Human adaptation to levels of environmental stimulation

This paper examines the environment as a source of dimensions of stimulation that are directly related to the individual's affective response to his environment, and his behavioral adaptation to it. The concept of an optimal level of stimulation is introduced, along with a view of environmental stress as resulting from conditions of excessive deviation from such optimal levels, with particular reference to variations in intensity, diversity, and patterning of the stimulus input. This analysis provides the framework for a consideration of behavioral adaptation to the environment by reference to the concept of adaptation level. Levels of adaptation to particular environmental dimensions, established as a function of past exposure, are shown to act as potent determiners of the individual's evaluation of his environment, as well as representing a plausible basis for the optimal level of stimulation principle itself. The presentation proceeds to an examination of the process of adaptation to the environment as a multilayered process, and to a discussion of the concept of the cost of adaptation as it applies in the behavioral realm. Finally, adaptation is contrasted with an alternative mechanism, adjustment, involving active alteration of the environment by the individual, and the relative place to be accorded to these two processes in the individual's relation to the environment is considered.     

A behavioural trait displayed in an artificial novel environment correlates with dispersal in a wild bird

Behaviour shown in a novel environment has important consequences for fitness in many animals. It is widely studied with standard tests by placing the individuals into an unfamiliar experimental area, that is the so-called open-field or novel environment test. The biological relevance of traits measured under such artificial conditions is questionable and could be validated by establishing a link with variables that truly reflect exploration in the wild. Our aim in this field study was to characterize behaviours measured in an artificial novel environment (an aviary) and assess the biological relevance of them in the collared flycatcher (Ficedula albicollis). Therefore, we measured the repeatability and the association of multiple behavioural traits, as well as their relationship with breeding dispersal (that reflects exploration in the wild). We found evidence for non-zero repeatability for number of crosses between the quarters, number of hops and perching latency in the aviary, and these repeatabilities were high when assessed at shorter time windows. Additionally, birds with short perching latency in the novel environment were more likely residents and bred closer to their breeding nest box in the previous year, which may suggest that latency to perch is connected to dispersal in the wild. In sum, our results indicate that behaviours assessed in an artificial environment are individual-specific at least on smaller timescales, and at least, one component of these behaviours is correlated with an ecologically relevant trait.     

Reaction of laying hens to humans in the home or a novel environment

Tests assessing the fear of humans by measuring avoidance or approach reactions of the test animals towards humans can be useful tools in welfare assessment schemes. In this study, we wanted to compare tests assessing the reactions of laying hens towards humans in the home environment to a test performed in a novel environment. As well we investigated inter-test correlations in the home environment. We performed several tests to assess the hens’ approach and avoidance reactions towards an unfamiliar human inside the home environment of laying hens in 14 caged flocks and 10 free-range flocks. We measured the reactions of hens to a stationary person and a moving person approaching individual hens in both systems, as well as reactions to a stationary person trying to touch individual hens in non-cage systems and reactions of caged hens to a person passing by. Additionally, a standardised arena test was performed outside the home environment to compare the birds’ avoidance reactions towards an approaching human in a novel environment. In caged hens no significant correlations of tests performed inside the home environment with the arena test could be found, but there were moderate to high correlations (r_s > 0.6) with one parameter of the arena test in non-caged hens. The different tests applied inside the home environment correlated significantly and moderately to highly with each other, supporting the validity of these tests to measure fear of humans. The caged laying hens in our study reacted differently in the novel environment from the non-caged birds, indicating that the birds’ reactions towards humans in an unfamiliar environment depend on the housing system. In summary, a comparison of the level of fear of humans between flocks in different housing systems by using an arena test outside the home environment seems difficult and was not possible in the present study.     

Proposal for a framework for optimizing artificial environments based on physiological feedback

We propose and then evaluate a new framework for finding the physical parameters of an artificial environment which give rise to given target physiological characteristics. We assume that a human is a system that takes as inputs the physical parameters of an artificial environment and outputs physiological parameters in response. We define our task as the inverse problem; we must find the best inputs from given target outputs. Our proposed framework solves the inverse problem using evolutionary computation techniques to optimize an artificial environment. We evaluate this framework using a simulation with a vibration environment and verify that it works.     

