INTPSY-10793; No of Pages 7 International Journal of Psychophysiology xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
International Journal of Psychophysiology journal homepage: www.elsevier.com/locate/ijpsycho
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Verena Leutgeb ⁎, Florian Schöngassner, Anne Schienle
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University of Graz, Department of Clinical Psychology, Universitätsplatz 2/III, A-8010 Graz, Austria
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Article history: Received 15 January 2014 Received in revised form 5 May 2014 Accepted 6 May 2014 Available online xxxx
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Keywords: Dentophobia Attention regulation Event-related potentials Late positive potential Fear
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Fear of pain is a main motivator for avoidance or delay of dental treatment in patients afflicted with dentophobia. Studies employing passive viewing paradigms found motivated attention to the phobic object to be associated with enhanced amplitudes of the late positive potential (LPP). The aim of the current study was to investigate, if explicit attention-guiding instructions are able to modify the LPP. Twenty-three patients suffering from dentophobia and 23 controls were presented with pictures showing disorder-relevant or neutral contents, which were combined with different instructions: to distract the attention away from the picture, to classify the content, or to decide whether the scene elicited fear of pain. Relative to controls, dentophobics displayed enhanced late positivity (300–1000 ms after picture onset) in the fear of pain condition at frontal and central recording sites, whereas there was no group difference during classification and distraction. Within patients, fear of pain elicited greater positivity than classification and distraction. The findings are discussed within the framework of attentional direction. Future studies could investigate whether psychotherapy differentially affects neural correlates of attention regulation. © 2014 Published by Elsevier B.V.
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1. Introduction
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Patients suffering from dentophobia frequently report to have experienced excessive pain during dental treatment. Moreover, they expect future treatments to be very painful (Jöhren and Sartory, 2002). This expectation of pain is the main motivator for avoidance or delay of dental treatment. The fact that the threshold for the perception of pain is generally lowered when participants are in an anxious mood might be one cause for the vicious cycle of fear and avoidance in dentophobia (Lautch, 1971). Cognitive behavioral therapy (CBT) has consistently proven to be effective in managing fear of dental treatment (Gordon et al., 2013). Empirical evidence emphasizes the importance of exposure techniques, which include directing the patients' attention to the feared stimulus. However, distraction strategies have also been found to be useful (e.g., relaxation techniques), leaving the role of attentional direction in dentophobia unresolved. The goal of the current investigation was to study electrocortical correlates of different attentional strategies during symptom provocation. The electroencephalogram (EEG) was chosen for the experiment because of its excellent temporal resolution. It provides researchers with the opportunity to study attentional processes that are characterized by a rather short duration as in specific phobia. According to the theory
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Electrocortical effects of directing attention during visual exposure in dentophobia
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⁎ Corresponding author. Tel.: +43 316 380 8507; fax: +43 316 380 9808. E-mail addresses: [email protected] (V. Leutgeb), fl[email protected] (F. Schöngassner), [email protected] (A. Schienle).
of motivated attention (Lang et al., 1997; for a discussion see Bradley, 2009) late positive event-related potentials (ERPs) can be interpreted as indicators of emotional significance and attention allocation. There is a long tradition of studies, showing that emotionally significant stimuli automatically draw attention in order to recruit resources for a deeper processing (for a review, see Olofsson et al., 2008). The electrocortical substrate is reported to be a sustained positive slow wave at posterior recording sites. One typical component, the late positive potential (LPP), is a central-parietal positivity which can be seen about 300 ms after picture onset (e.g., Cuthbert et al., 2000). Research with dentophobics (Leutgeb et al., 2011; Schienle et al., 2011) showed enhanced LPPs (300 to 1500 ms after picture onset) in response to slides showing dental treatment relative to controls. However, the LPP is not only an indicator of orienting to salient stimuli, but also seems to be modulated by topdown attentional processing (Li et al., 2010). Several investigations report that directing the attentional spotlight toward or away from emotionally relevant scenes influences the magnitude of the LPP amplitude. For example, an explicit distractor task seems to tax perceptual resources and to reduce affective ERP modulation (De Cesarei et al., 2009; Pessoa, 2005; Schupp et al., 2007). Moreover, a reliable reduction of the LPP magnitude has been reported, when attention is directed to neutral features of unpleasant pictures (for a review, see Hajcak et al., 2010). As all published investigations on ERPs in dentophobia (Leutgeb et al., 2011; Schienle et al., 2011) employed a passive viewing paradigm, the interpretation of attentional direction remains somewhat speculative. Therefore, in the current study the attentional focus of participants onto the emotional quality of the pictures and their own emotional
http://dx.doi.org/10.1016/j.ijpsycho.2014.05.003 0167-8760/© 2014 Published by Elsevier B.V.
Please cite this article as: Leutgeb, V., et al., Electrocortical effects of directing attention during visual exposure in dentophobia, Int. J. Psychophysiol. (2014), http://dx.doi.org/10.1016/j.ijpsycho.2014.05.003
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2.1. Participants
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Twenty-three right-handed and non-medicated patients (18 females and 5 males) suffering from dental phobia (DSM-5: 300.29; APA, 2013) and 23 non-phobic controls (15 females and 8 males) participated in this study. They were recruited via announcements at the campus and the Internet. Diagnoses were made by a board-certified clinical psychologist. The two groups did not differ with respect to age (phobics: M (SD) = 29.4 (10.2) years; controls: M (SD) = 27.2 (8.0) years; T(44) = 0.8, p = .424). All participants gave written informed consent after the nature of the study had been explained to them. The study was approved by the local ethics committee.
