Formation of visual evoked potentials and development of visually guided behavior in the Ficedula hypoleuca nestling

Age dynamics of evoked potentials (EPs) of Wulst area of the dorsal hyperstriatum (functional analogue of mammalian visual cortex) was investigated in 2-7 days old nestlings. EPs in response to light stimuli, with the duration and intensity imitating natural alimentary signals for 5-7 days-old nestlings, were recorded parallel with the behaviour. It was found that the development of the visual system in precocious nestlings became completed in postembryonal ontogenesis. The most essential changes in the parameters of visual EPs occur between 2.5 and 4 days of nest life. By the end of the 4-th day the EPs parameters resemble those of the definite EPs. During the same period the visually directed form of the alimentary behaviour appears for the first time. Both the visual EPs and the visually directed alimentary behaviour first appear in the ontogenesis in response to the second component of two-fold luminosity change--the natural signal of alimentary behaviour.     

CRE-mediated gene transcription in neocortical neuronal plasticity during the developmental critical period

Neuronal activity-dependent processes are believed to mediate the formation of synaptic connections during neocortical development, but the underlying intracellular mechanisms are not known. In the visual system, altering the pattern of visually driven neuronal activity by monocular deprivation induces cortical synaptic rearrangement during a postnatal developmental window, the critical period. Here, using transgenic mice carrying a CRE-lacZ reporter, we demonstrate that a calcium- and cAMP-regulated signaling pathway is activated following monocular deprivation. We find that monocular deprivation leads to an induction of CRE-mediated lacZ expression in the visual cortex preceding the onset of physiologic plasticity, and this induction is dramatically downregulated following the end of the critical period. These results suggest that CRE-dependent coordinate regulation of a network of genes may control physiologic plasticity during postnatal neocortical development.     

Foraging strategy and predator avoidance behaviour: an intraspecific approach

Relationships between predator avoidance behaviour (scanning and flocking) and foraging were studied in Calidris alpina, to test predictions regarding the effect of foraging techniques on such behaviours. The scanning hypothesis predicts that individuals with a tactile hunting technique and individuals with a visual hunting technique (both continuous searchers) do not differ in any variable related to scanning behaviour. The flocking hypothesis predicts that visually hunting individuals witl tend to form smaller flocks than tactile-foraging individuals. The two continuous feeding strategies did not differ among individuals in vigilance rate, nor in vigilance time or mean scan duration. However, with respect to flocking behaviour, visual foragers differed from tactile foragers in foraging flock size. The relationships between flocking behaviour and foraging strategy are discussed. The pattern found at the intraspecific level are the same as those found at interspecific level.     

地下啮齿动物视觉系统的形态结构与机能进化

感觉系统的适应进化机制一直是动物行为学研究的焦点。生活在特殊环境中的动物,其感觉系统在进化过程中表现出的显著差异更是引人注目。由于适应地下黑暗生活环境,地下啮齿动物感觉系统在各个组织水平都表现出进化和退化镶嵌的形态特征,其视觉系统表现得最为突出：视觉器官退化,有关图象分析结构、由视觉诱导产生行为反应的脑区及视觉投射严重退化,有关感受光周期的“非成像” 视觉通路结构高度发达。本文综述了地下啮齿动物视觉系统的结构、功能、进化与发育等方面的研究进展,旨在阐明地下啮齿动物视觉系统的特点,有助于开展地下啮齿动物视觉系统适应进化机制的研究。     

Foraging behaviour of the slender loris (Loris lydekkerianus lydekkerianus): implications for theories of primate origins

