Cognitive components of color vision in honey bees: how conditioning variables modulate color learning and discrimination

Since the demonstration of color vision in honey bees 100 years ago by Karl von Frisch, appetitive conditioning to color targets has been used as the principal way to access behavioral aspects of bee color vision. Yet, analyses on how conditioning parameters affect color perception remained scarce. Conclusions on bee color vision have often been made without referring them to the experimental context in which they were obtained, and thus presented as absolute facts instead of realizing that subtle variations in conditioning procedures might yield different results. Here, we review evidence showing that color learning and discrimination in bees are not governed by immutable properties of their visual system, but depend on how the insects are trained and thus learn a task. The use of absolute or differential conditioning protocols, the presence of aversive reinforcement in differential conditioning and the degrees of freedom of motor components determine dramatic variations in color discrimination. We, thus, suggest top-down attentional modulation of color vision to explain the changes in color learning and discrimination reviewed here. We discuss the possible neural mechanisms of this modulation and conclude that color vision experiments require a careful consideration of how training parameters shape behavioral responses.     

Nonlinear regression methods in design of experiments and mathematical modelling. Applications to the analysis of the steady-state kinetics of glutathione reductase.

A branching reaction pathway involving a ping pong and a sequential loop has been proposed for glutathione reductase (Biochem. Biophys. Res. Commun. 53 (1973) 1151). In the present investigation nonlinear regression methods have been applied in the fitting of rate equations to experimental data to test the validity of the model proposed and to discriminate between alternative mathematical models (cf. FEBS Lett. 26 (1972) 252). In the best rate law, some of the parameters were numerically redundant. Therefore, a feature-wise analysis of the rate equation was carried out by varying one substrate concentration at a time. The overall strategy used was a cyclic procedure involving: experimentation - analysis of data - modelling - design of experiments - new experimentation etc. Consideration was given to the experimental error structure and to the importance of weighting in the regression analysis. In the design of experiments for discrimination between rival models, a previously defined discrimination function was used. The results of the analysis support the branching reaction scheme proposed for glutathione reductase.     

Goldfish color vision sensitivity is high under light-adapted conditions

The wavelength discrimination threshold of three goldfish was examined in a series of behavioral experiments. Using an auto-shaping technique, detection thresholds were established for 531 and 648 nm spectral increments presented on a 6.6 cd m^–2 white background. Next, discrimination between the wavelengths was established at equal, suprathreshold, intensities. Finally, the intensities of the two stimuli were reduced to establish the intensity threshold for the wavelength discrimination. The results indicate that goldfish, like several mammalian species, can discriminate wavelength at detection threshold intensity. This finding suggests that high color sensitivity is not confined to mammals or dependent upon a very high percentage of wavelength opponent ganglion cells. Rather, high color vision sensitivity may be based upon an inherent sensitivity advantage of wavelength opponent receptive fields compared to non-wavelength opponent receptive fields and be an important selective advantage of wavelength opponency and color vision.     

Colour cues proved to be more informative for dogs than brightness

The results of early studies on colour vision in dogs led to the conclusion that chromatic cues are unimportant for dogs during their normal activities. Nevertheless, the canine retina possesses two cone types which provide at least the potential for colour vision. Recently, experiments controlling for the brightness information in visual stimuli demonstrated that dogs have the ability to perform chromatic discrimination. Here, we show that for eight previously untrained dogs colour proved to be more informative than brightness when choosing between visual stimuli differing both in brightness and chromaticity. Although brightness could have been used by the dogs in our experiments (unlike previous studies), it was not. Our results demonstrate that under natural photopic lighting conditions colour information may be predominant even for animals that possess only two spectral types of cone photoreceptors.     

Probabilistic reinforcement and neurotic breakdown in unrestrained dogs]

The substitution of a constant reinforcement for a random one with a probability of 0.5 in experiments on two dogs with a simple motor stereotype was attended with nervous breakdowns with motor excitation, inadequate orienting reactions or passive-defensive behaviour. The change in the probability of reinforcement from 0.5 to 0.3 had a positive effect in experiments on one dog, while in the other it developed drowsiness. In two other dogs with a complicated stereotype, the change in the mode of reinforcement was attended with a peculiar preventive effect of probabilistic, but ordered reinforcement in experimental surroundings, including signals with a probabilistic random reinforcement as well. In this case the dogs displayed primarily signs of emotional stress only. Behaviour was somewhat disturbed in one animal only when testing signals with a probabilistic random reinforcement.     

