How specific is specific phobia? Different neural response patterns in two subtypes of specific phobia

Abstract

Specific phobia of the animal subtype has been employed as a model disorder exploring the neurocircuitry of anxiety disorders, but evidence is lacking whether the detected neural response pattern accounts for all animal subtypes, nor across other phobia subtypes. The present study aimed at directly comparing two subtypes of specific phobia: snake phobia (SP) representing the animal, and dental phobia (DP) representing the blood-injection-injury subtype. Using functional magnetic resonance imaging (fMRI), brain activation and skin conductance was measured during phobogenic video stimulation in 12 DP, 12 SP, and 17 healthy controls. For SP, the previously described activation of fear circuitry structures encompassing the insula, anterior cingulate cortex and thalamus could be replicated and was furthermore associated with autonomic arousal. In contrast, DP showed circumscribed activation of the prefrontal and orbitofrontal cortex (PFC/OFC) when directly compared to SP, being dissociated from autonomic arousal. Results provide preliminary evidence for the idea that snake and dental phobia are characterized by distinct underlying neural systems during sustained emotional processing with evaluation processes in DP being controlled by orbitofrontal areas, whereas phobogenic reactions in SP are primarily guided by limbic and paralimbic structures. Findings support the current diagnostic classification conventions, separating distinct subtypes in DSM-IV-TR. They highlight that caution might be warranted though for generalizing findings derived from animal phobia to other phobic and anxiety disorders. If replicated, results could contribute to a better understanding of underlying neurobiological mechanisms of specific phobia and their respective classification.

Initial and sustained brain responses to threat anticipation in blood-injection-injury phobia

“…Increased activation was found in brain regions that were previously suggested to play a role in anticipation of phobia-specific stimuli in spider phobia (Münsterkötter et al, 2015, Straube et al, 2007). This stands in contrast to studies on phobia-specific picture processing, which found similar (Caseras et al, 2010b) but also distinct brain activations (Caseras et al, 2010a, Lueken et al, 2011) for animal phobia in comparison to BII phobia. Taken together, these findings suggest that diagnostic classifications for specific phobia are meaningful for emotional processing during confrontation with phobia-specific stimuli, but that anticipatory anxiety could be a common denominator among specific phobia subtypes.…”

“…The current fMRI results support this assumption, as findings replicate activation patterns previously shown for anticipatory anxiety in spider phobia (Münsterkötter et al, 2015, Straube et al, 2007), social anxiety disorder (Boehme et al, 2014, Lorberbaum et al, 2004) and panic disorder (Boshuisen et al, 2002, Wittmann et al, 2014). This is especially interesting in the light of fMRI studies that investigated confrontation with phobia-relevant stimuli in BII phobia which suggest inconclusive and unspecific results (Caseras et al, 2010a, Caseras et al, 2010b, Hermann et al, 2007, Lueken et al, 2011, Schienle et al, 2003). More specifically, direct comparison between BII and animal phobics showed distinct neural substrates for the two subtypes (Caseras et al, 2010a, Caseras et al, 2010b, Lueken et al, 2011).…”

“…This is especially interesting in the light of fMRI studies that investigated confrontation with phobia-relevant stimuli in BII phobia which suggest inconclusive and unspecific results (Caseras et al, 2010a, Caseras et al, 2010b, Hermann et al, 2007, Lueken et al, 2011, Schienle et al, 2003). More specifically, direct comparison between BII and animal phobics showed distinct neural substrates for the two subtypes (Caseras et al, 2010a, Caseras et al, 2010b, Lueken et al, 2011). …”

“…Direct comparison between BII and animal phobics revealed that only spider phobics showed activations in key areas for emotional processing, i.e. insula and ACC, when confronted with phobia-specific pictures (Caseras et al, 2010a, Lueken et al, 2011). In contrast, another study reported similar activation patterns in BII and spider phobics in the amygdala, insula, ACC, thalamus and orbitofrontal cortex (OFC) (Caseras et al, 2010b).…”

Psychotherapy and Mental Health as a Psychological Science Discipline

“…Emotional responses like fear and anxiety are grounded in 'complex systems' that feed back to sensory systems, heightening vigilance and information gathering (if a threat is expected or detected) and, importantly, prompting for example defensive reflexive, autonomic, and motor responses that in evolutionary history acted directly to counter threats and escape punishments [Arch and Craske, 2009]. Comparative research across different forms of mental disorders is necessary to detect such core aspects of dysfunctions shared by all disorders in contrast to disorder-specific features [Etkin and Wager, 2007;Haber and Rauch, 2010;Lueken et al, 2011;Domschke and Deckert, 2012] and to inform how therapeutic interventions can be optimized, e.g. by component, mediator and moderator analyses.…”