Heart rate measures in blind cave crayfish during environmental disturbances and social interactions

Most animals continually assess the environment in which they live and alter their behavior according to various stimuli. As an observer, one looks for changes in a behavior indicating that an animal responded to a particular event. When the animal does not make significant behavioral changes as measured by bodily movements, the animal may be characterized as unresponsive to a given stimulus. This study demonstrates that when behavioral body movements can not be observed an internal physiological measure of heart rate (HR) shows dramatic changes following presentation of defined stimuli. This study used the blind cave crayfish and examined their responsiveness to the following stimuli: light (infrared, dim red, and white), water-borne vibrations, removal of water, olfactory cues, and social interaction with partners. This study demonstrates that there is substantial individual variation of HR at basal levels and with the intensity of an social interaction. We find HR is a reasonable measure of the responsiveness of blind cave crayfish to given stimuli even in the absence of observable behavioral changes. This enables the observer to determine if an individual is responsive to and making an assessment of particular cues.     

Cardiac activity of freshwater crayfish at wakefulness, rest, and “animal hypnosis”

In laboratory experiments, simultaneous continuous recording of the circadian cycle of behavioral reactions and cardiac activity of freshwater crayfish Astacus astacus and Procambarus clarkii was carried out. A non-invasive fiber-optic method of recording of the heart rate (HR) was used. The obtained data were analyzed by the method of variational pulsometry (VP). It was revealed that certain values of HR and characteristics of VP corresponded to the physiological states of active wakefulness and rest. It was found that during long immobilization of crayfish it is possible to identify the states of operative rest and sleep by the animal behavioral reactions and parameters of cardiac activity. Crayfish were studied in the state of artificially evoked immobilization (“animal hypnosis”). During this state, a high HR level, an increase of indexes of tension and autonomic equilibrium, and changes of other VP characteristics were observed. It is suggested that the different level of cardiac activity in different physiological states of crayfish (active wakefulness, operative rest, sleep, and “animal hypnosis”) is regulated by nervous influences analogous to sympathetic and parasympathetic influences in vertebrates. It was concluded that freshwater crayfish as a representative of the highly organized invertebrates can serve an effective model for studying mechanisms of sleep-like states and “animal hypnosis” in animals.     

Heart rate within male crayfish: social interactions and effects of 5-HT

Behaviors, such as those that establish dominant and subordinate social status, are thought to be driven by various neuromodulators and hormones. In crustaceans, the level of serotonin (5-HT) in the hemolymph is correlated with degree of aggressiveness. The crustacean heart is neurogenic and is modulated by neural secretion of 5-HT in the hemolymph, which bathes the cardiac tissue. We discuss and present the results of measuring heart rate (HR) of crayfish during interactions, as an indication of their state of excitability. HR is the result of multiple influences: a cocktail of hormones and modulators. HR was monitored during the periods in which crayfish established aggressive and submissive social status, during sham injections, and following injections of various doses of 5-HT. Crayfish, during an interaction to establish social status, can increase HR. Both the aggressive and submissive crayfish can dampen their HR within seconds during a pause in the interaction, while still posturing in an aggressive or submissive state. Injections of 5-HT to obtain systemic levels of approximately 100 nM-10 microM increase HR substantially for hours. This suggests that aggressive interactions and the establishment of a dominant posture may not be related to large increases in the free concentrations of 5-HT within the circulating hemolymph, since a sustained HR is not observed in aggressive animals. Instead, the results may demonstrate that inhibitory cardiac regulation is present in the aggressors during interactions and that a regulator is possibly 5-HT.     

Pten and the brain: sizing up social interaction

In a comprehensive set of experiments in this issue of Neuron, Kwon et al. demonstrate that conditional inactivation of Pten leads to behavioral abnormalities and neuropathological changes. Pten mutants displayed reduced social interaction and heightened responses to sensory stimuli. Additionally, neuronal hypertrophy, as well as macrocephaly was observed. Based on rare human mutations in PTEN and the PI3K pathway, the authors suggest they have produced a potential animal model of autism with macrocephaly.     

