Predictable versus unpredictable shock conditions and physiological measures of stress: A reply to Arthur.

Responds to the critique by A. Z. Arthur (see record 1987-09623-001) of the literature review by the authors and L. S. Schoen (see record 1984-28077-001) dealing with the effects of predictable vs unpredictable shock conditions on physiological measures of stress. The classification of studies as short- and long-term is defended, and it is argued that Arthur's criteria for including studies to be reviewed are overly restrictive in that they limit identification of potentially important variables and eliminate most of the relevant literature. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention, unpredictability, and reports of physical symptoms: Eliminating the benefits of predictability.

Conducted 3 experiments with 135 undergraduates to investigate the established finding from the unpredictability literature that exposure to unpredictable noise leads to reports of more severe physical symptoms than does exposure to predictable noise. In Exp I, Ss performed a reaction time (RT) task while they listened to loud bursts of either predictable or unpredictable noise. As expected, RTs were slower when the noise was unpredictable than when it was not. This finding suggests that more attention had been directed to the unpredictable than the predictable noise. In Exp II and III, Ss were exposed to either predictable or unpredictable noise and were instructed to attend to the noise or were given no instructions. In both cases, Ss not instructed to attend to the noise reported more severe symptoms when the noise was unpredictable than when it was not, thus replicating the previous finding. Of greater interest, however, was the fact that equating the amount of attention directed to the unpredictable and predictable noise (by asking Ss to attend to the noise) eliminated the apparent benefits of predictability. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impact of stress on objectively recorded menopausal hot flushes and on flush report bias.

Investigated the association between stress and both objective (i.e., physiologically recorded) and subjective hot flushes (HFs) among 21 37–71 yr old postmenopausal women who reported having frequent HFs. Ss underwent psychophysiological monitoring during stressful and nonstressful laboratory sessions. Significantly more objective HFs were recorded during the stress session than during the nonstress session. The stress manipulation, however, did not affect Ss' propensity to report HFs. Results suggest that the observed association between reported HFs and stress is not due to changes in report bias. The physiological mechanisms through which stress may stimulate HFs are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stress of predictable and unpredictable shock.

Examined the claim that unpredictable shock is more stressful than predictable shock in short-term studies (B. B. Abbott et al; see record 1984-28077-001). The classification of studies as short- or long-term, the conceptualization of predictability studies, and the failure to note contrary evidence are discussed. It is concluded that predictable shock (the presence of a warning signal before shock) makes the situation more stressful both in short- and long-term studies. It is suggested that conflicting results are probably due to the presence of additional and confounding variables in contrary studies. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prediction of vertebral failure loads from spinal and femoral dual-energy X-ray absorptiometry, and calcaneal ultrasound: an in situ analysis with intact soft tissues

The anatomic and physiological bases for nociception are present even in very preterm neonates. Neonates show the same behavioral, endocrine, and metabolic responses to noxious stimuli as older subjects. Preterm infants appear to be more sensitive to painful stimuli and have heightened responses to successive stimuli. Infants receiving intensive care are subjected to frequent stressful procedures and also chronic noxious influences related to the environment of care. Inflammatory conditions such as necrotizing enterocolitis may also cause pain. Untreated pain in babies is associated with increased major morbidity and mortality. Nonpharmacological interventions, including environmental modification and comforting during procedures reduce stress. Intravenous opiates are the mainstay of pharmacological analgesia. A pure sedative agent can provide physiological stability in settings in which there are less acutely painful stimuli or when there are adverse effects from, or tolerance to, opiates. Local anesthesia of skin and mucous membranes is helpful for invasive procedures. Antipyretic analgesics such as acetaminophen have a role in inflammatory pain.     

Sex differences in effects of predictable and unpredictable footshock on fentanyl self-administration in rats.