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2.2. Procedure
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At first, the participants were contacted by phone and a short interview on the diagnostic criteria of dentophobia and the most common mental disorders was conducted. Afterward, participants underwent a diagnostic session consisting of a clinical interview (Mini-DIPS; Margraf, 1994). Additionally, a self-constructed interview on diagnostic criteria of dental phobia according to DSM-5 (APA, 2013) was conducted. Patients who suffered from any other mental disorder than dentophobia were excluded. Control group participants who suffered from any mental disorder were also excluded. Participants filled out the Dental Anxiety Scale (DAS; Corah, 1969), which consists of four questions targeting subjective anxiety during anticipation and dental treatment (e.g., “If you had to go to the dentist tomorrow, how would you feel about it?”). The first question is answered on a five-point scale from “I would look forward to it as a reasonably enjoyable experience.” to “I would be very frightened of what the dentist might do.” The three remaining questions concern feelings in anticipation of or during actual treatment (e.g., “When you are waiting in the dentist's office for your turn in the chair, how do you feel?”). They are answered on a five-point scale from 1 = “Relaxed” to 5 = “So anxious that I sometimes break out in a sweat or almost feel physically sick.” Resulting sum scores range from 4 to 20. Mean values are reported to be 9.33 (SD = 3.17) for controls and 17.18 (SD = 1.8) for phobics. According to the authors (Corah, 1969) the DAS shows sufficient reliability (Kuder–Richardson formula coefficient = 0.86) and test– retest stability (correlation coefficient r = 0.82). Moreover, participants filled out the Fear of Dental Pain Questionnaire (FDP; Van Wijk and Hoogstraten, 2003), which measures pain-related fear of a variety of painful stimuli. The questionnaire consists of 18 items (e.g., “An old filling
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2.3. Data recording and analysis
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The EEG was recorded with a Brain Amp 32 system (Brain Products GmbH, Gilching). Data were sampled with 500 Hz and passband was set to 0.016–70 Hz. We employed an Easy-Cap electrode system (Falk Minow Services, Munich) and recorded the EEG from 30 sites (Fp1, Fp2, F3, F4, F7, F8, Fc1, Fc2, Fc5, Fc 6, C3, C4, T7, T8, Cp1, Cp2, Cp5, Cp6, P3, P4, P7, P8, O1, O2, Fz, Cz, Pz, POz) including the mastoids (Tp9,
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that's being removed.”) for which subjects are asked to think about the pain and to indicate the amount of anxiety experienced on a scale from 1 (not at all) to 5 (extreme). Resulting sum scores range from 18 to 90. Mean sum scores in the general populations are reported to be 43.3 (SD = 13.0). The authors report high internal consistency (Cronbach's alpha = 0.93) and satisfactory test–retest reliability (correlation coefficient r = 0.75; Van Wijk and Hoogstraten, 2003). In addition, participants completed the trait scale of the State-Trait Anxiety Inventory (STAI; Laux et al., 1981). This questionnaire is widely used to measure trait anxiety in adults (e.g., “I worry too much over something that really doesn't matter.”). The scale consists of 20 items, which have to be judged on 4-point scales (1 = “hardly ever”; 4 = “nearly ever”). Sum scores range from 20 to 80. In samples afflicted with specific phobia or other anxiety disorders mean scores are reported to be 53.3 (SD = 11.4). According to the authors the Chronbach's alpha is sufficient with a value of α = 0 .90. After diagnostics, participants underwent an electroencephalographic (EEG) session. They were exposed to 28 phobia-relevant and 28 neutral scenes. The phobia-relevant pictures have been previously used (Leutgeb et al., 2011; Schienle et al., 2011, 2013) and have been reported to successfully induce phobic symptoms in patients suffering from dental phobia. Neutral pictures were taken from the International Affective Picture System (IAPS; Lang et al., 1999) and showed household articles. The pictures were shown in three different conditions varying in attentional engagement: In the “Distraction” condition a small line was displayed either in a vertical or a horizontal orientation in the foreground of the pictures. For half of the pictures the line was horizontal and for the other half the line was vertical. The participant was asked to decide whether the line in the foreground was horizontal (“Is the line horizontal?”). This task distracted the attention of the participant from the background picture. In the “Classification” task, the participants had to decide whether the pictures show dental treatment situations or objects related to dental treatment (“Dental treatment?”). This task requested a conceptual decision, but the participant was not forced to attend to his own emotional response. In the “Fear of Pain” task subjects had to indicate if the picture elicited fear of pain within them (“Fear of pain?”). This task explicitly required the participants to refer to their own emotional involvement. Each picture was shown for 1.5 s in blocks consisting of 28 pictures. A block included 14 neutral and 14 dental treatment scenes in random order. The whole experiment consisted of six blocks. Prior to a block a fixation cross (11 s) and the instruction (key question) were presented for 3 s. After each picture presentation, the response options “yes” and “no” were shown on a black screen in white letters for a maximum of 4 s. For a judgment of each picture, subjects use a two-button device (computer mouse) with either the first or the middle finger of the right hand. Afterward a fixation cross was shown with the average duration of 700 ms. When a participant answered before the deadline, a fixation cross was shown for the rest of the 4-s interval. Subsequently, the next picture was shown. Each key question was presented twice during the experiment (once for each block). The order of tasks and assignment of response buttons to the answer alternatives were counterbalanced across subjects. After the EEG session, participants rated the pictures of each category by means of the Self-Assessment Manikin (Bradley and Lang, 1994) for valence (1 = very unpleasant to 9 = very pleasant) and arousal (1 = not arousing to 9 = very arousing).
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involvement was systematically increased across three tasks. A similar paradigm has already been employed in a functional magnetic resonance imaging study by Straube and Miltner (2011). The authors presented subjects with threatening and neutral pictures and increased the emotional involvement by means of four different tasks (distraction task, classification of living vs. non-living stimuli, classification of threatening vs. non-threatening stimuli, rating of one's own emotional response). The main result was an increase of activation with increasing attention focus on one's own emotional experience in the right posterior insula and in the right somatosensory cortex. These regions are crucial for the awareness of bodily states. The goal of the current investigation was to identify whether attention-guiding instructions are able to modify late positivity in patients suffering from dental phobia. Participants were presented with images of dental treatment and neutral scenes, and were asked to either decide, whether a line displayed in the foreground of the picture was horizontal, whether the scene showed a dental treatment situation or not, or whether the picture elicited fear of pain within them. As the emotional involvement was systematically increased across the three different tasks, we expected enhanced late positivity with increasing self-directed attention in dentophobics relative to controls.
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Please cite this article as: Leutgeb, V., et al., Electrocortical effects of directing attention during visual exposure in dentophobia, Int. J. Psychophysiol. (2014), http://dx.doi.org/10.1016/j.ijpsycho.2014.05.003
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impedances of the EEG electrodes were below 5 kΩ. For analyses, EEG data were down-sampled to 250 Hz. Afterward, the EEG was rereferenced to the average of Tp9 and Tp10. A raw data analysis was performed and massive artifacts were excluded via visual inspection. Independent component analysis (ICA) was computed in order to correct for EOG artifacts. EOG relevant ICs were identified by visual inspection and
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Tp10). All sites were referenced to FCz. A unipolar horizontal electrooculogram (EOG) was recorded from the epicanthus of the right eye, and a unipolar vertical EOG was recorded from the infra-orbital position of the right eye. The EEG and the EOG were recorded with Ag/AgCl electrodes. Prior to the placement of the electrodes, the sites on the participants' scalp and face were cleaned with alcohol and gently abraded. All
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Fig. 1. Grand average waveforms of phobics and controls in response to the three tasks (Distraction, Classification, Fear of Pain) at the representative electrode sites Fz, Cz, and Pz. Data are referenced to the average of Tp9 and Tp10. The line marks the time frame of the late positive potential (LPP; 300–1000 ms).
Please cite this article as: Leutgeb, V., et al., Electrocortical effects of directing attention during visual exposure in dentophobia, Int. J. Psychophysiol. (2014), http://dx.doi.org/10.1016/j.ijpsycho.2014.05.003
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Patients scored significantly higher on both disorder-specific questionnaires than controls (DAS: T(44) = 14.7, p b .001; FDP: T(44) = 16.5, p b .001; see Table 1). Phobics and controls did not differ in their overall trait anxiety according to their STAI scores (T(44) = 1.6, p = .126). Patients reported to experience lower valence and higher arousal than controls (valence: T(44) = 6.3, p b .001; arousal: T(44) = 7.8, p b .001) during the viewing of dental treatment scenes relative to neutral pictures.
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3.1. Questionnaire data and affective ratings
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3. Results
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affective ratings (experienced valence and arousal) were submitted separately to between-samples t-tests. The difference scores for ERPamplitudes (Phobia minus Neutral) were submitted to ANOVAs with the between-subjects factor group (phobics, controls), and repeatedmeasurements factors task (Distraction, Classification, Fear of Pain), caudality (frontal, central, parietal), and laterality (left, midline, right). For the ANOVAs, Greenhouse–Geisser correction was applied if appropriate and we report partial η2 as effect sizes. To clarify significant interactions, further analyses were conducted by means of factor reduction and between and within-samples Students' t-tests.
