Physiological parameters within three paradigms and perceived symptoms in social phobia

Abstract

This study undertakes an effort to contribute to a better understanding concerning patterns of activation versus non-activation of the assumed underlying fear network in a Spanish sample of social phobic participants (n = 23) in comparison to a control group (n = 20). Symptoms typical for social phobia, general anxiety, and depressive symptomatology were assessed by questionnaires. Participants physiological activation, measured in heart rate, heart rate variability, blood pressure, pulse, respiration, skin conductance and startle reflex were assessed across the defense, picture and imagery paradigm. Participants gave an affective rating towards presented pictures and scenes on the dimensions of valence, arousal and dominance. Concerning questionnaire-based data, social phobic participants reported having more severe social fear, more general anxiety related symptoms, more worries and more severe depressive symptomatology compared to controls. Concerning the defense paradigm the tendency towards a lower heart rate variability and an elevated defense response in social phobic participants can be interpreted in terms of an activation of the defensive behavioral system but also in terms of an underlying fear network structure that is characterized by general apprehension, hypervigilance and poor autonomic control. As with regard to the picture paradigm physiological activation did not occur consistently across measured parameters and also affective report did not reveal consistent differences, results are interpreted in this way that unpleasant pictures as aversive stimuli do not necessarily lead to an activation of the fear network in social phobic participants. Outcome measures pertaining to the imagery paradigm are characterized by a discordance found between the report of affective rating which points towards an activation of the assumed underlying fear network and physiological reactivity which do not consistently support the activation of the fear network. Results due to pictures and images can be interpreted more in line with a hyporeactivity and an underlying fear network that is characterized by vigilance, apprehension and a lower overall associative strength. Overall, results are discussed in terms of a less reactive autonomous nervous system that is associated with a sustained arousal, which might explain the hyperreactivity found towards the defense stimulus, but also impaired reactance, which might explain the lower heart rate variability during a preceding baseline and the hyporeactivity towards picture and imagery material. Under the perspective of brain functioning, the hyperreactivity can be explained by the activation of the behavioral activation system, triggering fight-flight reactions based on the amygdala circuit, whereas the non-activation or hyporeactivity can be interpreted as an approach-avoidance conflict related to an assumed behavioral inhibition system, which in turn is associated with the septal-hippocampal circuit, that mediates suppression of approach and excessive avoidance of threat. Alternatively the bed nucleus of the stria terminalis as anxiety path is discussed. In the context of applied clinical psychology, the observed hyporeactivity should be considered in terms of a lower probability to access the related fear network, thus impeding emotional processing necessary to improve symptomatology in social phobia and hence for a successful treatment outcome.