Lisa M. McTeague

Aversive Imagery in Posttraumatic Stress Disorder: Trauma Recurrence, Comorbidity, and Physiological Reactivity

BACKGROUND Posttraumatic stress disorder (PTSD) is characterized as a disorder of exaggerated defensive physiological arousal. The novel aim of the present research was to investigate within PTSD a potential dose-response relationship between past trauma recurrence and current comorbidity and intensity of physiological reactions to imagery of trauma and other aversive scenarios. METHODS A community sample of principal PTSD (n = 49; 22 single-trauma exposed, 27 multiple-trauma exposed) and control (n = 76; 46 never-trauma exposed, 30 trauma exposed) participants imagined threatening and neutral events while acoustic startle probes were presented and the eye-blink response (orbicularis occuli) was recorded. Changes in heart rate, skin conductance level, and facial expressivity were also indexed. RESULTS Overall, PTSD patients exceeded control participants in startle reflex, autonomic responding, and facial expressivity during idiographic trauma imagery and, though less pronounced, showed heightened reactivity to standard anger, panic, and physical danger imagery. Concerning subgroups, control participants with and without trauma exposure showed isomorphic patterns. Within PTSD, only the single-trauma patients evinced robust startle and autonomic responses, exceeding both control participants and multiple-trauma PTSD. Despite greater reported arousal, the multiple-trauma relative to single-trauma PTSD group showed blunted defensive reactivity associated with more chronic and severe PTSD, greater mood and anxiety disorder comorbidity, and more pervasive dimensional dysphoria (e.g., depression, trait anxiety). CONCLUSIONS Whereas PTSD patients generally show marked physiological arousal during aversive imagery, concordant with self-reported distress, the most symptomatic patients with histories of severe, cumulative traumatization show discordant physiological hyporeactivity, perhaps attributable to sustained high stress and an egregious, persistent negative affectivity that ultimately compromises defensive responding.

Fearful imagery in social phobia: Generalization, comorbidity, and physiological reactivity

BACKGROUND Social phobia has been characterized as a disorder of exaggerated fear of social threat and heightened sensitivity to imagery of social failure. METHODS To assess the physiological basis of this description, social phobia patients (n=75) and demographically matched control participants (n=75) imagined neutral and fearful events while acoustic startle probes were occasionally presented and eye-blink responses (orbicularis occuli) recorded. Changes in heart rate, skin conductance level, and facial expressivity were also indexed. In addition to comparing control participants and social phobia patients, the influences of diagnostic subtype (circumscribed, generalized), comorbid depression, and chronicity were assessed. RESULTS Patients exceeded control participants in startle reflex and autonomic responding during imagery of social threat, whereas the groups evinced commensurate reactivity to contents depicting commonly shared fears (survival threat). Individuals with circumscribed performance phobia were similar to control participants, with the exception of more robust reactions to idiographic, performance fear imagery. In contrast, generalized phobic patients were characterized by longer disorder chronicity and demonstrated heightened sensitivity to a broader range of fear contents. Those with generalized phobia plus comorbid depression showed attenuation of fear-potentiated startle and reported the most protracted social anxiety. CONCLUSIONS Subtypes of social phobia can be objectively distinguished in patterns of physiological reactivity. Furthermore, subtypes vary systematically in chronicity and defensive engagement with the shortest disorder duration (circumscribed phobia) associated with the most robust and focal physiological reactivity, followed by broader defensive sensitivity in more chronic generalized phobia, and finally attenuation of the formerly exaggerated fear potentiation in the comorbidly depressed, the most chronic form.

The anxiety disorder spectrum: Fear imagery, physiological reactivity, and differential diagnosis

Abstract This review considers recent research assessing psychophysiological reactivity to fear imagery in anxiety disorder patients. As in animal subjects, fear cues prompt in humans a state of defensive motivation in which autonomic and somatic survival reflexes are markedly enhanced. Thus, a startle stimulus presented in a fear context yields a stronger (potentiated) reflex, providing a quantitative measure of fearful arousal. This fear potentiation is further exaggerated in specific or social phobia individuals when viewing pictures or imagining the phobic object. Paradoxically, fear imagery studies with more severe anxiety disorder patients – panic disorder with agoraphobia, generalized anxiety disorder, or anxious patients with comorbid depression – show a blunted, less robust fear potentiated response. Furthermore, this reflex blunting appears to systematically be more pronounced over the anxiety disorder spectrum, coincident with lengthier chronicity, worsening clinician-based judgments of severity and prognosis, and increased questionnaire-based indices of negative affectivity, suggesting that normal defensive reactivity may be compromised by an experience of long-term stress.