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comparison to EOG channels. EEG data were segmented into epochs of 1700 ms starting 200 ms before the onset of the stimulus. Subsequently, segments were semiautomatically inspected to discard remaining artifacts. After artifact correction data were low-pass filtered (20 Hz, 24 dB/octave) and a baseline correction was performed using the first 200 ms as reference. Epochs were averaged separately for each condition. The mean numbers of artifact-free trials were as follows: Phobics: Distraction = 27.3, Classification = 27.4, Fear of Pain = 26.9; Controls: Distraction = 26.8, Classification = 27.2, Fear of Pain = 27.6. A subsequent Principal Component Analysis did not reveal clearly separable components of the ERP. Therefore, average LPP amplitudes in response to the three tasks were extracted in the time window from 300 to 1000 ms in accordance with visual inspection of grand average waveforms (see Fig. 1). We calculated topographical maps for activation differences between phobics and controls for the contrast of the two picture categories (Phobia minus Neutral) for each task separately (see Fig. 2). These topographical maps were inspected to assure the typical scalp distribution of ERP components. Subsequent statistical analyses were conducted including frontal (F3, Fz, F4), central (C3, Cz, C4) and parietal (P3, Pz, P4) sites. For statistical data analyses IBM SPSS Statistics 20 (IBM, Armonk) was used. Questionnaire data were submitted separately to betweensamples t-tests. The difference scores (Phobia minus Neutral) for
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Fig. 2. Topographical maps for activation differences between phobics and controls for the contrast of the two picture categories for each task (Distraction, Classification, Fear of Pain) separately: phobics (Phobia minus Neutral) minus controls (Phobia minus Neutral). Data are referenced to the average of Tp9 and Tp10.
Please cite this article as: Leutgeb, V., et al., Electrocortical effects of directing attention during visual exposure in dentophobia, Int. J. Psychophysiol. (2014), http://dx.doi.org/10.1016/j.ijpsycho.2014.05.003
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V. Leutgeb et al. / International Journal of Psychophysiology xxx (2014) xxx–xxx Table 1 Questionnaire data and affective responses (means, M and standard deviations, SD) of phobics and control group participants.
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Questionnaires DAS FDP STAI
16.3 (2.4) 72.3 (6.2) 33.7 (8.2)
7.6 (1.5) 37.8 (7.8) 30.3 (6.2)
Picture rating (Phobia minus Neutral) Valence Arousal
−5.1 (1.8) 4.2 (1.9)
−2.2 (1.2) 0.7 (1.0)
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Grand average waveforms of phobics and controls in response to the three tasks (Distraction, Classification, Fear of Pain) at Fz, Cz, and Pz are shown in Fig. 1. The line marks the time frame of the late positive potential (LPP; 300–1000 ms). Difference maps (phobics (Phobia minus Neutral) minus controls (Phobia minus Neutral)) are shown in Fig. 2. Voltage differences (Phobia minus Neutral) of phobics and controls in response to the three tasks (Distraction, Classification, Fear of Pain) at the three sensor sites Fz, Cz, and Pz for the LPP are shown in Fig. 3. The ANOVA revealed significant main effects for task (F(2,88) = 43.8, p b .001, η2 p = .499), caudality (F(1.3,59.1) = 15.7, p b .001, η2p = 0.263), and laterality (F(2,88) = 13.9, p b .001, η2 p = .240), but not for group (F(1,44) = 3.1, p = .083, η2 p = .067). Moreover, there were significant interactions for task × group (F(2,88) = 3.7, p = .029, η2 p = .077) and task × caudality (F(2.5,109.6) = 3.6, p = .023, η2 p = .075), whereas all other interactions failed to reach significance (all p's N .066). The main effect for task stemmed from highest amplitudes in response to fear of pain as compared to the other tasks (all p's b .005) and higher amplitudes to classification than to distraction (p b .001). The main effect of caudality stemmed from smallest amplitudes at frontal sites as compared to central and parietal sites (all p's b .003), whereas there was no significant difference between central and parietal sites (p = .118). The main effect of laterality stemmed from the highest amplitudes at midline sites compared to sites of the left or right hemisphere (all p's b .001), whereas there was no significant differences between left and right hemisphere (p = .400). To follow-up on the group × task and task × caudality interactions we compared patients and controls across the three tasks separately for each region (frontal, central, parietal). In the frontal region (pooling of F3, Fz and F4) there was a significant main effect for task (F(2,88) = 16.2, p b .001, η2 p = .269), but not for group (F(1,44) = 2.7, p = .107, η2 p = .058), and a significant task × group interaction (F(2,88) = 4.4, p = .015, η2 p = .091). In the central region (pooling of C3, Cz and C4) there was a significant main effect for task (F(2,88) = 43.7, p b .001, η2 p = .498), but not for group (F(1,44) = 2.8, p = .100, η2 p = .060), and a significant task × group interaction (F(2,88) = 4.0, p = .022, η2 p = .083). In the parietal region (pooling of P3, Pz and P4) there was a significant main effect for task (F(2,88) = 56.9, p b .001, η 2 p = .564), but not for group (F(1,44) = 2.7, p = .109, η2 p = .057), and there was no significant task × group interaction (F(2,88) = 1.2, p = .317, η2 p = .026). Post hoc t-tests showed higher LPP amplitudes in response to Fear of Pain for phobics relative to controls in the frontal (T(44) = 3.0, p = .004) and central (T(44) = 2.8, p = .008) region. There were no significant group differences in response to the other two tasks (all p's N .515). Within-groups t-tests revealed for both phobics and controls, that Fear of Pain elicited higher amplitudes than Distraction in the frontal (phobics: T(22) = 6.1, p b .001; controls: T(22) = 2.4, p = .026) and
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The main goal of the current investigation was to investigate whether attention-guiding instructions that systematically increase the emotional involvement during the viewing of disorder-relevant pictures are able to modify late ERPs in dentophobic patients. The participants performed three tasks: in the “Distraction” task, they were asked to decide whether a line displayed in the foreground of the picture was horizontal. The purpose was to distract subjects' attention away from the picture content to prevent deeper processing. In the “Classification” task the participants had to decide, whether the scene showed a dental treatment situation or not. This implied a conceptual decision about the semantic content of the picture (is this dental treatment or not?), but the participants were not required to attend to their own emotional response. In the “Fear of Pain” task, subjects were asked to indicate, whether the picture elicited fear of pain. This explicitly required that the participants referred to their own emotional/pain-related involvement.
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4. Discussion
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DAS = Dental Anxiety Scale, FDP = Fear of Dental Pain Questionnaire, STAI = State-Trait Anxiety Inventory.
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central region (phobics: T(22) = 8.6, p b .001; controls: T(22) = 5.3, p b .001). In both groups, Classification elicited higher amplitudes than Distraction in the frontal (phobics: T(22) = 2.1, p = .048; controls: T(22) = 3.5, p = .002) and central region (phobics: T(22) = 3.9, p = .001; controls: T(22) = 4.7, p b .001). Moreover, only within phobics Fear of Pain elicited higher amplitudes than Classification in the frontal (T(22) = 2.6, p = .015) and central region (T(22) = 3.2, p = .004), whereas there were no significant differences within controls (all p's N .575).
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Fig. 3. Mean voltage differences (Phobia minus Neutral) and standard errors of phobics and controls in response to the three tasks (Distraction, Classification, Fear of Pain) at the representative electrode sites Fz, Cz, and Pz for the late positive potential (300–1000 ms). Data are referenced to the average of Tp9 and Tp10.
