Fear processing in dental phobia during crossmodal symptom provocation: an fMRI study

Abstract

While previous studies successfully identified the core neural substrates of the animal subtype of specific phobia, only few and inconsistent research is available for dental phobia. These findings might partly relate to the fact that, typically, visual stimuli were employed. The current study aimed to investigate the influence of stimulus modality on neural fear processing in dental phobia. Thirteen dental phobics (DP) and thirteen healthy controls (HC) attended a block-design functional magnetic resonance imaging (fMRI) symptom provocation paradigm encompassing both visual and auditory stimuli. Drill sounds and matched neutral sinus tones served as auditory stimuli and dentist scenes and matched neutral videos as visual stimuli. Group comparisons showed increased activation in the insula, anterior cingulate cortex, orbitofrontal cortex, and thalamus in DP compared to HC during auditory but not visual stimulation. On the contrary, no differential autonomic reactions were observed in DP. Present results are largely comparable to brain areas identified in animal phobia, but also point towards a potential downregulation of autonomic outflow by neural fear circuits in this disorder. Findings enlarge our knowledge about neural correlates of dental phobia and may help to understand the neural underpinnings of the clinical and physiological characteristics of the disorder.

Figure 1

Behavioral data. Upper half: subjective ratings for auditory (a) and visual (b) dental stimuli. Lower half: phasic (CDA.SCR; (c)) and tonic (CDA.tonic; (d)) skin conductance responses. HC: healthy control group; DP: dental phobia group. *P < 0.05; **P < 0.01; ***P < 0.001.

Figure 2

Neural activation patterns of the between-group comparison for auditory stimulus material (DAA > DAN): dental phobics versus healthy controls (upper three) and healthy controls versus dental phobics (below). DP: dental phobia group; HC: healthy control group; ACC: anterior cingulate cortex; MCC: middle cingulate cortex; L: left side; analysis: minimum cluster size = 58; *P < 0.05; **P < 0.01; ***P < 0.001.