Alterations in habituation of the tail flip response in epigean and troglobitic crayfish

We demonstrate that the probability of the crayfish, P. clarkii, to tail flip in response to a touch on the dorsal tail fan is dependent on both the size and the behavioral state of the animal. Alterations in the animal's internal physical state, such as when the animal autotomizes its chelipeds, will cause larger-sized animals to tail flip; if they were not autotomized, then no tail flip response would occur. Altering the external environment by removal of water causes small crayfish, which normally habituate slowly, to rapidly habituate. Observation of large adult crayfish in a species, O. australis packardi, one that evolved to live in total cave darkness, revealed that they are more likely to tail flip than are the sighted, adult P. clarkii. Results indicate that the behavioral state of the crayfish can result in rapid and long-term alterations in the tail flip response and in habituation rates to repetitive stimuli. This ability to show plasticity in gain setting may be regulated by neuromodulators and can occur in large adults of the sighted crayfish. Differences between the two species indicate that size may not be the sole contributing factor to account for tail flip behaviors. J. Exp. Zool. 290:163-176, 2001.     

Novelty stress and reproductive state alters responsiveness to sensory stimuli and 5-HT neuromodulation in crayfish

Sensory stimuli can produce varied responses depending on the physiological state of an animal. Stressors and reproductive stage can result in altered biochemical status that changes the responsiveness of an animal to hormones and neuromodulators, which affects whole animal behavior in relation to sensory stimuli. Crayfish serve as a model for examining the effects of neuromodulators at the neuromuscular junctions (NMJs) and for alterations in stereotypic behaviors for particular stimuli. Thus, we used crayfish to examine the effect of novelty stressors in males and the effect of being gravid in female crayfish to exogenous application of serotonin (5-HT). The responsiveness of neuromuscular junctions to 5-HT revealed that stressed as well as gravid crayfish have a reduced response to 5-HT at NMJs. The stressed crayfish were not fatigued since the basal synaptic responses are large and still showed a pronounced response to 5-HT. Using intact animals to examine a tail flip behavior, we showed that the rate of habituation in tail flipping to a strong repetitive stimulus on the telson is reduced in stressed males. Gravid females show no tail flipping behavior upon telson stimulation.     

Peculiarities of Cardiac Activity in the Crayfish Astacus astacus in Different Functional States

Analyzed are changes of temporal and amplitude characteristics of the cycles in animals in different functional states, using a non-invasive method of recording of cardiac activity in the adult noble crayfish Astacus astacus L. under laboratory conditions. It has been shown that the state of excitation in the crayfish after action of an intense stimulus lasts for a long time (more than 1 h) and can have no manifestations in some observed behavioral responses. Based only on the cardiac response (the heart rate), the real physiological state of the animal could be evaluated. Characteristic of the excited animal is a short-term response to the stimulus. In a high excitement of the animal (a high heart rate), significant transformations of the heart activity in response to other current stimuli may be barely noticeable. For the quiet animal, the response to a stimulus is longer than for the excited animal at the same stimulus intensity; for a comparative search for significant readjustments of the animal state, based on the heart activity parameters, the cardiograms typical of the quiet animal should be used. In the quiet animals, the cardiogram parameters change to a greater extent than in the excited ones. The quiet animals have longer diastole duration (DD) than the systole duration (SD). The diastole amplitude (DA) is higher than the systole amplitude (SA), and DA changes more markedly than SA. The healthy animals are characterized by equal values of DD and SD, sometimes by longer SD than DD, but, on the background of a continuing action, their values and the values of DA and SA become equal. There were noted a negative correlation between the systolic and diastolic phases by temporal parameters for healthy animals and an increase of the correlation significance in transition of the animal into the excited state. Based on the cardiovascular system response, the chief features of a shift of the functional crayfish state to pathological direction seem to include a stable heart rate reduction, a decrease of the heart contraction amplitude, a more frequent predominance of SD over DD, an increase of the means and the standard deviations of the parameters, especially of the cycle amplitudes. Changes of the sign and significance of correlation relations between inotropic and chronotropic parameters of cardiac activity in sick animals appear to indicate a disturbed mechanism of central coordination of the cardiovascular system work with its autonomic mechanisms. The results are discussed on the basis of known mechanisms of the heart activity control in Decapoda. The records of cardiac activity, such as laser light cardiograms (LLC), in testaceous invertebrates may be useful and interesting in studies on mechanisms and processes of internal control and management of the cardiovascular system activity of the animals.     