An operant conditioning paradigm was used to examine effects of predictable and unpredictable footshock on oral fentanyl (50 μg/ml) self-administration (SA) in 12 female and 12 male Wistar rats (Rattus norvegicus). Rats were tested for drug SA under a progressive ratio schedule with and without repeated predictable or unpredictable footshock over 8 weeks. Female rats consumed greater amounts of fentanyl than did male rats. Male rats exhibited greater withdrawal behaviors following naloxone challenge. Predictable footshock with repeated exposure (i.e., chronic stress) was accompanied by greater fentanyl SA than was unpredictable footshock, particularly for female rats. Corticosterone levels were positively correlated with fentanyl SA. Predictability of the stressor also had a greater effect on maintenance of fentanyl SA than it did on relapse to fentanyl SA. Results suggest that sex plays an important role in drug-taking behavior by rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of adult attachment and presence of romantic partners on physiological responses to stress.

The effects of presence vs absence of a romantic partner on psychophysiological responses to a stressful laboratory situation were examined in a sample of 35 college women involved in serious dating relationships. Participants performed a standard psychological stress task both in the presence and in the absence of their romantic partners, with order counterbalanced across participants. Heart rate and blood pressure were measured in each of these conditions during both baseline and task performance periods. Avoidant (but not secure) and anxious (but not nonanxious) participants displayed heightened physiological responses across all conditions and periods if the partner-absent condition came first rather than second. Discussion focuses on 2 explanations for the findings in terms of (a) the anxiety-reducing function of attachment relationships and (b) the anxiety-producing effect of separation in a stressful situation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Smoking, caffeine, and stress: Effects on blood pressure and heart rate in male and female college students.

Examined the independent and joint effects of cigarette smoking and caffeine consumption on blood pressure (BP) and heart rate (HR) reactions to stress in 38 male and 38 female college students. Following an initial physiological baseline, Ss received 1 of 4 experimental treatments (paced smoking, caffeine, smoking plus caffeine, or neither) and had BP and HR measured before, during, and after 2 stressful tasks. Compared with the control condition, caffeine ingestion enhanced the magnitude of stress-induced systolic BP and HR reactions. Smoking combined with stress, and the joint effect of smoking and caffeine was no greater than either taken alone. Males and females were generally similar in their responses to smoking, caffeine, and stress. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceived self-efficacy in coping with cognitive stressors and opioid activation.

This experiment tested the hypothesis that perceived self-inefficacy in exercising control over cognitive stressors activates endogenous opioid systems. Subjects performed mathematical operations under conditions in which they could exercise full control over the cognitive task demands or in which the cognitive demands strained or exceeded their cognitive capabilities. Subjects with induced high perceived self-efficacy exhibited little stress, whereas those with induced low perceived self-efficacy experienced a high level of stress and autonomic arousal. Subjects were then administered either an inert saline solution or naloxone, an opiate antagonist that blocks the analgesic effects of endogenous opiates, whereupon their level of pain tolerance was measured. The self-efficacious nonstressed subjects gave no evidence of opioid activation. The self-inefficacious stressed subjects were able to withstand increasing amounts of pain stimulation under saline conditions. However, when endogenous opioid mechanisms that control pain were blocked by naloxone, the subjects were unable to bear much pain stimulation. This pattern of changes suggests that the stress-induced analgesia found under the saline condition was mediated by endogenous opioid mechanisms and counteracted by the opiate antagonist. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Greater sustained anxiety but not phasic fear in women compared to men.

Startle reflex studies in rodents indicate that female are more reactive than rats in experimental models of sustained anxiety but not in models of phasic fear (Toufexis, 2007). This study examined evidence for a similar effect in humans. Participants were exposed to three conditions, (1) predictable aversive shocks signaled by a cue, (2) unpredictable shocks, and (3) no shocks. Acoustic startle stimuli were delivered regularly across conditions. Phasic startle potential to the threat cue in the predictable condition was not affected by sex. In contrast, and consistent with basic research, the sustained increase in startle in the predictable and unpredictable conditions was greater in women compared to men. Animal studies suggest that such an effect may be mediated by the effects of sexual dimorphism in limbic structures, including the bed nucleus of the stria terminalis. However, psychosocial factors may also contribute to this effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The contribution of adrenal and reproductive hormones to the opposing effects of stress on trace conditioning males versus females.

