Stimulus control of antipredator behavior in newborn and juvenile garter snakes (Thamnophis).

Used neonate and juvenile garter snakes (Thamnophis sirtalis, T. melanogaster, and T. butleri) to investigate the role of visual stimuli in mediating antipredator behaviors and to examine the validity of techniques used to assess defensive responses. Experiment 1 demonstrated that a human hand and a model predator were more effective than other stimuli in eliciting defensive responses in neonates with no prior experience with threatening stimuli. Experiment 2 showed that yearlings responded similarly to a realistic predator model and a human hand. Experiment 3 showed that the level of antipredator behaviors was affected by stimulus size. Experiment 4 indicated that the same snakes gave similar quantitative results when tested by different experimenters with the human hand. The final study demonstrated that stimulus movement influenced defensive responses in some species but not others and found litter and experiential effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Defensive behaviors of laboratory and wild Rattus norvegicus..

Examined in 2 studies, with 29 wild rats, 15 Long-Evans laboratory rats, and 11 1st-generation offspring from 3 sets of wild-trapped parents, the defensive repertoire of wild rats in a variety of situations and compared these behaviors with those of domestic rats under identical conditions. Analysis of the defensive behaviors of wild rats to an inescapable approaching threat stimulus (the experimenter) indicated a pattern of freezing to distant stimuli, giving way to vocalization, jumps, and jump attacks at shorter defensive distances. Comparisons of the defensive reactions of wild-trapped and laboratory-bred wild rats to a variety of threatening stimuli, in escapable and inescapable situations, indicated that the 2 wild strains were similar and consistently more defensive than laboratory rats to both human and conspecific threat stimuli. Results suggest that the defensive behaviors of rats have been substantially reduced during the process of domestication, with relatively little of this reduction being attributable to housing in standard laboratory conditions. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence that the behaviors in the Mouse Defense Test Battery relate to different emotional states: a factor analytic study

The Mouse Defense Test Battery (MDTB) has been designed to investigate defensive responses of Swiss-Webster mice confronted with a natural threat, a rat. These behaviors include flight, avoidance, defensive threat/attack reactions, and risk assessment activities. In the present study, a factor analysis was used to examine potential relationships between these behavioral responses. Five independent Factors were extracted from the 17 parameters obtained in the MDTB. Both Factor 1 and Factor 2 include cognitive aspects of defensive behaviors that appear to be related to the process of acquiring and analyzing information in the presence of threatful stimuli (i.e., risk assessment). Flight/avoidance responses heavily loaded on Factor 3 and to a lesser extent on Factor 4. Several defensive threat/attack reactions (i.e., upright postures and biting) highly loaded on Factor 4 and biting also loaded on Factor 3. Finally, the variables that loaded highly on Factor 5 were the number of wall rearings and climbings following the removal of the rat and the immobility time when the subject was trapped in a straight alley. Although the meaning of this latter Factor is not clear at present. Factors 1 to 4 seemingly relate to anxiety. Taken together with recent drug findings from the MDTB, the present analysis further supports the idea that this model provides measures that reflect different aspects of anxiety.     

Development of antipredator responses in snakes: I. Defensive and open-field behaviors in newborns and adults of three species of garter snakes (Thamnophis melanogaster, T. sirtalis, T. butleri).

A comparative study of defensive behavior in multiple litters of newborn garter snakes and adult female garter snakes from 3 species was conducted in the laboratory. In Exp I, 241 1-day-old Ss, roughly equally divided among the 3 species, were tested for defensive behaviors directed toward a moving or nonmoving stimulus. T. melanogaster babies were the most reactive in terms of strikes, bites, and defensive tongue flicks. T. sirtalis and T. butleri were less reactive and not significantly different from each other. In Exp II, 32 adult females reacted in ways similar to the neonates, except that the T. sirtalis females were more reactive toward the moving stimulus than were the T. butleri females. Exp III showed large and significant differences in open-field behavior among the newborn of the 3 species but few significant correlations between open-field measures and antipredator responses. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral effects of phenelzine in an experimental model for screening anxiolytic and anti-panic drugs: correlation with changes in monoamine-oxidase activity and monoamine levels