Color discrimination in wild boars

Two experiments were carried out in order to clarify the color perception of Japanese wild boarsSus scrofa leucomystax. Two females were trained using an operant conditioning technique to press a switch under a positive stimulus color card in order to receive food as a reward. In Exp. 1, they were tested for discrimination between 3 colors (red, green and blue) and gray. The luminosity of all colors was the same. The wild boars succeeded in discrimination tests between blue and gray, but failed to discriminate red from gray. They also did not discriminate green from gray so clearly as blue from gray. In Exp. 2, the same wild boars were tested to discriminate between 8 kinds of color, which were created by gradating green yellow into red purple except for the 3 colors used in Exp. 1, and gray. They could clearly discriminate blue, purple blue and a part of purple from gray. In these experiments, wild boars were capable of recognizing bluish colors. However, for colors approaching green or yellow, they failed the test by degrees.     

Automatic imitation in dogs

After preliminary training to open a sliding door using their head and their paw, dogs were given a discrimination task in which they were rewarded with food for opening the door using the same method (head or paw) as demonstrated by their owner (compatible group), or for opening the door using the alternative method (incompatible group). The incompatible group, which had to counterimitate to receive food reward, required more trials to reach a fixed criterion of discrimination performance (85% correct) than the compatible group. This suggests that, like humans, dogs are subject to ‘automatic imitation’; they cannot inhibit online the tendency to imitate head use and/or paw use. In a subsequent transfer test, where all dogs were required to imitate their owners'' head and paw use for food reward, the incompatible group made a greater proportion of incorrect, counterimitative responses than the compatible group. These results are consistent with the associative sequence learning model, which suggests that the development of imitation depends on sensorimotor experience and phylogenetically general mechanisms of associative learning. More specifically, they suggest that the imitative behaviour of dogs is shaped more by their developmental interactions with humans than by their evolutionary history of domestication.     

基于图像几何变换映射的色盲矫正方法

为了提高色盲患者分辨色彩的能力,提出了基于图像几何变换映射的色盲矫正方法。首先根据图像中颜色面两侧的颜色比例对颜色空间各个平面进行相应的几何变换,进而划分不同的颜色映射区域,通过颜色变换,生成色盲患者较易分辨颜色的图像。实验表明,该方法可以改善色盲患者对原本难以区分的颜色的分辨能力,同时计算速度快,有望满足实时处理的需要,性能上优于已有的方法。     

Can humans discriminate between dogs on the base of the acoustic parameters of barks?

In this study we tested the often suggested claim that people are able to recognize their dogs by their barks. Earlier studies in other species indicated that reliable discrimination between individuals cannot be made by listening to chaotically noisy vocalizations. As barking is typically such a chaotic noisy vocalization, we have hypothesized that reliable discrimination between individuals is not possible by listening to barks. In this study, playback experiments were conducted to explore (1) how accurately humans discriminate between dogs by hearing only their barks, (2) the impact of the eliciting context of calls on these discrimination performances, and (3) how much such discrimination depends on acoustic parameters (tonality and frequency of barks, and the intervals between the individual barks). Our findings were consistent with the previous studies: human performances did not pass the empirical threshold of reliable discrimination in most cases. But a significant effect of tonality was found: discrimination between individuals was more successful when listeners were listening to low harmonic-to-noise ratio (HNR) barks. The contexts in which barks were recorded affected significantly the listeners' performances: if the dog barked at a stranger, listeners were able to discriminate the vocalizations better than if they were listening to sounds recorded when the dog was separated from its owner. It is rendered probable that the bark might be a more efficient communication system between humans and dogs for communicating the motivational state of an animal than for discrimination among strange individuals.     

