Adaptability of the receptive fields of neurons of the posterior temporal cortex and their sensitivity to parameters of photic stimulation in the cat

Study of receptive fields (RFs) of neurones in the postero-temporal cortex (field 21) of alert cat at three levels of visual adaptation: light photopic, light mesopic and practically dark or extremely low scotopic adaptations--revealed invariance of the most part of the studied RFs to the level of visual adaptation. Reorganization of RFs, connected with change of background luminosity were observed only in 12% of visually activated neurones. Significant reduction of responses to optic stimulation is shown at increase of the level of luminosity in 75% of neurones, revealing adaptive reorganizations. It is suggested that these reorganizations may take place in analogy with neurones of the field 17 on account of different involvement of intracortical inhibitory mechanisms (and, probably, not only in the postero-temporal cortex, but also in structures which precede it in visual hierarchy). Study of neurones sensitivity in the field 21 to parameters of optic stimulation revealed their considerable invariance to the length and orientation of the optic stimulus moving through the RF (60% of cases). Testing of RF by a rhombic optic stimulus did not change neuronal reactions, the form and dimensions of RF did not significantly change.     

四指马鲅视网膜早期发育的组织学研究

本文采用石蜡连续切片技术、H.E染色和显微测量法,对四指马鲅(Eleutheronema tetradactylum)早期发育过程中视网膜的结构、分化和形成过程以及视觉特性进行了研究。结果显示,受精后8 h54 min,视杯已经形成。初孵仔鱼视网膜没有分化。2日龄仔鱼可以清晰的辨认出色素上皮层、外核层、内核层和神经节细胞层。3日龄仔鱼内核层已经分化出水平细胞、双极细胞和无长突细胞。4日龄仔鱼视网膜10层结构完整。9日龄至14日龄,外核层胞核数目与神经节细胞数目的比值增大,视网膜会聚程度升高,是该鱼视觉特性发生变化的过渡期,这与其从浮游到浅海中下层和泥沙质海底活动的生态迁移相适应。在生长发育的早期阶段,其视网膜内核层水平细胞仅有1到2层,属于感光系统不甚发达的类型。该鱼在仔鱼浮游生活阶段,视敏度较高,视觉对其行为和摄食活动具有重要作用,适应生活于光照较充足的环境中,转入浅海中下层和泥沙质海底后,光敏度和视敏度均较差,视觉在其行为和摄食活动中不具有主要作用。     

Visual fields of butterfly interneurons

A relatively novel and precise technique was employed for the detailed plotting of the extent and nature of the fields of fibres in the visual pathway of 11 species of butterflies. For these experiments, a moving, flashing spot of light on the face of an oscilloscope was used as a photostimulator. Some 160 fibres were analysed by this technique. In many cases, the response to light adaptation was observed. Unlike many previous reports, units were found to have exceedingly complex fields, not easily described.Two major categories of optic lobe units were detected. These included: (1) fibres with large diffuse fields with many ‘holes’ and channels within their substance, which were markedly altered by light adaptation, and (2) relatively uncommon, smaller visual fields, which were somewhat more uniform in responsiveness.Four categories of visual fields were recorded in the protocerebrum. These included: (1) units with a large, diffuse field with a sharp boundary corresponding to the horizon, (2) binocular fields with much, little, or no overlap, (3) large diffuse fields, not unlike those discovered in the optic lobe, and (4) fibres demonstrating an inhibitory influence and resulting decrease in the size of the visual field as a result of contralateral stimulation.     

Functional characteristics of visual cortical neurons during local photic stimulation of their receptive fields in cats

A group of functional characteristics of 103 neurons in visual cortical area 17 was investigated in acute experiments on curarized, light-adapted cats during a change in various parameters of the local photic stimuli. The average threshold sensitivity of the neuron population was 32 dB (0.052 nit), the sharpness of orientation tuning was 37°, the critical summation time was 57 msec, and the reactivity recovery time 190 msec. Photic sensitivity was lower during light adaptation than during dark adaptation, orientation selectivity of the neurons was increased, temporal summation was lengthened, and the time required by the neuron to recovery from after-inhibition was shortened. Several properties of the cortical neurons depended on the accentricity of their receptive fields: Cells with centrally localized receptive fields on average had lower thresholds and shorter summation time and they recovered their reactivity more quickly; their activity was of a higher frequency and they more often generated short phasic discharges than neurons with receptive fields in the peripheral part of the visual field. The mechanisms responsible for changes in the properties of neurons in the central and peripheral visual channels during dark and light adaptation are discussed. The presence of several inhibitory subsystems in the cortex regulating unit activity in the primary visual projection area is postulated.     