The environmental zero‐point problem in evolutionary reaction norm modeling

There is a potential problem in present quantitative genetics evolutionary modeling based on reaction norms. Such models are state‐space models, where the multivariate breeder's equation in some form is used as the state equation that propagates the population state forward in time. These models use the implicit assumption of a constant reference environment, in many cases set to zero. This zero‐point is often the environment a population is adapted to, that is, where the expected geometric mean fitness is maximized. Such environmental reference values follow from the state of the population system, and they are thus population properties. The environment the population is adapted to, is, in other words, an internal population property, independent of the external environment. It is only when the external environment coincides with the internal reference environment, or vice versa, that the population is adapted to the current environment. This is formally a result of state‐space modeling theory, which is an important theoretical basis for evolutionary modeling. The potential zero‐point problem is present in all types of reaction norm models, parametrized as well as function‐valued, and the problem does not disappear when the reference environment is set to zero. As the environmental reference values are population characteristics, they ought to be modeled as such. Whether such characteristics are evolvable is an open question, but considering the complexity of evolutionary processes, such evolvability cannot be excluded without good arguments. As a straightforward solution, I propose to model the reference values as evolvable mean traits in their own right, in addition to other reaction norm traits. However, solutions based on an evolvable G matrix are also possible.     

A model for the emergence of adaptive subsystems

We investigate the interaction of learning and evolution in a changing environment. A stable learning capability is regarded as an emergent adaptive system evolved by natural selection of genetic variants. We consider the evolution of an asexual population. Each genotype can have ‘fixed’ and ‘flexible’ alleles. The former express themselves as synaptic connections that remain unchanged during ontogeny and the latter as synapses that can be adjusted through a learning algorithm. Evolution is modelled using genetic algorithms and the changing environment is represented by two optimal synaptic patterns that alternate a fixed number of times during the ‘life’ of the individuals. The amplitude of the change is related to the Hamming distance between the two optimal patterns and the rate of change to the frequency with which both exchange roles. This model is an extension of that of Hinton and Nowlan in which the fitness is given by a probabilistic measure of the Hamming distance to the optimum. We find that two types of evolutionary pathways are possible depending upon how difficult (costly) it is to cope with the changes of the environment. In one case the population loses the learning ability, and the individuals inherit fixed synapses that are optimal in only one of the environmental states. In the other case a flexible subsystem emerges that allows the individuals to adapt to the changes of the environment. The model helps us to understand how an adaptive subsystem can emerge as the result of the tradeoff between the exploitation of a congenital structure and the exploration of the adaptive capabilities practised by learning.     

Effect of heat acclimation on anxiety-like behavior of rats in an open field

To mitigate the impacts of heat exposure, animals can take some actions to maintain their core body temperature, such as heat acclimation; however, the effect of heat acclimation on anxiety-like behavior in an open field is still not understood. The purpose of this study was to examine the anxiety-like behavior of heat acclimated rats in a temperate or heated open field. After being raised in a 23 °C environment for one week, male Wistar rats were exposed to a heated environment (32 °C) for 3 h (3H), 14 days (14D), or 28 days (28D), with free access to food and water, and compared with rats reared in a temperate environment (23 °C; Cont). After heat exposure, behavioral changes were monitored using an open field test (OFT) in a heated (32 °C) or temperate environment (23 °C). Compared with those in the Cont group, the body weights of rats in the 14D and 28D groups were lower. The OFT in the heated environment showed that grooming time was longer in 3H and 14D rats. In the temperate environment, grooming time was longer in all the heated groups. Rats from the 3H and 28D groups spent longer time in the center square when tested in the temperate environment. Rearing activity increased in 28D rats in the temperate environment, while the number of line crossings did not differ significantly between the heated groups and the two open fields. These results suggest that heat acclimation affected not only the physiological index such as core body temperature but also the anxiety-like behavior, mainly in the temperate open field. These changes might be beneficial when rats are faced with an open field.     