Survey of environmental enhancement programs for laboratory primates

Animal welfare regulations in the United States require that nonhuman primate environmental enhancement plans be made in accordance with currently accepted professional standards; however, little information is available for quantifying common practice. Here we report the results of a 2003 survey that was sent to individuals overseeing enrichment programs at a variety of primate research institutions. The surveys requested information on program administration and management, implementation standards, procedures, and constraints pertaining to major categories of environmental enrichment, as well as intervention plans for animals exhibiting behavioral pathologies. Data were obtained on the management of 35,863 primates in 22 facilities. Behavioral scientists performed program oversight at the majority of facilities. Most programs reported recent changes, most commonly due to external site visits, and least commonly resulting from internal review. Most facilities' institutional animal care and use committees (IACUCs) included of individuals with behavioral expertise, and about two-thirds reported that enrichment issues could influence research protocol design. While most primates were reported to be housed socially (73%), social housing for indoor-housed primates appears to have changed little over the past 10 years. Research protocol issues and social incompatibility were commonly cited constraints. Implementation of feeding, manipulanda, and structural enrichment was relatively unconstrained, and contributions to these aspects of behavioral management generally included individuals in a wide variety of positions within a facility. In contrast, enrichment devices were used on a less widespread basis within facilities, and positive reinforcement programs that involved dedicated trainers were rare. We suggest that altering the role of the IACUC would be a productive avenue for increasing the implementation of social housing, and that an emphasis on prevention rather than intervention against behavioral pathology is warranted. The data from this survey may be useful for anticipating future program evaluations, establishing more effective internal evaluations, and assessing program progress and resource allocation.     

The Commonality of Loss Aversion across Procedures and Stimuli

Individuals tend to give losses approximately 2-fold the weight that they give gains. Such approximations of loss aversion (LA) are almost always measured in the stimulus domain of money, rather than objects or pictures. Recent work on preference-based decision-making with a schedule-less keypress task (relative preference theory, RPT) has provided a mathematical formulation for LA similar to that in prospect theory (PT), but makes no parametric assumptions in the computation of LA, uses a variable tied to communication theory (i.e., the Shannon entropy or information), and works readily with non-monetary stimuli. We evaluated if these distinct frameworks described similar LA in healthy subjects, and found that LA during the anticipation phase of the PT-based task correlated significantly with LA related to the RPT-based task. Given the ease with which non-monetary stimuli can be used on the Internet, or in animal studies, these findings open an extensive range of applications for the study of loss aversion. Furthermore, the emergence of methodology that can be used to measure preference for both social stimuli and money brings a common framework to the evaluation of preference in both social psychology and behavioral economics.     

Parallel changes in agonistic and non-agonistic behaviors during dominance hierarchy formation in crayfish

Agonistic and non-agonistic behaviors were studied before, during, and after the formation of social status in crayfish. Differences in the expression of a non-agonistic behavior by dominant and subordinate crayfish developed in parallel with the differences in agonistic behaviors that indicate the animals' social status. An increase in burrowing behavior marked the ascendancy of the dominant animal, while an immediate suppression of burrowing paralleled the inhibition of aggressive behavior in the new subordinate. The strikingly similar changes in both agonistic and non-agonistic behaviors following the decision on status suggest related underlying neural mechanisms.     

Intrinsic and extrinsic influences on cardiac rhythms in crustaceans

Several factors cause predictable changes in heart rate of crustaceans thus affecting basic heart rhythms. In decapod crustaceans these consist of: many internal factors including influences from neural and neurohormonal systems and chemosensory influences; many external factors including startling stimuli and other disturbance; ventilatory (scaphognathite) reversals; tail flips and other postural movements including locomotor activity; and variations in environmental factors such as oxygen level, temperature and air-exposure. In many cases the initial response involves temporary bradycardia or cardiac arrest. These responses may quickly facilitate to sustained low level stimuli although maintained strong stimulation will eventually be associated with cardio-acceleration and escape responses. Measurement of change in heart rate alone is rarely a sensible monitor of cardiac performance in crustaceans since simultaneous changes in cardiac stroke volume occur which may confound diagnosis. Hypoxia for instance causes decrease in heart rate of adult crustaceans but the apparent decrease in cardiac output is offset or reversed by increase in stroke volume. Concomitant changes occur in cardiac output and in the proportion of cardiac output which is delivered to particular tissues. In fact change in heart rhythm is only one factor in a complex suite of responses involving several physiological systems which compensate uniquely for changes in environmental or other stimuli. Both neural and neuro-hormonal factors are known to play a role in control of these complex responses.     