Members of the Order Primates are characterised by a wide overlap of visual fields or optic convergence. It has been proposed that exploitation of either insects or angiosperm products in the terminal branches of trees, and the corresponding complex, three-dimensional environment associated with these foraging strategies, account for visual convergence. Although slender lorises (Loris sp.) are the most visually convergent of all the primates, very little is known about their feeding ecology. This study, carried out over 10 (1/2) months in South India, examines the feeding behaviour of L. lydekkerianus lydekkerianus in relation to hypotheses regarding visual predation of insects. Of 1238 feeding observations, 96% were of animal prey. Lorises showed an equal and overwhelming preference for terminal and middle branch feeding, using the undergrowth and trunk rarely. The type of prey caught on terminal branches (Lepidoptera, Odonata, Homoptera) differed significantly from those caught on middle branches (Hymenoptera, Coleoptera). A two-handed catch accompanied by bipedal postures was used almost exclusively on terminal branches where mobile prey was caught, whereas the more common capture technique of one-handed grab was used more often on sturdy middle branches to obtain slow moving prey. Although prey was detected with senses other than vision, vision was the key sense used upon the final strike. This study strongly supports the notion that hunting for animal prey was a key ecological determinant in selecting for visual convergence early on in primate evolution. The extreme specialisations of slender lorises, however, suggest that early primates were not dedicated faunivores and lend further support to the emerging view that both insects and fruits were probably important components of the diet of basal primates, and that exploitation of fruits may account for other key primate traits.     

Effective visual working memory capacity: an emergent effect from the neural dynamics in an attractor network

The study of working memory capacity is of outmost importance in cognitive psychology as working memory is at the basis of general cognitive function. Although the working memory capacity limit has been thoroughly studied, its origin still remains a matter of strong debate. Only recently has the role of visual saliency in modulating working memory storage capacity been assessed experimentally and proved to provide valuable insights into working memory function. In the computational arena, attractor networks have successfully accounted for psychophysical and neurophysiological data in numerous working memory tasks given their ability to produce a sustained elevated firing rate during a delay period. Here we investigate the mechanisms underlying working memory capacity by means of a biophysically-realistic attractor network with spiking neurons while accounting for two recent experimental observations: 1) the presence of a visually salient item reduces the number of items that can be held in working memory, and 2) visually salient items are commonly kept in memory at the cost of not keeping as many non-salient items.OUR MODEL SUGGESTS THAT WORKING MEMORY CAPACITY IS DETERMINED BY TWO FUNDAMENTAL PROCESSES: encoding of visual items into working memory and maintenance of the encoded items upon their removal from the visual display. While maintenance critically depends on the constraints that lateral inhibition imposes to the mnemonic activity, encoding is limited by the ability of the stimulated neural assemblies to reach a sufficiently high level of excitation, a process governed by the dynamics of competition and cooperation among neuronal pools. Encoding is therefore contingent upon the visual working memory task and has led us to introduce the concept of effective working memory capacity (eWMC) in contrast to the maximal upper capacity limit only reached under ideal conditions.     

Some observations of Octopus joubini reared in an inland aquarium

Octopus joubini Robson were hatched and reared in a closed circulating sea-water system. Mortality was greatest during the period of hatching. The longest surviving octopus lived for 128 days—it had increased its weight × 5, from 0·04–0·19 g, mantle length × 3, from 3–9 mm, head width × 2, from 3–5 mm. Observations of (1) general behaviour, (2) feeding behaviour, (3) social behaviour of the newly hatched octopuses (0–3 days) and the three longest surviving octopuses (93–119 days) are described. In particular it was observed that the older octopuses would readily grasp and eat small live crabs when these were made to touch the suckers or arms. On no occasion did the attacks appear to be visually elicited. This result is discussed with reference to the memory and learning experiments using O. vulgaris. Possible reasons for the limited survival are also discussed.     

Visual flight control in naturalistic and artificial environments

Although the visual flight control strategies of flying insects have evolved to cope with the complexity of the natural world, studies investigating this behaviour have typically been performed indoors using simplified two-dimensional artificial visual stimuli. How well do the results from these studies reflect the natural behaviour of flying insects considering the radical differences in contrast, spatial composition, colour and dimensionality between these visual environments? Here, we aim to answer this question by investigating the effect of three- and two-dimensional naturalistic and artificial scenes on bumblebee flight control in an outdoor setting and compare the results with those of similar experiments performed in an indoor setting. In particular, we focus on investigating the effect of axial (front-to-back) visual motion cues on ground speed and centring behaviour. Our results suggest that, in general, ground speed control and centring behaviour in bumblebees is not affected by whether the visual scene is two- or three dimensional, naturalistic or artificial, or whether the experiment is conducted indoors or outdoors. The only effect that we observe between naturalistic and artificial scenes on flight control is that when the visual scene is three-dimensional and the visual information on the floor is minimised, bumblebees fly further from the midline of the tunnel. The findings presented here have implications not only for understanding the mechanisms of visual flight control in bumblebees, but also for the results of past and future investigations into visually guided flight control in other insects.     

