Avoidance of 20% carbon dioxide-enriched air with humans.

Four college students were exposed to a Sidman avoidance procedure to determine if an avoidance contingency involving 20% carbon dioxide-enriched air (CO2) would produce and maintain responding. In Phase 1, two conditions (contingent and noncontingent) were conducted each day. These conditions were distinguished by the presence or absence of a blue or green box on a computer screen. In the contingent condition, CO2 presentation were delivered every 3 s unless a subject pulled a plunger. Each plunger pull postponed CO2 presentations for 10 s. In the noncontingent condition, CO2 presentations occurred on the average of every 5 min independent of responding. Following stable responding in Phase 1, condition-correlated stimuli were reversed. In both conditions, plunger response rate was high during the contingent condition and low or zero during the noncontingent condition. Furthermore, subjects avoided most CO2 presentations. However, CO2 presentations did not increase verbal reports of fear. Overall, the results from the present study suggest that CO2 can be used effectively in basic studies of aversive control and in laboratory analogues of response patterns commonly referred to as anxiety.     

Offset control during recurrent 20% carbon dioxide-enriched air induction: relation to individual difference variables

Although control over aversive events maintains a central role in contemporary models of anxiety pathology, particularly panic disorder, there is little understanding about the emotional consequences of specific types of control processes. In the present study, offset control over 8 20% carbon dioxide-enriched air administrations was experimentally manipulated in a large nonclinical population (n = 96) varying in anxiety sensitivity (high or low) and gender. Dependent measures included self-reported anxiety, affective reports of valence, arousal, emotional control, and physiological indices of heart rate and skin conductance. High anxiety-sensitive participants who lacked offset control reported significantly greater elevations in self-reported anxiety, emotional displeasure, arousal, and dyscontrol relative to their yoked counterparts with offset control. In contrast, low anxiety-sensitive individuals responded with similar levels of cognitive and affective distress regardless of the offset control manipulation. Although the provocation procedure reliably produced bodily arousal relative to baseline, at a physiological level of analysis, no significant differences emerged across conditions. These findings are discussed in relation to offset control during recurrent interoceptive arousal, with implications for better understanding anxiety about abrupt bodily sensations.     

Response to hyperventilation and inhalation of 5.5% carbon dioxide-enriched air across the DSM-III-R anxiety disorders.

Anxiety disorder patients (n = 198; under criteria of the Diagnostic and Statistical Manual of Mental Disorders; rev. 3rd ed.; American Psychiatric Association, 1987) and nonanxious control subjects (n = 25) underwent challenges of 90 s of voluntary hyperventilation and 15 min of 5.5% carbon dioxide in air. Panic disorder subjects showed a greater subjective response to both challenges than did subjects with other anxiety disorders, who in turn responded more than did control subjects. Furthermore, subjects with panic disorder as an additional diagnosis tended to report more subjective response than did anxiety disorder subjects without panic disorder. The best prechallenge predictor of response to each procedure was a measure of fear of physical symptoms. The findings support previous results that have pointed to a greater fear or anxiety-inducing effect of these challenge procedures in panic disorder patients, as compared with other subjects.     

Evoking analogue subtypes of panic attacks in a nonclinical population using carbon dioxide-enriched air

The increasing recognition that panic attacks are heterogeneous phenomena necessitates better and more objective criteria to define and examine what constitutes a panic attack. The central aim of the present study was to classify subtypes of panic attacks (i.e. prototypic, cognitive, and non-fearful) in a nonclinical sample (N = 96) based on the concordance/discordance between subjective and physiological responding to multiple inhalations of 20 and 13% CO2-enriched air. Results show that a substantial proportion of this nonclinical sample (55.2%) responded to the CO2 challenge in a manner consistent with clinical and research definitions of different subtypes of panic attacks. The implications of this dimensional approach for discriminating subtypes of panic in the laboratory are discussed as a means to better understand the phenomenology and nature of panic attacks.     

The effects of offset control over 20% carbon-dioxide-enriched air on anxious responding

Control over the offset of repeated administrations of 20% carbon-dioxide-enriched air was assessed in nonclinical participants (n = 30) reporting elevated levels of anxiety sensitivity--a population at an increased risk for experiencing panic attacks and possibly developing panic disorder. In Phase I, participants were randomly assigned to 1 of 2 conditions: one that permitted offset control over gas inhalation and one that did not. These conditions were reversed in Phase II. Across phases, a lack of offset control resulted in greater self-reported anxiety compared with having control, although no significant differences were observed for heart rate. Whereas all participants demonstrated a Stroop interference effect for general (e.g., coffin) compared with specific (e.g., dizzy) physical threat word types prior to the first experimental phase, this effect persisted only for participants who had offset control in Phase I. We discuss these results in relation to the differential effects of offset control, with implications for better understanding anxious responding during elevated bodily arousal.     

Patterns of emotion-specific appraisal,coping, and cardiovascular reactivity during an ongoing emotional episode

The authors examined emotion-specific patterns of appraisal, coping, and cardiovascular reactivity during real ongoing emotional episodes. In this study, 109 participants performed a neutral opinion-expression task, where a confederate elicited anger, shame, or pride using verbal and nonverbal behavior. The authors assessed cognitive appraisals, emotional reactions, coping, outcomes (state self-esteem and outcome satisfaction), and cardiovascular reactivity. Results indicated substantial and theoretically consistent differences between the 3 emotions (and differences from a nonemotion condition) for cognitive appraisals, self-reported coping, behavioral coping, self-esteem, and cardiovascular reactivity. The results are discussed in relation to their implications for emotion theory and for psychological and physical health. Overall, the results suggest that researchers can study emotion-related issues using authentic emotional reactions.     