Please cite this article as: Leutgeb, V., et al., Electrocortical effects of directing attention during visual exposure in dentophobia, Int. J. Psychophysiol. (2014), http://dx.doi.org/10.1016/j.ijpsycho.2014.05.003
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re-exposure images with a distraction history elicited larger LPP amplitudes than images with an attend history. Lastly, it should also be noted, that the current study did not include a passive viewing condition, and therefore the interpretation that attention was successfully directed away from the phobic stimulus has to be dealt with cautiously. For the treatment of dental phobia, CBT (especially graded exposure combined with relaxation) has been shown to be superior to general anesthesia and pharmacological treatment on the long-term (for a review, see Berggren, 2001). In contrast, distraction via auditory or visual stimulation has been found to be useful in moderately anxious (but not in highly anxious) subjects (e.g., Frere et al., 2001; Lahmann et al., 2008). It might be possible, that differential attention regulation strategies are indicated for individual patients with varying disorder severity and at different stages of therapy: for example, distraction from pain might be efficient at mild pain intensity or in very early therapy, while at high intensities or during actual (painful) treatment, redefinition seems to be superior (e.g., McCaul and Malott, 1984). Trained dentists try to respond to patients, e.g., by announcing the beginning of a painful intervention or permitting the patient to exercise some form of control strategies for terminating the treatment (i.e., raising his hand if they cannot be tolerate the pain anymore; Jöhren and Sartory, 2002). However, this might not be useful for all patients, as it requires them to focus on their own emotional involvement and their feelings of pain.
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The current investigation showed that explicit instructions to direct attention during dentophobic confrontation have an impact on late ERPs. We suggest that the current paradigm could be valuable to investigate the role of fear of pain in dentophobia and, moreover, the importance of its modification in the course of exposure therapy. Therapies could be evaluated with respect to possible changes in ERPs to different emotion regulation strategies.
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Results revealed that explicit direction guiding in dental phobia indeed has an impact on amplitudes of late ERPs. Phobics displayed higher frontal and central late positivity (300–1000 ms) than controls when they had to think about their own pain-related involvement, whereas there was no group difference in response to the “Classification” and the “Distraction” task. Within phobics, there was a significant increase in late positivity with increasing self-directed attention (Distraction b Classification b Fear of Pain). Interestingly, controls showed a similar pattern of increasing late positivity, however, Fear of Pain and Classification did not differ from each other. A decision about one's own pain-related involvement in a picture requires self-referential processing of the affective meaning and might be causal for the enhancement of LPP amplitude in phobics relative to controls. The result is in line with a number of studies, showing that the LPP is sensitive to top-down attentional processing (e.g., Deveney and Pizzagalli, 2008; Dunning and Hajcak, 2009; Foti and Hajcak, 2008; Hajcak and Nieuwenhuis, 2006; Hajcak et al., 2010, 2013; Moser et al., 2006; 2009; Thiruchselvam et al., 2011; Wiens et al., 2011). Very consistently, results revealed that a decrease in the intensity of emotional experience was accompanied by reduced amplitudes of the LPP (e.g., Moser et al., 2006). Dunning and Hajcak (2009) for example found that the direction of attention toward non-arousing aspects of unpleasant images resulted in decreased amplitudes of late posterior positivity from 1000 to 3000 ms after picture onset. In this investigation, subjects were instructed to explicitly focus their attention and look only at an area within a circle while it remained on the screen. Hajcak and Nieuwenhuis (2006) instructed participants to reappraise unpleasant images (to reinterpret them in a less negative way), which was accompanied by reduced LPP amplitudes from 200 to 2000 ms after picture onset. Whereas ERP studies on motivated attention in specific phobias mainly found effects at posterior recording sites (for a review, see Olofsson et al., 2008), the effect in the current study was located at central and frontal regions. This might be interpreted to reflect top-down attentional processing as frontal regions are primarily involved in executive control and goal-directed target detection (Li et al., 2010). Additionally, there are published studies on spider phobic patients who underwent exposure therapy. The main correlate of successful therapy was an enhancement of late fronto-central ERPs in response to pictures of spiders, which was interpreted as an effect of enhanced attention to the formerly phobic object (Leutgeb et al., 2009, 2012). Moreover, Schienle et al. (in press) conducted a functional magnetic resonance imaging investigation with healthy control subjects employing the same paradigm as in the current study. The fear of pain condition was associated with increased activation of the dorsomedial prefrontal cortex relative to the two other conditions, and this activation was positively correlated with self-reported dental anxiety. In the current study, amplitudes of the late positive potential were significantly reduced in response to tasks designed to distract attention from the phobic stimulus (“Distraction” and “Classification”) as compared to the task requiring self-directed attention (“Fear of Pain“). Classifying pictures might present a way of encouraging patients to direct their attention toward the phobic stimulus without including deeper processing or reappraisal. These results are in line with studies showing, that an explicit distractor task taxes perceptual resources and reduces affective ERP modulation (De Cesarei et al., 2009; Pessoa, 2005; Schupp et al., 2007). However, recent studies showed that spider fearful subjects still displayed clear enhanced late positivity even during a distraction task (e.g., peripheral letter discrimination; Norberg et al., 2010; Norberg & Wiens, 2013). Additionally, this effect was independent of perceptual load. Moreover, a recently published study suggests that attention distraction might only be effective in the short-term: Thiruchselvam and colleagues (2013) confronted participants with either neutral or emotional pictures. In a first exposure phase reactions to pictures were watched or regulated by using either distraction or reappraisal. In a re-exposure phase pictures were passively viewed. In the first phase distraction reduced the LPP earlier than reappraisal. However, during
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Norberg, J., Peira, N., Wiens, S., 2010. Never mind the spider: late positive potentials to phobic threat at fixation are unaffected by perceptual load. Psychophysiology 47, 1151–1158. Olofsson, J.K., Nordin, S., Sequeira, H., Polich, J., 2008. Affective picture processing: an integrative review of ERP findings. Biol. Psychol. 77, 247–265. Pessoa, L., 2005. To what extent are emotional visual stimuli processed without attention and awareness? Curr. Opin. Neurobiol. 15, 188–196. Schienle, A., Köchel, A., Leutgeb, V., 2011. Frontal late positivity in dental phobia: a study on gender differences. Biol. Psychol. 88, 263–269. Schienle, A., Scharmüller, W., Leutgeb, V., Schäfer, A., Stark, R., 2013. Sex diffrences in the functional and structural neuroanatomy of dental phobia. Brain Struct. Funct. 218, 779–787. Schienle, A., Wabnegger, A., Schöngassner, F., Scharmüller, W., 2014. Neuronal correlates of three attentional strategies during affective picture processing: an fMRI study. Cogn. Affect. Behav. Neurosci. (in press). Schupp, H.T., Stockburger, J., Bublatzky, F., Junghöfer, M., Weike, A.I., Hamm, A.O., 2007. Explicit attention interferes with selective emotion processing in human extrastriate cortex. BMC Neurosci. 8, 16. Straube, T., Miltner, W.H.R., 2011. Attention to aversive emotion and specific activation of the right insula and right somatosensory cortex. NeuroImage 54, 2534–2538. Thiruchselvam, R., Blechert, J., Sheppes, G., Rydstrom, A., Gross, J.J., 2011. The temporal dynamics of emotion regulation: an EEG study of distraction and reappraisal. Biol. Psychol. 87, 84–92. Van Wijk, A.J., Hoogstraten, J., 2003. The Fear of Dental Pain questionnaire: construction and validity. Eur. J. Oral Sci. 111, 12–18. Wiens, S., Anders, S., Olofsson, J.K., 2011. Nonemotional features suppress early and enhance late emotional electrocortical responses to negative pictures. Biol. Psychol. 86, 83–89.
