去视皮层和视剥夺不影响猫外膝体神经元的两类方向敏感特性

方向选择性是视皮层细胞重要的感受野特性。最近的工作表明,视觉系统皮层下的部分外膝体细胞(约占32％)和视网膜神经节细胞(约占25％)亦存在着方向敏感性。这种方向敏感性在去视皮层猫和视觉剥夺猫(dark--reared cat)外膝体神经元也存在。周逸峰等依反应特性将外膝体的方向敏感性细胞分为两类,其中一类只在以刺激后时间直方图(PSTH)的富里叶变换(FFC)基频幅度为反应指标的情况下才呈现方向敏感性。另一类细胞则以FFC基频幅度和细胞平均发放等为反应指标的情况下均呈现方向敏感性,其中一些细胞对移动光棒和移动光点刺激亦呈现方向敏感性。两类方向敏感性细胞约各占50％。

Acute lesions of primary visual cortical areas in adult cats inactivate responses of neurons in higher visual cortices

Psychophysical studies suggest that lateral extrastriate visual cortical areas in cats may mediate the sparing of vision largely by network reorganization following lesions of early visual cortical areas. To date, however, there is little direct physiological evidence to support this hypothesis. Using in vivo single-anit recording techniques, we examined the response of neurons in areas 19, 21, and 20 to different types of visual stimulation in cats with or without acute bilateral lesions in areas 17 and 18. Our results showed that, relative to the controls, acute lesions inactivated the response of 99.3% of neurons to moving gratings and 93% of neurons to flickering square stimuli＇in areas 19, 21, and 20. These results indicated that acute lesions of primary visual areas in adult eats may impair most visual abilities. Sparing of vision in cats with neonatal lesions in early visual cortical areas may result largely from a postoperative reorganization of visual pathways from subcortical nucleus to extrastriate visual cortical areas.

Effects of urethane on the response properties of visual cortical neurons in young adult and old cats

Previous studies have shown that visual cortical neurons in old mammals exhibit higher spontaneous activity,higher responsiveness to visual stimuli,and lower selectivity for stimulus orientations and motion directions than did neurons in young adult counterparts.However,whether the responsive difference in cortical neurons between young and old animals resulted from different effects induced by anesthetics has remained unclear.To clarify this issue,we recorded the response properties of individual neurons in the primary visual cortex of old and young adult cats while systematically varying the anesthesia level of urethane,a widely used anesthetic in physiology experiments.Our results showed that cumulatively administrating 50 mg and 100 mg of urethane upon the minimal level of urethane required to anesthetize an old or young adult cat did not significantly alter the degree of neuronal response selectivity for stimulus orientations and motion directions nor significantly change the visually-driven response and spontaneous activity of neurons in old and young adult cats.Cumulatively administrating 150 mg of urethane decreased neuronal responsiveness similarly in both age groups.Therefore,urethane appears to exert similar effects on neuronal response properties of old and young adult animals.

Retinal Prosthesis:A Potential Benefit for the Blind

Retinal degenerative diseases may induce the degeneration of outer retina and in turn,blindness.Nevertheless,due to the maintenance of inner retina,the coding and processing of visual neurons responses are still able to be executed naturally.Therefore,an effective retinal prosthesis device may be developed by mimicking the function of outer retina:transferring the visual light into artificial stimulus and delivering the stimulus to the retina aiming to evoke the neural responses.As two main developing directions for current retinal prosthesis,epiretinal(ER)and subretinal(SR)prosthesis are both undergoing experimental stage and possessing advantages and limitations.Further investigations in power supply,biocompatibility,etc.are still required.Additionally,suprachoroidal transretinal stimulation(STS)and neurotransmitter-induced stimulation as some other alternatives in retinal prosthesis are also considered as promising research directions,although they are not mature enough to be applied commercially,either.

Identification of connexin 50 and 57 mRNA in A-type horizontal cells of the rabbit retina

Horizontal cells (HCs) mediate negative feedback to photoreceptors. In the mammalian retina, there are two types of HCs, which are extensively coupled to neighboring cells through homologous gap junctions. The permeability and therefore the strength of feedback can be regulated by light intensity, dopamine and many other factors. However, the component(s) of the most prominent gap junctions, those between A-type HCs in the rabbit retina, is still unknown. In this study, we compared the sequences of many types of mammalian connexins, obtained partial sequences of rabbit connexin 50 and 57. Using specific primers designed against the rabbit sequences, we identified mRNAs of connexin 50 and/or 57 in visually selected single A-type HC using multiplex RT-PCR.

