Causes and consequences of stress

Stress involves real or perceived changes within an organismin the environment that activate an organism's attempts to copeby means of evolutionarily ancient neural and endocrine mechanisms.Responses to acute stressors involve catecholamines releasedin varying proportion at different sites in the sympatheticand central nervous systems. These responses may interact withand be complemented by intrinsic rythms and responses to chronicor intermittent stressors involving the hypothalamic-pituitary-adrenalaxis. Varying patterns of responses to stressors are also affectedby an animal's assessment of their prospects for successfulcoping. Subsequent central and systemic consequences of thestress response include apparent changes in affect, motivation,and cognition that can result in an altered relationship toenvironmental and social stimuli. This review will summarizerecent developments in our understanding of the causes and consequencesof stress. Special problems that need to be explored involvethe manner in which ensembles of adaptive responses are assembled,how autonomic and neurohormonal reflexes of the stress responsecome under the influence of environmental stimuli, and how somespecific aspects of the stress response may be integrated intothe life history of a species.     

Early life conditions that impact song learning in male zebra finches also impact neural and behavioral responses to song in females

Early life stressors can impair song in songbirds by negatively impacting brain development and subsequent learning. Even in species in which only males sing, early life stressors might also impact female behavior and its underlying neural mechanisms, but fewer studies have examined this possibility. We manipulated brood size in zebra finches to simultaneously examine the effects of developmental stress on male song learning and female behavioral and neural response to song. Although adult male HVC volume was unaffected, we found that males from larger broods imitated tutor song less accurately. In females, early condition did not affect the direction of song preference: all females preferred tutor song over unfamiliar song in an operant test. However, treatment did affect the magnitude of behavioral response to song: females from larger broods responded less during song preference trials. This difference in activity level did not reflect boldness per se, as a separate measure of this trait did not differ with brood size. Additionally, in females we found a treatment effect on expression of the immediate early gene ZENK in response to tutor song in brain regions involved in song perception (dNCM) and social motivation (LSc.vl, BSTm, TnA), but not in a region implicated in song memory (CMM). These results are consistent with the hypothesis that developmental stressors that impair song learning in male zebra finches also influence perceptual and/or motivational processes in females. However, our results suggest that the learning of tutor song by females is robust to disturbance by developmental stress. © 2018 Wiley Periodicals, Inc. Develop Neurobiol, 2018     

Do smart birds stress less? An interspecific relationship between brain size and corticosterone levels

Vertebrates respond to unpredictable noxious environmental stimuli by increasing secretion of glucocorticoids (CORT). Although this hormonal stress response is adaptive, high levels of CORT may induce significant costs if stressful situations are frequent. Thus, alternative coping mechanisms that help buffer individuals against environmental stressors may be selected for when the costs of CORT levels are elevated. By allowing individuals to identify, anticipate and cope with the stressful circumstances, cognition may enable stress-specific behavioural coping. Although there is evidence that behavioural responses allow animals to cope with stressful situations, it is unclear whether or not cognition reduces investment in the neuroendocrine stress response. Here, we report that in birds, species with larger brains relative to their body size show lower baseline and peak CORT levels than species with smaller brains. This relationship is consistent across life-history stages, and cannot be accounted for by differences in life history and geographical latitude. Because a large brain is a major feature of birds that base their lifetime in learning new things, our results support the hypothesis that enhanced cognition represents a general alternative to the neuroendocrine stress response.     

A Bayesian Perspective on Sensory and Cognitive Integration in Pain Perception and Placebo Analgesia

The placebo effect is a component of any response to a treatment (effective or inert), but we still ignore why it exists. We propose that placebo analgesia is a facet of pain perception, others being the modulating effects of emotions, cognition and past experience, and we suggest that a computational understanding of pain may provide a unifying explanation of these phenomena. Here we show how Bayesian decision theory can account for such features and we describe a model of pain that we tested against experimental data. Our model not only agrees with placebo analgesia, but also predicts that learning can affect pain perception in other unexpected ways, which experimental evidence supports. Finally, the model can also reflect the strategies used by pain perception, showing that modulation by disparate factors is intrinsic to the pain process.     