This study investigated the effects of acute and chronic (one daily i.p. injection for 14 days) treatments with the non-selective irreversible monoamine-oxidase (MAO) inhibitor phenelzine (10 and 30 mg/kg) on defensive behaviors of Swiss mice in the mouse defense test battery (MDTB) which has been designed for screening anxiolytic and anti-panic drugs. In the MDTB, subjects were confronted with a natural threat (a rat) and situations associated with this threat. MAO-A and MAO-B activities and levels of brain monoamines (serotonin (5-HT), dopamine (DA) and norepinephrine (NE)) and their deaminated metabolites were subsequently measured. Behavioral results showed that acute administration of phenelzine did not specifically modify defensive behaviors. By contrast, after chronic treatment, phenelzine produced a significant reduction in avoidance distance when the rat was approaching, an effect which is consistent with an anti-panic-like action. In addition, phenelzine displayed weak anxiolytic-like effects as it increased risk assessment responses when mice were constrained in one part of the apparatus facing the rat which remained at a constant distance. No other specific drug effect was observed. These behavioral changes were associated with a dramatic increase in 5-HT levels, in particular after chronic treatment, while levels of DA and NE increased only slightly. Importantly, no significant differences in DA and NE levels between acute and chronic regimens were observed. Levels of deaminated metabolites of monoamines were markedly decreased. Measurements of MAO activity revealed substantial reductions in both type A and B forms with a full inhibition of both forms being observed only after chronic treatment with phenelzine. These results suggest that the effects of phenelzine may be due mainly to its effects on the 5-HT system and presumably related to the full inhibition of MAO-A and/or MAO-B.     

Specificity of the cardiac response to conspecific vocalizations in chimpanzees.

Used heart rate measures to examine the functional response of young chimpanzees and orangutans to acoustic stimuli, including white noise and chimpanzee vocalizations (threat, stress, and alarm). The initial response of the Ss to all stimuli was characterized by a cardiac (CAR) deceleration and an increase in heart period variability. The deceleratory responses persisted with repeated presentations of the noise, stress, and alarm stimuli. In contrast, the response of chimpanzees to the conspecific threat stimulus reverted over trials to a notable CAR acceleration. The features of the CAR response, together with the results of frequency-domain analyses of heart period variability, suggest that this acceleratory response was consistent with the evocation of an aversive or a defensive reaction characterized by sympathetic activation. This pattern of CAR response appeared early in ontogeny (within 48 hr postnatally) and was not manifest in orangutans. Taken together, results suggest the existence of specialized perceptual processing mechanisms for vocal stimuli in the chimpanzee. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A parametric study of the N40 auditory evoked response in rats

BACKGROUND: The N40 auditory evoked potential (EP) in rats is used to study "sensory gating." Our first goal was to compare the effects of systematically varying the characteristics of the pairs of clicks (S1-S2), on the degree of attenuation of the responses to S2 stimuli. A second goal was to examine the effects of changing S2 stimuli on the degree of attenuation of the responses to the deviant stimulus. METHODS: The N40 EP was recorded from 10 rats in eight identical-pair conditions and from 11 rats in two paradigms: nonidentical pairs and short trains of identical stimuli followed by a deviant stimulus. RESULTS: In eight identical-pair conditions changing stimulus duration, intensity, or frequency had no effect on the degree of attenuation of S2 responses. Changing S2 stimulus or presenting a deviant stimulus following a train of identical stimuli had a significant effect on the degree of attenuation of the response to the deviant stimulus. CONCLUSIONS: We conclude that the rat N40 EP is sensitive to stimulus change and can contribute to the study of both habituation and dishabituation mechanisms of "sensory gating."     

Responses to escalating predatory threat in garter and ribbon snakes (Thamnophis).

Several models suggest that animals perform a stable sequence of responses during increasing threat from a potential predator. To test the comparative utility of such models, 45 garter and ribbon snakes from 4 species were given an antipredator behavior test in which the snakes were exposed to a series of 5 levels of escalating threat: (1) threat is out of view, (2) threat looms over arena, (3) threat is nonmoving human hand near snake's head, (4) threat is moving human hand, and (5) threat is experimenter's tapping the snake's body. Five different antipredator behaviors were measured. It was found that both qualitative and quantitative changes in behavior occurred between threat levels. However, species differences were also found in the occurrence and amount of every behavior recorded, which indicates that even closely related species may differ in behaviors exhibited in different phases of a predatory encounter. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotional-aversive nature of the behavioral response induced by carbachol in cats

Intrahypothalamic-preoptic application of carbachol induces a characteristic, emotional-aversive response in cats similar to their natural defensive behavior. This study was undertaken to provide quantitative evidence that the magnitude of the carbachol-induced, emotional-aversive response follows the same rules as natural responses to threat. An aversive emotional response can be described in terms of a spatiotemporal relationship between the animal and the relevant threat stimulus (potential danger). The physical distance to the threat stimulus and its movements should be predictive of the magnitude of the emotional response. The goal of the study was to test the relationship for the carbachol-induced response. The presentation of a threat stimulus (a human hand) to cats injected with carbachol caused a significant increase in vocalization. The magnitude of the response was inversely proportional to the physical distance between the cat and the threat stimulus. The hand in motion caused significantly longer vocalization than the immobile hand and cats not familiar with the experimental situation vocalized significantly more than those that had been exposed to the hand before. The spatiotemporal relationship between the animal and the threat stimulus strongly suggests that the carbachol-induced response is emotional and aversive in nature and does not differ from the relevant natural responses.     