Restoration of the behavioral reactions of Rana esculenta frogs during regeneration of visual nerve fibers]

After sectioning the optic nerve, various forms of visually guided behaviour in the frog R. esculenta recover unevenly. Within 16--20 days, the onset of reactions was observed which are associated with perception of relatively large unmoving objects during active locomotion of animals (1); within 55 days -- avoidance reactions (2); within 90 days -- feeling reactions (3) were formed. In electrophysiological experiments it was shown that axons of the ganglionic retinal cells from various classes form contacts with the tectum also at different periods. The data obtained confirm the significance of specialized "canalization" of the retino--central nervous systems of transmission and evaluation of visual information for organization of separate forms of visually monitored behaviour in frogs.     

The importance of hormonal circadian rhythms in daily feeding patterns: An illustration with simulated pigs

The interaction between hormonal circadian rhythms and feeding behaviour is not well understood. This study aimed to deepen our understanding of mechanisms underlying circadian feeding behaviour in animals, using pigs, Sus scrofa, as a case study. Pigs show an alternans feeding pattern, that is, a small peak of feed intake at the beginning of the day and a larger peak at the end of the day. We simulated the feeding behaviour of pigs over a 24 h period. The simulation model contained mechanisms that regulate feeding behaviour of animals, including: processing of feed in the gastrointestinal tract, fluctuation in energy balance, circadian rhythms of melatonin and cortisol and motivational decision-making. From the interactions between these various processes, feeding patterns (e.g. feed intake, meal frequency, feeding rate) emerge. These feeding patterns, as well as patterns for the underlying mechanisms (e.g. energy expenditure), fitted empirical data well, indicating that our model contains relevant mechanisms. The circadian rhythms of cortisol and melatonin explained the alternans pattern of feeding in pigs. Additionally, the timing and amplitude of cortisol peaks affected the diurnal and nocturnal peaks in feed intake. Furthermore, our results suggest that circadian rhythms of other hormones, such as leptin and ghrelin, are less important in circadian regulation of feeding behaviour than previously thought. These results are relevant to animal species with a metabolic and endocrine system similar to that of pigs, such as humans. Moreover, the modelling approach to understand feeding behaviour can be applied to other animal species.     

Approach behaviour and embryonic visual experience in chicks: studies on the effect of rate of visual flicker

It has been demonstrated that visual stimulation during the latter part of embryonic development will have its effect on subsequent approach behaviour in the chick. Stimulation here had been of a non-specific type, i.e. mere presence or absence of illumination. This study was conducted to see how much specific stimulation like visual flicker applied during the latter part of embryonic development would affect approach to the same or similar stimuli. In experiment 1 extremely slow flicker (6·6 and 20 c/min) was applied to the eggs under incubation. Treatment groups were tested for approach on flickering and non-flickering stimuli after hatching. Results show that exposing the eggs to flicker has an effect on approach behaviour. Groups that received flicker at a rate of 20 c/min approach faster than those which received flicker at the rate of 6·6 c/min. A significant improvement over trials was only found in the group which received flicker of 20 c/min during the embryonic period. In experiment 2 which employed a range of very much faster flicker no significant treatment effects became apparent. These results suggest that visual flicker as embryonic stimulation is effective in priming the embryo to yield better approach performance after hatching. Results of experiment 2 indicate that the effect of flicker as embryonic stimulation may operate over a certain range in affecting subsequent approach performance.     

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200...     