Distance in motion: response trajectories reveal the dynamics of number comparison

Cognitive and neuroscientific evidence has challenged the widespread view that perception, cognition and action constitute independent, discrete stages. For example, in continuous response trajectories toward a target response location, evidence suggests that a decision on which target to reach for (i.e., the cognition stage) is not reached before the movement starts (i.e., the action stage). As a result, instead of a straight trajectory to the correct target response, movement trajectories may curve toward competing responses or away from inhibited responses. In the present study, we examined response trajectories during a number comparison task. Participants had to decide whether a target number was smaller or larger than 5. They had to respond by moving to a left or a right response location. Replicating previous results, response trajectories were more curved toward the incorrect response location when distance to 5 was small (e.g., target number 4) than when distance to 5 was large (e.g., target number 1). Importantly, we manipulated the response mapping, which allowed us to demonstrate that this response trajectory effect results from the relative amount of evidence for the available responses across time. In this way, the present study stresses the tight coupling of number representations (i.e., cognition) and response related processes (i.e., action) and shows that these stages are not separable in time.     

社会神经科学研究进展

社会神经科学是研究人类的社会行为及其神经机制的综合性学科.从1992年学科成立至今,社会神经科学研究取得了丰硕的成果.本文系统介绍了该领域4个主要研究方向:社会知觉、社会认知、社会调节和社会互动的研究成果,并在此基础上总结了各研究方向的核心问题,即社会知觉加工的模块化问题、人类社会认知的独特性问题和社会调节加工的跨文化一致性问题.已有研究表明,社会知觉加工至少在计算算法层面是特异化的;心智化系统是人类独有的加工模块;人类社会调节不具备跨文化的一致性;大脑间耦合可能是社会互动共有的神经机制.最后,展望了社会神经科学未来的发展方向.     

Inhalation of environmental stressors & chronic inflammation: autoimmunity and neurodegeneration

Human life expectancy and welfare has decreased because of the increase in environmental stressors in the air. An environmental stressor is a natural or human-made component present in our environment that upon reaching an organic system produces a coordinated response. This response usually involves a modification of the metabolism and physiology of the system. Inhaled environmental stressors damage the airways and lung parenchyma, producing irritation, recruitment of inflammatory cells, and oxidative modification of biomolecules. Oxidatively modified biomolecules, their degradation products, and adducts with other biomolecules can reach the systemic circulation, and when found in higher concentrations than normal they are considered to be biomarkers of systemic oxidative stress and inflammation. We classify them as metabolic stressors because they are not inert compounds; indeed, they amplify the inflammatory response by inducing inflammation in the lung and other organs. Thus the lung is not only the target for environmental stressors, but it is also the source of a number of metabolic stressors that can induce and worsen pre-existing chronic inflammation. Metabolic stressors produced in the lung have a number of effects in tissues other than the lung, such as the brain, and they can also abrogate the mechanisms of immunotolerance. In this review, we discuss recent published evidence that suggests that inflammation in the lung is an important connection between air pollution and chronic inflammatory diseases such as autoimmunity and neurodegeneration, and we highlight the critical role of metabolic stressors produced in the lung. The understanding of this relationship between inhaled environmental pollutants and systemic inflammation will help us to: (1) understand the molecular mechanism of environment-associated diseases, and (2) find new biomarkers that will help us prevent the exposure of susceptible individuals and/or design novel therapies.     

Post‐traumatic stress disorder and beyond: an overview of rodent stress models

Post‐traumatic stress disorder (PTSD) is a psychiatric disorder of high prevalence and major socioeconomic impact. Patients suffering from PTSD typically present intrusion and avoidance symptoms and alterations in arousal, mood and cognition that last for more than 1 month. Animal models are an indispensable tool to investigate underlying pathophysiological pathways and, in particular, the complex interplay of neuroendocrine, genetic and environmental factors that may be responsible for PTSD induction. Since the 1960s, numerous stress paradigms in rodents have been developed, based largely on Seligman's seminal formulation of ‘learned helplessness’ in canines. Rodent stress models make use of physiological or psychological stressors such as foot shock, underwater trauma, social defeat, early life stress or predator‐based stress. Apart from the brief exposure to an acute stressor, chronic stress models combining a succession of different stressors for a period of several weeks have also been developed. Chronic stress models in rats and mice may elicit characteristic PTSD‐like symptoms alongside, more broadly, depressive‐like behaviours. In this review, the major existing rodent models of PTSD are reviewed in terms of validity, advantages and limitations; moreover, significant results and implications for future research—such as the role of FKBP5, a mediator of the glucocorticoid stress response and promising target for therapeutic interventions—are discussed.     

Management-related stress in the red-shouldered hawk

Disturbance stress can prevent or disrupt successful management of captive birds of prey. Using heart rate as an indicator of stress, two female red-shouldered hawks (Buteo lineatus) were monitored via radio telemetry. Spontaneous heart rate fluctuations in response to stressors involved in management-related activities, as well as some in response to naturally occurring activities, were recorded. In nearly every case, stressors caused dramatic increases in the heart rate of each bird, the magnitude of which was directly related to the degree of human contact involved. The increased heart rates occurred in response to stressors whether or not any behavioral stress symptoms were exhibited. Under the conditions of this study, the use of a falconer's hood did not completely eliminate stress in restrained hawks.     

