Gender Differences in Biobehavioral Aftereffects of Stress on Eating,Frustration, and Cardiovascular Responses1

Eating, persistence, and cardiovascular responses were evaluated after exposure to a 25‐min noise stressor with or without perceived control. Participants were healthy men (n = 29) and women (n = 34), aged 21 to 45 years. There were no group differences in cognitive task performance or blood pressure during the stressor. However, perceived control resulted in lower mean blood pressure and heart rate after cessation of the stressor for men and women. Women without perceived control displayed greater frustration levels following the stressor, and frustrated women ate more bland food than did nonfrustrated women. Perceived control and frustration did not affect food consumption among men following the stressor. These findings indicate that there are health‐relevant gender differences in biobehavioral responses that occur in the aftermath of stressor exposure. In addition, perceived control was especially important for women to attenuate the behavioral and biological effects of stressor exposure.     

The effects of exposure to an acute naturalistic stressor on working memory, state anxiety and salivary cortisol concentrations

Exposure to an acute naturalistic stressor induces both psychological and physiological changes in humans. The two studies reported here explored the impact of exposure to an acute naturalistic stressor on state anxiety, working memory and HPA axis activation (salivary cortisol). In both experiments, ten healthy male participants were exposed to an acute naturalistic stressor, helicopter underwater evacuation training (HUET), and their physiological and behavioural responses before (first study) and after (second study) the stressor were compared to ten non-stressed controls. The results of both experiments showed that working memory performance was preserved during anticipation of an acute stressor, but impairments were observed immediately after stress exposure. Participants reported significantly higher state anxiety levels during anticipation and following stress exposure, whereas significant elevations in cortisol levels were only observed 25 min post exposure to stress, but not before or immediately after stress exposure. The results of both experiments demonstrated a dissociation between behavioural and biochemical measures and provided evidence for a dissociation of the effects of stress on cognitive and physiological measures depending on the time of testing, with cognitive impairments most evident following stress exposure.     

Music causes deterioration of source memory: Evidence from normal ageing

Previous research has shown that music exposure can impair a wide variety of cognitive and behavioural performance. We investigated whether this is the case for source memory. Forty-one younger adults and 35 healthy elderly were required to retain the location in which pictures of coloured objects were displayed. On a subsequent recognition test they were required to decide whether the objects were displayed in the same location as before or not. Encoding took place (a) in silence, (b) while listening to street noise, or (c) while listening to Vivaldi's “Four Seasons”. Recognition always took place during silence. A significant reduction in source memory was observed following music exposure, a reduction that was more pronounced for older adults than for younger adults. This pattern was significantly correlated with performance on an executive binding task. The exposure to music appeared to interfere with binding in working memory, worsening source recall.     

Some effects of the opioid antagonist, naloxone, upon the rat's reactions to a heat stressor

Eight experiments examined the apparently paradoxical analgesia that accrues when rats are repeatedly injected with an opiate antagonist, naloxone, and exposed to a heat stressor. Experiments 1 and 2 showed that such pairings came to enhance in a dose-dependent manner the latencies with which rats paw-licked in response to the stressor. Experiment 3 demonstrated that the latencies to paw-lick in saline-treated rats decreased with increases in the intensity of the heat, indicating that naloxone had not provoked long latencies to paw-lick by increasing the functional intensity of the stressor. Experiment 4 documented a role for conditioning processes in recruiting the naloxone-induced analgesia. Experiment 5 showed that the analgesic effect was due to the pairings of the drug and the heat stressor, as a history of exposure to naloxone in a distinctive environment did not render the animals analgesic when challenged with the drug and the stressor. Experiments 6 and 7 provided evidence that the conditioned analgesia that accrued from drug-stressor pairings was non-opioid in nature, as the analgesia was observed in morphine-tolerant rats and was not reversed by an administration of naloxone in advance of exposure to the conditioning context. Experiment 8 demonstrated that the administration of morphine in the context previously associated with naloxone-stressor pairings provoked a superanalgesia. Although analgesic on the paw-lick assay, naloxone-treated subjects did not appear to be insensitive to the heat or impaired motorically, as they persistently reared with short latencies. The results were discussed in terms of the collateral inhibition model of the endogenous pain control system, and some speculations were offered concerning the relation between paw-licking and rearing.     