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Lang, P.J., Bradley, M.M., Cuthbert, B.N., 1997. Motivated attention: affect, activation, and action. In: Lang, P.J., Simmons, R.F., Balaban, M. (Eds.), Attention and orienting: sensory and motivational processes. Erlbaum, Hillsdale, NJ, pp. 97–135. Lang, P.J., Bradley, M.M., Cuthbert, B., 1999. International affective picture system. , Center for Research in Psychophysiology, University of Florida, Gainsville. Lautch, H., 1971. Dental phobia. Br. J. Psychiatry 119, 151–158. Laux, L., Glanzmann, P., Schaffner, P., Spielberger, L., 1981. Das State-Trait- Angstinventar. , Beltz Testgesellschaft, Weinheim. Leutgeb, V., Schäfer, A., Schienle, A., 2009. An event-related potential study on exposure therapy for patients suffering from spider phobia. Biol. Psychol. 82, 293–300. Leutgeb, V., Schäfer, A., Schienle, A., 2011. Late cortical positivity and cardiac responsitivity in female dental phobics when exposed to phobia-relevant pictures. Int. J. Psychophysiol. 79, 410–416. Leutgeb, V., Köchel, A., Schienle, A., 2012. Exposure therapy leads to enhanced late frontal positivity in 8- to 13-year-old spider phobic girls. Biol. Psychol. 90, 97–104. Li, L., Gratton, C., Yao, D., Knight, R.T., 2010. Role of frontal and parietal cortices in the control of bottom-up and top-down attention in humans. Brain Res. 1344, 173–184. Margraf, J., 1994. Diagnostisches Kurz-Interview bei psychischen Störungen, Mini-DIPS. , Springer, Berlin. McCaul, K.D., Malott, J.M., 1984. Distraction and coping with pain. Psychol. Bull. 95, 516–533. Moser, J.S., Hajcak, G., Bukay, E., Simons, R.F., 2006. Intentional modulation of emotional responding to unpleasant pictures: an ERP study. Psychophysiology 43, 292–296. Moser, J.S., Krompinger, J.W., Dietz, J., Simons, R.F., 2009. Electrophysiological correlates of decreasing and increasing emotional responses to unpleasant pictures. Psychophysiology 46, 17–27. Norberg, J., Wiens, S., 2013. Effects of attention manipulations on motivated attention to feared and nonfeared negative distracters in spider fear. BMC Neurosci. 4, 139.
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Contents lists available at ScienceDirect
International Journal of Psychophysiology journal homepage: www.elsevier.com/locate/ijpsycho
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Verena Leutgeb ⁎, Florian Schöngassner, Anne Schienle
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Article history: Received 15 January 2014 Received in revised form 5 May 2014 Accepted 6 May 2014 Available online xxxx
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Keywords: Dentophobia Attention regulation Event-related potentials Late positive potential Fear
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Fear of pain is a main motivator for avoidance or delay of dental treatment in patients afflicted with dentophobia. Studies employing passive viewing paradigms found motivated attention to the phobic object to be associated with enhanced amplitudes of the late positive potential (LPP). The aim of the current study was to investigate, if explicit attention-guiding instructions are able to modify the LPP. Twenty-three patients suffering from dentophobia and 23 controls were presented with pictures showing disorder-relevant or neutral contents, which were combined with different instructions: to distract the attention away from the picture, to classify the content, or to decide whether the scene elicited fear of pain. Relative to controls, dentophobics displayed enhanced late positivity (300–1000 ms after picture onset) in the fear of pain condition at frontal and central recording sites, whereas there was no group difference during classification and distraction. Within patients, fear of pain elicited greater positivity than classification and distraction. The findings are discussed within the framework of attentional direction. Future studies could investigate whether psychotherapy differentially affects neural correlates of attention regulation. © 2014 Published by Elsevier B.V.
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Patients suffering from dentophobia frequently report to have experienced excessive pain during dental treatment. Moreover, they expect future treatments to be very painful (Jöhren and Sartory, 2002). This expectation of pain is the main motivator for avoidance or delay of dental treatment. The fact that the threshold for the perception of pain is generally lowered when participants are in an anxious mood might be one cause for the vicious cycle of fear and avoidance in dentophobia (Lautch, 1971). Cognitive behavioral therapy (CBT) has consistently proven to be effective in managing fear of dental treatment (Gordon et al., 2013). Empirical evidence emphasizes the importance of exposure techniques, which include directing the patients' attention to the feared stimulus. However, distraction strategies have also been found to be useful (e.g., relaxation techniques), leaving the role of attentional direction in dentophobia unresolved. The goal of the current investigation was to study electrocortical correlates of different attentional strategies during symptom provocation. The electroencephalogram (EEG) was chosen for the experiment because of its excellent temporal resolution. It provides researchers with the opportunity to study attentional processes that are characterized by a rather short duration as in specific phobia. According to the theory
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⁎ Corresponding author. Tel.: +43 316 380 8507; fax: +43 316 380 9808. E-mail addresses: [email protected] (V. Leutgeb), fl[email protected] (F. Schöngassner), [email protected] (A. Schienle).
of motivated attention (Lang et al., 1997; for a discussion see Bradley, 2009) late positive event-related potentials (ERPs) can be interpreted as indicators of emotional significance and attention allocation. There is a long tradition of studies, showing that emotionally significant stimuli automatically draw attention in order to recruit resources for a deeper processing (for a review, see Olofsson et al., 2008). The electrocortical substrate is reported to be a sustained positive slow wave at posterior recording sites. One typical component, the late positive potential (LPP), is a central-parietal positivity which can be seen about 300 ms after picture onset (e.g., Cuthbert et al., 2000). Research with dentophobics (Leutgeb et al., 2011; Schienle et al., 2011) showed enhanced LPPs (300 to 1500 ms after picture onset) in response to slides showing dental treatment relative to controls. However, the LPP is not only an indicator of orienting to salient stimuli, but also seems to be modulated by topdown attentional processing (Li et al., 2010). Several investigations report that directing the attentional spotlight toward or away from emotionally relevant scenes influences the magnitude of the LPP amplitude. For example, an explicit distractor task seems to tax perceptual resources and to reduce affective ERP modulation (De Cesarei et al., 2009; Pessoa, 2005; Schupp et al., 2007). Moreover, a reliable reduction of the LPP magnitude has been reported, when attention is directed to neutral features of unpleasant pictures (for a review, see Hajcak et al., 2010). As all published investigations on ERPs in dentophobia (Leutgeb et al., 2011; Schienle et al., 2011) employed a passive viewing paradigm, the interpretation of attentional direction remains somewhat speculative. Therefore, in the current study the attentional focus of participants onto the emotional quality of the pictures and their own emotional
http://dx.doi.org/10.1016/j.ijpsycho.2014.05.003 0167-8760/© 2014 Published by Elsevier B.V.
Please cite this article as: Leutgeb, V., et al., Electrocortical effects of directing attention during visual exposure in dentophobia, Int. J. Psychophysiol. (2014), http://dx.doi.org/10.1016/j.ijpsycho.2014.05.003
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Twenty-three right-handed and non-medicated patients (18 females and 5 males) suffering from dental phobia (DSM-5: 300.29; APA, 2013) and 23 non-phobic controls (15 females and 8 males) participated in this study. They were recruited via announcements at the campus and the Internet. Diagnoses were made by a board-certified clinical psychologist. The two groups did not differ with respect to age (phobics: M (SD) = 29.4 (10.2) years; controls: M (SD) = 27.2 (8.0) years; T(44) = 0.8, p = .424). All participants gave written informed consent after the nature of the study had been explained to them. The study was approved by the local ethics committee.
