Functions of the vibrissae in the defensive and aggressive behavior of the rat

Removal of mystacial vibrissae for strange rats placed in an established rat colony produced reliable decrements in defensive boxing for these animals, and corresponding increases in freezing. In a subsequent experiment, removal of the vibrissae of the attacking colony males did not change the attack behavior of the vibrissectomized animals. These results indicate that the vibrissae are involved in defensive boxing behavior, but play no essential role in the elicitation or maintenance of conspecific attack in the rat.     

Reflexive fighting in the albino rat: Aggressive or defensive behavior?

Specific agonistic responses of albino rats were compared for dominant colony rats and intruders, and for rats in a “reflexive fighting” task. The “reflexive fighters” showed high levels of defensive responses such as boxing and freezing, and very low levels of aggressive behaviors such as piloerection, biting, and the lateral display. This pattern clearly suggests that the behaviors measured in the reflexive fighting task reflect conspecific defensive reactions, rather than “shockelicited aggression.” Moreover, striking responses seen in the reflexive fighting task also occur at a high rate when footshock is given to a solitary rat held in a boxing posture. Thus it appears that “reflexive fighting” primarily involves defensive rather than aggressive responses.     

Serotonin metabolism and serotonergic receptors in Norway rats selected for low aggressiveness to man

Selection of Norway rats (24–27 generations) for low aggressiveness to man resulting in the loss of aggressive responding to handling markedly influences the brain serotonergic system. In “domesticated” Norway rats levels of serotonin in the midbrain and hypothalamus and 5-hydroxyindole acetic acid in the hypothalamus were higher than in non-selected aggressive rats. The activity of the key enzyme in serotonin biosynthesis, tryptophan hydroxylase, in midbrain of rats with genetically determined lack of aggressiveness to man was higher than in aggressive animals, although there was no difference in tryptophan hydroxylase activity in the hypothalamus. B_max and K_D of [³H]spiperone-specific binding in frontal cortex membranes were increased in tame rats. No significant differences in B_max and K_D were found between “domesticated” and aggressive rats in [³H]serotonin binding in the frontal cortex.     

Ventral and dorsolateral regions of the midbrain periaqueductal gray (PAG) control different stages of defensive behavior: Dorsolateral PAG lesions enhance the defensive freezing produced by massed and immediate shock

Rats that receive nociceptive electric shock in an environment normally show the conditional fear-induced defensive response of freezing when returned to that environment. If several electric shocks are given in a massed manner they will condition less freezing than the same shocks given in a distributed manner. If a single shock is given immediately after placement in the chamber it does not support any conditioning, although the same shock given after a brief delay does. Electrolytic lesions of the dorsolateral periaqueductal gray (PAG), which damaged dorsomedial, dorsolateral, and lateral PAG, enhanced freezing under these conditions. Lesions of the ventral PAG, which caused extensive damage to the central gray below the aqueduct, reduced conditioning under the more optimal parameters (distributed or delayed shock). This was taken to indicate that both of these regions support different modes of defensive behavior and that when activated, the dorsolateral PAG inbits conditional fear-induced defensive behavior. © 1995 Wiley-Liss, Inc.     

Antipredator behavior of Swiss-Webster mice in a visible burrow system

Swiss-Webster mice living in a visible burrow system (VBS) reacted to presentation of a live cat in the surface area of the VBS by retreat to the burrows and reductions in nondefensive behaviors such as eating and drinking. Live eat-exposed subjects remained in the burrows 14 hr or more, while subjects exposed to a toy (plush) cat prior to live cat exposure reemerged almost immediately and made many contacts with the toy cat. However, subjects exposed first to the cat and later to a toy cat showed intermediate surface reemergence times and cat contacts during toy cat tests, indicating strong sensitization effects of prior live cat exposure. Previous studies indicated that rats in this situation show retreat to the burrows, surface avoidance, and reduction in nondefensive behaviors. The mouse pattern was similar, with the notable exception that in the first 5min block after cat presentation, mice rapidly alternated retreat to the burrow chambers with reappearance in the tunnel segment near the surface, to scan the surface visually and sniff. Movement during this time block involved a stretch attend posture characteristic also of risk assessment activities in rats. Such visual and olfactory inspection of the cat is not seen in rats in the VBS. This difference may be related to the finding that rats, but not mice, emit ultrasonic “alarm cries” during and after cat exposure. © 1995 Wiley-Liss, Inc.     

Selection for reduced aggressiveness towards man and dopaminergic activity in Norway rats

The brain dopaminergic system is involved in the process of long-term selection for reduced aggressive reaction towards man in Norway rats. The dopamine levels in the striatum as well as the nucleus accumbens with the tuberculum olfactorium were significantly lower in domesticated rats than in their wild counterparts. A substantial decrease was found in homovanillic acid level in the n. accumbens and tuberculum olfactorium. Specific binding of [³H]spiperone which labels D-2 dopamine receptors was higher in the mesolimbic structure of tame rats, whereas binding of [³H]SCH 23390 (D-1 receptors) was unchanged in this area. No substantial differences were detected in D-1 and D-2 binding in striatum. Apomorphine (0.3 mg/kg) elicited less locomotion in tame animals, reflecting a decrease of sensitivity of postsynaptic dopamine receptors. Tame rats showed fewer aggressive contacts in a foot-shock test than wild rats and the D-2 receptor antagonist sulpiride (25 mg/kg) significantly decreased the foot-shock aggression only in wild rats. Therefore, domestication, which diminishes defensive behavior and emotional reactivity of animals, is associated with decreases of dopamine level in the striatum, changed metabolism of dopamine in mesolimbic system, and an alteration in density and senstivity of D-2 receptors.     