THE ANXIETY SPECTRUM AND THE REFLEX PHYSIOLOGY OF DEFENSE: FROM CIRCUMSCRIBED FEAR TO BROAD DISTRESS

Guided by the diagnostic nosology, anxiety patients are expected to show defensive hyperarousal during affective challenge, irrespective of the principal phenotype. In the current study, patients representing the whole spectrum of anxiety disorders (i.e., specific phobia, social phobia, panic disorder with or without agoraphobia, obsessive‐compulsive disorder, generalized anxiety disorder (GAD), posttraumatic stress disorder(PTSD)), and healthy community control participants, completed an imagery‐based fear elicitation paradigm paralleling conventional intervention techniques. Participants imagined threatening and neutral narratives as physiological responses were recorded. Clear evidence emerged for exaggerated reactivity to clinically relevant imagery—most pronounced in startle reflex responding. However, defensive propensity varied across principal anxiety disorders. Disorders characterized by focal fear and impairment (e.g., specific phobia) showed robust fear potentiation. Conversely, for disorders of long‐enduring, pervasive apprehension and avoidance with broad anxiety and depression comorbidity (e.g., PTSDsecondary to cumulative trauma, GAD), startle responses were paradoxically diminished to all aversive contents. Patients whose expressed symptom profiles were intermediate between focal fearfulness and broad anxious‐misery in both severity and chronicity exhibited a still heightened but more generalized physiological propensity to respond defensively. Importantly, this defensive physiological gradient—the inverse of self‐reported distress—was evident not only between but also within disorders. These results highlight that fear circuitry could be dysregulated in chronic, pervasive anxiety, and preliminary functional neuroimaging findings suggest that deficient amygdala recruitment could underlie attenuated reflex responding. In summary, adaptive defensive engagement during imagery may be compromised by long‐term dysphoria and stress—a phenomenon with implications for prognosis and treatment planning.

Social vision: Sustained perceptual enhancement of affective facial cues in social anxiety

Heightened perception of facial cues is at the core of many theories of social behavior and its disorders. In the present study, we continuously measured electrocortical dynamics in human visual cortex, as evoked by happy, neutral, fearful, and angry faces. Thirty-seven participants endorsing high versus low generalized social anxiety (upper and lower tertiles of 2104 screened undergraduates) viewed naturalistic faces flickering at 17.5 Hz to evoke steady-state visual evoked potentials (ssVEPs), recorded from 129 scalp electrodes. Electrophysiological data were evaluated in the time-frequency domain after linear source space projection using the minimum norm method. Source estimation indicated an early visual cortical origin of the face-evoked ssVEP, which showed sustained amplitude enhancement for emotional expressions specifically in individuals with pervasive social anxiety. Participants in the low symptom group showed no such sensitivity, and a correlational analysis across the entire sample revealed a strong relationship between self-reported interpersonal anxiety/avoidance and enhanced visual cortical response amplitude for emotional, versus neutral expressions. This pattern was maintained across the 3500 ms viewing epoch, suggesting that temporally sustained, heightened perceptual bias towards affective facial cues is associated with generalized social anxiety.

Sustained preferential processing of social threat cues: Bias without competition?

Stimuli of high emotional significance such as social threat cues are preferentially processed in the human brain. However, there is an ongoing debate whether or not these stimuli capture attention automatically and weaken the processing of concurrent stimuli in the visual field. This study examined continuous fluctuations of electrocortical facilitation during competition of two spatially separated facial expressions in high and low socially anxious individuals. Two facial expressions were flickered for 3000 msec at different frequencies (14 and 17.5 Hz) to separate the electrocortical signals evoked by the competing stimuli (“frequency tagging”). Angry faces compared to happy and neutral expressions were associated with greater electrocortical facilitation over visual areas only in the high socially anxious individuals. This finding was independent of the respective competing stimulus. Heightened electrocortical engagement in socially anxious participants was present in the first second of stimulus viewing and was sustained for the entire presentation period. These results, based on a continuous measure of attentional resource allocation, support the view that stimuli of high personal significance are associated with early and sustained prioritized sensory processing. These cues, however, do not interfere with the electrocortical processing of a spatially separated concurrent face, suggesting that they are effective at capturing attention, but are weak competitors for resources.

