幼年大鼠视皮层神经元对闪光刺激的反应特性

哺乳动物视觉系统的发育延续到出生后,大鼠出生后 3~5 周是视觉系统发育的关键期 . 在关键期中,视皮层的兴奋性和抑制性突触连接逐渐成熟,形成有效的皮层内回路 . 为了观察发育关键期大鼠视皮层神经元的反应特性与成年大鼠的异同,使用胞外单细胞记录的方法对比研究了幼年和成年大鼠对闪光刺激的视觉反应特性 . 结果显示：与成年大鼠相比较,幼年大鼠视皮层神经元对持续闪光刺激显示出更强的适应性,对光刺激的诱发放电频率更低,而在没有光刺激时的自发放电频率更高,从而导致信噪比更低 . 这一结果表明,幼年大鼠视皮层对连续刺激的反应能力下降,对信号的分辨能力也更弱,其原因可能是兴奋性突触和抑制性突触发育的不同步所致 .     

Developmental Changes in the Visual Pigments of the Yellowfin Tuna, Thunnus Albacares

Previous studies have suggested that adult tunas have only two visual pigments in their retinas - a rod pigment with a wavelength at maximum absorbance ( λmax ) around 485 nm and one with similar λmax in both twin and single cones inferred from extraction data. Using microspectrophotometry we confirm the presence of a λmax 483 nm visual pigment in the rods of adult yellowfin tuna and a λmax 485 nm pigment in both members of the twin cones. However, all single cones contain a previously undetected violet visual pigment with λmax 426 nm making the adult yellowfin tuna a photopic dichromat. The situation for larvae and early juveniles is different from that of the adults. The all single-cone retina of preflexion larvae shows a wide distribution in individual cone absorbances suggesting not only mixtures of the two adult cone pigments, but the presence of at least a third visual pigment with λmax greater than 560 nm. With growth, the variation in cone absorbances decreases with convergence to the adult condition coincident with cone twinning. The significance of λmax variability, multiple visual pigment expression and age-related differences are discussed in terms of the visual ecology of larval, juvenile and adult tunas.     

Circadian synchronization and rhythmicity in larval photoperception-defective mutants of Drosophila

A single light episode during the first larval stage can set the phase of adult Drosophila activity rhythms, showing that a light-sensitive circadian clock is functional in larvae and is capable of keeping time throughout development. These behavioral data are supported by the finding that neurons expressing clock proteins already exist in the larval brain and appear to be connected to the larval visual system. To define the photoreceptive pathways of the larval clock, the authors investigated circadian synchronization during larval stages in various visual systems and/or cryptochrome-defective strains. They show that adult activity rhythms cannot be entrained by light applied to larvae lacking both cryptochrome and the visual system, although such rhythms were entrained by larval stage-restricted temperature cycles. Larvae lacking either pathway alone were light entrainable, but the phase of the resulting adult rhythm was advanced relative to wild-type flies. Unexpectedly, adult behavioral rhythms of the glass60j and norpAP24 visual system mutants that were entrained in the same conditions were found to be severely impaired, in contrast to those of the wild type. Extension of the entrainment until the adult stage restored close to wild-type behavioral rhythms in the mutants. The results show that both cryptochrome and the larval visual system participate to circadian photoreception in larvae and that mutations affecting the visual system can impair behavioral rhythmicity.     

Developmental Changes in the Visual Pigments of the Yellowfin Tuna,Thunnus Albacares

Previous studies have suggested that adult tunas have only two visual pigments in their retinas - a rod pigment with a wavelength at maximum absorbance (u max) around 485 nm and one with similar u max in both twin and single cones inferred from extraction data. Using microspectrophotometry we confirm the presence of a u max 483 nm visual pigment in the rods of adult yellowfin tuna and a u max 485 nm pigment in both members of the twin cones. However, all single cones contain a previously undetected violet visual pigment with u max 426 nm making the adult yellowfin tuna a photopic dichromat. The situation for larvae and early juveniles is different from that of the adults. The all single-cone retina of preflexion larvae shows a wide distribution in individual cone absorbances suggesting not only mixtures of the two adult cone pigments, but the presence of at least a third visual pigment with u max greater than 560 nm. With growth, the variation in cone absorbances decreases with convergence to the adult condition coincident with cone twinning. The significance of u max variability, multiple visual pigment expression and age-related differences are discussed in terms of the visual ecology of larval, juvenile and adult tunas.     

