Bruce H. Friedman

An autonomic flexibility-neurovisceral integration model of anxiety and cardiac vagal tone.

Research on heart rate variability (HRV), cardiac vagal tone, and their relationship to anxiety is reviewed in the context of the autonomic flexibility and neurovisceral integration models of adaptive functioning. These perspectives address the qualities of response flexibility and inhibition across multiple levels, incorporating central and autonomic nervous system mechanisms of environmental engagement, as well as principles derived from non-linear dynamics. These models predict reduced HRV and vagal tone in anxiety, and the literature has generally supported this prediction, with exceptions as are noted. State, trait, and clinical expressions of anxiety are considered, along with the clinical, methodological, and theoretical implications of this research. A portrayal of anxiety as a restricted response range across biological and behavioral realms of functioning is drawn from the literature on anxiety and HRV.

Phasic heart period reactions to cued threat and nonthreat stimuli in generalized anxiety disorder.

The hallmark of generalized anxiety disorder (GAD) is chronic uncontrollable worry. A preattentive bias toward threat cues and hypervigilance may support this ongoing state of apprehension. A study was conducted to bridge the attentional and physiological underpinnings of GAD by examining phasic heart period (HP) responses to cued threat and nonthreat stimuli. Thirty-three GAD clients and 33 nonanxious control participants engaged in an S1-S2 procedure that employed cued threat and nonthreat word stimuli, during which phasic HP reactions were recorded. As compared with the control group, the GAD group showed (1) smaller cardiac orienting responses and impaired habituation of cardiac orienting to neutral words, (2) HR acceleration in response to threat words, and (3) a conditioned anticipatory HR deceleration to threat words over repeated trials. The cardiac-autonomic underpinnings of GAD appear to rigidly maintain precognitive defensive responses against threat. This portrayal is discussed in the context of an integrative model that depicts diminished global adaptive variability in GAD.

Stop that! Inhibition, sensitization, and their neurovisceral concomitants.

There is increasing evidence that the behavior of living systems can be conceptualized as a self-organizing dynamical system. Moreover, evidence suggests that inhibitory processes give these systems the flexibility that is necessary for efficient functioning in the face of changing environmental demands. The process of sensitization can be conceived as a breakdown of inhibitory neural processes that can lead to maladaptive, perseverative behavior. In this paper we describe a model of inhibition and sensitization from a dynamical systems perspective. We show that inhibition is important for adaptive behavior across a number of levels of system functioning. Using our work on attention, emotion, and anxiety disorders we show the importance of both central - for example gamma-aminobutyric acid (GABA)-ergic - and peripheral - for example heart rate variability (HRV) - inhibitory processes and how they may be linked by a network of neural structures that guide the organism from one state of relative stability to another.

Autonomic specificity of basic emotions: Evidence from pattern classification and cluster analysis

Autonomic nervous system (ANS) specificity of emotion remains controversial in contemporary emotion research, and has received mixed support over decades of investigation. This study was designed to replicate and extend psychophysiological research, which has used multivariate pattern classification analysis (PCA) in support of ANS specificity. Forty-nine undergraduates (27 women) listened to emotion-inducing music and viewed affective films while a montage of ANS variables, including heart rate variability indices, peripheral vascular activity, systolic time intervals, and electrodermal activity, were recorded. Evidence for ANS discrimination of emotion was found via PCA with 44.6% of overall observations correctly classified into the predicted emotion conditions, using ANS variables (z=16.05, p<.001). Cluster analysis of these data indicated a lack of distinct clusters, which suggests that ANS responses to the stimuli were nomothetic and stimulus-specific rather than idiosyncratic and individual-specific. Collectively these results further confirm and extend support for the notion that basic emotions have distinct ANS signatures.

Heart period variability and depressive symptoms: gender differences

BACKGROUND Deceased heart period variability has been associated with cardiac events and depressive symptoms; however, the results of studies are not unequivocal. We hypothesize that gender differences in the various study samples may have contributed to the lack of uniformity of findings. METHODS Time and frequency domain measures of heart period variability during a 5-min resting baseline were examined in 15 depressed (8 female) and 11 nondepressed (6 female) college students. RESULTS Both time and frequency domain measures indicated an interaction between gender and depressive symptoms, such that depressed male subjects showed less heart period variability, whereas depressed female subjects showed more heart period variability compared to their nondepressed counterparts. CONCLUSIONS These results suggest that future studies investigating the relationship between heart period variability and depressive symptoms examine gender differences.

Respiratory sinus arrhythmia: a marker for positive social functioning and receptive language skills in children with autism spectrum disorders.

