Y Boyle

Selective modulation of nociceptive processing due to noise distraction

&NA; This study investigates the effects of noise distraction on the different components and sources of laser‐evoked potentials (LEPs) whilst attending to either the spatial component (localisation performance task) or the affective component (unpleasantness rating task) of pain. LEPs elicited by CO2 laser stimulation of the right forearm were recorded from 64 electrodes in 18 consenting healthy volunteers. Subjects reported either pain location or unpleasantness, in the presence and absence of distraction by continuous 85 dBa white noise. Distributed sources of the LEP peaks were identified using Low Resolution Electromagnetic Tomography (LORETA). Pain unpleasantness ratings and P2 (430 ms) peak amplitude were significantly reduced by distraction during the unpleasantness task, whereas the localisation ability and the corresponding N1/N2 (310 ms) peak amplitude remained unchanged. Noise distraction (at 310 ms) reduced activation in the anterior cingulate cortex (ACC) and precuneus during attention to localisation and unpleasantness, respectively. This suggests a complimentary role for these two areas in the control of attention to pain. In contrast, activation of the occipital pole and SII were enhanced by noise during the localisation and unpleasantness task, respectively, suggesting that the presence of noise was associated with increased spatial attentional load. This study has shown selective modulation of affective pain processing by noise distraction, indicated by a reduction in the unpleasantness ratings and P2 peak amplitude and associated activity within the medial pain system. These results show that processing of the affective component of pain can be differentially modulated by top‐down processes, providing a potential mechanism for therapeutic intervention.

Acoustic noise in functional magnetic resonance imaging reduces pain unpleasantness ratings

Functional magnetic resonance imaging (fMRI) is increasingly used in cognitive studies. Unfortunately, the scanner produces acoustic noise during the image acquisition process. Interference from acoustic noise is known to affect auditory, visual and motor processing, raising the possibility that acoustic interference may also modulate processing of other sensory modalities such as pain. With the increasing use of fMRI in the investigation of the mechanisms of pain perception, particularly in relation to attention, this issue has become highly relevant. Pain is a complex experience, composed of sensory-discriminative, affective-motivational and cognitive-evaluative components. The aim of this experiment was to assess the effect of MRI scanner noise, compared to white noise, on the affective (unpleasantness) and the sensory-discriminative (localisation) components of pain. Painful radiant heat from a CO(2) laser was delivered to the skin of the right forearm in 24 healthy volunteers. The volunteers attended to either pain location or pain unpleasantness during three conditions: i) no noise, ii) exposure to MRI scanner noise (85 dB) or iii) exposure to white noise (85 dB). Both MRI scanner noise and white noise significantly reduced unpleasantness ratings (from 5.1 +/- 1.6 in the control condition to 4.7 +/- 1.5 (P = 0.002) and 4.6 +/- 1.6 (P < 0.001) with scanner and white noise respectively), whereas the ability to localise pain was not significantly affected (from 85.4 +/- 9.2% correct in the control condition to 83.1 +/- 10.3% (P = 0.06) and 83.9 +/- 9.5% (P = 0.27) with MRI scanner and white noise respectively). This phenomenon should be taken into account in the design of fMRI studies into human pain perception.

284 5-HT MODULATION OF PAIN EXPERIENCE: A TRYPTOPHAN DEPLETION STUDY

Introduction: Pain associated with menstruation. A most frequent gynecological disorder, it is classified into primary and secondary. Its pathogenesis is not always understood. Prostaglandins seem to be intimately involved in primary dysmenorrhoea. Medication is usually required for all cases of moderate to severe painful menstruation. Apart from pharmacological agents, several techniques have been used including relaxation therapy, hypnosis, manipulation, psychotherapy, acupuncture, biofeedback techniques, surgery. Material and methods: It was a descriptive study. The study included 215 virgin students of reproductive age (19–22 yrs). The study subjects completed a questionnaire. Results: The median age of menarche was 12 years and the mean was11.92. Frequency of primary dysmenorrhea was 62 %(mild24.5%, moderate 22.5%, severe 15%) but the daily activity was hampered only in 15%. They had poor knowledge about dysmenorea and menstruation abnormality. 35.5% treated themselves with iboprophen, codeine vitb6, mefnamic acid and . . . and some of them used from herbal drugs and some of them only had rest and eat some sweet. Conclusion: It seems the rate of dysmenorea in our study was like other studies, and our girls needed education about the abnormalities of menstruation.

285 SENSORY MODULATION OF LASER EVOKED POTENTIALS BY TRYPTOPHAN DEPLETION

Introduction: Pain associated with menstruation. A most frequent gynecological disorder, it is classified into primary and secondary. Its pathogenesis is not always understood. Prostaglandins seem to be intimately involved in primary dysmenorrhoea. Medication is usually required for all cases of moderate to severe painful menstruation. Apart from pharmacological agents, several techniques have been used including relaxation therapy, hypnosis, manipulation, psychotherapy, acupuncture, biofeedback techniques, surgery. Material and methods: It was a descriptive study. The study included 215 virgin students of reproductive age (19–22 yrs). The study subjects completed a questionnaire. Results: The median age of menarche was 12 years and the mean was11.92. Frequency of primary dysmenorrhea was 62 %(mild24.5%, moderate 22.5%, severe 15%) but the daily activity was hampered only in 15%. They had poor knowledge about dysmenorea and menstruation abnormality. 35.5% treated themselves with iboprophen, codeine vitb6, mefnamic acid and . . . and some of them used from herbal drugs and some of them only had rest and eat some sweet. Conclusion: It seems the rate of dysmenorea in our study was like other studies, and our girls needed education about the abnormalities of menstruation.