Experience-dependent plasticity in adult visual cortex

Experience-dependent plasticity is a prominent feature of the mammalian visual cortex. Although such neural changes are most evident during development, adult cortical circuits can be modified by a variety of manipulations, such as perceptual learning and visual deprivation. Elucidating the underlying mechanisms at the cellular and synaptic levels is an essential step in understanding neural plasticity in the mature animal. Although developmental and adult plasticity share many common features, notable differences may be attributed to developmental cortical changes at multiple levels. These range from shifts in the molecular profiles of cortical neurons to changes in the spatiotemporal dynamics of network activity. In this review, we will discuss recent progress and remaining challenges in understanding adult visual plasticity, focusing on the primary visual cortex.     

The Optokinetic Response as a Quantitative Measure of Visual Acuity in Zebrafish

Zebrafish are a proven model for vision research, however many of the earlier methods generally focused on larval fish or demonstrated a simple response. More recently adult visual behavior in zebrafish has become of interest, but methods to measure specific responses are new coming. To address this gap, we set out to develop a methodology to repeatedly and accurately utilize the optokinetic response (OKR) to measure visual acuity in adult zebrafish. Here we show that the adult zebrafish''s visual acuity can be measured, including both binocular and monocular acuities. Because the fish is not harmed during the procedure, the visual acuity can be measured and compared over short or long periods of time. The visual acuity measurements described here can also be done quickly allowing for high throughput and for additional visual procedures if desired. This type of analysis is conducive to drug intervention studies or investigations of disease progression.     

老年猫视皮层细胞对刺激反应的对比敏感度下降伴随皮层内抑制作用减弱(英文)

对人类和动物的心理学研究证实,老年个体的视觉对比敏感度相对青年个体显著下降。为揭示其可能的神经机制,采用在体细胞外单细胞记录技术研究青、老年猫(Felis catus)初级视皮层(primary visual cortex,V1)细胞对不同视觉刺激对比度的调谐反应。结果显示,老年猫V1细胞对视觉刺激反应的平均对比敏感度比青年猫显著下降,这与灵长类报道的研究结果相一致,表明衰老影响视皮层细胞对视觉刺激反应的对比敏感度是灵长类和非灵长类哺乳动物中普遍存在的现象,并可能是介导老年性视觉对比敏感度下降的神经基础。另外,与青年猫相比,老年猫初级视皮层细胞对视觉刺激的反应性显著增强,信噪比下降,感受野显著增大,表明衰老导致的初级视皮层细胞对视觉刺激反应的对比敏感度下降伴随着皮层内抑制性作用减弱。     

Remodeling of the Nauplius Eye into the Adult Ocelli during Metamorphosis of the Barnacle, Balanus amphitrite hawaiiensis

The planktonic barnacle larva has a single median ocellus (nauplius eye), while the adult possesses two distinct sets of photoreceptors; a pair of lateral ocelli and a single median ocellus. The nauplius eye of the cypris larva of Balanus amphitrite hawaiiensis is composed of 14 visual cells grouped into three components (a pair of lateral components and a single ventral component) surrounding two centrally located pigment cells; each lateral component consists of 5 visual cells and the ventral component, 4 visual cells. In each component, the rhabdom is made up of apposing microvilli arising directly from the neighboring visual cell bodies.
During metamorphosis into the adult form, the three components of the median ocellus become separated. Each lateral component migrates laterally on the mantle and is remodeled into the adult lateral ocellus, losing two visual cells but gaining new pigment and tapetum cells in the process. The ventral component remains in the mid portion and becomes the adult median ocellus without fundamental modification in composition. The visual cells in both ocelli undergo a marked increase in volume and form many finger-like dendrites. Rhabdomes are made up of interdigitating microvilli arising from the the dendrite tips.     

Brain plasticity in the adult: modulation of function in amblyopia with rTMS

Amblyopia is a cortically based visual disorder caused by disruption of vision during a critical early developmental period. It is often thought to be a largely intractable problem in adult patients because of a lack of neuronal plasticity after this critical period [1]; however, recent advances have suggested that plasticity is still present in the adult amblyopic visual cortex [2-6]. Here, we present data showing that repetitive transcranial magnetic stimulation (rTMS) of the visual cortex can temporarily improve contrast sensitivity in the amblyopic visual cortex. The results indicate continued plasticity of the amblyopic visual system in adulthood and open the way for a potential new therapeutic approach to the treatment of amblyopia.     