Effect of electric stimulation of the somatosensory cortex and caudate nucleus on extinctive inhibition of a conditioned alimentary reflex to sound]

In experiments performed on 9 dogs with alimentary method, extinctive inhibition was deepened and its elaboration was aceelerated by electrical stimulation of somatosensory and motor cortical areas and ventral segment of the caudate nucleus head. The extinction of the conditioned reflex was slowed down by stimulation of the anterolateral gyrus and the central segment of the caudate nucleus head. General motor excitation of animals during stimulation of the dorsal zone of caudate nucleus head impaired the elaboration of extinctive inhibition.     

Modification of instinctive herding dog behavior using reinforcement and punishment

Abstract

“Instinctive” behavior may be modified using operant techniques. We report here on a field study of training herding dogs in which reinforcers and punishers were used by owners, who were themselves being trained to control their dogs. Access to sheep was assumed to be a primary reinforcer for herding dogs. While blocking their access was aversive to them. Over several months, the number of blocking and access actions by the human were scored during the training of seven naïve herding dogs. We found that rates of punishment by blocking the dog's access to sheep or by stopping the dog occurred at higher levels than positive reinforcement from access or verbal praise. While positive reinforcement can be used exclusively for the training of certain behaviors, it is suggested that in the context of instinctive motor patterns, negative reinforcement and punishment may be desirable and necessary additions to positive reinforcement techniques.     

Implantable Electrical Vesical Stimulator: Review of the Literature and Report of a Successful Case

Considerable interest has been shown recently in electrical stimulation of the incompetent urinary bladder. Two types of bladder stimulation have been attempted in dogs and in humans: (a) stimulation of nervi erigentes and (b) direct stimulation of the detrusor urinae muscle.After several years of animal experimentation, a vesical stimulator, built on a new electronic principle, was implanted successfully in a paraplegic patient who has a complete post-traumatic lower motor neuron lesion. The stimulator has been working satisfactorily since November 1965.This stimulator could eventually also be used in purely sensory sacral lesions, in well-selected incomplete lower motor neuron lesions, and in flaccid detrusors of the myogenic type.A review of the literature up to the time of this report shows only a few encouraging but incomplete results in humans. The techniques and the complexities involved in this problem are discussed.     

Role of the parietal associative cortex in "counting" behavior of dogs

Influence of the combined and isolated lesions of areas 5 and 7 of the parietal cortex on the counting behavior was studied in experiments with 6 dogs. Instrumental feeding reaction (lifting and placing the forepaw on the foodwell) was established. The positive conditioned stimulus was a series of 5 clicks with variable interclicks intervals and the negative (non-reinforced) conditioned stimulus was a series of 3 clicks, so that asymmetrical differentiation was elaborated. Combined bilateral lesions of areas 5 and 7 and an isolated lesion of area 5 resulted in a severe impairment of the numerical discrimination for two months, whereas the isolated lesion of area 7 did not lead to any problems in differentiation. The conclusion was made that area 5 is critical for numerical discrimination of sequential stimuli.     

Reduction of instrumental discrimination performance by post-conditioning devaluation of discriminative stimulus: the effects of novelty in reinforcing outcome and extended training

In three experiments the effects of post-conditioning pairings of a discriminative stimulus (Sd) with an illness-inducing agent (lithium chloride, LiCl) on subsequent discrimination performance in extinction and consumption of reinforcing outcome were investigated. Rats were trained to choose a correct lever to obtain food pellets, with a light presented on a bulb just above the correct lever serving for the Sd on each trial. After achievement of a criterion of the discrimination, animals received paired or unpaired presentations of the Sds and LiCl injection. In Experiment 1, in which a familiar outcome was given throughout the discrimination training, Sd-LiCl pairings did not reduce either lever-press performance during presentation of the Sds or amount of consumption of outcomes. On the other hand, in Experiment 2 where a novel outcome was introduced in the final two sessions of the discrimination training, subsequent Sd devaluation reduced lever-press performance during presentations of the Sds. Similar findings were obtained in Experiment 3, in which animals were given extended discrimination training with introduction of novel outcomes in the final two sessions. These findings suggest that a representation of the outcome, evoked by presentation of the Sd, and illness were associated in the course of Sd-LiCl pairings but only when a novel outcome was used.     