Kind to kin: weak interference competition among white stork Ciconia ciconia broodmates

Altricial nestlings in structured families show a diverse array of behavioural mechanisms to compete for food, ranging from signalling scrambles to aggressive interference. Rates of filial infanticide are moderately high in white storks. It has been hypothesized that this unusual behaviour is an adaptive parental response to the absence of efficient mechanisms of brood reduction (aggression or direct physical interference) by nestlings. To test this latter assumption, we analyzed video recordings of 41 complete feeding episodes at 32 broods during the first half of the nestling period, when nestlings complete 90% of growth and chick mortality and size asymmetries are highest. Parents delivered food to all nestlings simultaneously by regurgitating on the nest floor. No direct (bill to bill) feeding was recorded. Senior nestlings were never observed to limit their junior nestlings from eating food, either by aggression or physical interference. Experimental feeding tests revealed that heavier nestlings handled prey items more efficiently and ate food at a higher speed. The high degree of tolerance shown by senior nestlings is unusual among birds with similar ecological and phylogenetic affinities, such as herons. Tolerance by seniors cannot be easily explained by absence of parental favouritism or proximate factors known to affect the occurrence of sibling aggression in other species (rate of food transfer, brood size, hatching asynchrony or length of nestling period).     

The neural selection and control of saccades by the frontal eye field

Recent research has provided new insights into the neural processes that select the target for and control the production of a shift of gaze. Being a key node in the network that subserves visual processing and saccade production, the frontal eye field (FEF) has been an effective area in which to monitor these processes. Certain neurons in the FEF signal the location of conspicuous or meaningful stimuli that may be the targets for saccades. Other neurons control whether and when the gaze shifts. The existence of distinct neural processes for visual selection and saccade production is necessary to explain the flexibility of visually guided behaviour.     

Ten days of darkness causes temporary blindness during an early critical period in felines

Extended periods of darkness have long been used to study how the mammalian visual system develops in the absence of any instruction from vision. Because of the relative ease of implementation of darkness as a means to eliminate visually driven neural activity, it has usually been imposed earlier in life and for much longer periods than was the case for other manipulations of the early visual input used for study of their influences on visual system development. Recently, it was shown that following a very brief (10 days) period of darkness imposed at five weeks of age, kittens emerged blind. Although vision as assessed by measurements of visual acuity eventually recovered, the time course was very slow as it took seven weeks for visual acuity to attain normal levels. Here, we document the critical period of this remarkable vulnerability to the effects of short periods of darkness by imposing 10 days of darkness on nine normal kittens at progressively later ages. Results indicate that the period of susceptibility to darkness extends only to about 10 weeks of age, which is substantially shorter than the critical period for the effects of monocular deprivation in the primary visual cortex, which extends beyond six months of age.     

Brown planthopper (N. lugens Stal) feeding behaviour on rice germplasm as an indicator of resistance

Background

The brown planthopper (BPH) Nilaparvata lugens (Stal) is a serious pest of rice in Asia. Development of novel control strategies can be facilitated by comparison of BPH feeding behaviour on varieties exhibiting natural genetic variation, and then elucidation of the underlying mechanisms of resistance.

Methodology/Principal Findings

BPH feeding behaviour was compared on 12 rice varieties over a 12 h period using the electrical penetration graph (EPG) and honeydew clocks. Seven feeding behaviours (waveforms) were identified and could be classified into two phases. The first phase involved patterns of sieve element location including non penetration (NP), pathway (N1+N2+N3), xylem (N5) [21] and two new feeding waveforms, derailed stylet mechanics (N6) and cell penetration (N7). The second feeding phase consisted of salivation into the sieve element (N4-a) and sieve element sap ingestion (N4-b). Production of honeydew drops correlated with N4-b waveform patterns providing independent confirmation of this feeding behaviour.

Conclusions/Significance

Overall variation in feeding behaviour was highly correlated with previously published field resistance or susceptibility of the different rice varieties: BPH produced lower numbers of honeydew drops and had a shorter period of phloem feeding on resistant rice varieties, but there was no significant difference in the time to the first salivation (N4-b). These qualitative differences in behaviour suggest that resistance is caused by differences in sustained phloem ingestion, not by phloem location. Cluster analysis of the feeding and honeydew data split the 12 rice varieties into three groups: susceptible, moderately resistant and highly resistant. The screening methods that we have described uncover novel aspects of the resistance mechanism (or mechanisms) of rice to BPH and will in combination with molecular approaches allow identification and development of new control strategies.     

