. These neurons fired spikes in nearly synchronous bursts lasting a few seconds and separated by 1 to 2 minutes of silence. Individual bursts consisted of a wave of excitation, several hundred micrometers wide, sweeping across the retina at about 100 micrometers per second. These concerted firing patterns have the appropriate spatial and temporal properties to guide the refinement of connections between the retina and the lateral geniculate nucleus. 相似文献
8.
用HRP法研究了猪左心室外侧壁的交感神经节后神经元的分布,结果表明:标记细胞位于左侧颈中神经节、右侧椎神经节、双侧颈胸神经节及第二至第四胸交感神经节。标记细胞以颈胸节最多,占59.4％。左侧出现的标记细胞数明显多于右侧。标记细胞为多突起的星形运动神经元,以直径20～30μ为主,占67％。颈胸神经节内的标记细胞,大部分位于节的前腹侧部。颈前神经节内未发现标记细胞。 相似文献
9.
Tbx5 and the retinotectum projection 总被引：1，自引：0，他引：1
Koshiba-Takeuchi K Takeuchi JK Matsumoto K Momose T Uno K Hoepker V Ogura K Takahashi N Nakamura H Yasuda K Ogura T 《Science (New York, N.Y.)》2000,287(5450):134-137
Dorsal and ventral aspects of the eye are distinct from the early stages of development. The developing eye cup grows dorsally, and the choroidal fissure is formed on its ventral side. Retinal axons from the dorsal and ventral retina project to the ventral and dorsal tectum, respectively. Misexpression of the Tbx5 gene induced dorsalization of the ventral side of the eye and altered projections of retinal ganglion cell axons. Thus, Tbx5 is involved in eye morphogenesis and is a topographic determinant of the visual projections between retina and tectum. 相似文献
10.
Adenosine receptors: autoradiographic evidence for their location on axon terminals of excitatory neurons 总被引：11，自引：0，他引：11
Adenosine receptors were made visible on light microscopy by autoradiography with tritiated cyclohexyladenosine. In the cerebellum, adenosine receptors were absent in Weaver mice, which lack granule cells, and were displaced in Reeler mice, which have displacements of granule cells. Thus, adenosine receptors appear to be located on the axon terminals of excitatory granule cells in the cerebellum. Removal of one eye of a rat depleted adenosine receptors in the contralateral superior colliculus, suggesting that the receptors occur on axon terminals of excitatory projections from retinal ganglion cells. The presence of adenosine receptors on excitatory axon terminals may explain synaptic inhibition by adenosine and the behavioral effects of xanthines. 相似文献
11.
Retinal cells have been induced to project into the medial geniculate nucleus, the principal auditory thalamic nucleus, in newborn ferrets by reduction of targets of retinal axons in one hemisphere and creation of alternative terminal space for these fibers in the auditory thalamus. Many cells in the medial geniculate nucleus are then visually driven, have large receptive fields, and receive input from retinal ganglion cells with small somata and slow conduction velocities. Visual cells with long conduction latencies and large contralateral receptive fields can also be recorded in primary auditory cortex. Some visual cells in auditory cortex are direction selective or have oriented receptive fields that resemble those of complex cells in primary visual cortex. Thus, functional visual projections can be routed into nonvisual structures in higher mammals, suggesting that the modality of a sensory thalamic nucleus or cortical area may be specified by its inputs during development. 相似文献
12.
比目鱼类的眼睛移位和不对称的进化起源 总被引：3，自引：3，他引：0
鲍宝龙 《上海海洋大学学报》2012,21(5):728-736
比目鱼类外形不对称产生的机制引起人们兴趣已逾一个多世纪。从比目鱼类(鲽形目)的类群和分布、变态过程中眼睛移位机械力的来源、甲状腺激素调控眼睛移位的信号通路、比目鱼类外形左右不对称与内脏左右不对称两者调控机制之间的关系以及比目鱼类眼睛左右不对称的进化起源等5个方面,系统地介绍了比目鱼类变态发育过程中眼睛移位的研究历史。重点介绍了本实验室提出的关于眼睛移位的组织学模型,以及眼睛移位信号调控途径的最新研究进展。发现并证明眶下皮肤组织细胞分裂导致眼睛移动,而眼睛移动进一步导致额骨变形,纠正了以往假说的谬误。最后,对比目鱼类眼睛移位和不对称进化起源进行了探讨,提出了解释比目鱼类不对称进化起源的新假说。 相似文献
13.