Functional genomics of neural and behavioral plasticity

How does the environment, particularly the social environment, influence brain and behavior and what are the underlying physiologic, molecular, and genetic mechanisms? Adaptations of brain and behavior to changes in the social or physical environment are common in the animal world, either as short-term (i.e., modulatory) or as long-term modifications (e.g., via gene expression changes) in behavioral or physiologic properties. The study of the mechanisms and constraints underlying these dynamic changes requires model systems that offer plastic phenotypes as well as a sufficient level of quantifiable behavioral complexity while being accessible at the physiological and molecular level. In this article, I explore how the new field of functional genomics can contribute to an understanding of the complex relationship between genome and environment that results in highly plastic phenotypes. This approach will lead to the discovery of genes under environmental control and provide the basis for the study of the interrelationship between an individual's gene expression profile and its social phenotype in a given environmental context.     

Photoperiodic Mediation of Seasonal Breeding and Immune Function In Rodents: A Multi-Factorial Approach

SYNOPSIS. Winter is energetically-demanding; thermoregulatorydemands increase when food availability usually decreases. Physiologicaland behavioral adaptations, including termination of breeding,have evolved among nontropical animals to cope with winter energyshortages. Presumably, selection for mechanisms that permitphysiological and behavioral anticipation of seasonal ambientchanges have led to current seasonal breeding patterns for manypopulations. Energetically—challenging winter conditionscan directly induce death via hypothermia, starvation, or shock;surviving these demanding conditions likely evokes significantstress responses. The stress of coping with energetically-demandingconditions may increase adrenocortical steroid levels to theextent that immune function is compromised. Individuals wouldenjoy a survival advantage if seasonally-recurring stressorscould be anticipated and countered by shunting energy reservesto bolster immune function. The primary environmental cue thatpermits physiological anticipation of season is daily photoperiod,a cue that is mediated by melatonin. However, other environmentalfactors, such as low food availability and ambient temperatures,may interact with photoperiod to affect immune function anddisease processes. Laboratory studies of seasonal changes inmammalian immune function consistently report that immune functionis enhanced in short day lengths. Prolonged melatonin treatmentmimics short days, and also enhances immune function in rodents.In sum, melatonin may be part of an integrative system to coordinatereproductive, immunologic, and other physiological processesto cope successfully with energetic stressors during winter.Social factors influence immune function and changes in socialinteractions may also contribute to seasonal changes in immunefunction. The mechanisms by which social factors are transducedinto immune responses are largely unspecified. In order to understandthe optimization of immune function it is necessary to understandthe interaction of factors, on both mechanistic and functionallevels, that affect immunity.     

Reproductive synchronization in squirrel monkeys (Saimiri)

Groups of squirrel monkeys (Saimiri) that are exposed to certain seasonal environmental stimuli experience a yearly reproductive cycle with discrete mating and birth seasons. Seasonal rainfall or some rainfall induced seasonal changes (such as changes in vegetation or insect fauna) appear to be responsible for timing theSaimiri reproductive cycle. Animals of both sexes show significant physiological and behavioral changes during the yearly cycle. Whether the environmental timing factors affect both the males and the females equally, or affect only one sex directly and the other sex indirectly through social communication is not clear. Three mechanisms by which the reproductive activity of both males and females could be synchronized are presented, and data from a laboratory study and a field study relevant to each mechanism are presented. Several social interaction patterns frequently observed in the field study suggest that (1) male sexual activity may excite female sexual activity through male penile display and/or other stereotyped interactions and/or (2) female sexual activity may excite male sexual activity through pheromone and/or other communication channels.     

Endocrine mechanisms,behavioral phenotypes and plasticity: known relationships and open questions