The current study builds on the emerging autism spectrum disorder (ASD) literature that associates autonomic nervous system activity with social function, and examines the link between respiratory sinus arrhythmia (RSA) and both social behavior and cognitive function. The RSA response pattern was assessed in 23 4- to 7-year-old children diagnosed with an ASD. Higher baseline RSA amplitudes were associated with better social behavior (i.e., more conventional gestures, more instances of joint attention) and receptive language abilities. Similar to reports of typically developing children, ASD children with higher RSA amplitude at baseline showed greater RSA and HP reactivity during an attention-demanding task. These results highlight the importance of studying RSA as a marker of positive function in children with ASD.

Explicit memory bias for threat words in generalized anxiety disorder

Although findings of an implicit memory bias for threat words in generalized anxiety disorder (GAD) are fairly robust, the data regarding an explicit bias in this disorder are less consistent. This issue was investigated in the context of two studies directed primarily at the examination of attentional and physiological underpinnings of GAD. In these experiments, GAD clients and nonanxious control participants (35 and 29 in Study 1, and 22 and 31 in Study 2, respectively) engaged in an S1–S2 conditioning procedure that involved the presentation of a series of neutral stimuli (colored dots) paired with threat and nonthreat words, followed by a free recall test. Instructions were to simply look at the dot and read the word silently. A free recall task was administered at the end of each experimental session. Contrary to previous trends in the literature, a marked bias in the GAD group toward recall of the threat words emerged in both studies. These results are considered in the light of methodological differences with previous research, information processing characteristics of GAD, and the role of physiological assessment in cognitive studies of anxiety.

Validity concerns of common heart-rate variability indices

Time- and frequency-domain analyses of HRV have provided researchers with important measures of cardiac vagal activity. Stationarity is of theoretical importance for such analyses in the frequency domain but may not be of practical significance in any particular data set. It has been argued that if a stationarity test is available, it should be used. On the other hand, it is also possible that the RSA is quite robust to nonstationarity; the spectral data support that contention. Furthermore, procedures that correct for nonstationary data segments may compromise the representativeness of the data set. With regard to the time domain, MSD is advantageous in that it is conceptually and computationally simple, does not require respiration data, and under many conditions may be a reasonable alternative to HF spectral power or RSA. All told, the selection of cardiac vagal control indices and use of correction procedures should be based upon experimental situation and availability to the researcher, rather than orthodox adherence to idealized standards.

Cardiovascular activity during laboratory tasks in women with high and low worry

Worry has been related to delayed stress recovery and cardiovascular disease risk. Cardiovascular responses to a range of laboratory tasks were examined in this study of high and low worriers. Undergraduate women were recruited with the Penn State Worry Questionnaire to form low (n=19) and high (n=22) worry groups. These individuals engaged in six laboratory tasks (orthostatic stress, supine rest, hand cold pressor, mental arithmetic, and worry and relaxation imagery) while heart rate (HR), HR spectral analysis, impedance cardiography, and blood pressure were acquired. The only significant group difference found was a consistently greater HR across tasks in high worriers (p<.05). No group by condition interactions emerged. High trait worry in healthy young women appears to be marked by elevated HR in the absence of autonomic abnormalities. These findings are discussed relative to the literature on worry, with particular reference to its health implications.

Hostility and anger-in: Cardiovascular reactivity and recovery to mental arithmetic stress

BACKGROUND Hostility and anger have been attributed as psychosocial risk factors for coronary heart disease. Heightened cardiovascular reactivity (CVR), and poor recovery, to provocative stressors are thought to hasten this risk. PURPOSE To examine the relationship between hostility and anger inhibition (AI), and the moderating situational influences of harassment and evaluation, in predicting CVR and recovery to mental arithmetic (MA) stress using a multiple regression approach. METHODS 48 male undergraduate students engaged in the following 3 minute tasks during recording of the electrocardiogram, impedance cardiography, and blood pressure: baseline, MA, and evaluation. Hostility and AI were assessed with the Cook-Medley Hostility Scale and the Speilberger Anger In subscale, respectively. RESULTS An interaction between hostility and AI showed high diastolic blood pressure reactivity to the MA task among hostile anger inhibitors. Harassment did not modify this effect. However, harasser evaluation predicted prolonged systolic blood pressure (SBP) responding among men scoring high in AI, and facilitated SBP recovery among those scoring low on AI. CONCLUSIONS The findings highlight the interactive influences of AI and hostility in predicting CVR to stress and underscore the importance of recovery assessments in understanding the potentially pathogenic associations of these constructs.