The differential effects of emotional salience on direct associative and relational memory during a nap

Relational memories are formed from shared components between directly learned memory associations, flexibly linking learned information to better inform future judgments. Sleep has been found to facilitate both direct associative and relational memories. However, the impact of incorporating emotionally salient information into learned material and the interaction of emotional salience and sleep in facilitating both types of memory is unknown. Participants encoded two sets of picture pairs, with either emotionally negative or neutral objects paired with neutral faces. The same objects were present in both sets, paired with two different faces across the sets. Baseline memory for these directly paired associates was tested immediately after encoding, followed by either a 90-min nap opportunity or wakefulness. Five hours after learning, a surprise test assessed relational memory, the indirect association between two faces paired with the same object during encoding, followed by a retest of direct associative memory. Overall, negative information was remembered better than neutral for directly learned pairs. A nap facilitated both preservation of direct associative memories and formation of relational memories, compared to remaining awake. Interestingly, however, this sleep benefit was observed specifically for neutral directly paired associates, while both neutral and negative relational associations benefitted from a nap. Finally, REM sleep played opposing roles in neutral direct and relational associative memory formation, with more REM sleep leading to forgetting of direct associations but promoting relational associations, suggesting that, while not benefitting memory consolidation for directly learned details, REM sleep may foster the memory reorganization needed for relational memory.     

Cardiovascular reactivity in hypertensives: differential effect of expressing and inhibiting emotions during moments of interpersonal stress

This study investigated cardiovascular reactivity of hypertensive adults during periods of emotional stress. Two types of instructions were given at different moments, to the same subject, either to express or to suppress feelings during role-play. Expressing, but not inhibiting, emotions elicited significantly higher reactivity during responding to negative scenes, followed by responding during the positive interactions. Blood pressure increases in both expressing and inhibiting conditions, were also found during the instruction periods. Results indicated that socially demanding situations represent a stressor whose effects may vary depending on whether or not respondents regulate expression of emotions. It is suggested that the difficulty in expressing emotions found in some hypertensive individuals may have the function of controlling or reducing blood pressure reactivity.     

Preference between onset predictable and unpredictable administrations of 20% carbon-dioxide-enriched air: implications for better understanding the etiology and treatment of panic disorder

Predictability of aversive events impacts the development and maintenance of anxiety, particularly panic disorder. Although animal studies typically have found a preference for signaled (predictable) over unsignaled (unpredictable) aversive events, results of research with human participants have been less clear. Using a panic-relevant paradigm, the authors examined predictability preference with humans as a function of anxiety sensitivity and gender during repeated administrations of 20% carbon-dioxide-enriched air. Participants preferred predictable administrations, with high-anxiety individuals showing greater preference than low-anxiety individuals and women showing greater preference than men. In addition to providing information to better understand human predictability preference for panic-related events, results also may aid in determining the applicability of predictability to the cognitive-behavioral treatment of panic disorder.     

Anxiety sensitivity-physical concerns as a moderator of the emotional consequences of emotion suppression during biological challenge: an experimental test using individual growth curve analysis

Anxiety-related responding to, and recovery from, a 5-min 10% carbon dioxide-enriched air presentation among 80 participants with no history of psychopathology was examined. Half of participants were instructed to suppress challenge-induced emotional responses, whereas their matched counterparts were instructed to observe such responses. Responding from immediately post-challenge through a 10-min recovery period was analyzed as a function of Anxiety Sensitivity-Physical Concerns and experimental condition using individual growth curve modeling. Anxiety Sensitivity-Physical Concerns moderated the effect of suppression only on emotion valence during recovery. In terms of main effects, suppression resulted in increased heart rate during recovery and Anxiety Sensitivity-Physical Concerns was positively associated with post-challenge self-reported anxiety. Results are discussed in terms of the potential role of inhibition-oriented affect regulation processes in the etiology of panic disorder.     

Interoceptive fear conditioning as a learning model of panic disorder: an experimental evaluation using 20% CO(2)-enriched air in a non-clinical sample

Despite the role afforded interoceptive fear conditioning in etiologic accounts of panic disorder, there are no good experimental demonstrations of such learning in humans. The aim of the present study was to evaluate the interoceptive conditioning account using 20% carbon dioxide (CO(2))-enriched air as an interoceptive conditioned stimulus (CS) (i.e., physiologically inert 5-s exposures) and unconditioned stimulus (US) (i.e., physiologically prepotent 15-s exposures). Healthy participants (N=42) were randomly assigned to one of three conditions: a CS-only, contingent CS-US pairings, or unpaired/non-contingent CS and US presentations. Electrodermal and self-report (e.g., distress, fear) served as indices of conditioned emotional responding. Results showed greater magnitude electrodermal and evaluative fear conditioning in the paired relative to the CS-only condition. The explicitly unpaired condition showed even greater electrodermal and evaluative responding during acquisition, and marked resistance to extinction. The latter results are consistent with the possibility that the unpaired procedure constituted a partial reinforcement procedure in which CO(2) onset was paired with more extended CO(2) exposure on 50% of the trials. Overall, the findings are consistent with contemporary learning theory accounts of panic.