Effects of botanical gardens on student environmental perception

This paper examines the role of the classroom environment in promoting student well-being and, more specifically, a sense of responsibility towards nature in the city. The study analyzed how indoor vs outdoor educational environments affect students' perception of events and phenomena focusing on emotional, behavioral and cognitive processes. It was conducted in the Kayakyolu Secondary School, Erzurum, Turkey with 282 students ranging in age from 11 to 14 in grades 5–8. They participated in reading a story in two distinct environments: an enclosed indoor classroom and an outdoor botanical garden. Significant differences in the emotional, behavioral and cognitive approaches of the students in these two environments were obtained at p < .05. All three approaches (emotional behavioral and cognitive) in the botanical garden environment produced higher positive values than those of the classroom environment. The rate of negative emotions of the students in the botanical garden was 23.3% and increased to 40.1% in a closed classroom environment. It was clearly observed that the environmental awareness and sensitivity of the students educated in botanical garden was absolutely higher than those of an indoor environment. The responses indicating behaviors of not adversely interfering with natural processes and indicating the value of living in harmony with nature increased in the botanical garden. The findings of this research demonstrate that environmental education conducted in a natural environment is more effective as compared to the education given in the classroom setting. The study supports the proposition that future generations educated in natural surroundings will be better able to make more accurate, creative, and resilient decisions for the environment.     

Changing the school environment to increase physical activity in children

We examined the hypothesis that elementary school-age children will be more physically active while attending school in a novel, activity-permissive school environment compared to their traditional school environment. Twenty-four children were monitored with a single-triaxial accelerometer worn on the thigh. The students attended school in three different environments: traditional school with chairs and desks, an activity-permissive environment, and finally their traditional school with desks which encouraged standing. Data from the school children were compared with another group of age-matched children (n = 16) whose physical activity was monitored during summer vacation. When children attended school in their traditional environment, they moved an average (mean +/- s.d.) of 71 +/- 0.4 m/s(2). When the children attended school in the activity-permissive environment, they moved an average of 115 +/- 3 m/s(2). The children moved 71 +/- 0.7 m/s(2) while attending the traditional school with standing desks. Children moved significantly more while attending school in the activity-permissive environment compared to the amount that they moved in either of the traditional school environments (P < 0.0001 for both). Comparing children's activity while they were on summer vacation (113 +/- 8 m/s(2)) to school-bound children in their traditional environment showed significantly more activity for the children on summer vacation (P < 0.0001). The school children in the activity-permissive environment were as active as children on summer vacation. Children will move more in an activity-permissive environment. Strategies to increase the activity of school children may involve re-designing the school itself.     

How the Harsh Environment of an Army Training Camp Changes Human (Homo sapiens) Facial Preferences

Previous studies suggest that facial preferences may be contingent on an individual's environment, yet no study has traced how the preferences of the same individuals change as their environment changes. We therefore sought to determine if, and to what extent, adiposity and masculinity preferences are malleable by repeatedly testing students whose environment was not changing as well as students undergoing intensive training at an army camp. Our results showed that at baseline, the students at the training camp preferred more feminine male faces. This suggests that even before the training commenced, participants in the training camp may have been in a psychological state that predisposed them to prefer more trustworthy (i.e., more feminine) men. Additionally, we found that the students at the training camp reported increases in multiple stressors as well as showed changes in adiposity preferences. More specifically, we found that increases in the harshness of the environment led to an increased male attraction to cues of higher weight in female faces. Such changes in preferences may be adaptive because they allow men more opportunities to mate with women who are better equipped to survive and reproduce. These findings thus provide new evidence for the malleability of preferences depending on the environment.     

Dynamic spleen mass in wild and domestic American mink

The immune system is considered to be an energetically expensive component of an individual's life history. Investment in the immune system can depend on the environment that an individual finds itself in. The American mink, Neovison vison, exists in the natural environment and on fur farms. The natural environment and mink farm differ in many ways, such as wild mink being exposed to many parasites that are less prevalent and less abundant in the domestic environment because of veterinary care. We collected free‐ranging mink from commercial trappers and domestic mink from fur farmers in Ontario and Nova Scotia, Canada, and examined relative spleen mass. Wild male mink had larger spleens than domestic mink in Nova Scotia, with a similar trend in Ontario. Female mink that escaped from farms (feral) in Nova Scotia had significantly larger spleens than their domestic counterparts on the farms. Both of these results are consistent with the prediction that the natural environment contains parasites and pathogens that require enhanced investment in the immune system. In Nova Scotia, females had larger spleens than males, whether considering wild or domestic populations. Finally, wild mink showed greater condition dependence of spleen mass than domestic populations. Further investigations should include experimental approaches such as providing veterinary care to wild populations to assess the effects of parasites and pathogens on the immune system. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 107 , 624–631.     