Characteristics of the receptive fields of neurons of the posterior temporal area of the cortex of the cat

In records of 219 single units in the posterotemporal cortical area (field 21) of nonanaesthetized cats, 51% of cells reacted to visual stimulation. The neurones had receptive fields (RFs) with central (0-10 degrees) or peripheral (10-52 degrees) localization in the visual field, their size increasing with eccentricity. Carting of RFs by a light bar scanning the visual field revealed a considerable variability of RFs shape, size and orientation in different cells. RFs sizes of the majority of recorded cells (100-1000 grad) were very large and exceeded the size of large RFs of neurones in the primary projection zone of the visual cortex.     

Relationship between level of vigilance and changes in the receptive fields of the cat visual cortex]

The activity of 118 neurones of the primary visual cortex (17th field) was studied in unanesthetized cats, immobilized with d-tubocurarine, in a state of calm wakefulness and in strained attention, alarm. The strained attention was elicited by an air-puff directed to the corner of the closed eye, not used for the photic stimulation. Considerable rearrangments of the receptive field of neurones (94%) were observed in the state of strained attention. In the majority of the studied cortical cells (75%) during 10-30 minutes the excitatory centres of their receptive fields became narrower while their inhibitory periphery widened; in the cells with the inhibitory centres of the receptive fields they were larger in 80% of the cases. It is shown that with dark, mesopic and scotopic adaptation the major characteristics of the changes in the receptive fields remain unaltered. It is assumed that these effects have a behavioural value for the organism, because the created rise in the level of alertness is accompanied by a sharpening of the receptive fields, i.e. by a greater ability to a fine analysis and recognition of visual images.     

Fixation-sensitive areas in the eyes of the walking fly,Calliphora erythrocephala

In Calliphora erythrocephala the visual fixation behaviour in one-eyed flies and partial blinded flies has been investigated. One-eyed flies show approximately the same stripe and edge fixation response as intact flies. Elimination of the frontal eye parts including the binocular field of vision does not effect the visual stripe fixation. On the other hand, if only the frontal areas of both eyes including the binocular field of vision are left open, no preferential direction can be observed (Fig. 1–3). The results imply the existence of a fixation-sensitive area of the eye located outside the binocular field of vision.     

Plasticity contributes to a fine‐scale depth gradient in sticklebacks’ visual system

The light environment influences an animal's ability to forage, evade predators, and find mates, and consequently is known to drive local adaptation of visual systems. However, the light environment may also vary over fine spatial scales at which genetic adaptation is difficult. For instance, in aquatic systems, the available wavelengths of light change over a few metres depth. Do animals plastically adjust their visual system to such small‐scale environmental light variation? Here, we show that in three‐spine stickleback (Gasterosteus aculeatus), opsin gene expression (an important determinant of colour vision) changes over a 2‐m vertical gradient in nest depth. By experimentally altering the light environment using light filters to cover enclosures in a lake, we found that opsin expression can be adjusted on a short time frame (weeks) in response to the local light environment. This is to our knowledge the smallest spatial scale on which visual adjustments through opsin expression have been recorded in a natural setting along a continuously changing light environment.     

The three-dimensional optomotor torque system ofDrosophila melanogaster

Summary The well known optomotor yaw torque response in flies is part of a 3-dimensional system. Optomotor responses around the longitudinal and transversal body axes (roll and pitch) with strinkingly similar properties to the optomotor yaw response are described here forDrosophila melanogaster. Stimulated by visual motion from a striped drum rotating around an axis aligned with the measuring axis, a fly responds with torque of the same polarity as that of the rotation of the pattern. In this stimulus situation the optomotor responses for yaw, pitch and roll torque have about the same amplitudes and dynamic properties (Fig. 2). Pronounced negative responses are measured with periodic gratings of low pattern wavelengths due to geometrical interference (Fig. 3). The responses depend upon the contrast frequency rather than the angular velocity of the pattern (Fig. 4). Like the optomotor yaw response, roll and pitch responses can be elicited by small field motion in most parts of the visual field; only for motion below and behind the fly roll and pitch responses have low sensitivity.The mutantoptomotor-blind ^H31 (omb ^H31) in which the giant neurones of the lobula plate are missing or severely reduced, is impaired in all 3 optomotor torque responses (Fig. 5) whereas other visual responses like the optomotor lift/thrust response and the landing response (elicited by horizontal front-to-back motion) are not affected (Heisenberg et al. 1978).We propose that the lobula plate giant neurons mediate optomotor torque responses and that the VS-cells in particular are involved in roll and pitch but not in lift/thrust control. This hypothesis accommodates various electrophysiological and anatomical observations about these neurons in large flies.Abbreviation EMD elementary movement detector     