Temporary activation of perceptual–motor associations: A stimulus–response interpretation of automaticity.

Some types of automaticity can be attributed to simple stimulus–response associations (G. D. Logan, 1988). This can be studied with paradigms in which associations to an irrelevant stimulus automatically influence responding to a relevant stimulus. In 1 example, the irrelevant and relevant stimuli were presented successively with the 1st, irrelevant, stimulus masked. Although this stimulus was not phenomenally visible, it influenced responding to the 2nd, visible, stimulus. This influence was substantial only if associations to the 1st stimulus had been activated by recent responding (S. T. Klapp & B. W. Haas, 2005). These associations were not processed deeply; instead, they only relate specific stimuli to specific responses. Whereas these conclusions were demonstrated previously with masking so that participants were not aware of the irrelevant stimulus and thus had no basis to permit control of its influence, the present research demonstrated the same principles when all stimuli were visible. Furthermore, activation of the associations was not subject to substantial intentional control. These findings imply that association-based automaticity occurs independently of, and uninfluenced by, awareness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control of defensive behaviors of garter snakes (Thamnophis sirtalis): Effects of eye spots and movement.

The purpose of these experiments was to examine the effects of eye spots and stimulus movement as mediators of antipredator responses in garter snakes. In Experiment 1, 13 Eastern garter snakes (Thamnophis sirtalis) at 6–8 weeks of age were confronted with a series of threatening models that varied in the configuration of the eyes (artificial glass eyes, circular black spots, elongated black bars, or no eyespots). There were significant differences in the number of strikes elicited by the models, and the model with realistic glass eyes elicited the most strikes. In Experiment 2, we examined the effects of erratic and consistent stimulus movement on defensive behavior in 12 garter snakes at 12–26 weeks of age. The snakes delivered significantly more strikes to an erratically moving model than to a model oscillated at a regular rate. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Species-specific danger signals, endogenous opioid analgesia, and defensive behavior.

Examined the effects of handling stimuli and stress odors on species-specific defensive behavior and pain sensitivity with a total of 100 female Sprague-Dawley derived rats in 4 experiments. Ss not adapted to handling had longer jump latencies on the hotplate test of pain sensitivity than those with extensive handling experience. In a postshock freezing test in Exp II, naltrexone (7 mg/kg, intraperitoneally) enhanced defensive freezing relative to saline controls in nonadapted Ss. However, naltrexone produced no such effect in Ss that were adapted to handling. These 2 studies indicate that the handling procedure triggered an endogenous opioid analgesic response in Ss not adapted to handling. Exp III showed that a similar naltrexone-reversible opioid analgesia could be triggered by stress odors. Naltrexone, when compared to saline, enhanced postshock freezing in the presence of conspecific stress odors but not in their absence. In Exp IV, stress odors and nonadapted handling were able to activate defensive freezing directly when tested in compound but not in isolation. Results are consistent with the view that stress odors and handling stimuli are danger signals that activate endogenous opioid analgesia as well as defensive behavior, suggesting that analgesia is a component of the rat's defensive behavior system. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of antipredator responses in snakes: II. Effects of recent feeding on defensive behaviors of juvenile garter snakes (Thamnophis sirtalis).

The effect of having eaten a large meal (50% of body weight) on the defensive behavior of juvenile garter snakes (Thamnophis sirtalis) was investigated. Twenty-five 10-wk-old snakes were tested for antipredator responses (strikes) directed toward a threatening stimulus (moving and nonmoving human hand) before and after having eaten a large worm segment. Snakes directed significantly (p?     

A model for adaptation-level effects on stimulus generalization.

Presents a quantitative model of adaptation-level (AL) effects on stimulus generalization and integrates results from single stimulus, go–no-go, and choice discrimination training paradigms. The model accurately predicts (1) the gradualness of the shift in responding during the course of asymmetrical generalization testing, (2) the relation between the degree of asymmetry and the amount of shift, (3) the effect of overrepresenting certain stimuli during testing, and (4) the effect of varying the amount of training. With the discrimination training paradigms, the effects of the degree of separation between the training stimuli and of the relative frequency of their presentation during training and subsequent generalization testing are consistent with an extension of the basic model. Finally, new research is described affirming the applicability of the AL model to several infrahuman species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serum sterilization in the cold with peracetic acid]

In previous research scopolamine reduced fear or defense responses of rats to a cat, and removal of the rats' olfactory bulbs had the same effect. This suggested that scopolamine might have affected defense responses by blocking olfactory perception of the stimulus cat. The present experiments studied this possibility and explored further the effects of scopolamine on defense responses of the hooded rat. In Experiment 1 rats treated with scopolamine were found to be responsive to olfactory cues from a cat. When cat smell, but not a cat, was present in the apparatus, scopolamine-treated rats showed a large and significant suppression of food consumption. In Experiment 2 the effects of scopolamine on defense responses were shown to be generalizable to an inanimate stimulus, mechanical robot. Scopolamine caused significantly less freezing and avoidance and significantly shorter latencies to drink in the presence of the robot. One of the primary findings of the present research is that scopolamine has now been shown to reduce the defensive response of freezing in a variety of stimulus situations. This finding was thought to have important implications for the literature relating anticholinergic drugs and avoidance behavior.     