Exposure to an acute stressful experience facilitates classical conditioning in male rats but impairs conditioning in female rats (T. J. Shors, C. Lewczyk, M. Paczynski, P. R. Mathew, & J. Pickett, 1998; G. E. Wood & T. J. Shots, 1998). The authors report that these effects extend to performance on the hippocampal-dependent task of trace conditioning. The stress-induced impairment of conditioning in females was evident immediately, 24 hr and 48 hr after stress, depending on the stage of estrus. Moreover, the effect could be reactivated days later by reexposure to the stressful context. Corticosterone levels correlated with overall performance in males but not in females. Unlike the effect seen in males, adrenalectomy did not prevent the stress-induced effect on conditioning in females. These data indicate that exposure to the same experience can have opposite effects on learning in males versus females and that these opposing effects are mediated by differing hormonal systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An experimental investigation of consistency in female undergraduates' reports of coping efforts for the same versus different stressful situations.

For each of 3 event categories (harm/loss, threat, challenge), with a 6-week test-retest time interval, female undergraduates were randomly assigned to report on coping efforts (problem- vs. emotion-focused coping) for the same stressful event or a different stressful event across the 2 sessions. For problem-focused coping and each category of stressor, test-retest correlations were strongest when subjects reported on coping efforts for the same situation but were still of moderate size and significant for reports of coping with different stressful situations. This difference between conditions was found only for the challenge stressor for emotion-focused coping. These findings imply that stressor context, type of coping, and response tendencies across different stressors relate to the reliability of self-reported coping efforts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reacting to and recovering from a stressful situation: The negative affectivity-physiological arousal relationship.

Although it is one of the most widely researched personality correlates of psychological reactions, the relationship between negative affectivity (NA) and physiological arousal has received little attention. This study examined the associations between NA and physiological outcomes of heart rate, skin temperature, and muscle tension. The authors hypothesized that when individuals are in a stressful situation, persons high in NA experience more heightened physiological arousal than those low in NA. After personality and demographic data were collected, 230 individuals participated in a stressful intervention. Individuals high in NA experienced a significantly greater rate of increase in electromyogram during the stress intervention and a lesser rate of decrease in electromyogram after the stressful event than those low in NA. In regard to skin temperature, those high in NA did not recover from the stress intervention as well as those low in NA. Negative affectivity was not related to heart rate. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychophysiological effects of progressive relaxation in anxiety neurotic patients and of progressive relaxation and alpha feedback in nonpatients.

Gave 10 anxiety neurotic patients 4 sessions of individual instruction in progressive relaxation; 10 patients served as waiting list controls. 10 nonpatients were assigned to each of the same conditions, and an additional 10 nonpatients were given 4 sessions of alpha feedback. Nonpatients showed more psychophysiological habituation over sessions than patients in response to hearing 5 very loud tones and to a reaction time task. Patients, however, showed greater physiological response to relaxation than did nonpatients. After relaxation, the autonomic responses of the patients resembled those of the nonpatients. The effects of relaxation were more pronounced in measures of physiological reactivity than in measures of physiological activity. Defensive reflexes yielded to orienting reflexes more readily in nonpatients than in patients. There was also a tendency for progressive relaxation to generalize to autonomic functions more than alpha feedback. (56 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determination of Shear-Wave Velocities and Shear Moduli of Completely Decomposed Tuff

Based on theoretical derivations and considerations, five series of laboratory tests were planned to investigate and differentiate the degrees of inherent and stress-induced anisotropy, to study the effect of void ratio changes on shear-wave velocities and shear moduli, and to determine the relationship between shear-wave velocity and stress state on a completely decomposed tuff (CDT). Shear-wave velocities in three orthogonal horizontal and vertical planes [vs(hh), vs(hv), and vs(vh)] were measured in both vertically and horizontally cut block and Mazier specimens. Under isotropic stress conditions (K = 1.0), the degrees of inherent anisotropy [vs(hh)2/vs(hv)2 = Ghh/Ghv] were 1.48 and 1.36 for the block and Mazier specimens, respectively. At the anisotropic stress state (K = 0.4), the degrees of anisotropy of the block and Mazier specimens were 1.26 and 1.15, respectively, 15% reduction from the measured inherent anisotropy due to stress-induced effects. The measured higher shear-wave velocity in the horizontal plane of the CDT was confirmed by testing both vertically and horizontally cut specimens and the measured results reflect a stronger layering structure in the horizontal bedding plane of the natural material, in which K0 less than 1.0 is commonly assumed in designs. Under both isotropic and anisotropic stress states, the shear-wave velocities [vs(hh), vs(hv), and vs(vh)] of the block specimens are on average about 27% higher than those of the Mazier specimens.     