Psychosocial effects associated with dental fear in adult dental patients with avoidance behaviours

Abstract

The most obvious consequence of a genuine dental phobic reaction is the avoidance of necessary dental care. Previous research has indicated that such avoidance has adverse effects on an individual's oral health status, and also reduces the quality of life. However, systematic investigations in this area of dentistry are few and clinical observations and interviews may often fail to elicit information regarding the impairment created outside the dental situation. The present investigation assessed the presence and levels of emotional and social life effects among dental phobic patients with regard to the prevalence of dental and general fears and the length of time for which dentistry had been avoided. It was shown that a majority of the patients felt that they had to curtail their social relations, and many, especially long-term avoiders, reported wide-spread negative social life effects. Often this had extended into feelings of loneliness or to overt social isolation. It remains to be seen whether fear of dentistry itself produces disadvantage or whether these effects are mainly related to personality factors, which can also promote the development of dental fear. Alternatively, poor dental health, which is probably more frequent in anxious patients, may be perceived by these patients and thus impair social relationships.     

The influence of between and within-person hope among emergency responders on daily affect in a stress and coping model

This study reports on daily hope, coping, stress, and affect among 84 fire service members who completed a 21-day diary. Multilevel modeling showed that between-person hope was related to higher positive affect. Three-way interactions were found for within-person hope, stress, and daily coping in the prediction of daily affect. When under high stress and if low in hope, more emotion–expression coping predicted higher next day positive affect whereas if high in hope, more problem-focused coping predicted more positive affect. Within-person hope, stress, and emotion–expression coping interacted to predict negative affect. Findings for the prediction of negative affect necessitate further research to determine if the nature of coping under low hope and low stress is qualitatively distinct from high hope states.     

Authoritarian reactions to terrorist threat: Who is being threatened,the Me or the We?

Endorsement of authoritarian attitudes has been observed to increase under conditions of terrorist threat. However, it is not clear whether this effect is a genuine response to perceptions of personal or collective threat. We investigated this question in two experiments using German samples. In the first experiment (N = 144), both general and specific authoritarian tendencies increased after asking people to imagine that they were personally affected by terrorism. No such effect occurred when they were made to think about Germany as a whole being affected by terrorism. This finding was replicated and extended in a second experiment (N = 99), in which personal and collective threat were manipulated orthogonally. Authoritarian and ethnocentric (ingroup bias) reactions occurred only for people highly identified with their national ingroup under personal threat, indicating that authoritarian responses may operate as a group‐level coping strategy for a threat to the personal self. Again, we found no effects for collective threat. In both studies, authoritarianism mediated the effects of personal threat on more specific authoritarian and ethnocentric reactions. These results suggest that the effects of terrorist threat on authoritarianism can, at least in part, be attributed to a sense of personal insecurity, raised under conditions of terrorist threat. We discuss the present findings with regard to basic sociomotivational processes (e.g., group‐based control restoration, terror management) and how these may relate to recent models of authoritarianism.     

Control situacional y focalización en la tarea en pesimistas defensivos y optimistas

Resumen

El presente estudio trata de contribuir a la comprensión de la naturaleza y funcionalidad de las estrategias cognitivas de pesimistas defensivos y optimistas.Para ello manipulamos la controlabilidad de la situación. Pensamos que la valoración de control situacional es un proceso básico que puede estar subyaciendo a los efectos encontrados por estudios previos cuando inducen respuestas congruentes o incongruentes con el estilo valorativo de estos sujetos. Utilizamos un diseño factorial 2 (Grupo: pesimistas defensivos, optimistas) X 2 (Control situacional: alto, bajo). Pretend'amos estimular un nivel de control situacional congruente o no con cada estrategia, con vistas a evaluar su influencia en la estrategia de la focalización en la tarea, y en otras respuestas de tipo motivacional (intención de esfuerzo, importancia de los resultados) y adaptativo (cambio en ansiedad y rendimiento).

Los resultados mostraron 1) que el control situacional es un factor relevante en la activación diferencial de la estrategia de la focalización; 2) en los pesimistas defensivos la condición congruente (preferida) es la de control bajo, que estimula una focalización negativa en la tarea; en los optimistas, por el contrario, la condición preferida es la de control alto, que estimula una baja focalización (distracción). En la discusión relacionamos el nivel de control y de focalización preferido por cada grupo con diferencias individuales en orientación motivacional: a la incertidumbre, en los pesimistas defensivos, y a la certidumbre en los optimistas. Asimismo, diferenciamos entre la estrategia de distracción de los optimistas y mecanismos de defensa como la negación y la represión.