Effects of morphine and naloxone upon the reactions of rats to a heat stressor

Five experiments used rats to examine the conditioned hypoalgesia induced by exposure to a heated floor. Experiments 1 and 2 demonstrated that this hypoalgesia is mediated by non-opioid mechanisms of pain control, as evidenced by insensitivity to the opioid antagonist naloxone and by the absence of cross-tolerance with the opioid agonist morphine. Although non-opioid in nature, the acquisition of conditioned hypoalgesia was facilitated by naloxone and impaired by morphine (Experiments 3 and 4). These effects did not appear to be due to an opioid regulation of pain. (1) Pairing morphine with the heated floor attenuated acquisition in drug-tolerant rats. (2) This attenuation by morphine was removed when naloxone was given after exposure to the heated floor. (3) Conditioning was facilitated when naloxone was given after exposure to the heated floor (Experiment 5). The results were discussed in terms of an opioid regulation of (a) surprise, (b) arousal of an aversive motivational system, and (c) the affective component of pain.     

Influence of Regularity of Exposure to Chronic Stress on the Pattern of Habituation of Pituitary-Adrenal Hormones, Prolactin and Glucose

The effect of regularity of exposure to two different chronic stressors (noise or immobilization (IMO)) on the pattern of habituation of pituitary-adrenal (PA) hormones, prolactin and glucose was evaluated in adult male rats. Animals were chronically subjected to either regular or irregular time schedule of noise (30 min/day) or IMO (2 h/day) for two weeks. The day after the last stress session the rats were killed without stress or after having been subjected to 30 min of the homotypic stressor. Whereas regular noise did not affect food intake, body weight gain or adrenal weight, irregular noise decreased body weight gain and induced a moderate adrenal hypertrophy. In addition, previous daily exposure to regular but not to irregular noise reduced both prolactin and corticosterone responses to acute noise. In contrast, glucose response to acute noise was reduced after both regular and irregular exposure to chronic noise. Either regular or irregular exposure to chronic IMO decreased food intake and body weight and increased adrenal weight to the same extent. Likewise, no influence of regularity of exposure to chronic IMO on corticosterone and prolactin responses to acute IMO was observed. However, habituation of the ACTH response to acute IMO was observed in rats subjected to chronic regular IMO, but not in rats subjected to chronic irregular IMO. Finally, acute IMO-induced hyperglycemia diminished to the same extent after regular and irregular IMO. From these results we can conclude that: first, the process of habituation of the PA axis to chronic stress is greatly dependent upon factors such as regularity of exposure to the stressor and stressor intensity, and second, the influence of regularity on the pattern of habituation to a repeated stressor is dependent on the physiological variable we are dealing with.     

Acute stress rapidly and persistently enhances memory formation in the male rat

Previous studies, as well as the present one, report that acute exposure to intermittent tailshocks enhances classical eyeblink conditioning in male rats when trained 24 h after stressor cessation. In Experiment 1, it was determined that the facilitating effect of stress on conditioning could also be obtained in response to a stressor of acute inescapable swim stress but not inescapable noise or the unconditioned stimulus of periorbital eyelid stimulation. These selective responses arose despite comparable enhancements of the stress-related hormone corticosterone in response to tailshocks, periorbital eyelid stimulation, noise stress, and supraelevation in response to swim stress. Although corticosterone is necessary for the enhanced learning in response to stress (Beylin & Shors, 1999), these results suggest that it is not sufficient. In addition, the results suggest that the enhancement is not dependent on common characteristics between the stressor and the conditioning stimuli (stimulus generalization). In Experiment 2, it was determined that the facilitating effect of the stressor on conditioning occurs within 30 min of stressor cessation. Thus, the mechanism responsible for facilitating memory formation is rapidly induced as well as persistently expressed. In Experiment 3, it was determined that exposure to the stressor does not enhance performance of the conditioned response after the response has been acquired. Thus, exposure to the stressor enhances the formation of new associations rather than affecting retention or performance of the motor response. These studies extend the circumstances under which stress is known to enhance associative learning and implicate neural mechanisms of memory enhancement that are rapidly induced and persistently expressed.     