成年斑马鱼OKR行为学分析

作为视功能检测和与视觉有关突变体筛选的方法, 眼动(Optokinetic response, OKR)和视动(Optomoter response, OMR)行为学是简单有效的视功能检测手段, 广泛用于幼年斑马鱼研究中, 而成年斑马鱼OKR的分析方法却很少有报道。文章介绍了成年斑马鱼眼动反应诱导方式, 以及使用模板匹配(Pattern match)的方法程序跟踪眼部运动, 实现了成年斑马鱼OKR的定量分析。使用该方法, 检测到斑马鱼双眼视觉区对OKR行为的产生具有一定的贡献作用, 并且成年斑马鱼单眼对运动光栅表现出一定的方向敏感性。同样的方法也可适用于幼年斑马鱼的OKR行为学分析。利用此方法初步检测到了钟基因period1b突变体幼鱼的OKR异常。     

Visual scanning by common marmosets (Callithrix jacchus): Functional aspects and the specialrrole of adult males

The rates of visual scanning and vocalizations were studied in a group of captive marmosets (Callinthrix jacchus) after the presentation of five different stimuli (artificial flower, playback of long calls, female/male conspecific, stuffed wild cat) in order to assess the function of visual scanning. Only the presentation of a stuffed cat induced a significant response. The adult males in particular increased their scanning rate and all adult individuals decreased their rate of vocalizations. The results indicate that visual scanning in marmosets is an appropriate measure of vigilance which seems to serve the function of predator detection and avoidance. The strong response of adult males suggests that they play a special role in predator detection.     

Elimination of inhibitory synapses is a major component of adult ocular dominance plasticity

During development, cortical plasticity is associated with the rearrangement of excitatory connections. While these connections become more stable with age, plasticity can still be induced in the adult cortex. Here we provide evidence that structural plasticity of?inhibitory synapses onto pyramidal neurons is?a major component of plasticity in the adult neocortex. In?vivo two-photon imaging was used to monitor the formation and elimination of fluorescently labeled inhibitory structures on pyramidal neurons. We find that ocular dominance plasticity in the adult visual cortex is associated with rapid inhibitory synapse loss, especially of those present on dendritic spines. This occurs not only with monocular deprivation but also with subsequent restoration of binocular vision. We propose that in the adult visual cortex the experience-induced loss of inhibition may effectively strengthen specific visual inputs with limited need for rearranging the excitatory circuitry.     

Sine Oculis Is a Homeobox Gene Required for Drosophila Visual System Development

The so(mda) (sine oculis-medusa) mutant is the result of a P element insertion at position 43C on the second chromosome. so(mda) causes aberrant development of the larval photoreceptor (Bolwig's) organ and the optic lobe primordium in the embryo. Later in development, adult photoreceptors fail to project axons into the optic ganglion. Consequently optic lobe development is aborted and photoreceptor cells show age-dependent retinal degeneration. The so gene was isolated and characterized. The gene encodes a homeodomain protein expressed in the optic lobe primordium and Bolwig's organ of embryos, in the developing adult visual system of larvae, and in photoreceptor cells and optic lobes of adults. In addition, the SO product is found at invagination sites during embryonic development: at the stomadeal invagination, the cephalic furrow, and at segmental boundaries. The mutant so(mda) allele causes severe reduction of SO embryonic expression but maintains adult visual system expression. Ubiquitous expression of the SO gene product in 4-8-hr embryos rescues all so(mda) mutant abnormalities, including the adult phenotypes. Thus, all deficits in adult visual system development and function result from failure to properly express the so gene during embryonic development. This analysis shows that the homeodomain containing SO gene product is involved in the specification of the larval and adult visual system development during embryogenesis.     

苯甲醛对果蝇视觉联想记忆的阻断

采用飞行模拟系统,以视觉模式为线索、热惩罚为负强化因子,对于在不同发育时期经受苯甲醛处理过的果蝇的视觉飞行定向条件化进行了检验。苯甲醛气味分别作用于果蝇幼虫和成虫阶段,将阻断果蝇成虫建立视觉联想记忆的能力;雌性果蝇在处女期对苯甲醛气味的接触,会阻断其子代建立视觉联想记忆,这种视觉联想记忆的能力可以通过对其子代连续３代的正常饲养而逐渐得到恢复。     

Eye size and the time of arrival of birds at garden feeding stations in winter

A nationwide volunteer survey was conducted to investigate the time at which common species of birds arrived at garden feeders in the morning during winter, and over 5,800 participants submitted observations. We examined the relationship between species’ eye size and their time of arrival at feeders, in order to investigate whether the time at which foraging was initiated was constrained by visual capability. There was a negative correlation between eye size and time of arrival at garden feeders across species, and this relationship remained significant when body mass was taken into account. This suggests that the time at which garden birds begin to forage on winter mornings may be limited by their visual capability at low light intensities.     

