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N310-T7. Condition. #. -5. 0. GFP. -4. 10. -1. 3. -3. Condition. 5. -2. 2.5. -2. T7. 2. FCz. Amplitude ( m V). Amplitude ( m V). -3. -1. 0. -100. 500. 1500. 1.5. -500. 0. N310-T7 Peak Amplitude ( m V). -4. 1. -5. 1. 0.5. -5. % change. Adjusted latency (ms). 0. - PowerPoint PPT PresentationTRANSCRIPT
Pain is composed of 3 components: sensory-discriminative, affective-motivational and cognitive-evaluative.
Both the experience of pain and corresponding laser-pain evoked potentials (LEPs) are reduced when we are distracted.
The N2-P2 LEP complex is reduced by distraction. This effect is thought to be due to a reduction in P2 amplitude.
We have previously shown that only pain unpleasantness ratings and not localisation ability are reduced by distraction1.
This study investigates the effects of distraction on these aspects of pain and the different components of LEPs.
To investigate if the ability to localise pain and rate pain unpleasantness are modulated differentially by distraction and if the LEP components are modulated differentially.
Subjects reported either pain Location or Unpleasantness, in the presence (Distraction) and absence (Control) of a distracter (continuous 85dBa white noise).
LEPs, elicited by CO2 laser stimulation to the right forearm, were recorded from 61 electrodes
18 right handed healthy volunteers
LEP components were named by polarity, latency and electrode.
Amplitude and latency of each LEP peak was compared between the two tasks in the Control condition.
The percentage change in LEP peak amplitude between the Distraction and Control tasks was calculated and compared between the two tasks.
Behavioural results
The mean unpleasantness rating during the Unpleasantness Control condition was 4.9 1.2.
Pain Unpleasantness ratings were reduced by 11 14.9% in the Distraction condition.
The mean percentage of correct responses during the pain Localisation Control condition was 86.4 6.7 %
The ability to localise pain was reduced by 0.8 6.9 % in the Distraction condition
Only pain unpleasantness ratings were significantly reduced by distraction (**p<0.01) (Fig. 1), confirming previous results 1.
LEP results
The LEP data from all subjects and all tasks comprised two main Global Field Power (GFP) peak at 310 and 430ms, reflecting N310-T7 (N2) and P430-Cz (P2) LEP peaks (Fig. 2).
Although non-significant (p=0.06), there was a trend for the amplitude of N310-T7 to be greater during the pain Localisation task than the Unpleasantness task (Control condition) (Fig. 3) in
11 subjects who showed a contralateral maximum at 310ms, confirming previous results 2.
The topography of this peak suggests a source in somatosensory cortices. This supports evidence that the somatosensory cortex processes pain localisation 2,3,4.
The peak amplitude of P430-Cz but not N310-T7 was significantly different between Control and Distraction conditions for the Unpleasantness task only (Fig. 4).
This was due to a reduction in P430-Cz peak amplitude with distraction only during the Unpleasantness task (Fig. 5)
These results show selective modulation of affective pain processing by auditory distraction, indicated by a reduction in behavioural unpleasantness ratings.
The reduction in P430-Cz amplitude suggests P430-Cz might relate to affective processing and the topography of this peak suggests a source in medial cerebral generators such as cingulate 5.
These results show that processing of the affective and sensory components of pain can be differentially modulated by top-down processes.
This work was supported by the Arthritis Research Campaign (UK).
(1) Boyle, Y, Bentley, D. E., Watson, A. and Jones, A.K.P . 2003; Differential effects distractions on electively attending to affective –motivational and sensory-discriminative components of pain unpleasantness Journal of Psychophysiology 17 (4) pp.230
(2) Bentley, D.E., Watson, A., Treede, R.-D., Barrett, G., Youell, P.D., Kulkarni, B. and Jones, A.K.P. 2004, Differential effects on the laser evoked potential of selectively attending to pain localisation versus pain unpleasantness. Clin Neurophysiol 115, pp.1846-1856.
(3) Kanda, M., Shindo, K., Xu, X., Fujiwara, N., Ikeda, A., Nagamine, T. and Shibasaki, H., 1999. Cortical mechanisms underlying point localisation of pain spot as studied by event-related potentials following CO2 laser stimulation in man. Exp Brain Res 127, pp. 131–140.
(4) Valeriani, M., Restuccia, D., Le Pera, D., Fiaschetti, L.., Tonali, P. and Arendt-Nielsen, L.., 2000. Unmasking of an early laser evoked potential by a point localisation task. Clin Neurophysiol.111, pp. 1927–1933.
(5) Bentley,D.E., Youell,P.D., and Jones,A.K.P. 2002, Anatomical localization and intra-subject reproducibility of laser evoked potential source in cingulate cortex, using a realistic head model. Clin Neurophysiol. 113, pp.1351-1356
Introduction
Aim
Methods
Results
Summary & Conclusions
Acknowledgments
References
Fig. 1 % Change between Control and Distraction conditions for Unpleasantness ratings (Unp) and Localisation performance (Loc). Blue, Localisation condition; Red, Unpleasantness condition. (**p<0.01) Mean & SD (n =18).
Fig. 2. Grand average LEPs, global field power (GFP) plot and topographic maps for all subjects and all conditions (n =18).
Fig 5. Unpleasantness Distraction condtion-specific decrease in P430 peak amplitude at electrode Cz. (*p<0.05) (n=18) Group LEPs at electrode Cz for Localisation Control (blue) and Distraction (green) conditions (left figure) and Unpleasantness Control (red) and Distraction (black) conditions (right figure).
Fig. 3. Localisation task-specific Increase (# p=0.06) in N310 peak amplitude at electrode T7. Left figure: grouped LEPs (n = 11). Right figure: N310-T7 peak amplitude. Blue, Localisation Control task; Red, Unpleasantness rating Control task
Fig. 4 N310-T7 and P430-Cz peak amplitude for Control (Con) and Distraction (Dis) conditions for the Unpleasantness ratings task (Unp) and Localisation performance (Loc) task. (*p<0.05) Mean & SD (n =18)
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Modulation of pain affect, spatial discrimination and laser evoked potentials by distraction Y. Boyle, D. E. Bentley, A. Watson, and A. K. P. Jones.
Human Pain Research Group, University of Manchester Rheumatic Diseases Centre, Hope Hospital, Salford, M6 8HD, UK.
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