Speech‐perception‐in‐noise deficits in dyslexia

Speech perception deficits in developmental dyslexia were investigated in quiet and various noise conditions. Dyslexics exhibited clear speech perception deficits in noise but not in silence. Place‐of‐articulation was more affected than voicing or manner‐of‐articulation. Speech‐perception‐in‐noise deficits persisted when performance of dyslexics was compared to that of much younger children matched on reading age, underscoring the fundamental nature of speech‐perception‐in‐noise deficits. The deficits were not due to poor spectral or temporal resolution because dyslexics exhibited normal ‘masking release’ effects (i.e. better performance in fluctuating than in stationary noise). Moreover, speech‐perception‐in‐noise predicted significant unique variance in reading even after controlling for low‐level auditory, attentional, speech output, short‐term memory and phonological awareness processes. Finally, the presence of external noise did not seem to be a necessary condition for speech perception deficits to occur because similar deficits were obtained when speech was degraded by eliminating temporal fine‐structure cues without using external noise. In conclusion, the core deficit of dyslexics seems to be a lack of speech robustness in the presence of external or internal noise.     

The effects of an acute psychosocial stressor on episodic memory

Although stressors are believed to impair memory, experimental studies with humans have provided inconsistent support for this conclusion. The current study was designed to examine the effect of an acute psychosocial stressor, and subsequent reactivity, on episodic memory. One hundred participants completed a list-recall task before and after random assignment into a stressor or nonstressor condition. Participants assigned to the stressor condition exhibited both impaired delayed and immediate recall, and also exhibited increasesin the commission of intrusions and perseverations. The experience of off-task thoughts and intentional suppression of such thoughts, were associated with greater impairment of immediate recall. Changes in state anxiety, negative mood, and heart rate were unrelated to changes in memory. These data indicate that exposure to a stressor impaired the recall of previously learned information, and compromised the recall of newly acquired information. Furthermore, cognitive interference is an important factor regarding stress-related impairments of episodic memory.     

Arousal, Mood, and the Mozart Effect

The "Mozart effect" refers to claims that people perform better on tests of spatial abilities after listening to music composed by Mozart. We examined whether the Mozart effect is a consequence of between-condition differences in arousal and mood. Participants completed a test of spatial abilities after listening to music or sitting in silence. The music was a Mozart sonata (a pleasant and energetic piece) for some participants and an Albinoni adagio (a slow, sad piece) for others. We also measured enjoyment, arousal, and mood. Performance on the spatial task was better following the music than the silence condition, but only for participants who heard Mozart. The two music selections also induced differential responding on the enjoyment, arousal, and mood measures. Moreover, when such differences were held constant by statistical means, the Mozart effect disappeared. These findings provide compelling evidence that the Mozart effect is an artifact of arousal and mood.     

Impairment of spontaneous alternation performance by an NMDA antagonist: attenuation with non-NMDA treatments.

N-Methyl-D-aspartate (NMDA) receptor antagonists disrupt learning on a variety of tasks. Previous findings indicate that glucose, naloxone, and physostigmine ameliorate learning deficits produced by several treatments. The present experiment examines whether these agents also reverse the amnestic effects of NMDA receptor blockade. Mice were tested for spontaneous alternation performance in a Y-maze. The animals received either saline or the NMDA antagonist, NPC 12626 (35 mg/kg, IP), 50 min prior to testing and received an additional injection of saline, glucose, naloxone, or physostigmine 30 min prior to testing. NPC 12626 significantly decreased alternation scores. Glucose (250 mg/kg), physostigmine (0.01 mg/kg), and naloxone (1 mg/kg) reversed the effects of NPC 12626. Thus, impairments of learning after NMDA receptor blockade share with other amnestic conditions the susceptibility to attenuation by glucose, naloxone, and physostigmine.     