Stress, neuropeptides, and feeding behavior: a comparative perspective

Stress inhibits feeding behavior in all vertebrates. Data frommammals suggest an important role for hypothalamic neuropeptides,in particular the melanocortins and corticotropin-releasinghormone (CRH)-like peptides, in mediating stress-induced inhibitionof feeding. The effects of CRH on food intake are evolutionarilyancient, as this peptide inhibits feeding in fishes, birds,and mammals. The effects of melanocortins on food intake havenot been as extensively studied, but available evidence suggeststhat the anorexic role of neuronal melanocortins has been conserved.Although there is evidence that CRH and the melanocortins influencehypothalamic circuitry controlling food intake, these peptidesmay have a more primitive role in modulating visuomotor pathwaysinvolved in the recognition and acquisition of food. Stressrapidly reduces visually guided prey-catching behavior in toads,an effect that can be mimicked by administration of CRH, whilecorticosterone and isoproterenol are without effect. Melanocortinsalso reduce prey-oriented turning movements and, in addition,facilitate the acquisition of habituation to a moving prey item.The effects of these neuropeptides are rapid, occurring within30 min after administration. Thus, changes in neuroendocrinestatus during stress may dramatically influence the efficacywith which visual stimuli release feeding behavior. By modulatingvisuomotor processing these neuropeptides may help animals makeappropriate behavioral decisions during stress.     

Competition between perch (Perca fluviatilis) and ruffe (Gymnocephalus cernuus): the advantage of turning night into day

1. The outcome of interspecific competition for food resources depends both on the competitors’ sensory abilities and on environmental conditions. In laboratory experiments we tested the influence of daylight and darkness on feeding behaviour and specific growth rate (SGR) of two species with different sensory abilities. 2. We used perch (Perca fluviatilis) as a visually orientated, and ruffe (Gymnocephalus cernuus) as a mechano‐sensory oriented predator and tested their growth rates and behaviour under conditions of interspecific and intraspecific competition. Three different foraging conditions were used: food supplied (i) only during the day, (ii) only during the night or (iii) during both day and night. 3. In perch neither SGR nor feeding behaviour were influenced substantially by interspecific competition during daylight. During darkness their foraging behaviour changed markedly and their access to the food source as well as their SGR were negatively affected by the presence of ruffe. 4. Ruffe's foraging behaviour did not change during either day or night with interspecific competition. During the night ruffe's SGR was higher with interspecific competition, probably because of a release from intraspecific competition and the competitive inferiority of perch during the night. 5. Because of its seonsory abilities ruffe feeds predominantly at night, thereby reducing competitive interference from perch.     

What blindness can tell us about seeing again: merging neuroplasticity and neuroprostheses

Significant progress has been made in the development of visual neuroprostheses to restore vision in blind individuals. Appropriate delivery of electrical stimulation to intact visual structures can evoke patterned sensations of light in those who have been blind for many years. However, success in developing functional visual prostheses requires an understanding of how to communicate effectively with the visually deprived brain in order to merge what is perceived visually with what is generated electrically.     

Developmental regulation of spine and filopodial motility in primary visual cortex: reduced effects of activity and sensory deprivation

Dendritic protrusions are highly motile during postnatal development. Although spine morphological plasticity could be associated with synaptic plasticity, the function of rapid spine/filopodial motility is still unknown. To investigate the role of spine motility in the development of the visual cortex and its relation with critical periods, we used two-photon imaging of neurons from layers receiving visual input in developing mouse primary visual cortex and compared motility between control and visually deprived animals. Spine and filopodia motility was prominent during early synaptogenesis (P11-P13) but greatly decreased after P15. This "switch" was coincident with a 2.5-fold increase in protrusion density and spine formation. Spine motility was not regulated during the critical period for monocular deprivation (P19-P34). Moreover, delaying the critical period by dark rearing did not delay the normal developmental decrease of spine motility, but caused a modest further reduction in motility at P28-P35. Dark rearing and enucleation also mildly reduced spine motility before eye opening and dark rearing reduced the proportion of filopodia. We conclude that (1) rapid spine motility is not related to critical period plasticity, but is likely to play a role in early synaptogenesis, and (2) neuronal activity stimulates spine motility during synaptogenesis and promotes the appearance of dendritic filopodia.