Neuronal networks in vivo are characterized by considerable spontaneous activity, which is highly complex and intrinsically generated by a combination of single-cell electrophysiological properties and recurrent circuits. As seen, for example, during waking compared with being asleep or under anesthesia, neuronal responsiveness differs, concomitant with the pattern of spontaneous brain activity. This pattern, which defines the state of the network, has a dramatic influence on how local networks are engaged by inputs and, therefore, on how information is represented. We review here experimental and theoretical evidence of the decisive role played by stochastic network states in sensory responsiveness with emphasis on activated states such as waking. From single cells to networks, experiments and computational models have addressed the relation between neuronal responsiveness and the complex spatiotemporal patterns of network activity. The understanding of the relation between network state dynamics and information representation is a major challenge that will require developing, in conjunction, specific experimental paradigms and theoretical frameworks. 相似文献
14.
Connectivity patterns of crayfish giant interneurons: visualization of synaptic regions with cobalt dye 总被引：1，自引：0，他引：1
Intracellular injection of cobalt dye was used to visualize electrical synapses between two pairs of central giant interneurons and giant motoneurons in the crayfish central nervous system. A pair of giant motoneurons in each ganglion contacts the interneurons, but not all contact points are functional synapses. Cobalt dye reveals numerous fine projections that are present at synaptic contact points and absent at nonsynaptic contacts; intracellular recording confirms this correlation. The different connectivity patterns of the two pairs of interneurons are consistent with the different behavior patterns which they evoke. 相似文献
15.
林大诚 《中国农业大学学报》1983,(3):85-88
解剖了三支大猫熊的心神经。观察了心神经的发出部位及其分布。右侧的迷走神经心支,接受返神经的心支和推神经节的腹侧心支后入心包,分支入主动脉及肺动脉再分支入左右冠状丛。另一椎神经节的心支入右心房壁。左侧速走神神经心支,椎神经节心支及颈胸神经节的心支常互相交通。主要分布到主动脉弓,食管,气管及右肺动脉。左侧返神经的心支入心包及左心房内侧壁。大猫熊的心神经与家畜中马、牛、羊猪、狗的比较均有不同。大猫熊的冠状从,主要来自右侧心神经,而家畜多来自左侧或两侧。 相似文献
16.
Dark adaptation: an interocular light-adaptation effect 总被引：1，自引：0，他引：1
Presentation of iight to the left eye simultaneously with adaptation of the right eye to light may accelerate dark adaptation in the right eye. The result is that the rod-cone-break and the final threshold of the rods are achieved earlier than when the right eye alone is adapted to light. 相似文献
17.
18.
Direction-selective ganglion cells (DSGCs) in the retina respond strongly when stimulated by image motion in a preferred direction but are only weakly excited by image motion in the opposite null direction. Such coding represents an early manifestation of complex information processing in the visual system, but the cellular locus and the synaptic mechanisms have yet to be elucidated. We recorded the synaptic activity of DSGCs using strategies to observe the asymmetric inhibitory inputs that underlie the generation of direction selectivity. The critical nonlinear interactions between the excitatory and inhibitory inputs took place postsynaptically within the dendrites of the DSGCs. 相似文献
19.
Changes of simple and complex spike activity of cerebellar purkinje cells with sleep and waking 总被引：1，自引：0，他引：1
N Mano 《Science (New York, N.Y.)》1970,170(964):1325-1327
Action potentials of cerebellar Purkinje cells were observed in intact monkeys during sleep and waking. Purkinje cells exhibit two sorts of action potentials, called simple and complex spikes, and these two sorts of spikes were differently affected by sleep. Simple-spike activity (generated by the parallel fiber inputs to the Purkinje cell) was highest during sleep with rapid eye movements as compared with both waking and sleep with electroencephalographic slow waves. In contrast, complex-spike activity (generated by the climbing fiber inputs to the Purkinje cell) was lowest during sleep with rapid eye movements. The complex action potential of the Purkinje cell consists of an initial large spike followed by one or more smaller secondary spikes, and the number of these secondary spikes was found to be independent of the background discharge frequency of the simple spike. This independence suggests a possible role of presynaptic factors rather than the excitability level of the Purkinje cell itself in determining the number of secondary discharges occurring in the complex spike. 相似文献
20.
Brief visutal stimuli presented in rapid sequience, one to the left and one to the right, appear to occur left first, then right, regardless of the actual order of presentation. This illutsion persists under conditions of forced-choice testing and does not vary with presemitation to the same or opposite retinal hemifields, A series of experiments suggests that this illutsion may be the product of an internal mechanism that scans visual inputs in a left-to-right order. 相似文献