Receptive fields of visual cortical neurons during changes in parameters of photic stimulation in cats

Spatial excitability contours in receptive fields of visual cortical neurons during changes in the physical and physiological parameters of photic stimulation were investigated in acute experiments on immobilized cats under conditions of dark, mesopic, and low photopic adaptation. With the change from dark to low mesopic adaptation the shape and size of the receptive fields detected by testing with flashes of constant intensity are unchanged, but with the transition to low photopic adaptation the receptive field becomes long and very narrow in 72% of cases, and the acuity of its orientational and directional tuning becomes much sharper. Against an unchanged background illumination, loss of brightness of the test light slit leads to narrowing of the measurable receptive field. Excitability contours of the receptive field estimated on the basis of absolute threshold of the cell response and level of intensity necessary to obtain the same number of spikes in the response become much narrower as the threshold criterion rises and during dark adaptation. Reactivity contours of the receptive field in response to stimulation of physiologically equal intensities (equal to the increase in threshold) under conditions of photopic adaptation also are much narrower than reactivity contours under conditions of dark adaptation. Evaluation of receptive fields with allowance for the possible contribution of effects of light scatter on the screen and in the ocular media showed that in most cases their size cannot be explained by these phenomena.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 12, No. 2, pp. 115–123, March–April, 1980.     

The dynamics of the activating and inhibitory types of cortical neuron synchronization during the realization of a defensive reflex and internal inhibition

In the visual and sensorimotor areas of the neocortex and in the hippocampus of alert nonimmobilized rabbits, in response to combinations of light flashes with electrocutaneous limb stimulation an increase was observed of synchronization in the activity of the near-by neurones by activation by inhibitory type (coincidence of the presence and absence of impulse activity). In response to flashes against the light background--conditioned inhibitor--in the visual cortex synchronization of neurones increased by inhibitory type, and in the sensorimotor cortex and hippocampus changes of synchronization appeared, similar to the action of pain reinforcement but considerably weaker. The increase of synchronization by the activation type took place mainly in the neurones pairs with unidirected increase of impulses frequency and by the inhibitory one--with its decrease. Along with this, in a considerable part of neurones pairs both changes of synchronization appeared at the impulses frequency changes of different direction.     

Theory and Measurement of the buffer value of bicarbonate in saliva

All known sensory systems have at least two components, which will tend to counteract and compensate for each other. For light, the sensitivity of the eye is some function of the area of the pupil (aperture of the iris diaphragm) and the relative amount of unbleached pigment (visual purple or rhodopsin). An intermittent light will result in a constriction of the pupil and a bleaching of the pigment. The interaction between these two processes results in a total response with components of both a logarithmic and an arithmetic function of the light intensity and duration. The sensitivity of the eye is a linear function of the logarithm of the intensity of incident light (Weber's and Fechner's laws, Fig. 6), yet a rapidly oscillating light causes approximately the same sensitivity as a steady light of the same intensity as the arithmetic average of the fluctuating light (Talbot's and Bloch's laws, Fig. 9c).     