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At first, the participants were contacted by phone and a short interview on the diagnostic criteria of dentophobia and the most common mental disorders was conducted. Afterward, participants underwent a diagnostic session consisting of a clinical interview (Mini-DIPS; Margraf, 1994). Additionally, a self-constructed interview on diagnostic criteria of dental phobia according to DSM-5 (APA, 2013) was conducted. Patients who suffered from any other mental disorder than dentophobia were excluded. Control group participants who suffered from any mental disorder were also excluded. Participants filled out the Dental Anxiety Scale (DAS; Corah, 1969), which consists of four questions targeting subjective anxiety during anticipation and dental treatment (e.g., “If you had to go to the dentist tomorrow, how would you feel about it?”). The first question is answered on a five-point scale from “I would look forward to it as a reasonably enjoyable experience.” to “I would be very frightened of what the dentist might do.” The three remaining questions concern feelings in anticipation of or during actual treatment (e.g., “When you are waiting in the dentist's office for your turn in the chair, how do you feel?”). They are answered on a five-point scale from 1 = “Relaxed” to 5 = “So anxious that I sometimes break out in a sweat or almost feel physically sick.” Resulting sum scores range from 4 to 20. Mean values are reported to be 9.33 (SD = 3.17) for controls and 17.18 (SD = 1.8) for phobics. According to the authors (Corah, 1969) the DAS shows sufficient reliability (Kuder–Richardson formula coefficient = 0.86) and test– retest stability (correlation coefficient r = 0.82). Moreover, participants filled out the Fear of Dental Pain Questionnaire (FDP; Van Wijk and Hoogstraten, 2003), which measures pain-related fear of a variety of painful stimuli. The questionnaire consists of 18 items (e.g., “An old filling
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The EEG was recorded with a Brain Amp 32 system (Brain Products GmbH, Gilching). Data were sampled with 500 Hz and passband was set to 0.016–70 Hz. We employed an Easy-Cap electrode system (Falk Minow Services, Munich) and recorded the EEG from 30 sites (Fp1, Fp2, F3, F4, F7, F8, Fc1, Fc2, Fc5, Fc 6, C3, C4, T7, T8, Cp1, Cp2, Cp5, Cp6, P3, P4, P7, P8, O1, O2, Fz, Cz, Pz, POz) including the mastoids (Tp9,
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that's being removed.”) for which subjects are asked to think about the pain and to indicate the amount of anxiety experienced on a scale from 1 (not at all) to 5 (extreme). Resulting sum scores range from 18 to 90. Mean sum scores in the general populations are reported to be 43.3 (SD = 13.0). The authors report high internal consistency (Cronbach's alpha = 0.93) and satisfactory test–retest reliability (correlation coefficient r = 0.75; Van Wijk and Hoogstraten, 2003). In addition, participants completed the trait scale of the State-Trait Anxiety Inventory (STAI; Laux et al., 1981). This questionnaire is widely used to measure trait anxiety in adults (e.g., “I worry too much over something that really doesn't matter.”). The scale consists of 20 items, which have to be judged on 4-point scales (1 = “hardly ever”; 4 = “nearly ever”). Sum scores range from 20 to 80. In samples afflicted with specific phobia or other anxiety disorders mean scores are reported to be 53.3 (SD = 11.4). According to the authors the Chronbach's alpha is sufficient with a value of α = 0 .90. After diagnostics, participants underwent an electroencephalographic (EEG) session. They were exposed to 28 phobia-relevant and 28 neutral scenes. The phobia-relevant pictures have been previously used (Leutgeb et al., 2011; Schienle et al., 2011, 2013) and have been reported to successfully induce phobic symptoms in patients suffering from dental phobia. Neutral pictures were taken from the International Affective Picture System (IAPS; Lang et al., 1999) and showed household articles. The pictures were shown in three different conditions varying in attentional engagement: In the “Distraction” condition a small line was displayed either in a vertical or a horizontal orientation in the foreground of the pictures. For half of the pictures the line was horizontal and for the other half the line was vertical. The participant was asked to decide whether the line in the foreground was horizontal (“Is the line horizontal?”). This task distracted the attention of the participant from the background picture. In the “Classification” task, the participants had to decide whether the pictures show dental treatment situations or objects related to dental treatment (“Dental treatment?”). This task requested a conceptual decision, but the participant was not forced to attend to his own emotional response. In the “Fear of Pain” task subjects had to indicate if the picture elicited fear of pain within them (“Fear of pain?”). This task explicitly required the participants to refer to their own emotional involvement. Each picture was shown for 1.5 s in blocks consisting of 28 pictures. A block included 14 neutral and 14 dental treatment scenes in random order. The whole experiment consisted of six blocks. Prior to a block a fixation cross (11 s) and the instruction (key question) were presented for 3 s. After each picture presentation, the response options “yes” and “no” were shown on a black screen in white letters for a maximum of 4 s. For a judgment of each picture, subjects use a two-button device (computer mouse) with either the first or the middle finger of the right hand. Afterward a fixation cross was shown with the average duration of 700 ms. When a participant answered before the deadline, a fixation cross was shown for the rest of the 4-s interval. Subsequently, the next picture was shown. Each key question was presented twice during the experiment (once for each block). The order of tasks and assignment of response buttons to the answer alternatives were counterbalanced across subjects. After the EEG session, participants rated the pictures of each category by means of the Self-Assessment Manikin (Bradley and Lang, 1994) for valence (1 = very unpleasant to 9 = very pleasant) and arousal (1 = not arousing to 9 = very arousing).
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involvement was systematically increased across three tasks. A similar paradigm has already been employed in a functional magnetic resonance imaging study by Straube and Miltner (2011). The authors presented subjects with threatening and neutral pictures and increased the emotional involvement by means of four different tasks (distraction task, classification of living vs. non-living stimuli, classification of threatening vs. non-threatening stimuli, rating of one's own emotional response). The main result was an increase of activation with increasing attention focus on one's own emotional experience in the right posterior insula and in the right somatosensory cortex. These regions are crucial for the awareness of bodily states. The goal of the current investigation was to identify whether attention-guiding instructions are able to modify late positivity in patients suffering from dental phobia. Participants were presented with images of dental treatment and neutral scenes, and were asked to either decide, whether a line displayed in the foreground of the picture was horizontal, whether the scene showed a dental treatment situation or not, or whether the picture elicited fear of pain within them. As the emotional involvement was systematically increased across the three different tasks, we expected enhanced late positivity with increasing self-directed attention in dentophobics relative to controls.
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impedances of the EEG electrodes were below 5 kΩ. For analyses, EEG data were down-sampled to 250 Hz. Afterward, the EEG was rereferenced to the average of Tp9 and Tp10. A raw data analysis was performed and massive artifacts were excluded via visual inspection. Independent component analysis (ICA) was computed in order to correct for EOG artifacts. EOG relevant ICs were identified by visual inspection and
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Patients scored significantly higher on both disorder-specific questionnaires than controls (DAS: T(44) = 14.7, p b .001; FDP: T(44) = 16.5, p b .001; see Table 1). Phobics and controls did not differ in their overall trait anxiety according to their STAI scores (T(44) = 1.6, p = .126). Patients reported to experience lower valence and higher arousal than controls (valence: T(44) = 6.3, p b .001; arousal: T(44) = 7.8, p b .001) during the viewing of dental treatment scenes relative to neutral pictures.