A Normative Theory of Forgetting: Lessons from the Fruit Fly

Recent experiments revealed that the fruit fly Drosophila melanogaster has a dedicated mechanism for forgetting: blocking the G-protein Rac leads to slower and activating Rac to faster forgetting. This active form of forgetting lacks a satisfactory functional explanation. We investigated optimal decision making for an agent adapting to a stochastic environment where a stimulus may switch between being indicative of reward or punishment. Like Drosophila, an optimal agent shows forgetting with a rate that is linked to the time scale of changes in the environment. Moreover, to reduce the odds of missing future reward, an optimal agent may trade the risk of immediate pain for information gain and thus forget faster after aversive conditioning. A simple neuronal network reproduces these features. Our theory shows that forgetting in Drosophila appears as an optimal adaptive behavior in a changing environment. This is in line with the view that forgetting is adaptive rather than a consequence of limitations of the memory system.     

Predictability rather than amplitude of temperature fluctuations determines stress resistance in a natural population of Drosophila simulans

The adaptability of organisms to novel environmental conditions depends on the amount of genetic variance present in the population as well as on the ability of individuals to adjust their phenotype through phenotypic plasticity. Here, we investigated the phenotypic plasticity induced by a single generation's exposure to three different temperature regimes with respect to several life‐history and stress‐resistance traits in a natural population of Drosophila simulans. We studied a constant as well as a predictably and an unpredictably fluctuating temperature regime. We found high levels of phenotypic plasticity among all temperature regimes, suggesting a strong influence of both temperature fluctuations and their predictability. Increased heat tolerance was observed for flies developed in both types of fluctuating thermal environments compared with flies developed in a constant environment. We suggest that this was due to beneficial hardening when developing in either fluctuating temperature environment. To our surprise, flies that developed in constant and predictably changing environments were similar to each other in most traits when compared to flies from the unpredictably fluctuating environment. The unpredictably changing thermal environment imposed the most stressful condition, resulting in the lowest performance for stress‐related traits, even though the absolute temperature changes never exceeded that of the predictably fluctuating environment. The overall decreased stress resistance of flies in the unpredictably fluctuating environment may be the consequence of maladaptive phenotypic plasticity in this setting, indicating that the adaptive value of plasticity depends on the predictability of the environment.     

Boundary coding in the rat subiculum

The spatial mapping function of the hippocampal formation is likely derived from two sets of information: one based on the external environment and the other based on self-motion. Here, we further characterize ‘boundary vector cells’ (BVCs) in the rat subiculum, which code space relative to one type of cue in the external environment: boundaries. We find that the majority of cells with fields near the perimeter of a walled environment exhibit an additional firing field when an upright barrier is inserted into the walled environment in a manner predicted by the BVC model. We use this property of field repetition as a heuristic measure to define BVCs, and characterize their spatial and temporal properties. In further tests, we find that subicular BVCs typically treat drop edges similarly to walls, including exhibiting field repetition when additional drop-type boundaries are added to the testing environment. In other words, BVCs treat both kinds of edge as environmental boundaries, despite their dissimilar sensory properties. Finally, we also report the existence of ‘boundary-off cells’, a new class of boundary-coding cells. These cells fire everywhere except where a given BVC might fire.     

Digital Microfluidic Dynamic Culture of Mammalian Embryos on an Electrowetting on Dielectric (EWOD) Chip

Current human fertilization in vitro (IVF) bypasses the female oviduct and manually inseminates, fertilizes and cultivates embryos in a static microdrop containing appropriate chemical compounds. A microfluidic microchannel system for IVF is considered to provide an improved in-vivo-mimicking environment to enhance the development in a culture system for an embryo before implantation. We demonstrate a novel digitalized microfluidic device powered with electrowetting on a dielectric (EWOD) to culture an embryo in vitro in a single droplet in a microfluidic environment to mimic the environment in vivo for development of the embryo and to culture the embryos with good development and live births. Our results show that the dynamic culture powered with EWOD can manipulate a single droplet containing one mouse embryo and culture to the blastocyst stage. The rate of embryo cleavage to a hatching blastocyst with a dynamic culture is significantly greater than that with a traditional static culture (p<0.05). The EWOD chip enhances the culture of mouse embryos in a dynamic environment. To test the reproductive outcome of the embryos collected from an EWOD chip as a culture system, we transferred embryos to pseudo-pregnant female mice and produced live births. These results demonstrate that an EWOD-based microfluidic device is capable of culturing mammalian embryos in a microfluidic biological manner, presaging future clinical application.     

Do mites evolving in alternating host plants adapt to host switch?