In vivo two-photon imaging reveals a role of arc in enhancing orientation specificity in visual cortex

Cortical representations of visual information are modified by an animal's visual experience. To investigate the mechanisms in mice, we replaced the coding part of the neural activity-regulated immediate early gene Arc with a GFP gene and repeatedly monitored visual experience-induced GFP expression in adult primary visual cortex by in vivo two-photon microscopy. In Arc-positive GFP heterozygous mice, the pattern of GFP-positive cells exhibited orientation specificity. Daily presentations of the same stimulus led to the reactivation of a progressively smaller population with greater reactivation reliability. This adaptation process was not affected by the lack of Arc in GFP homozygous mice. However, the number of GFP-positive cells with low orientation specificity was greater, and the average spike tuning curve was broader in the adult homozygous compared to heterozygous or wild-type mice. These results suggest a physiological function of Arc in enhancing the overall orientation specificity of visual cortical neurons during the post-eye-opening life of an animal.     

Adaptation to left-right reversed vision rapidly activates ipsilateral visual cortex in humans.

The brain mechanisms of adaptation to visual transposition are of increasing interest, not only for research on sensory-motor coordination, but also for neuropsychological rehabilitation. Sugita [Nature 380 (1996) 523] found that after adaptation to left-right reversed vision for one and a half months, monkey V1 neurons responded to stimuli presented not only in the contralateral visual field, but also in the ipsilateral visual field. To identify the underlying neuronal mechanisms of adaptation to visual transposition, we conducted fMRI and behavioral experiments for which four adult human subjects wore left-right reversing goggles for 35/39 days, and investigated: (1) whether ipsilateral V1 activation can be induced in human adult subjects; (2) if yes, when the ipsilateral activity starts, and what kind of behavioral/psychological changes occur accompanying the ipsilateral activity; (3) whether other visual cortices also show an ipsilateral activity change. The results of behavioral experiments showed that visuomotor coordinative function and internal representation of peripersonal space rapidly adapted to the left-right reversed vision within the first or second week. Accompanying these behavioral changes, we found that both primary (V1) and extrastriate (MT/MST) visual cortex in human adults responded to visual stimuli presented in the ipsilateral visual field. In addition, the ipsilateral activity started much sooner than the one and a half months, which had been expected from the monkey neurophysiological study. The results of the present study serve as physiological evidence of large-scale, cross-hemisphere, cerebral plasticity that exists even in adult human brain.     

Two visual systems in one eyestalk: The unusual optic lobe metamorphosis in the stomatopod Alima pacifica

The compound eyes of adult stomatopod crustaceans have two to six ommatidial rows at the equator, called the midband, that are often specialized for color and polarization vision. Beneath the retina, this midband specialization is represented as enlarged optic lobe lamina cartridges and a hernia‐like expansion in the medulla. We studied how the optic lobe transforms from the larvae, which possess typical crustacean larval compound eyes without a specialized midband, through metamorphosis into the adults with the midband in a two midband‐row species Alima pacifica. Using histological staining, immunolabeling, and 3D reconstruction, we show that the last‐stage stomatopod larvae possess double‐retina eyes, in which the developing adult visual system forms adjacent to, but separate from, the larval visual system. Beneath the two retinas, the optic lobe also contains two sets of optic neuropils, comprising of a larval lamina, medulla, and lobula, as well as an adult lamina, medulla, and lobula. The larval eye and all larval optic neuropils degenerate and disappear approximately a week after metamorphosis. In stomatopods, the unique adult visual system and all optic neuropils develop alongside the larval system in the eyestalk of last‐stage larvae, where two visual systems and two independent visual processing pathways coexist. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 78: 3–14, 2018     

Behavioral genetic approaches to visual system development and function in zebrafish

The zebrafish is a recent vertebrate model system that shows great potential for a genetic analysis of behavior. Early development is extraordinarily rapid, so that larvae already display a range of behaviors 5 days after fertilization. In particular the visual system develops precociously, supporting a number of visually mediated behaviors in the larva. This provides the opportunity to use these visually mediated behaviors to screen chemically mutagenized strains for defects in vision. Larval optokinetic and optomotor responses have already been successfully employed to screen for mutant strains with defects in the visual system. In the adult zebrafish a visually mediated escape response has proved useful for screening for dominant mutations of the visual system. Here, I summarize visually mediated behaviors of both larval and adult zebrafish and their applicability for genetic screens, and present, the approaches and results of visual behavior carried out to date.