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affective ratings (experienced valence and arousal) were submitted separately to between-samples t-tests. The difference scores for ERPamplitudes (Phobia minus Neutral) were submitted to ANOVAs with the between-subjects factor group (phobics, controls), and repeatedmeasurements factors task (Distraction, Classification, Fear of Pain), caudality (frontal, central, parietal), and laterality (left, midline, right). For the ANOVAs, Greenhouse–Geisser correction was applied if appropriate and we report partial η2 as effect sizes. To clarify significant interactions, further analyses were conducted by means of factor reduction and between and within-samples Students' t-tests.
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comparison to EOG channels. EEG data were segmented into epochs of 1700 ms starting 200 ms before the onset of the stimulus. Subsequently, segments were semiautomatically inspected to discard remaining artifacts. After artifact correction data were low-pass filtered (20 Hz, 24 dB/octave) and a baseline correction was performed using the first 200 ms as reference. Epochs were averaged separately for each condition. The mean numbers of artifact-free trials were as follows: Phobics: Distraction = 27.3, Classification = 27.4, Fear of Pain = 26.9; Controls: Distraction = 26.8, Classification = 27.2, Fear of Pain = 27.6. A subsequent Principal Component Analysis did not reveal clearly separable components of the ERP. Therefore, average LPP amplitudes in response to the three tasks were extracted in the time window from 300 to 1000 ms in accordance with visual inspection of grand average waveforms (see Fig. 1). We calculated topographical maps for activation differences between phobics and controls for the contrast of the two picture categories (Phobia minus Neutral) for each task separately (see Fig. 2). These topographical maps were inspected to assure the typical scalp distribution of ERP components. Subsequent statistical analyses were conducted including frontal (F3, Fz, F4), central (C3, Cz, C4) and parietal (P3, Pz, P4) sites. For statistical data analyses IBM SPSS Statistics 20 (IBM, Armonk) was used. Questionnaire data were submitted separately to betweensamples t-tests. The difference scores (Phobia minus Neutral) for
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Fig. 2. Topographical maps for activation differences between phobics and controls for the contrast of the two picture categories for each task (Distraction, Classification, Fear of Pain) separately: phobics (Phobia minus Neutral) minus controls (Phobia minus Neutral). Data are referenced to the average of Tp9 and Tp10.
Please cite this article as: Leutgeb, V., et al., Electrocortical effects of directing attention during visual exposure in dentophobia, Int. J. Psychophysiol. (2014), http://dx.doi.org/10.1016/j.ijpsycho.2014.05.003
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V. Leutgeb et al. / International Journal of Psychophysiology xxx (2014) xxx–xxx Table 1 Questionnaire data and affective responses (means, M and standard deviations, SD) of phobics and control group participants.
t1:4
Group
Phobics, M (SD)
Controls, M (SD)
t1:5 t1:6 t1:7 t1:8 t1:9 t1:10 t1:11 t1:12
Questionnaires DAS FDP STAI
16.3 (2.4) 72.3 (6.2) 33.7 (8.2)
7.6 (1.5) 37.8 (7.8) 30.3 (6.2)
Picture rating (Phobia minus Neutral) Valence Arousal
−5.1 (1.8) 4.2 (1.9)
−2.2 (1.2) 0.7 (1.0)
284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311
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µV
C
9 8 7 6 5 4 3 2 1 0
Phobics Controls
| Distraction
Cz
µV
283
Fz
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LPP
R
277 278
N C O
275 276
9 8 7 6 5 4 3 2 1 0
Pz
| Classification Task
| Distraction
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273 274
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Grand average waveforms of phobics and controls in response to the three tasks (Distraction, Classification, Fear of Pain) at Fz, Cz, and Pz are shown in Fig. 1. The line marks the time frame of the late positive potential (LPP; 300–1000 ms). Difference maps (phobics (Phobia minus Neutral) minus controls (Phobia minus Neutral)) are shown in Fig. 2. Voltage differences (Phobia minus Neutral) of phobics and controls in response to the three tasks (Distraction, Classification, Fear of Pain) at the three sensor sites Fz, Cz, and Pz for the LPP are shown in Fig. 3. The ANOVA revealed significant main effects for task (F(2,88) = 43.8, p b .001, η2 p = .499), caudality (F(1.3,59.1) = 15.7, p b .001, η2p = 0.263), and laterality (F(2,88) = 13.9, p b .001, η2 p = .240), but not for group (F(1,44) = 3.1, p = .083, η2 p = .067). Moreover, there were significant interactions for task × group (F(2,88) = 3.7, p = .029, η2 p = .077) and task × caudality (F(2.5,109.6) = 3.6, p = .023, η2 p = .075), whereas all other interactions failed to reach significance (all p's N .066). The main effect for task stemmed from highest amplitudes in response to fear of pain as compared to the other tasks (all p's b .005) and higher amplitudes to classification than to distraction (p b .001). The main effect of caudality stemmed from smallest amplitudes at frontal sites as compared to central and parietal sites (all p's b .003), whereas there was no significant difference between central and parietal sites (p = .118). The main effect of laterality stemmed from the highest amplitudes at midline sites compared to sites of the left or right hemisphere (all p's b .001), whereas there was no significant differences between left and right hemisphere (p = .400). To follow-up on the group × task and task × caudality interactions we compared patients and controls across the three tasks separately for each region (frontal, central, parietal). In the frontal region (pooling of F3, Fz and F4) there was a significant main effect for task (F(2,88) = 16.2, p b .001, η2 p = .269), but not for group (F(1,44) = 2.7, p = .107, η2 p = .058), and a significant task × group interaction (F(2,88) = 4.4, p = .015, η2 p = .091). In the central region (pooling of C3, Cz and C4) there was a significant main effect for task (F(2,88) = 43.7, p b .001, η2 p = .498), but not for group (F(1,44) = 2.8, p = .100, η2 p = .060), and a significant task × group interaction (F(2,88) = 4.0, p = .022, η2 p = .083). In the parietal region (pooling of P3, Pz and P4) there was a significant main effect for task (F(2,88) = 56.9, p b .001, η 2 p = .564), but not for group (F(1,44) = 2.7, p = .109, η2 p = .057), and there was no significant task × group interaction (F(2,88) = 1.2, p = .317, η2 p = .026). Post hoc t-tests showed higher LPP amplitudes in response to Fear of Pain for phobics relative to controls in the frontal (T(44) = 3.0, p = .004) and central (T(44) = 2.8, p = .008) region. There were no significant group differences in response to the other two tasks (all p's N .515). Within-groups t-tests revealed for both phobics and controls, that Fear of Pain elicited higher amplitudes than Distraction in the frontal (phobics: T(22) = 6.1, p b .001; controls: T(22) = 2.4, p = .026) and
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322 323
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269 270
The main goal of the current investigation was to investigate whether attention-guiding instructions that systematically increase the emotional involvement during the viewing of disorder-relevant pictures are able to modify late ERPs in dentophobic patients. The participants performed three tasks: in the “Distraction” task, they were asked to decide whether a line displayed in the foreground of the picture was horizontal. The purpose was to distract subjects' attention away from the picture content to prevent deeper processing. In the “Classification” task the participants had to decide, whether the scene showed a dental treatment situation or not. This implied a conceptual decision about the semantic content of the picture (is this dental treatment or not?), but the participants were not required to attend to their own emotional response. In the “Fear of Pain” task, subjects were asked to indicate, whether the picture elicited fear of pain. This explicitly required that the participants referred to their own emotional/pain-related involvement.