Behavior of wild vertebrate individuals can vary in response to environmental or social factors. Such within-individual behavioral variation is often mediated by hormonal mechanisms. Hormones also serve as a basis for among-individual variations in behavior including animal personalities and the degree of responsiveness to environmental and social stimuli. How do relationships between hormones and behavioral traits evolve to produce such behavioral diversity within and among individuals? Answering questions about evolutionary processes generating among-individual variation requires characterizing how specific hormones are related to variation in specific behavioral traits, whether observed hormonal variation is related to individual fitness and, whether hormonal traits are consistent (repeatable) aspects of an individual's phenotype. With respect to within-individual variation, we need to improve our insight into the nature of the quantitative relationships between hormones and the traits they regulate, which in turn will determine how they may mediate behavioral plasticity of individuals. To address these questions, we review the actions of two steroid hormones, corticosterone and testosterone, in mediating changes in vertebrate behavior, focusing primarily on birds. In the first part, we concentrate on among-individual variation and present examples for how variation in corticosterone concentrations can relate to behaviors such as exploration of novel environments and parental care. We then review studies on correlations between corticosterone variation and fitness, and on the repeatability over time of corticosterone concentrations. At the end of this section, we suggest that further progress in our understanding of evolutionary patterns in the hormonal regulation of behavior may require, as one major tool, reaction norm approaches to characterize hormonal phenotypes as well as their responses to environments.In the second part, we discuss types of quantitative relationships between hormones and behavioral traits within individuals, using testosterone as an example. We review conceptual models for testosterone-behavior relationships and discuss the relevance of these models for within-individual plasticity in behavior. Next, we discuss approaches for testing the nature of quantitative relationships between testosterone and behavior, concluding that again reaction norm approaches might be a fruitful way forward.We propose that an integration of new tools, especially of reaction norm approaches into the field of behavioral endocrinology will allow us to make significant progress in our understanding of the mechanisms, the functional implications and the evolution of hormone–behavior relationships that mediate variation both within and among individuals. This knowledge will be crucial in light of already ongoing habitat alterations due to global change, as it will allow us to evaluate the mechanisms as well as the capacity of wild populations to adjust hormonally-mediated behaviors to altered environmental conditions.     

Effect of Familiarity on Reward Anticipation in Children with and without Autism Spectrum Disorders

Background

Previous research on the reward system in autism spectrum disorders (ASD) suggests that children with ASD anticipate and process social rewards differently than typically developing (TD) children—but has focused on the reward value of unfamiliar face stimuli. Children with ASD process faces differently than their TD peers. Previous research has focused on face processing of unfamiliar faces, but less is known about how children with ASD process familiar faces. The current study investigated how children with ASD anticipate rewards accompanied by familiar versus unfamiliar faces.

Methods

The stimulus preceding negativity (SPN) of the event-related potential (ERP) was utilized to measure reward anticipation. Participants were 6- to 10-year-olds with (N = 14) and without (N = 14) ASD. Children were presented with rewards accompanied by incidental face or non-face stimuli that were either familiar (caregivers) or unfamiliar. All non-face stimuli were composed of scrambled face elements in the shape of arrows, controlling for visual properties.

Results

No significant differences between familiar versus unfamiliar faces were found for either group. When collapsing across familiarity, TD children showed larger reward anticipation to face versus non-face stimuli, whereas children with ASD did not show differential responses to these stimulus types. Magnitude of reward anticipation to faces was significantly correlated with behavioral measures of social impairment in the ASD group.

Conclusions

The findings do not provide evidence for differential reward anticipation for familiar versus unfamiliar face stimuli in children with or without ASD. These findings replicate previous work suggesting that TD children anticipate rewards accompanied by social stimuli more than rewards accompanied by non-social stimuli. The results do not support the idea that familiarity normalizes reward anticipation in children with ASD. Our findings also suggest that magnitude of reward anticipation to faces is correlated with levels of social impairment for children with ASD.     

Physiological Adaptations of Crayfish to the Hypoxic Environment

SYNOPSIS. Crayfish routinely encounter waters of reduced oxygentension, resulting in a broad array of behavioral and physiologicalresponses. Many animals when faced with this stress will simplyremove themselves from the irritating environment through voluntarymigration. When an animal, either by choice or through physicalconstraints remains in a hypoxic environment it must compensatefor the reduction in O₂ availability. Many crayfish have theability to maintain oxygen consumption independent of waterPo₂ down to some critical level; below this the animal can nolonger maintain normoxic levels of aerobic metabolism. Regulationof oxygen uptake is thought to be due to a hypoxia-induced hyperventilationalong with an increase in hemocyanin O₂ affinity and an improvementin the ability of the respiratory surfaces to transfer O₂. Crayfishexposed to a reduction in water oxygen also show a strong bradycardia,which is compensated for by an increase in stroke volume, resultingin a maintenance of cardiac output. The adaptive advantage ofthis response is uncertain. As water Po₂ drops crayfish havebeen shown to redistribute cardiac output, presumably throughthe action of the cardioarterial valves. Hemolymph is shuntedto the anterior end of the animal, resulting in a greater perfusionof nervous tissue. The animals' ability to detect changes inwater Po₂ appear to result from O₂ sensitive receptors locatedon the gills or in the branchiocardiac veins. The integratedphysiological response toward environmental hypoxia allows thecrayfish to not only deal with the stress but to maintain activity.     