Negative affect as a predisposing factor for cortisol release after an acute stress--the impact of unpleasant priming

Glucocorticoids have a key role in stress responses. There are, however, substantial differences in cortisol reactivity among individuals. We investigated if affective trait and mood induction influence the reactivity to psychological stress in a group of 63 young adults, male (n=27) and female (n=36), aged ca. 21 years. On the experimental day the participants viewed either a block of pleasant or unpleasant pictures for 5 min to induce positive or negative mood, respectively. Then, they had 5 min to prepare a speech to be delivered in front of a video-camera. Saliva samples were collected to measure cortisol, and questionnaire-based affective scales were used to estimate emotional states and traits. Compared to basal levels, a cortisol response to the acute speech stressor was only seen for those who had first viewed unpleasant pictures and scored above the average on the negative affect scale. There were no sex differences. In conclusion, high negative affect associated with exposure to an unpleasant context increased sensitivity to an acute stressor, and was critical to stimulation of cortisol release by the speech stressor.     

Stress applied during primary immunization affects the secondary humoral immune response in the rat: involvement of opioid peptides

The effect of unpredictable, inescapable and uncontrollable electric tail shocks (ES) on the humoral immune response to bovine serum albumin (BSA) was investigated in the rat. Contributions of the procedures that accompany shock delivery, such as witnessing the ES procedure (stress witnessing, SW) and exposure to the apparatus for shock delivery (apparatus control, AC) to the changes in specific immunity induced by ES were also tested. All procedures were applied during primary and/or secondary immunization. It was demonstrated that exposure to ES during primary immunization with BSA significantly suppressed specific anti-BSA antibody production after secondary and tertiary immunization with the same antigen. Exposure to the SW procedure during primary immunization with BSA enhanced the specific antibody level after secondary immunization, while exposure to the apparatus alone did not influence the development of either the primary or secondary humoral immune response to BSA. Both ES-induced suppression and SW-induced potentiation of the humoral immune response were partially inhibited by prior treatment with the opioid receptor antagonist naloxone. Additionally, treatments with the opioid peptides methionine- and leucine-enkephalin decreased anti-BSA antibody level, mimicking to some extent the effects of ES. It is suggested that ES and endogenous opioid peptides had long-term effects on humoral immunity through mechanisms involving immunologic memory.     

The effect of debriefing on laboratory induced helplessness: An attributional analysis1

Debriefing was assessed as means of reversing helplessness deficits through reattribution. Fifty-five subjects listened to escapable or inescapable tones. One inescapable group, prior to anagrams, was debriefed regarding noise uncontrollability. A second inescapable group was administered anagrams by a different experimenter. While exposure to inescapable noise led to performance deficits, switching experimenters obviated these deficits. Debriefing actually facilitated anagram performance. All inescapable subjects—debriefed or not—attributed their lack of control on the noise task to experimenter interference, casting some doubt on reattribution as an explanation of debriefing's effects. Results were discussed in terms of the reformulated learned helplessness model and the ethical implications of debriefing in learned helplessness research.     

Effects of daily morphine administration and deprivation on choice and demand for remifentanil and cocaine in rhesus monkeys

Choice procedures have indicated that the relative reinforcing effectiveness of opioid drugs increases during opioid withdrawal. The demand curve, an absolute measure of reinforcer value, has not been applied to this question. The present study assessed whether mild morphine withdrawal would increase demand for or choice of remifentanil or cocaine. Four rhesus monkeys chose between remifentanil and cocaine during daily sessions. Demand curves for both drugs were subsequently obtained. The effects of daily injections of 3.2 mg/kg morphine on both choice and demand for these drugs was assayed 3 and 20.5 hr after each morphine injection, and then during a postmorphine period. Three hours following morphine injections, choice of remifentanil over cocaine decreased and demand for remifentanil--but not cocaine--became more elastic. During morphine withdrawal (20.5 hr postinjection), choice of remifentanil increased and remifentanil demand became more inelastic in 3 of 4 monkeys. Cocaine demand also became more inelastic during this period. Four to five weeks following the morphine regimen, demand for both drugs was more inelastic relative to the initial determination. The results suggest that both the relative and absolute reinforcing effectiveness of remifentanil decreased following morphine administration and increased during morphine withdrawal. The absolute reinforcing effectiveness of cocaine also increased during morphine withdrawal. In addition, extended exposure to drug self-administration and/or exposure to the morphine regimen produced long-term increases in demand for both drugs.     

