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Tonic Immobility (TI) functions as anti-predator defense. Its duration depends on cues signaling predator proximity. One such cue includes alarm calls from conspecifics and non-conspecifics. This study aimed to determine the cue within alarm calls that controls TI duration. We induced TI in chicks (Gallus gallus) and found that their TI durations increased in the presence of adult conspecific alarm calls, non-conspecific alarm calls, and synthetic sounds made of white noise set to the repetition rate found in natural alarm calls. Moreover, chicks did not increase their TI durations when exposed to conspecific attraction calls, synthetic sounds made of white noise set to the repetition rate found in natural attraction calls, and derived sounds made of a natural alarm call lacking an internote interval. We then created: 1) sounds with white noise set to the internote interval found in natural alarm calls and the note duration found in natural attraction calls, and 2) sounds with white noise set to the internote interval found in natural attraction calls and the note duration found in natural alarm calls. Neither affected TI duration. We conclude that repetition rate acts as a salient cue that lengthens TI duration.

Elucidating the multi-faceted relationship between cognitive competence and affective states is a major pursuit in behavioral sciences. Mood disorders constitute a good research model for this question, as cognitive impairment may accompany clinical depression and persist after full remission. This suggests cognitive dysfunction as an etiological factor of depression, rather than an epiphenomenon. Complementing clinical studies, animal models utilizing well-controlled, systematic paradigms are essential to elucidate the complex relationship between cognitive competence and affective states. In current set of experiments, we investigated the extent to which cognitive competence determines the stress response in Wistar rats by utilizing two well-established spatial memory paradigms with different degrees of complexity together with the forced swim test. We revealed that rats with low cognitive competence as assessed by learning performance in the Y-Maze, but not in the radial arm maze, were significantly more vulnerable to behavioral despair. In contrast, rats with high cognitive competence were resilient to the negative effects of the forced swim test, irrespective of the spatial memory task used. These results point to a nonlinear relationship between spatial memory performance and behavioral despair, suggesting that different types of cognitive functioning may have differential effects on affective processes.

International audience; The positive aspect of emotions, like pleasure, remains overlooked in birds. Our aim was to contribute to the exploration of facial indicators of positive emotions. To observe contrasting emotional expressions, we used two lines of Japanese quail divergently selected on their inherent fearfulness: a fearful line (long tonic immobility duration: LTI) and a less fearful line (short tonic immobility duration: STI). To induce positive emotions, we gave individual quail the opportunity to perform a rewarding behaviour, dustbathing, in an unfamiliar cage. More STI than LTI quail expressed dustbathing and latencies to dustbathe were significantly shorter in STI than LTI quail. This result indicated that the lines of quail differed in their fearfulness of the situation. We observed crown feather height, throat feather angle and pupil surface before (control) and during dustbathing. We found significant increases in crown feather height, pupil area and angle of throat feathers between the control and the dustbathing phases in STI quail, and pupil area correlated positively with crown feather height. In LTI quail, the angle of throat feathers increased during dustbathing, but the other parameters did not differ. We argue that variation in crown feather height and pupil area may provide indications of positive emotions in Japanese quail.

Anxiety, trauma- and stressor-related disorders are severe psychiatric conditions that affect human population worldwide. Given their genetic tractability, evolutionarily conserved neurotransmitter systems, and extensive behavioral repertoire, zebrafish have become an emergent model organism in translational neuroscience. Here, we investigate whether a single exposure to conspecific alarm substance (CAS) produces fear conditioning in zebrafish using a conditioned place aversion (CPA) paradigm, as well as the persistence of aversive responses at different time intervals. While CAS elicited freezing and erratic movements at conditioning phase, zebrafish showed a robust avoidance for the CAS-paired compartment and increased risk assessment up to 7 days postconditioning. Additionally, we observed the existence of two behavioral phenotypes (high- and low-avoider fish) that present different fear-like responses at conditioning phase and evasion of the conditioning side at postconditioning trials. Collectively, we show a prolonged conditioned place aversion in zebrafish after a single CAS conditioning session, reinforcing the use of fear conditioning protocols as valuable strategies for modeling psychiatric disorders-related phenotypes in zebrafish.

Stressful experiences in the rat during early life increase the vulnerability to later signs of behavioral despair in adulthood, reflected in increased immobility in the forced swim test (FST). However, the possible immediate effects of stress in weanling rats have only been partially described. The present study tested whether a single session of mild restraint stress modifies immobility in the FST in 21-day-old Wistar rats. After evaluating any possible changes in locomotion using the open field test (OFT), the latency and total duration of immobility were assessed in a single FST session. Regardless of gender, mild restraint stress significantly reduced crossings in the OFT, shortened the latency to the first period of immobility, and increased immobility in the FST compared with a control group devoid of stress. We conclude that a single mild physical stress session, as early as postnatal day 21, produces signs of behavioral despair.