Phencyclidine animal models of schizophrenia: approaches from abnormality of glutamatergic neurotransmission and neurodevelopment

In humans, phencyclidine (PCP), a non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist, reproduces a schizophrenia-like psychosis including positive symptoms, negative symptoms and cognitive dysfunction. Thus, the glutamatergic neuronal dysfunction hypothesis is one of the main explanatory hypotheses and PCP-treated animals have been utilized as an animal model of schizophrenia. The adult rodents treated with PCP repeatedly exhibit hyperlocomotion as an index of positive symptoms, a social behavioral deficit in a social interaction test and enhanced immobility in a forced swimming test as indices of negative symptoms. They also show a sensorimotor gating deficits and cognitive dysfunctions in several learning and memory tests. Some of these behavioral changes endure after withdrawal from repeated PCP treatment. Furthermore, repeated PCP treatment induces some neurochemical and neuroanatomical changes. On the other hand, the exposure to viral or environmental insult in the second trimester of pregnancy increases the probability of subsequently developing schizophrenia as an adult. NMDA receptor has been implicated in controlling the structure and plasticity of developing brain circuitry. Based on neurodevelopment hypothesis of schizophrenia, schizophrenia model rats treated with PCP at the perinatal stage is developed. Perinatal PCP treatment impairs neuronal development and induces long-lasting schizophrenia-like behaviors in adult period. Many findings suggest that these PCP animal models would be useful for evaluating novel therapeutic candidates and for confirming pathological mechanisms of schizophrenia.     

Compensatory possibilities of the crayfish cardiovascular system under conditions of progressing hypoxia

Under laboratory conditions, the rate of oxygen consumption and changes of inotropic and chronotropic parameters of work of the crayfish heart were studied under conditions of hypoxia and anoxia. In all studied crayfishes regardless of species and sex there exists regulation of the rate of oxygen consumption until its concentration in water about 1 mg/l at room temperature, the rate of standard metabolism being independent of oxygen concentration above 24% from saturation; below this level the rate of oxygen consumption amounts to 54% of its standard consumption. The ability to regulate metabolism in hypoxia is also presents in small crayfishes; however, their respiration rate is several times higher than in adult animals. Under conditions of severe hypoxia the cardiovascular system (CVS) of crayfish functions in economic regime with use of dependent regimes of initiation of inotropic and chronotropic heart parameters; with increase of severity of the hypoxic factor, a tendency is observed for a decrease of the heart rate (HR) and for an increase of amplitude parameters. Under anoxic conditions the crayfish demonstrated the heart contractile activity for almost 10 h; analysis of the HR by the method of variation pulsometry has shown deterioration of the crayfish functional state, which was due to desynchronization of regulatory processes in the central and peripheral chains of control of CVS.     

Environmental variables that ameliorate extinction learning deficits in the 129S1/SvlmJ mouse strain

Fear conditioning is an associative learning process by which organisms learn to avoid environmental stimuli that are predictive of aversive outcomes. Fear extinction learning is a process by which avoidance of fear‐conditioned stimuli is attenuated when the environmental stimuli is no longer predictive of the aversive outcome. Aberrant fear conditioning and extinction learning are key elements in the development of several anxiety disorders. The 129S1 inbred strain of mice is used as an animal model for maladaptive fear learning because this strain has been shown to generalize fear to other nonaversive stimuli and is less capable of extinguishing fear responses relative to other mouse strains, such as the C57BL/6. Here we report new environmental manipulations that enhance fear and extinction learning, including the ability to discriminate between an aversively paired tone and a neutral tone, in both the 129S1 and C57BL/6 strains of mice. Specifically, we show that discontinuous (“pipped”) tone stimuli significantly enhance within‐session extinction learning and the discrimination between neutral and aversively paired stimuli in both strains. Furthermore, we find that extinction training in novel contexts significantly enhances the consolidation and recall of extinction learning for both strains. Cumulatively, these results underscore how environmental changes can be leveraged to ameliorate maladaptive learning in animal models and may advance cognitive and behavioral therapeutic strategies.