The association between attention control,anxiety, and depression: the indirect effects of repetitive negative thinking and mood recovery

Background and objectives: Attention control deficits and repetitive negative thinking (RNT; i.e., rumination) may be key factors in the development and persistence of depression and anxiety, although their role in symptom development remains poorly understood. This represents a gap in the literature, as interventions targeting attention control and associated RNT may enhance interventions and prevent costly relapse. The current study was designed to examine the serial indirect effects of transdiagnostic RNT and negative affect recovery following a lab-induced stressor on the association between attention control deficits and trait anxiety and depression.

Methods: Participants were N?=?583 university students who completed validated measures of RNT, anxiety, depression, and mood ratings pre- and post-stressor. Stress was induced using a modified version of the Trier Social Stress Test.

Results: Results of cross-sectional indirect effects models indicated that RNT and mood recovery explained the association between attention control deficits and trait anxiety and depression. Results from reversed models indicated that only the indirect effect of RNT was significant.

Conclusions: Findings suggest that RNT and mood recovery processes play an important role in explaining anxiety and depression symptoms. Additional work is needed to examine their role in symptom development and maintenance over time.     

An apparent new instance of stimulus intensity dynamism during discrimination of duration of repeating auditory stimuli

Rats were trained on a VI/EXT discrimination using barpressing in a Skinner box for food reinforcement. The discriminanda consisted of different proportions of noise to silence within a fixed 3^-s noise-plus-silence repeating cycle. These stimuli were easily discriminated by human subjects, but the rats formed the discrimination only poorly and after considerable training. Analysis of response rates during noise and silence separately within the 3^-s noise-plus-silence cycle showed higher response rates during noise, irrespective of whether this was during the positive or during the negative stimulus, or whether relatively long duration of noise or relatively short duration of noise (within the 3^-s cycle) constituted the positive stimulus. These results are seen as providing an instance of the dynamogenic effects of stimulus intensity on response vigour to which the Perkins-Logan generalization of inhibition hypothesis of stimulus intensity dynamism cannot apply.     

Learned helplessness and the detection of contingency: A direct test

Two studies tested a basic hypothesis of the learned helplessness model: That performance deficits associated with exposure to uncontrollable outcomes are directly mediated by an individual's perception of response-outcome independence. In the first experiment 48 subjects were exposed to noise bursts. For one experimental group, the termination of the noise was response-contingent. For five other groups, noise-burst termination was independent of subjects' responses. These five groups varied in the number of trials on which they received positive feedback: As predicted, subjects overestimated the amount of control they had over noise termination as a positive linear function of the amount of noncontingent positive feedback they received. Although subjects exposed to either noncontingent positive or negative feedback showed subsequent performance deficits on an anagrams task, the expected relation between perceived control and subsequent performance failed to emerge. These findings were replicated in a second experiment. In addition, subjects' locus, stability, and globality attributions failed to predict subsequent performance. These results call into question the central premises of helplessness theory: That perceived uncontrollability and causal attributions mediate learned helplessness.     

Acute and chronic stress effects on performance in a forced-swim task

The effects of uncontrollable stressors on performance in a subsequent forced-swim paradigm were assessed in mice. Uncontrollable shock initially induced behavioral invigoration; however, within 24 h of stressor application, swimming behavior was depressed relative to nonstressed mice. The controllability of the stressor did not influence the initial invigoration, being present among escapably shocked mice as well as among mice that received (yoked) inescapable shock. In contrast, the depression of responding evident 24 h after stressor application was related to the availability of behavioral coping methods. Finally, following repeated exposure to footshock there was no indication of adaptation to the behavioral changes ordinarily induced by acute shock stress. The data were related to the effects of uncontrollable stressors on escape performance, and with respect to the use of this preparation as an animal model of human depression.