Aversive Imagery in Panic Disorder: Agoraphobia Severity, Comorbidity, and Defensive Physiology

BACKGROUND Panic is characterized as a disorder of interoceptive physiologic hyperarousal, secondary to persistent anticipation of panic attacks. The novel aim of this research was to investigate whether severity of agoraphobia within panic disorder covaries with the intensity of physiological reactions to imagery of panic attacks and other aversive scenarios. METHODS A community sample of principal panic disorder (n = 112; 41 without agoraphobia, 71 with agoraphobia) and control (n = 76) participants imagined threatening and neutral events while acoustic startle probes were presented and the eye-blink response (orbicularis oculi) recorded. Changes in heart rate, skin conductance level, and facial expressivity were also measured. RESULTS Overall, panic disorder patients exceeded control participants in startle reflex and heart rate during imagery of standard panic attack scenarios, concordant with more extreme ratings of aversion and emotional arousal. Accounting for the presence of agoraphobia revealed that both panic disorder with and without situational apprehension showed the pronounced heart rate increases during standard panic attack imagery observed for the sample as a whole. In contrast, startle potentiation to aversive imagery was more robust in those without versus with agoraphobia. Reflex diminution was most dramatic in those with the most pervasive agoraphobia, coincident with the most extreme levels of comorbid broad negative affectivity, disorder chronicity, and functional impairment. CONCLUSIONS Principal panic disorder may represent initial, heightened interoceptive fearfulness and concomitant defensive hyperactivity, which through progressive generalization of anticipatory anxiety ultimately transitions to a disorder of pervasive agoraphobic apprehension and avoidance, broad dysphoria, and compromised mobilization for defensive action.

Competition effects of threatening faces in social anxiety.

Threatening faces involuntarily grab attention in socially anxious individuals. It is unclear, however, whether attention capture is at the expense of concurrent visual processing. The current study examined the perceptual cost effects of viewing fear-relevant stimuli (threatening faces) relative to a concurrent change-detection task. Steady-state visual evoked potentials (ssVEPs) were used to separate the neural response to 2 fully overlapping types of stimuli flickering at different frequencies: Task-irrelevant facial expressions (angry, neutral, happy) were overlaid with a task-relevant Gabor patch stream, which required a response to rare phase reversals. Groups of 17 high and 17 low socially anxious observers were recruited through online prescreening of 849 students. A prominent competition effect of threatening faces was observed solely in elevated social anxiety: When an angry face, relative to a neutral or happy face, served as a distractor, heightened ssVEP amplitudes were seen at the tagging frequency of that facial expression. Simultaneously, the ssVEP evoked by the task-relevant Gabor grating was reliably diminished compared with conditions with neutral or happy distractor faces. Thus, threatening faces capture and hold low-level perceptual resources in viewers symptomatic for social anxiety at the cost of a concurrent primary task. It is important to note that this competition in lower tier visual cortex was maintained throughout the viewing period and was unaccompanied by competition effects on behavioral performance.

Defensive mobilization in specific phobia: Fear specificity, negative affectivity and diagnostic prominence

BACKGROUND Understanding of exaggerated responsivity in specific phobia-its physiology and neural mediators-has advanced considerably. However, despite strong phenotypic evidence that prominence of specific phobia relative to co-occurring conditions (i.e., principal versus nonprincipal disorder) is associated with dramatic differences in subjective distress, there is yet no consideration of such comorbidity issues on objective defensive reactivity. METHODS A community sample of specific phobia (n = 74 principal; n = 86 nonprincipal) and control (n = 76) participants imagined threatening and neutral events while acoustic startle probes were presented and eyeblinks (orbicularis occuli) recorded. Changes in heart rate, skin conductance level, and facial expressivity were also measured. RESULTS Principal specific phobia patients far exceeded control participants in startle reflex and autonomic reactivity during idiographic fear imagery. Distinguishing between single and multiple phobias within principal phobia and comparing these with nonprincipal phobia revealed a continuum of decreasing defensive mobilization: single patients were strongly reactive, multiple patients were intermediate, and nonprincipal patients were attenuated-the inverse of measures of pervasive anxiety and dysphoria (i.e., negative affectivity). Further, as more disorders supplanted specific phobia from principal disorder, overall defensive mobilization was systematically more impaired. CONCLUSIONS The exaggerated responsivity characteristic of specific phobia is limited to those patients for whom circumscribed fear is the most impairing condition and coincident with little additional affective psychopathology. As specific phobia is superseded in severity by broad and chronic negative affectivity, defensive reactivity progressively diminishes. Focal fears may still be clinically significant but not reflected in objective defensive mobilization.

Aversive picture processing: Effects of a concurrent task on sustained defensive system engagement

Viewing a series of aversive pictures prompts emotional reactivity reflecting sustained defensive engagement. The present study examined the effects of a concurrent visual task on autonomic, somatic, electrocortical, and facial components of this defensive state. Results indicated that emotional activation was largely preserved despite continuous visual distraction, although evidence of attenuation was observed in startle reflex and electrocortical measures. Concurrent task-specific reactivity was also apparent, suggesting that motivational circuits can be simultaneously activated by stimuli with intrinsic survival significance and instructed task significance and that these processes interact differently across the separate components of defensive engagement.