D
3.2. ERP data
267 268
321
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4. Discussion
F
DAS = Dental Anxiety Scale, FDP = Fear of Dental Pain Questionnaire, STAI = State-Trait Anxiety Inventory.
312 313
µV
t1:13 t1:14
central region (phobics: T(22) = 8.6, p b .001; controls: T(22) = 5.3, p b .001). In both groups, Classification elicited higher amplitudes than Distraction in the frontal (phobics: T(22) = 2.1, p = .048; controls: T(22) = 3.5, p = .002) and central region (phobics: T(22) = 3.9, p = .001; controls: T(22) = 4.7, p b .001). Moreover, only within phobics Fear of Pain elicited higher amplitudes than Classification in the frontal (T(22) = 2.6, p = .015) and central region (T(22) = 3.2, p = .004), whereas there were no significant differences within controls (all p's N .575).
E
t1:1 t1:2 t1:3
5
9 8 7 6 5 4 3 2 1 0
| Classification Task
| Distraction
Fear of Pain
Fear of Pain
| Classification Task
Fear of Pain
Fig. 3. Mean voltage differences (Phobia minus Neutral) and standard errors of phobics and controls in response to the three tasks (Distraction, Classification, Fear of Pain) at the representative electrode sites Fz, Cz, and Pz for the late positive potential (300–1000 ms). Data are referenced to the average of Tp9 and Tp10.
Please cite this article as: Leutgeb, V., et al., Electrocortical effects of directing attention during visual exposure in dentophobia, Int. J. Psychophysiol. (2014), http://dx.doi.org/10.1016/j.ijpsycho.2014.05.003
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324 325 326 327 328 329 330 331 332 333 334 335 336
360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 Q5 398 399 400 401 402
F
O
R O
358 359
P
356 357
5. Conclusion
D
Q4354 Q3 355
re-exposure images with a distraction history elicited larger LPP amplitudes than images with an attend history. Lastly, it should also be noted, that the current study did not include a passive viewing condition, and therefore the interpretation that attention was successfully directed away from the phobic stimulus has to be dealt with cautiously. For the treatment of dental phobia, CBT (especially graded exposure combined with relaxation) has been shown to be superior to general anesthesia and pharmacological treatment on the long-term (for a review, see Berggren, 2001). In contrast, distraction via auditory or visual stimulation has been found to be useful in moderately anxious (but not in highly anxious) subjects (e.g., Frere et al., 2001; Lahmann et al., 2008). It might be possible, that differential attention regulation strategies are indicated for individual patients with varying disorder severity and at different stages of therapy: for example, distraction from pain might be efficient at mild pain intensity or in very early therapy, while at high intensities or during actual (painful) treatment, redefinition seems to be superior (e.g., McCaul and Malott, 1984). Trained dentists try to respond to patients, e.g., by announcing the beginning of a painful intervention or permitting the patient to exercise some form of control strategies for terminating the treatment (i.e., raising his hand if they cannot be tolerate the pain anymore; Jöhren and Sartory, 2002). However, this might not be useful for all patients, as it requires them to focus on their own emotional involvement and their feelings of pain.
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The current investigation showed that explicit instructions to direct attention during dentophobic confrontation have an impact on late ERPs. We suggest that the current paradigm could be valuable to investigate the role of fear of pain in dentophobia and, moreover, the importance of its modification in the course of exposure therapy. Therapies could be evaluated with respect to possible changes in ERPs to different emotion regulation strategies.
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Results revealed that explicit direction guiding in dental phobia indeed has an impact on amplitudes of late ERPs. Phobics displayed higher frontal and central late positivity (300–1000 ms) than controls when they had to think about their own pain-related involvement, whereas there was no group difference in response to the “Classification” and the “Distraction” task. Within phobics, there was a significant increase in late positivity with increasing self-directed attention (Distraction b Classification b Fear of Pain). Interestingly, controls showed a similar pattern of increasing late positivity, however, Fear of Pain and Classification did not differ from each other. A decision about one's own pain-related involvement in a picture requires self-referential processing of the affective meaning and might be causal for the enhancement of LPP amplitude in phobics relative to controls. The result is in line with a number of studies, showing that the LPP is sensitive to top-down attentional processing (e.g., Deveney and Pizzagalli, 2008; Dunning and Hajcak, 2009; Foti and Hajcak, 2008; Hajcak and Nieuwenhuis, 2006; Hajcak et al., 2010, 2013; Moser et al., 2006; 2009; Thiruchselvam et al., 2011; Wiens et al., 2011). Very consistently, results revealed that a decrease in the intensity of emotional experience was accompanied by reduced amplitudes of the LPP (e.g., Moser et al., 2006). Dunning and Hajcak (2009) for example found that the direction of attention toward non-arousing aspects of unpleasant images resulted in decreased amplitudes of late posterior positivity from 1000 to 3000 ms after picture onset. In this investigation, subjects were instructed to explicitly focus their attention and look only at an area within a circle while it remained on the screen. Hajcak and Nieuwenhuis (2006) instructed participants to reappraise unpleasant images (to reinterpret them in a less negative way), which was accompanied by reduced LPP amplitudes from 200 to 2000 ms after picture onset. Whereas ERP studies on motivated attention in specific phobias mainly found effects at posterior recording sites (for a review, see Olofsson et al., 2008), the effect in the current study was located at central and frontal regions. This might be interpreted to reflect top-down attentional processing as frontal regions are primarily involved in executive control and goal-directed target detection (Li et al., 2010). Additionally, there are published studies on spider phobic patients who underwent exposure therapy. The main correlate of successful therapy was an enhancement of late fronto-central ERPs in response to pictures of spiders, which was interpreted as an effect of enhanced attention to the formerly phobic object (Leutgeb et al., 2009, 2012). Moreover, Schienle et al. (in press) conducted a functional magnetic resonance imaging investigation with healthy control subjects employing the same paradigm as in the current study. The fear of pain condition was associated with increased activation of the dorsomedial prefrontal cortex relative to the two other conditions, and this activation was positively correlated with self-reported dental anxiety. In the current study, amplitudes of the late positive potential were significantly reduced in response to tasks designed to distract attention from the phobic stimulus (“Distraction” and “Classification”) as compared to the task requiring self-directed attention (“Fear of Pain“). Classifying pictures might present a way of encouraging patients to direct their attention toward the phobic stimulus without including deeper processing or reappraisal. These results are in line with studies showing, that an explicit distractor task taxes perceptual resources and reduces affective ERP modulation (De Cesarei et al., 2009; Pessoa, 2005; Schupp et al., 2007). However, recent studies showed that spider fearful subjects still displayed clear enhanced late positivity even during a distraction task (e.g., peripheral letter discrimination; Norberg et al., 2010; Norberg & Wiens, 2013). Additionally, this effect was independent of perceptual load. Moreover, a recently published study suggests that attention distraction might only be effective in the short-term: Thiruchselvam and colleagues (2013) confronted participants with either neutral or emotional pictures. In a first exposure phase reactions to pictures were watched or regulated by using either distraction or reappraisal. In a re-exposure phase pictures were passively viewed. In the first phase distraction reduced the LPP earlier than reappraisal. However, during
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Please cite this article as: Leutgeb, V., et al., Electrocortical effects of directing attention during visual exposure in dentophobia, Int. J. Psychophysiol. (2014), http://dx.doi.org/10.1016/j.ijpsycho.2014.05.003
500 501 502 503 504 505 506 507 508 509 510 511 512 Q6 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527