Forced Swimming Test (FST) models behavioural despair in animals by loss of motivation to respond or the refusal to escape. The present study characterizes the behavioural responses of 12-month-old male 3xTg-AD mice in FST as compared to age-matched no-transgenic (NTg) mice. Paradoxical results were consistently found from what would be expected from their BPSD (Behavioural and Psychological Symptoms of Dementia)-like profile. The comprehensive analysis of the ethogram shown in the FST considered the intervals of the test (0-2 and 2-6min), all the elicited behavioural responses (immobility, swimming and climbing) and their features (total duration, frequency of episodes and mean duration). Both genotypes showed equal number of swimming episodes and climbing attempts during the first interval, that resulted in high swimming times, short climbing and scarce immobility. Thereafter, the NTg mice showed a behavioural shift over time and the immobility response showed up. In contrast, all the measures consistently evidenced that 3xTg-AD persisted with the previous behavioural pattern. Genotype differences consisted in less number of episodes of immobility and swimming, and a low immobility time in favour of swimming. No differences were found in 'climbing' attempts. The behavioural response observed is discussed as a lack of ability of 3xTg-AD mice to shift behaviour over time that may result of poorest cognitive flexibility and copying with stress strategies more than behavioural despair per se.

Freezing responses to fearful stimuli are crucial for survival among all animal species within a prey-predator system. Generally, the degree of fearfulness correlates with intensity, duration, and frequency of freezing behaviours in response to fear-relevant stimuli. The present study examines innate fear responses to human handling in 144 newly hatched chicks through a tonic immobility (TI) test. Two fear responses-freezing duration and number of TI inductions-were examined. Individual variations in innate fear were investigated in chicks 1-2 days post-hatching when the restraint procedure was successively repeated 3 times within each day. Chicks showed sensitivity to fearful stimuli and considerable inter-individual variation in freezing duration and number of attempts required to induce TI. Moreover, differences were observed between breeds; White Leghorn chicks showed relatively low fear levels with gradual increases in TI duration, whereas Nagoya chicks showed extended TI duration and habituation to fearful stimuli. Our results suggest that TI reactions among newly hatched chicks are an innately determined behaviour specific to a breed or strain of chicken. Further, fearful responses among newborn chicks are not simple, but complex behaviours that involve multiple factors, such as breed-specific contextual fear learning and habituation/sensitisation processes.

Behavioral analyses of genetically modified and inbred strains of mice have revealed neural systems and molecules that are involved in memory formation. Many of these studies have examined memories that form in contextual fear conditioning, in which an organism learns that a particular context signals the occurrence of a footshock. During fear extinction, nonreinforced exposure to the context results in the loss of the conditioned fear response. The study of extinction has been instrumental for behavioral and molecular theories of memory. However, many of the transgenic, knockout, and inbred strains of mice that have been widely studied in memory have behavioral deficits in contextual fear conditioning, which makes the study of extinction in these mice particularly challenging. Here we explore several strategies for studying extinction in C57BL/6 and DBA/2 mice, two strains known to differ in contextual fear conditioning. First, we attempt to equate performance prior to extinction through several extensive conditioning protocols. Second, we examine extinction in subsets of mice matched for initial levels of context conditioning. Third, we examine within-strain effects of variables known to affect extinction. Differences between the strains persisted across extensive conditioning and extinction protocols, but both strains were sensitive to session duration and context manipulations during extinction. We describe the implications of our results for behavioral and neurobiological approaches to extinction, and we examine the general challenges in studying extinction in subjects that differ in learning or performance prior to extinction.

Research on the inhibition of learned fear currently relies almost exclusively on one specific procedure, namely extinction of the conditioned stimulus (CS). Importantly, however, learned fear responses can be reduced by a number of other procedures, including habituation of the unconditioned stimulus (US). We recently demonstrated that reductions in learned fear following US habituation, like CS extinction, were subject to both renewal and reinstatement (Storsve et al., 2010). The present study further investigates the associative and non-associative processes shared between habituation and extinction. Given that habituation is typically context-independent (Mackintosh, 1987), in the present study we directly compared renewal and reinstatement of both a conditioned response (CR; freezing) and an unconditioned response (UR; startle) following habituation. It was found that the reduction in conditioned freezing resulting from habituation was context specific (i.e., a change in context led to a renewal of the conditioned fear response; Experiment 1) and was attenuated when a pre-test shock was given (i.e., reinstatement of conditioned fear was observed; Experiment 2). In contrast, habituation of an unconditioned response elicited by the US (i.e., a startle response) was unaffected by either a change in test context or administration of a pre-test shock. This dissociation in the effects of habituation on learned and unlearned responses is discussed in relation to theories of fear extinction.