A note on select- and reject-controlling relations in the simple discrimination of capuchin monkeys (Cebus apella)

Controlling relations in the simple discrimination performances of capuchin monkeys (Cebus apella) were studied in two experiments using a blank-comparison procedure. The main goal was to determine whether monkeys would (a) select an S+ stimulus if another stimulus was substituted for the S- (indicating a select-controlling relation) and (b) reject an S- if another stimulus was substituted for S+ (indicating a reject-controlling relation). In experiment 1, two simple simultaneous discriminations were established, one of which was reversed repeatedly until rapid reversal learning was exhibited. During subsequent probe tests, some behavior was consistent with select- and reject-controlling relations, but there was also substantial variability. To control the variability, the procedures of experiment 2 were designed to establish select- and reject-control relations directly by training with the blank-comparison procedure. On subsequent probe trials, new stimuli were substituted for the blank comparison. Both animals exhibited consistent, reliable select- and reject-controlling relations. These experiments are the first to employ the blank-comparison procedure with non-human subjects. They also demonstrate a reliable method for generating select- and reject-controlling relations for experimental study.     

Canine Sense and Sensibility: Tipping Points and Response Latency Variability as an Optimism Index in a Canine Judgement Bias Assessment

Recent advances in animal welfare science used judgement bias, a type of cognitive bias, as a means to objectively measure an animal''s affective state. It is postulated that animals showing heightened expectation of positive outcomes may be categorised optimistic, while those showing heightened expectations of negative outcomes may be considered pessimistic. This study pioneers the use of a portable, automated apparatus to train and test the judgement bias of dogs. Dogs were trained in a discrimination task in which they learned to touch a target after a tone associated with a lactose-free milk reward and abstain from touching the target after a tone associated with water. Their judgement bias was then probed by presenting tones between those learned in the discrimination task and measuring their latency to respond by touching the target. A Cox''s Proportional Hazards model was used to analyse censored response latency data. Dog and Cue both had a highly significant effect on latency and risk of touching a target. This indicates that judgement bias both exists in dogs and differs between dogs. Test number also had a significant effect, indicating that dogs were less likely to touch the target over successive tests. Detailed examination of the response latencies revealed tipping points where average latency increased by 100% or more, giving an indication of where dogs began to treat ambiguous cues as predicting more negative outcomes than positive ones. Variability scores were calculated to provide an index of optimism using average latency and standard deviation at cues after the tipping point. The use of a mathematical approach to assessing judgement bias data in animal studies offers a more detailed interpretation than traditional statistical analyses. This study provides proof of concept for the use of an automated apparatus for measuring cognitive bias in dogs.     

Electrical Vestibular Stimuli to Enhance Vestibulo-Motor Output and Improve Subject Comfort

Electrical vestibular stimulation is often used to assess vestibulo-motor and postural responses in both clinical and research settings. Stochastic vestibular stimulation (SVS) is a recently established technique with many advantages over its square-wave counterpart; however, the evoked muscle responses remain relatively small. Although the vestibular-evoked responses can be enhanced by increasing the stimulus amplitude, subjects often perceive these higher intensity electrical stimuli as noxious or painful. Here, we developed multisine vestibular stimulation (MVS) signals that include precise frequency contributions to increase signal-to-noise ratios (SNR) of stimulus-evoked muscle and motor responses. Subjects were exposed to three different MVS stimuli to establish that: 1) MVS signals evoke equivalent vestibulo-motor responses compared to SVS while improving subject comfort and reducing experimentation time, 2) stimulus-evoked vestibulo-motor responses are reliably estimated as a linear system and 3) specific components of the cumulant density time domain vestibulo-motor responses can be targeted by controlling the frequency content of the input stimulus. Our results revealed that in comparison to SVS, MVS signals increased the SNR 3–6 times, reduced the minimum experimentation time by 85% and improved subjective measures of comfort by 20–80%. Vestibulo-motor responses measured using both EMG and force were not substantially affected by nonlinear distortions. In addition, by limiting the contribution of high frequencies within the MVS input stimulus, the magnitude of the medium latency time domain motor output response was increased by 58%. These results demonstrate that MVS stimuli can be designed to target and enhance vestibulo-motor output responses while simultaneously improving subject comfort, which should prove beneficial for both research and clinical applications.     

