Recent research has emphasized the importance of emotion regulation for understanding the (neural) processes underlying mental disorders (Campbell-Sills and Barlow, 2007
; Etkin and Wager, 2007
; Gross and Thompson, 2007
; Johnstone et al
; Linehan et al
). Also, in specific phobia strong emotional responses towards phobic objects can be described in terms of diminished down-regulation of emotions. Symptom provocation studies indicate increased neural activity related to phobic reactions in areas such as the amygdala, insula and dorsal anterior and mid-cingulate cortex (Carlsson et al
, Etkin and Wager, 2007
; Goossens et al
; Hermann, et al
; Schienle et al
). There are also studies that show diminished responses in prefrontal cortex (PFC) areas (Johanson et al
; Carlsson et al
; Hermann et al
; Schienle et al
), e.g. in the medial prefrontal cortex. Such hypoactivations have also been observed in anxiety disorders other than specific phobias (Milad and Rauch, 2006
; Etkin and Wager, 2007
). Emotion regulation studies indicate that these prefrontal cortex regions are involved in both effortful (dorsal PFC and anterior cingulate cortex regions) as well as automatic (ventral PFC regions) emotion regulation processes (Ochsner and Gross, 2005
). Dorsolateral PFC regions which are important for executive and working memory processes as implicated in effortful emotion regulation (Phelps, 2006
), have few direct reciprocal connections with emotional appraisal regions (Ochsner and Gross, 2007
). So, effortful regulation of emotions is considered to influence brain mechanisms related to automatic regulation processes in order to reduce activity in emotional appraisal regions such as the amygdala (Phelps, 2006
). Thus, previous results on the neural correlates of specific phobias might reflect a deficit in the automatic regulation of phobic responses as well as difficulties in the effortful cognitive control of these strong emotions (Hermann et al
). Furthermore, individuals with specific phobias are characterized by irrational cognitions in phobic situations. Such catastrophizing thoughts as a form of effortful up-regulation of emotions might be an important factor in the maintenance of phobic disorders. The neural correlates of these processes in spider phobics have not been investigated as yet.
Moreover, several studies indicate that considering the form and time course of the blood oxygen level-dependent (BOLD) response in various brain regions is especially important in phobic compared with non-phobic responses and during the investigation of emotion regulation processes. Larson et al
) reported that the amygdala response has a faster onset and earlier peak in phobics than in controls and also in response to phobic compared with other negative emotional stimuli. Another study concerning emotion regulation processes in healthy subjects (Goldin et al
) showed that different emotion regulation strategies can be distinguished by the temporal dynamics of the underlying response. All in all, an appropriate model for the underlying hemodynamic response is crucial for studying the neural correlates of emotion regulation especially in specific phobia.
The purpose of this study was to examine the neural correlates of (i) (phobic) emotional responses, (ii) automatic emotional dysregulation in response to phobic compared with non-phobic emotional stimuli, (iii) effortful (phobic) emotion regulation and (iv) deficits in the effortful regulation of phobic compared with generally aversive emotional responses within spider phobic subjects. Therefore, spider phobic individuals were asked to up- and down-regulate their emotions elicited by phobic and generally aversive emotional pictures or to look at the pictures (phobic, aversive, neutral) and respond naturally. A control group was not examined as spider pictures are experienced as affectively neutral by healthy controls (Schienle et al
) and are insofar no appropriate stimuli for the regulation processes investigated in this study.
Successful emotion induction should be reflected in enhanced activity in the amygdala, insula and dACC. Concerning an automatic regulation deficit of phobic compared with non-phobic emotional responses, reduced activity in ventromedial PFC (vmPFC) regions accompanied by higher activity in the amygdala, insula and dACC is assumed for looking at spider compared with aversive pictures. Furthermore, we hypothesize that dorsal and ventral PFC areas are involved in the effortful (up- and down-) regulation of emotional responses by modulating activity in structures like the insula and amygdala. A deficit in the down-regulation of phobic compared to generally aversive emotional reactions is expected to be related to diminished activity in the medial PFC in response to phobic compared with generally aversive stimuli, whereas easier up-regulation in response to phobic stimuli is assumed to more strongly activate the dACC, amygdala and insula accompanied by higher activity in regulatory medial PFC regions. To account for varying time courses and shapes of the BOLD response, we used finite impulse responses to model the underlying hemodynamic response without assuming a specific shape. We expect early and short-lasting responses in the amygdala whereas activity in regulatory prefrontal cortex areas is assumed to be more sustained.