Phenomenological Simulation Study of Neuronal Activity Synchronization in 110 Elements Network

The phenomenon of activity synchronization in biological neural network is considered. Simulation of neurons dynamics in the 6-layer neural network with 110 elements in different regimes： regular spikes, chaotic spikes, regular and chaotic bursting, etc was performed. Izhykevich＇s phenomenological model that displays different types of activity inherent for real biological neurons was used for simulation. Space-time diagram for the entire network and raster plots for the whole structure and for each layer separately were built for visual inspection of neural network activity synchronization. Synchronization coefficients based on cross-correlation times of action potentials for all neurons pairs were calculated for the whole neural system and for each layer separately.

Diabetic retinopathy: recent advances towards understanding neurodegeneration and vision loss

Diabetic retinopathy （DR） is one of the most common retinal diseases world-wide. It has a complex pathology that involves the vasculature of the inner retina and breakdown of the blood-retinal barrier. Extensive research has determined that DR is not only a vascular disease but also has a neurodegenerative component and that essentially all types of ceils in the retina are affected, leading to chronic loss of visual function. A great deal of work using animal models of DR has established the loss of neurons and pathology of other cell types, including supporting glial cells. There has also been an increased emphasis on measuring retinal function in the models, as well as further validation and extension of the animal studies by clinical and translational research. This article will attempt to summarize the more recent developments in research towards understanding the complexities of retinal neurodegeneration and functional vision loss in DR.

Continuous subcellular resolution three-dimensional imaging on intact macaque brain

To decipher the organizational logic of complex brain circuits,it is important to chart long-distance pathways while preserving micron-level accuracy of local network.However,mapping the neuronal projections with individual-axon resolution in the large and complex primate brain is still challenging.Herein,we describe a highly efficient pipeline for three-dimensional mapping of the entire macaque brain with subcellular resolution.The pipeline includes a novel poly-N-acryloyl glycinamide(PNAGA)-based embedding method for long-term structure and fluorescence preservation,high-resolution and rapid whole-brain optical imaging,and image post-processing.The cytoarchitectonic information of the entire macaque brain was acquired with a voxel size of 0.32μm×0.32μm×10μm,showing its anatomical structure with cell distribution,density,and shape.Furthermore,thanks to viral labeling,individual long-distance projection axons from the frontal cortex were for the first time reconstructed across the entire brain hemisphere with a voxel size of 0.65μm×0.65μm×3μm.Our results show that individual cortical axons originating from the prefrontal cortex simultaneously target multiple brain regions,including the visual cortex,striatum,thalamus,and midbrain.This pipeline provides an efficient method for cellular and circuitry investigation of the whole macaque brain with individual-axon resolution,and can shed light on brain function and disorders.

Regulatory effect of acupuncture on electrical activity level of optic cortex in amblyopia model rats

Objective To explore the abnormal changes in neuroelectric activity in the primary visual cortex of rats deprived of vision in one eye and to investigate the regulatory effect of acupuncture in the sensitive period on the abnormal coding and conduction of electrical signals of rats’optic neurons.Methods Sixty 14-day-old Sprague-Dawley rats were randomly divided into a blank group,a model group,an early-stage acupuncture group,a middle-stage acupuncture group,and a late-stage acupuncture group,with 12 rats in each group.Rats in every group except the blank group received right eyelid suturing to create a monocular deprivation model in the sensitive period of visual development(from the day rats open their eyes to the 45th day after their birth).Rats in the three acupuncture groups started to undergo acupuncture respectively on the 3rd,12th,and 21st days after the model replication was done,with each group receiving nine-day treatment.The activity level of the neuroelectrical signal of the primary visual cortex in each group,including the latency and amplitude of P100 wave,average discharge frequency and amplitude of neurons,the power spectral density(PSD),and interspike interval(ISI),were measured by neuroelectric evaluation technology after the acupuncture treatment was finished.Results Compared with the blank group,the latency of P100 wave in the visual center of vision-deprived eyes was significantly prolonged,and the amplitude was significantly reduced(P<0.05);the average discharge frequency and amplitude of the neurons in the visual cortex also decreased significantly(P<0.05);PSD decreased and ISI was prolonged significantly(P<0.05).Compared with the model group,the abnormal electrical activity of optic neurons in the three acupuncture groups ameliorated,the latency of P100 shortened,and the amplitude of P100 increased(P<0.05),the discharge frequency and amplitude increased significantly(P<0.05),the PSD reduced,and the ISI shortened(P<0.05).In addition,among the three acupuncture groups,the early-stage acupuncture group had the best effect on various indicators.Conclusion Abnormal electrophysiological activity is significant in the visual center of vision-deprived rats,and acupuncture treatment in the sensitive period of visual development can enhance the bioelectrical activity of visual nerve cells,improve the efficiency of optic nerve conduction,and regulate the inhibition and retardation of visual response caused by visual deprivation.