A fluctuating environment may be perceived as a composition of different environments, or as an environment per se, in which it is the fluctuation itself that poses a selection pressure. If so, then organisms may adapt to this alternation. We tested this using experimental populations of spider mites that have been evolving for 45 generations in a homogeneous environment (pepper or tomato plants), or in a heterogeneous environment composed of an alternation of these two plants approximately at each generation. The performance (daily oviposition rate and juvenile survival) of individuals from these populations was tested in each of the homogeneous environments, and in two alternating environments, one every 3 days and the other between generations. To discriminate between potential genetic interactions between alleles conferring adaptation to each host plant and environmental effects of evolving in a fluctuating environment, we compared the performance of all lines with that of a cross between tomato and pepper lines. As a control, two lines within each selection regime were also crossed. We found that crosses between alternating lines and between pepper and tomato lines performed worse than crosses between lines evolving in homogeneous environments when tested in that environment. In contrast, alternating lines performed either better or similarly to lines evolving in homogeneous environments when tested in a fluctuating environment. Our results suggest that fluctuating environments are more than the juxtaposition of two environments. Hence, tests for adaptation of organisms evolving in such environments should be carried out in fluctuating conditions.     

Environmental Unpredictability and the Value of Social Information for Foraging Starlings

Environmental and behavioral cues are useful sources of information that allow group foraging individuals to improve their foraging success. Few studies to date, however, have examined how varying degrees of environmental unpredictability may affect when and how individuals use the social information they obtain in foraging groups. In this experiment, European starlings (Sturnus vulgaris) were tested to determine in which type of environment, predictable or unpredictable, social information would be the most valuable. Subjects were placed under one of four conditions: an unpredictable environment with either (1) an informing demonstrator bird or (2) an uninforming demonstrator; or a predictable environment with either (3) an informing demonstrator or (4) an uninforming demonstrator. Environmental predictability was manipulated by altering the meaning of available color cues. Subjects in the unpredictable environment that had an informing demonstrator performed significantly better than subjects in an unpredictable environment with an uninforming demonstrator, although only on the second day of testing. Subjects in both the predictable conditions performed similarly to each other. The results suggest that social information is more valuable to individuals in an unpredictable environment than it is in a predictable environment; however, there appears to be a time lag in the ability of the birds to recognize the value of this information.     

The evolutionary role of the dependence of recombination on environment

Summary The recombination frequency (rf) is known to be dependent not only on genetic background, but on the environment as well. In our numerical experiments we examine the role of the dependence of recombination on environment in the evolution of the genetic system. Variable rf-strategies, ensuring mean fitnesses greater than the optimum constant rf^*-level, exist in both cyclical and stochastic environments. The conclusion that environment dependent recombination is evolutionary advantageous can be shown to be valid when variation in the frequency of recombination modifiers rather than mean fitness (which implies the concept of group selection) is used as a criterion for strategy comparisons. In this case, an evolutionary advantageous type of variable rf-strategies is the one ensuring restricted genetic variability dispersion in an optimal environment and an increase in released variation with the deterioration of environmental conditions. Another important result is that, taking into account the dependence of recombination on environment, it is possible to account for the maintenance of a higher level of population recombination than that predicted by models with the constant rf-level. On the whole, the data obtained indicate that the direct influence of external factors upon the rf-value could have been a significant factor in the evolution of the genetic system.     

Mechanical properties of native and ex vivo remodeled porcine saphenous veins

When grafted into an arterial environment in vivo, veins remodel in response to the new mechanical environment, thereby changing their mechanical properties and potentially impacting their patency as bypass grafts. Porcine saphenous veins were subjected for one week to four different ex vivo hemodynamic environments in which pressure and shear stress were varied independently, as well as an environment that mimicked that of an arterial bypass graft. After one week of ex vivo culture, the mechanical properties of intact saphenous veins were evaluated to relate specific aspects of the mechanical environment to vein remodeling and corresponding changes in mechanics. The compliance of all cultured veins tended to be less than that of fresh veins; however, this trend was more due to changes in medial and luminal areas than changes in the intrinsic properties of the vein wall. A combination of medial hypertrophy and eutrophic remodeling leads to significantly smaller (p<0.05) wall stresses measured in all cultured veins except those subjected to bypass graft conditions relative to stresses measured in fresh veins at corresponding pressures. Our results suggest that the mechanical environment effects changes in vessel size, as well as the nature of the remodeling, which contribute to altering vein mechanical properties.