Human Postural Responses to Vibratory Stimulation of Calf Muscles under Conditions of Visual Inversion

The authors studied postural responses to bilateral vibratory stimulation (70 Hz, 1 mm, 2 s) of the calf triceps proprioceptors or anterior tibial muscles. Anteroposterior body tilts evoked by vibration were recorded by stabilography. The authors compared the values of postural responses under various conditions of visual control, namely, with normal vision, eyes closed, right–left inversion of the visual space by prismatic spectacles, central vision, and diffuse light. Visual inversion influenced the subjects' proprioceptive postural responses. The amplitude of vibration-evoked shifts of the feet pressure center was minimal with eyes open and significantly increased with eyes closed and inverted vision. Postural responses with visual inversion were significantly stronger than with eyes closed. Since inversion spectacles enabled a subject to see only the central part of the visual field (20°), the reference point was the condition of central vision, i.e., spectacles with same visual angle and without prisms. Postural responses were significantly weaker under these conditions than with visual inversion and eyes closed. Visual field inversion by prismatic spectacles made it impossible to use visual information for stabilizing the human upright posture and, moreover, destabized it. True, this holds only for a randomized experimental protocol, which prevents adaptation to prisms.     

夜行性昆虫微光视觉行为及其视觉适应机制

作为昆虫种群的重要组成部分,夜行性昆虫成功进化出了与其生存环境相适应的感觉机制,普遍认为夜行性昆虫主要依靠嗅觉和机械性感受等来探索环境,其视觉器官发生了退化或功能丧失。近年来,随着红外夜视、视网膜电位(electroretinogram, ERG)和视觉神经等生物新技术的应用,昆虫视觉生态学研究出现了突破性进展,自2002年以来陆续发现蛾类、蜜蜂和蜣螂等夜行性昆虫进化出了非凡的微光视觉(dim-light vision)能力,在夜晚(光照强度低于0.3 lx)依然可以如同在明亮的白天一样清晰、准确地感知目标物体特定的视觉特性,如明暗、颜色、形状、大小、对比度、偏振光和运动状态等,展现出视觉调控夜行性昆虫行为活动的巨大潜力。此外,这些夜行性昆虫复眼瞳孔、小眼焦距、视杆和色素颗粒等方面进化出了一些相应的形态生理特征,以提高光学灵敏度适应夜间微光环境。鉴于夜行性昆虫微光视觉行为及其视觉适应机制的研究尚处于起步阶段,仅见于少数访花昆虫或粪食性昆虫,建议加强以下几个方面的研究：(1)重大夜行性农业害虫的微光视觉及其应用的研究;(2)非典型重叠复眼的光学结构特征及其应对微光环境的适应机制研究;(3)夜行性昆虫响应微光环境的视觉适应机制研究;(4)基于夜行性昆虫微光视觉行为研发新型害虫防控技术。     

Changes in the configuration of conditioned reactions of visual cortex neurons during changes in reinforcement parameters]

In order to study the influences of controlled changes of defensive integration on the activity of visual cortical units their responses to a conditioned light flash and electric cutaneous stimulation with a 600 msec interval between them were recorded in experiments on alert rabbits. It has been shown that in a third of the neurones the types of reaction to light flashes and electric stimuli coincide. The changes in parameters of the reinforcing shock led to a changed response of most cells to the conditioned photic stimulus and electric stimulation. The changes may have affected units which produce any activation phase, including cells with activity characteristic of detectory ("simple" and "complex") visual neurones. The data obtained suggest that the special function of the visual cortex is used in different ways in systemic mechanisms of conditioned and unconditioned defensive acts and that the integrated system of a behavioral act exerts control both on the use of the unit in a certain systemic process and on its receptive field.     

Physiological and anatomical properties of optical input-fibres to the mushroom body in the bee brain

More than 150 neurones in the nushroom body area of the bee brain were recorded and stained intracellularly with either Lucifer Yellow or Cobalt-Hexamminochloride (III). Among them 12 neurones have been characterized physiologically and anatomically which connect the medulla and the lobula with the mushroom bodies. All neurones responded to stationary or moving light stimuli exclusively. Movement-sensitive neurones were all direction-selective. Excitatory and inhibitory responses occurred in response to moving stripe patterns in the preferred and null directions respectively. Anatomically, the neurones could be clearly distinguished as belonging to three types depending on their input features in the optic lobes: (a) Neurones with small dendritic fields (up to 100 μm) in the lobula; (b) Neurones with large dendritic fields (up to 400 μm) in the lobula; (c) Neurones with small dendritic fields (up to 100 μm) in the medulla. The axons of all three cell types run from the optic lobes on each side to the outer ring tract around the pedunculus-calyx-transition and arborize in the collar region of the ipsilateral calyces. Additional branches invading the basal ring of the calyces had been observed; endings in the lip region were not found. The endings in the calyces often exhibited bleb-like specializations indicating their presynaptic nature. Retinotopic organization of the optic inputs into the calyces could not be proven. The results are compared with the characteristics of multimodal mushroom body output fibres and are discussed in context with the complex information processing and storage functions ascribed to the mushroom bodies.     

