BRIEF REPORT Effects of pain-related anxiety on components of the pain event-related potential TRACY WARBRICK, a,b DAVID SHEFFIELD, a and ARIE NOUWEN b a Staffordshire University, Stoke-on-Trent, Staffordshire, UK b School of Psychology, University of Birmingham, Edgbaston, Birmingham, UK Abstract The aim of this study was to investigate whether components of pain event-related potentials (ERPs) are modulated by anxiety. Pain ERPs in response to electrical stimulation were collected from 14 healthy individuals in a neutral condition and a condition where pain-related anxiety was induced. The amplitude of the N140 component of the ERP was found to be larger in the anxiety condition than the neutral condition. Arousal, as indicated by alpha power, did not differ between conditions. Differences in valence and focused attention to the painful stimuli may account for the increases in the N140 in the anxiety condition. Descriptors: Pain-related anxiety, ERP, Attention, Valence, Shock The salience of anxiety to the individual has been shown to in- fluence pain perception (Rhudy & Meagher, 2000; Staats, Staats, & Hekmat, 2001). Generally, non-pain-related anxiety has been shown to reduce the perceived intensity of pain whereas pain- related anxiety has been shown to increase it (Villemure & Bushn- ell, 2002). The exact mechanisms for the influence of pain-related anxiety on pain are not clear but may include motivational prim- ing (Lang, 1995) and changes in arousal (Logan et al., 2001). Another explanation that has been the focus of recent research concerns attention. It has been demonstrated that attentional focus alone can influence pain perception (Ahles, Blanchard, & Leventhal, 1983; Brewer & Karoly, 1989; Nouwen, Cloutier, Kappas, Warbrick, & Sheffield, 2006). Arntz, Dressen, and Me- rckelbach (1991) found that spider-phobic participants reported less pain in the presence of a spider than those asked to concentrate on the pain with no spider present. These studies suggest that anxiety may influence pain perception by changing the focus of attention toward or away from the source of the pain. However, these studies did not directly assess the role of attention in me- diating the relationship between anxiety and pain. Event-related potentials (ERPs) can provide a useful method for investigating psychological effects on pain perception (Bromm & Lorenz, 1998; Chen, 2001). Pain ERPs can generally be character- ised by a negative peak at around 130–240 ms poststimulus and a positive peak around 230–390 ms poststimulus (Bromm, 1985; Zaslansky, Sprecher, Tenke, Hemli, & Yarnitsky, 1996). Anxiety could influence pain ERPs by creating a negative affective context (Kenntner-Mabiala & Pauli, 2005; Rhudy et al., 2005), thus influ- encing spinal cord neurons before primary nociceptors are stimu- lated. Moreover, modulation of the ERP components by factors related to the stimulus, such as stimulus identification (Becker, Yingling, & Fein, 1993), emotional response (Zaslansky et al., 1996), and attention (Eimer & Forster, 2003), can also be reflected in specific ERP components. Attention has been shown to influence both the negative and late positive components of the pain event- related potential. For example, Kida, Nishihira, Wasaka, Nakata, and Sakamoto (2004) found that the amplitude of the N140 in- creased while attending to electrical stimuli compared to not at- tending. Miltner, Johnson, Braun, and Larbig (1989) and Zaslansky et al. (1996) have found amplitude of late positive ac- tivity to be larger in an attention to pain condition than an ignore pain condition. However, the tasks used in these studies are likely to elicit a cognitive P300-like component reflecting discrimination or overt responses to the stimulus (Becker, Haley, Urena, & Yingling, 2000), and therefore may not reflect attentional modulation of the pain ERP. To date, no study has specifically investigated the dif- ference in ERP components under anxious and nonanxious con- ditions. Given the increased amplitude of the N140 and the late positive components of the pain ERP with increased pain, it is expected that these components will be augmented by anxiety. Ac- cordingly, the aims of this study were (1) to investigate whether subjective ratings of pain differ between anxious and neutral con- ditions, and (2) to investigate whether the N140 and late positive components of the pain ERP are modulated by anxiety. The pain ERP components that differ between anxiety and neutral conditions will give an indication of how anxiety influences pain processing. We would like to thank three anonymous reviewers for their helpful comments on an earlier version of this article. Address reprint requests to: Tracy Warbrick, School of Psychology, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. E-mail: t.warbrick@bham.ac.uk. Psychophysiology, 43 (2006), 481–485. Blackwell Publishing Inc. Printed in the USA. Copyright r 2006 Society for Psychophysiological Research DOI: 10.1111/j.1469-8986.2006.00425.x 481