Neurobiological correlates of dental phobia

Extreme fear and avoidance of dental treatment are very common and affect both males and females. The neurobiology of dental phobia however is poorly understood. Therefore the planned study will explore electrocortical (EEG), electromyograhpic (EMG), electrocardiac (ECG) as well as affective responses to symptom provocation in dental phobia. Further, gender differences in the phobic response will be investigated. Finally, we attempt to identify subtypes of dental phobia which are rather fear-dominated (e.g., fear of drilling) or disgust- dominated (e.g., elevated gag reflex in response to the placement of dental instruments in the mouth). Participants of the planned study are 40 patients (20 males, 20 females) suffering from dental phobia and 40 non- phobic individuals. After a diagnostic interview, the participants will be presented with a total of 120 pictures depicting phobia-relevant, generally disgust-inducing, fear-inducing and affectively neutral contents. During the presentation the EEG, the ECG and the EMG of the musculus levator labii (specific disgust indicator) and the m. corrugator (`frowning muscle`) will be recorded. Afterwards, the participants are asked to give affective ratings for the pictures on the dimensions valence, arousal, fear and disgust. EEG data will be analyzed according to event- related potentials, which are indicators of motivated attention and affective processing (e.g., P300, late positive potential). Baseline corrected mean and maximum EMG responses as well as heart rate changes will be obtained for each picture category. We hypothesize that the phobia-relevant material will lead to elevated late ERPs in the patient sample. Depending on the subtype of dental phobia we expect increases in heart rate and corrugator activity in the fear-dominated subtype, whereas the disgust-dominated subtype shows a relative heart rate decrease together with increased levator activity. We also expect gender-specific neurobiological response components, e.g., larger ERP amplitudes in women. Correlation analyses between (gender-specific) neurobiological and clinical features of dental phobia will be computed. It is hoped that the planned study will contribute to a better understanding of neurobiological mechanisms implicated in dental phobia. This might contribute to an improvement of psychotherapeutic treatment strategies tailored to the different subtypes of dental phobia.

The knowledge about neurobiological characteristics of dental phobia is still limited. Therefore, the present study used psychophysiological measurement techniques, such as the electroencephalogram (EEG), the electrocardiogram (ECG), and the electromyogram (EMG) to investigate event-related potentials (ERPs), heart rate and facial muscle activity during symptom provocation in men and women afflicted with dental phobia. Dental phobia is a common mental disorder and according to DSM-IV-TR is classified as the blood-injection-injury (BII) subtype of specific phobia. In the current study, dentophobic women and men, as well as controls completed a session with combined EEG/ECG/EMG recording while they viewed pictures showing dental treatment, as well as disorder-irrelevant disgusting, fear-inducing and neutral contents. Both male and female dentophobics relative to controls were characterized by heart rate acceleration and enhanced late ERPs at posterior sites during the confrontation with disorder-specific materials, reflecting fear and motivated attention. This reaction pattern can also be found in the animal subtype of specific phobia, but not in blood-injection-injury (BII) phobia. Therefore, the current classification of dental phobia as BII phobia should be reconsidered. Gender differences concerned late ERPs at frontal EEG sites reflecting differential recruitment of neuronal networks involved in controlled attention focusing. Men showed enhanced frontal late ERPs to dental treatment scenes, while women did not. Moreover, females showed enhanced facial muscle activity of the levator labii indexing disgust expressions, while this could not be shown in men. This result could be interpreted to reflect higher emotional expressivity in females than males. Additionally, EEG source localization and comparison of data with results from studies on spider phobia indicated prolonged and deeper attentional involvement in phylogenetically based phobias (e.g., spider phobia) compared to ontogenetically based phobias (dental phobia).