Differential gastric ulceration in rats receiving shocks on either fixed-time or variable-time schedules.

Research suggests that predictable electric shocks produce less stress than unpredictable shocks. In this experiment, predictability was manipulated by using fixed-time (FT, predictable) and variable-time (VT, unpredictable) schedules of shock delivery. Rats receiving 3-mA, 1-s electric shocks on a FT 45-s schedule developed less gastric pathology than another group that was administered identical shocks on a VT 45-s schedule. It is argued that this finding represents a more subtle effect of predictability than has been obtained heretofore. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Morphine analgesia: Enhancement by shock-associated cues.

Recent research has shown that rats exposed to repeated stress display enhanced morphine analgesia. Six experiments, with 218 male Sprague-Dawley rats, examined the possible contribution of classically conditioned analgesia to this effect. Drug-naive Ss exposed to 9 daily sessions of stress, each consisting of a single exposure to footshock, subsequently displayed enhanced analgesic responsiveness to morphine sulfate (5 mg/kg, sc) 1 and 10 days after stress. This enhancement was also observed in morphine-experienced Ss 1 and 8 days after stress. The effect of footshock stress on morphine analgesia was specific to the environment in which stress was administered. Conditioned analgesia was found under the same conditions that yielded enhanced morphine analgesia, and both this conditioned analgesia and the acute analgesia elicited by the footshock stressor were attenuated by naloxone (20 mg/kg). Data are consistent with the hypothesis that the enhanced morphine analgesia observed after repeated footshock stress reflects the contribution of an opioid-mediated, conditioned analgesia elicited by cues formerly paired with the stressor. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Eye movement desensitization and reprocessing treatment for combat PTSD.

Four Vietnam veterans (aged 42–55 yrs) diagnosed with posttraumatic stress disorder (PTSD) were treated with 12 sessions of eye movement desensitization and reprocessing, targeting their combat memories. An extensive multimodal assessment battery showed very substantial clinical improvement for 3 of the veterans along a number of psychological dimensions that characterize the disorder, but not along several physiological parameters. A 4th veteran showed only very modest changes. Results are discussed in terms of the importance of several issues, including numbers of treatment sessions and differential effects of treatment on cognitive-behavioral and physiological symptoms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging, distraction, and the benefits of predictable location.

Three experiments examined the impact on reading time for younger and older adults in the absence vs. presence of distraction (marked by font type) in either fixed predictable locations (Experiments 1 and 2) or unpredictable locations (Experiment 3) . Consistent with earlier work (S. L. Connelly, L. Hasher, & R. T. Zacks; see record 1992-18667-001), older adults were markedly disrupted, relative to young adults, when distraction was present in unpredictable locations. When the location of distraction was fixed, however, the very large disadvantage that older adults otherwise experienced (slowed by as much as 46 s) diminished substantially (to as little as 2 s). Fixed location also eliminated the relatedness effect, by which older adults are especially susceptible to distraction from meaningfully related material. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned morphine tolerance in the rat: Absence of a compensatory response and cross-tolerance with stress.

In 4 experiments with 193 male Holtzman rats, evidence was obtained that tolerance development to morphine analgesia occurred most rapidly when morphine delivery was paired with salient contextual cues. Contextual cues previously paired with morphine did not elicit conditioned drug-compensatory responses when presented to nondrugged Ss. These results were obtained by different analgesia assessments, with different drug-administration analgesia-test latencies, and in environments differing with respect to stress level. Stress level influenced nociceptive response, as it was found that the combination of bright illumination, white noise, and a strong odor resulted in antinociception in the absence of drug. Ss that had a history of receiving morphine in this stressful context were tolerant to this stress-induced antinociception but only when morphine was present in their systems. In the final 2 studies, this antinociception, which was cross-tolerant with morphine, was characterized with respect to naloxone reversibility and brain levels of met- and leu-enkephalin as determined by radioimmunoassay. (87 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)