Temporal and spatial expression of Drosophila Neurexin during the life cycle visualized using a DNRX-Gal4/UAS-reporter

Drosophila neurexin(DNRX) plays a critical role in proper architecture development and synaptic function in vivo. However, the temporal and spatial expression pattern of DNRX still remains unclear. For this study, we generated a novel Drosophila transgenic strain termed the DNRX-Gal4 transgenic line, with characteristic features in agreement with the endogenous DNRX expression pattern. DNRX expression was examined by driving the expression of a GFP reporter(nuclear-localized and membrane-localized GFP) using the DNRX-Gal4 promoter. We found that DNRX was expressed preferentially in central and motor neurons in embryos, larvae and adults, but not in glial cells. DNRX was expressed in pre- and post-synaptic areas in third instar larvae neuromuscular junctions(NMJs). Reporter expression was also observed in the salivary glands, guts, wings and legs of adult flies. In the adult brain, reporter expression was observed throughout several brain regions, including the mushroom body(MBs), antennal lobe(AL) and optic lobe neurons, which is consistent with endogenous DNRX expression via antibody staining. Interestingly, DNRX was also expressed in clock neurons. Meanwhile, we found that DNRX expression in the MBs was required for olfactory learning and memory.

Association between retinal neuronal degeneration and visual function impairment in type 2 diabetic patients without diabetic retinopathy

The changes in retinal thickness and visual function in type 2 diabetic patients without clinical evidence of diabetic retinopathy were evaluated. A total of 141 diabetic subjects without retinopathy and 158 healthy subjects were enrolled in this study. Superior macular ganglion cell complex thicknesses were significantly decreased in diabetic cases, and no significant peripapillary retinal nerve fiber layer thickness changes were observed. The contrast sensitivities at all space frequencies were significantly different between diabetic patients and controls. The mean P50 amplitude from pattern electroretinogram results was reduced significantly in the diabetic group. In the diabetic group, average superior ganglion cell complex thicknesses positively correlated with both contrast sensitivities at high spatial frequencies and P50 amplitudes. The results indicated that ganglion cell complex thickness and visual function changes could be observed in diabetic subjects before the onset of any significant diabetic retinopathy. Macular ganglion cell complex reduction occurred much earlier than peripapillary retinal nerve fiber layer thinning in diabetic patients without retinopathy.

A bacterial artificial chromosome transgenic mouse model for visualization of neurite growth

Class Ⅲ β-tubulin （Tubb3） is a component of the microtubules in neurons and contributes to microtubule dynamics that are required for axon outgrowth and guidance during neuronal development. We here report a novel bacterial artificial chromosome （BAC） transgenic mouse line that expresses Class Ⅲ β-tubulin fused to mCherry, an improved monomeric red fluorescent protein, for the visualization of microtubules during neuronal development. A BAC containing Tubb3 gene was modified by insertion of mCherry complementary DNA downstream of Tubb3 coding sequence via homologous recombination, mCherry fusion protein was expressed in the nervous system and testis of the transgenic animal, and the fluorescent signal was observed in the neurons that located in the olfactory bulb, cerebral cortex, hippocampal formation, cerebellum, as well as the retina. Besides, Tubb3-mCherry fusion protein mainly distributed in neurites and colocalized with endogenous Class Ⅲ β-tubulin The fusion protein labels Purkinje cell dendrites during cerebellar circuit formation. Therefore, this transgenic line might be a novel tool for scientific community to study neuronal development both in vitro and in vivo.