运动对时距知觉的影响及其神经机制

在运动过程中,时距知觉的能力非常重要,能帮助个体对时长进行判断及对事件的发生做出预测和准备.近年来,越来越多的研究发现运动本身会直接影响个体的时距知觉.本文分别从运动参数、运动阶段、视觉运动刺激和运动有关的个体因素四个方面梳理了运动对时距知觉产生影响的行为学证据.目前已经有大量研究从不同角度证明,大脑运动系统组成了支持...     

Net effects of multiple stressors in freshwater ecosystems: a meta‐analysis

The accelerating rate of global change has focused attention on the cumulative impacts of novel and extreme environmental changes (i.e. stressors), especially in marine ecosystems. As integrators of local catchment and regional processes, freshwater ecosystems are also ranked highly sensitive to the net effects of multiple stressors, yet there has not been a large‐scale quantitative synthesis. We analysed data from 88 papers including 286 responses of freshwater ecosystems to paired stressors and discovered that overall, their cumulative mean effect size was less than the sum of their single effects (i.e. an antagonistic interaction). Net effects of dual stressors on diversity and functional performance response metrics were additive and antagonistic, respectively. Across individual studies, a simple vote‐counting method revealed that the net effects of stressor pairs were frequently more antagonistic (41%) than synergistic (28%), additive (16%) or reversed (15%). Here, we define a reversal as occurring when the net impact of two stressors is in the opposite direction (negative or positive) from that of the sum of their single effects. While warming paired with nutrification resulted in additive net effects, the overall mean net effect of warming combined with a second stressor was antagonistic. Most importantly, the mean net effects across all stressor pairs and response metrics were consistently antagonistic or additive, contrasting the greater prevalence of reported synergies in marine systems. Here, a possible explanation for more antagonistic responses by freshwater biota to stressors is that the inherent greater environmental variability of smaller aquatic ecosystems fosters greater potential for acclimation and co‐adaptation to multiple stressors.     

Involvement of ERK and protein tyrosine phosphatase signaling pathways in EGCG-induced cyclooxygenase-2 expression in Raw 264.7 cells

The cellular stress response which can be elicited by a variety of physical or chemical stressors challenges the homeostatic mechanisms of the cells. Two stressors may interact such that, for example, in the presence of a defined thermal stress ("costress") a second weak stressor like electromagnetic fields (50 MHz, 100 microT) produces strong biological effects. Based on the apparent interaction of these stressors a concept is suggested that explains the observed effects and defines the limits of cellular homeostasis in general terms. The homeostatic potential of a cell and hence the ability to cope with stressors can be altered by eliciting or depressing the heat shock response. This manipulation has several promising medical applications.     

Perceptions of medical school stressors: their relationship to age, year of study and trait anxiety

It has been noted that medical school is a stressful social environment. This study proposes to determine domains of medical school stressors and to investigate to what extent the perceived stressfulness of these domains is explained by age, year of study, marital status, sex, and trait anxiety. Data were obtained by self-administered questionnaires filled out by 131 students in four classes of a six-year medical school. Four clusters of stressors were revealed by factor analysis: "off-time death," "incurable condition," "patient contact," and "medical practice demands." Marital status, sex, and year of study did not correlate with any of these stressor domains. Age was positively correlated with the perception of off-time death as stressful and negatively correlated with patient contact. Trait anxiety was directly correlated with the perceived stressfulness of patient contact and medical practice demands. No independent variable explained differences in perception of all four domains. It is suggested that there are some experiences, such as facing off-time death, that are so painful that repeated exposure to them augments, rather than decreases, the perception of their stressfulness.     

Complex functions of the brain

Over the course of the last 50 years it has been possible to solve a number of basic problems in neurobiology. Interest is now turning more and more to problems concerning so-called “higherρ brain functions, including cognition. Examples from the visual system in primates are presented. First relatively elementary problems are illustrated, such as how long it takes to perceive an object or to respond to a stimulus or combinations of stimuli. Top-down modification of perception by expectation is demonstrated in an illusion of misdirected gaze. Interdisciplinary questions straddling the sciences and the humanities are also approached, such as which part of the brain mediates conscious perception. Finally, the problem of causality and freedom of will is addressed, taking into account the knowledge accumulated in the neurosciences during the last 5 decades.     