Phenotype–environment matching in sand fleas

Camouflage is perhaps the most widespread anti-predator strategy in nature, found in numerous animal groups. A long-standing prediction is that individuals should have camouflage tuned to the visual backgrounds where they live. However, while several studies have demonstrated phenotype–environment associations, few have directly shown that this confers an improvement in camouflage, particularly with respect to predator vision. Here, we show that an intertidal crustacean, the sand flea (Hippa testudinaria), has coloration tuned to the different substrates on which it occurs when viewed by potential avian predators. Individual sand fleas from a small, oceanic island (Ascension) matched the colour and luminance of their own beaches more closely than neighbouring beaches to a model of avian vision. Based on past work, this phenotype–environment matching is likely to be driven through ontogenetic changes rather than genetic adaptation. Our work provides some of the first direct evidence that animal coloration is tuned to provide camouflage to prospective predators against a range of visual backgrounds, in a population of animals occurring over a small geographical range.     

Conjugation of unit activity in the visual and sensomotor areas of the rabbit neocortex during a conditioned reflex to sound and light

Conjugation of unit activity in the visual and sensorimotor neocortical areas was studied by means of histograms of cross- and autocorrelation in rabbits with conditioned reflex to light (1st group) and sound (2nd group). Relative number of neurones pairs acting in correlation in the areas remote from each other, in intersignal intervals both before and after stimuli did not differ in the 1st and 2nd groups. At the same time delays in neuronal discharges in one area after the other were different. In the 1st group animals there was a predominance of the number of visual area neurones discharging after sensorimotor with a delay up to 125 ms, in comparison with the number of sensorimotor area neurones discharging after the visual one. In the 2nd group rabbits the number of visual area neurones with such a delay of discharges after sensorimotor was less and, on the contrary, a predominance of sensorimotor area neurones was observed discharging after the visual one. The obtained results allow to suggest that neurones of the visual and sensorimotor neocortex areas form a single functional system in cases when conditioned and unconditioned stimuli are addressed to these areas and when only one of the studied areas is the projection zone for the combined stimuli. Organization of the neurones activity in systems in these two cases is different.     

Illumination of upper and middle visual fields produces equivalent suppression of melatonin in older volunteers

Bright light treatment has become an important method of treating depression and circadian rhythm sleep disorders. The efficacy of bright light treatment may be dependent upon the position of the light-source, as it determines the relative illumination in each portion of the visual field. This study compared illumination of upper and middle visual fields to determine whether melatonin suppression is different or equivalent. Thirteen older volunteers received three illumination conditions in counterbalanced orders: 1000 lux in the upper visual field, 1000 lux in the middle visual field, or dim diffuse illumination < 5 lux. A four-choice reaction time task was performed during tests to ensure eye direction and illumination of the intended portion of the visual field. Illumination in the upper and middle visual fields significantly suppressed melatonin compared to < 5 lux (p < 0.001). Melatonin suppression was not significantly different with upper or middle field illumination. These results indicate that bright light treatments placed above the eye level might be as effective as those requiring patients to look directly at the light source. Clinical comparative testing would be valuable. In addition, this study demonstrates that significant suppression of melatonin may be achieved through the use of bright light in healthy older volunteers.     

Multimodal interneurones in the polyclad flatworm,Alloeoplana californica

Summary Two morphological types of interneurones were found in the brainof Alloeoplana californica (Figs. 1, 2). Both respond to water vibration and to light offset (Fig. 3). These responses are blocked by Mg⁺⁺ or Cd⁺⁺ (Fig. 4), and habituate to repetitive stimuli (Figs. 6, 10). Even when the light response is habituated, light offset will dishabituate the vibration response (Figs. 7, 10); no other regime tested produced dishabituation of either response. These neurones receive higher-order sensory input, and make subthreshold excitatory synapses on motor pathways; intracellular tetraethylammonium lengthens the time course of the spikes (Fig. 5), and each such spike elicits a contraction in the anterior margin of the animal. We believe that they form part of the neuronal circuitry underlying arousal.Abbreviation TEA tetraethylammonium