Learning by the parasitoid wasp, Aphidius ervi (Hymenoptera: Braconidae), alters individual fixed preferences for pea aphid color morphs

Learning, defined as changes in behavior that occur due to past experience, has been well documented for nearly 20 species of hymenopterous parasitoids. Few studies, however, have explored the influence of learning on population-level patterns of host use by parasitoids in field populations. Our study explores learning in the parasitoid Aphidius ervi Haliday that attacks pea aphids, Acyrthosiphon pisum (Harris). We used a sequence of laboratory experiments to investigate whether there is a learned component in the selection of red or green aphid color morphs. We then used the results of these experiments to parameterize a model that examines whether learned behaviors can explain the changes in the rates of parasitism observed in field populations in South-central Wisconsin, USA. In the first of two experiments, we measured the sequence of host choice by A. ervi on pea aphid color morphs and analyzed this sequence for patterns in biased host selection. Parasitoids exhibited an inherent preference for green aphid morphs, but this preference was malleable; initial encounters with red aphids led to a greater chance of subsequent orientation towards red aphids than predicted by chance. In a second experiment, we found no evidence that parasitoids specialize on red or green morphs; for the same parasitoids tested in trials separated by 2 h, color preference in the first trial did not predict color preference in the second, as would be expected if they differed in fixed preferences or exhibited long-term (> 2 h) learning. Using data from the two experiments, we parameterized a population dynamics model and found that learning of the magnitude observed in our experiments leads to biased parasitism towards the most common color morph. This bias is sufficient to explain changes in the ratio of aphid color morphs observed in field sites over multiple years. Our study suggests that for even relatively simple organisms, learned behaviors may be important for explaining the population dynamics of their hosts.     

Color analysis method for estimating the oxygen saturation of hemoglobin using an image-input and processing system

A color analysis method which enables both qualitative and quantitative analyses of an object's color was developed. The method uses a color image-input and processing system composed of a 3-tube video camera and a digital image analyzer, which quantizes a color image into values of red, green, and blue brightness, then processes these values. We introduced a spectrophotometric principle by the Beer-Lambert law, and were able to establish a color model to analyze an object's color. In the coordinate space based on our color model, the hue of the object's color is represented by the direction from the origin, and the density by the distance from the origin. This new method was used to analyze the colors of hemoglobin solutions at various oxygen saturations and concentrations. The results agreed with the known conditions, indicating the validity of the model and its usefulness for quantitative as well as qualitative analyses of color.     

Normalized Index of Synergy for Evaluating the Coordination of Motor Commands

Humans perform various motor tasks by coordinating the redundant motor elements in their bodies. The coordination of motor outputs is produced by motor commands, as well properties of the musculoskeletal system. The aim of this study was to dissociate the coordination of motor commands from motor outputs. First, we conducted simulation experiments where the total elbow torque was generated by a model of a simple human right and left elbow with redundant muscles. The results demonstrated that muscle tension with signal-dependent noise formed a coordinated structure of trial-to-trial variability of muscle tension. Therefore, the removal of signal-dependent noise effects was required to evaluate the coordination of motor commands. We proposed a method to evaluate the coordination of motor commands, which removed signal-dependent noise from the measured variability of muscle tension. We used uncontrolled manifold analysis to calculate a normalized index of synergy. Simulation experiments confirmed that the proposed method could appropriately represent the coordinated structure of the variability of motor commands. We also conducted experiments in which subjects performed the same task as in the simulation experiments. The normalized index of synergy revealed that the subjects coordinated their motor commands to achieve the task. Finally, the normalized index of synergy was applied to a motor learning task to determine the utility of the proposed method. We hypothesized that a large part of the change in the coordination of motor outputs through learning was because of changes in motor commands. In a motor learning task, subjects tracked a target trajectory of the total torque. The change in the coordination of muscle tension through learning was dominated by that of motor commands, which supported the hypothesis. We conclude that the normalized index of synergy can be used to evaluate the coordination of motor commands independently from the properties of the musculoskeletal system.