Cognitive and perceptual functions of the visual thalamus

The thalamus is classically viewed as passively relaying information to the cortex. However, there is growing evidence that the thalamus actively regulates information transmission to the cortex and between cortical areas using a variety of mechanisms, including the modulation of response magnitude, firing mode, and synchrony of neurons according to behavioral demands. We discuss how the visual thalamus contributes to attention, awareness, and visually guided actions, to present a general role for the thalamus in perception and cognition.     

Moderate exercise and chronic stress produce counteractive effects on different areas of the brain by acting through various neurotransmitter receptor subtypes: A hypothesis

Background  

Regular, "moderate", physical exercise is an established non-pharmacological form of treatment for depressive disorders. Brain lateralization has a significant role in the progress of depression. External stimuli such as various stressors or exercise influence the higher functions of the brain (cognition and affect). These effects often do not follow a linear course. Therefore, nonlinear dynamics seem best suited for modeling many of the phenomena, and putative global pathways in the brain, attributable to such external influences.     

Stress, behaviour and reproductive performance in female cattle and pigs

Female farm animals are exposed to a great variety of environmental and management related stressors. As a consequence, their reproductive and maternal abilities may be compromised through mechanisms acting on the hypothalamic, pituitary, ovarian and uterine function. Responses to short- and long-term stressors may differ as short-term stressors often fail to affect reproduction or even may have stimulatory effects. Thus, the stress response induces diverse neuroendocrine reactions that can either increase or decrease the probability of an animal reproducing depending on the specific situation. The aim of the present review is to summarise the current knowledge on the stress concept and its implications on behaviour and reproductive performance in cows and female pigs as phenomena reported in laboratory animals are unable to explain all effects encountered in domesticated farm animals.     

Specific and unspecific responses of plants to cold and drought stress

Different environmental stresses to a plant may result in similar responses at the cellular and molecular level. This is due to the fact that the impacts of the stressors trigger similar strains and downstream signal transduction chains. A good example for an unspecific response is the reaction to stressors which induce water deficiency e.g. drought, salinity and cold, especially frost. The stabilizing effect of liquid water on the membrane bilayer can be supported by compatible solutes and special proteins. At the metabolic level, osmotic adjustment by synthesis of low-molecular osmolytes (carbohydrates, betains, proline) can counteract cellular dehydration and turgor loss. Taking the example of Pinus sylvestris, changes at the level of membrane composition, and concomitantly of photosynthetic capacity during frost hardening is shown. Additionally the effect of photoperiod as measured via the phytochrome system and the effect of subfreezing temperatures on the incidence of frost hardening is discussed. Extremely hydrophilic proteins such as dehydrins are common products protecting not only the biomembranes in ripening seeds (late embryogenesis abundant proteins) but accumulate also in the shoots and roots during cold adaptation, especially in drought tolerant plants. Dehydrins are characterized by conserved amino acid motifs, called the K-, Y-or S-segments. Accumulation of dehydrins can be induced not only by drought, but also by cold, salinity, treatment with abscisic acid and methyl jasmonate. Positive effects of the overexpression of a wild chickpea (Cicer pinnatifidum) dehydrin in tobacco plants on the dehydration tolerance is shown. The presentation discusses the perception of cold and drought, the subsequent signal transduction and expression of genes and their products. Differences and similarities between the plant responses to both stressors are also discussed.     

Neurodynamics, tonality, and the auditory brainstem response

Tonal relationships are foundational in music, providing the basis upon which musical structures, such as melodies, are constructed and perceived. A recent dynamic theory of musical tonality predicts that networks of auditory neurons resonate nonlinearly to musical stimuli. Nonlinear resonance leads to stability and attraction relationships among neural frequencies, and these neural dynamics give rise to the perception of relationships among tones that we collectively refer to as tonal cognition. Because this model describes the dynamics of neural populations, it makes specific predictions about human auditory neurophysiology. Here, we show how predictions about the auditory brainstem response (ABR) are derived from the model. To illustrate, we derive a prediction about population responses to musical intervals that has been observed in the human brainstem. Our modeled ABR shows qualitative agreement with important features of the human ABR. This provides a source of evidence that fundamental principles of auditory neurodynamics might underlie the perception of tonal relationships, and forces reevaluation of the role of learning and enculturation in tonal cognition.     

From Musical Experience to Personality Transformation: The Practice of Musical Movement

This article explores the mechanisms of musical experience and how they are revealed in the practice of plastic improvisation in response to music. Musical movement creates conditions that activate and organize the processes of the emotional perception and experiencing of music in an outwardly expressed motoric form. Musical motor activity not only reflects but also transforms a person’s life experience and, thereby, initiates the complex work of becoming aware of, and reinterpreting, one’s values and motives and relating them to one’s capabilities and to the restructuring of one’s self-image on a mental and corporal level.