The Effects of Fear and Anger Facial Expressions on Approach- and Avoidance-Related Behaviors.

The facial expressions of fear and anger are universal social signals in humans. Both expressions have been frequently presumed to signify threat to perceivers and therefore are often used in studies investigating responses to threatening stimuli. Here the authors show that the anger expression facilitates avoidance-related behavior in participants, which supports the notion of this expression being a threatening stimulus. The fear expression, on the other hand, facilitates approach behaviors in perceivers. This contradicts the notion of the fear expression as predominantly threatening or aversive and suggests it may represent an affiliative stimulus. Although the fear expression may signal that a threat is present in the environment, the effect of the expression on conspecifics may be in part to elicit approach. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Excitability increase in withdrawal interneurons after conditioning in snail

Membrane mechanisms of conditioning of the defensive reflex in the snails Helix pomatia and H. lucorum were investigated. Tapping on the shell was used as a conditioned stimulus, which under normal conditions produces no defensive reaction. A light blow of air into the pneumostome, called the defensive closure reaction, was used as an unconditioned stimulus. When a combination of conditioned and unconditioned stimuli were presented with 2-4 min interval, the reflex developed over a period of 3 days. The separate conditioned and unconditioned stimuli presented randomly were used as an active control. The electrical characteristics of identified interneurons involved in this defensive behavior were then measured in an isolated preparation. There was shown to be a decrease in the threshold of action potential generation from 20.5 to 16.3 mV and depolarizing shift of membrane potential from -62.1 to -57.0 mV. The electrical characteristics of withdrawal interneurons of active control snails did not differ from those in intact animals. All results show an increase in excitability of withdrawal interneurons after associative learning.     

Defensive behaviors in rats following septal and septal-amygdala lesions.

Results of 2 experiments, utilizing 88 male albino Wistar rats, indicated that septal damage produced hyperdefensiveness rather than attack behavior or general hyperreactivity. Further division of this group indicated that damage to sites anterior and ventral to the septal area, sites previously implicated in the "septal syndrome," produced maximal effect on these behaviors. When amygdala lesions were combined with septal damage, enhanced defensive responding was almost eliminated. Results also indicate that amygdaloid mechanisms are involved in the regulation of conspecific defensive behaviors. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A model for stimulus generalization in Pavlovian conditioning.

Presents a review of experiments that demonstrate the effects of generalization decrement in Pavlovian conditioning and argues that an adequate theoretical explanation for them is currently not available. A theoretical account for the processes of generalization and generalization decrement in Pavlovian conditioning is developed. This model assumes that animals represent their environment by a stimulus array in a buffer and that this array in its entirety constitutes the conditioned stimulus/stimuli (CS). Generalization occurs when some stimuli represented in the array on a test trial are the same as some of those represented in the array during training; the magnitude of generalization is determined by the proportion of the array occupied by these common stimuli during training compared with the proportion of the array they occupy during testing. It is proposed that this model can explain all the results that were difficult for its predecessors to account for. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experimental reduction of stress based on ego-defense theory.

Previous research had shown that a silent film showing primitive adolescent "subincision" rites produced marked stress reactions. 3 sound tracks were created for the film and compared in impact with the silent version. 1, called the trauma track, pointed up the threatening aspect of the film. The other 2, based upon the theory of ego defense, were designed to encourage defensive interpretations of the film's contents so as to reduce threat. One consisted of denial and reaction formation statements about the film, the other was based on intellectualization. The trauma track increased evidences of stress response especially with respect to continuous recordings of skin conductance during the film. The defensive sound tracks reduced skin conductance evidence of stress response. The effectiveness of the defensive sound tracks interacted with the 2 S groups. Intellectualization was effective for the students and may have been also for the air executives, but denial was not as effective, at least for the student group. The findings supported the importance of the process of cognitive appraisal of threat in producing stress reactions, permitting the conclusion that the same visual stimulus varies in the amount of stress produced depending upon the nature of the cognitive appraisal the person makes regarding its significance for him. (PsycINFO Database Record (c) 2010 APA, all rights reserved)