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 w hen w e are distracted. The N 2-P2 LEP com plex 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 notlocalisation ability are reduced by distraction 1 . This study investigates the effects of distraction on these aspects ofpain and the differentcom ponents of LE Ps. To investigate if the ability to localise pain and rate pain unpleasantness are modulated differentially by distraction and ifthe LE P com ponents are m odulated differentially. Subjects reported either pain Location or Unpleasantness, in the presence (Distraction) and absence (Control) of a distracter (continuous 85dBa w hite noise). LE Ps, elicited by C O 2 laser stim ulation to the right forearm ,w ere recorded from 61 electrodes 18 righthanded healthy volunteers LE P com ponents w ere nam ed 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 com pared betw een the tw o tasks. B ehaviouralresults The mean unpleasantness rating during the U npleasantness C ontrol condition w as 4.9 1.2. Pain U npleasantness ratings w ere reduced by 11 14.9% in the D istraction condition. The m ean percentage of correct responses during the pain Localisation C ontrolcondition w as 86.4 6.7 % The ability to localise pain w as reduced by 0.8 6.9 % in the D istraction condition O nly pain unpleasantness ratings w ere significantly reduced by distraction (**p<0.01)(Fig.1),confirm ing previous results 1 . LEP results The LE P data from allsubjects and alltasks com prised tw o main Global Field Power (GFP) peak at 310 and 430ms, reflecting N 310-T7 (N 2)and P 430-C z (P2)LE P peaks (Fig.2). Although non-significant (p=0.06), there w as a trend for the am plitude ofN 310-T7 to be greaterduring the pain Localisation task than the U npleasantness task (C ontrolcondition)(Fig.3)in 11 subjects w ho showed a contralateral m axim um at 310m s, confirm ing previous results 2 . The topography of this peak suggests a source in somatosensory cortices. This supports evidence that the som atosensory cortex processes pain localisation 2,3,4 . The peak amplitude of P430-Cz but not N310-T7 was significantly differentbetw een C ontrol and D istraction conditions forthe U npleasantness task only (Fig.4). This w as due to a reduction in P430-C z peak am plitude w ith distraction only during the U npleasantness task (Fig.5) These results show selective m odulation ofaffective pain processing by auditory distraction,indicated by a reduction in behaviouralunpleasantness ratings. The reduction in P430-C z am plitude suggests P430- Cz might relate to affective processing and the topography of this peak suggests a source in m edial cerebral generators such as cingulate 5 . These results show thatprocessing of the affective and sensory com ponents of pain can be differentially m odulated by top-dow n processes. This work was supported by the Arthritis Research C am paign (U K). (1) Boyle,Y,Bentley,D .E.,W atson,A.and Jones,A.K.P. 2003;D ifferential effects distractions on electively attending to affective –m otivational and sensory-discrim inative com ponents ofpain unpleasantness J ournal of Psychophysiology 17 (4) pp.230 (2) Bentley,D .E.,W atson,A.,Treede,R .-D .,Barrett,G ., Youell,P.D .,Kulkarni,B.and Jones,A.K.P.2004,D ifferential effects on the laserevoked potential ofselectively attending to pain localisation versus pain unpleasantness. C lin Neurophysiol 115,pp.1846-1856. (3) Kanda,M .,Shindo,K.,Xu,X.,Fujiw ara,N .,Ikeda,A., N agam ine,T.and Shibasaki,H .,1999.C orticalm echanism s underlying pointlocalisation ofpain spotas studied by event- related potentials follow ing C O 2 laserstim ulation in m an. E xp Brain R es 127,pp.131–140. (4) Valeriani,M .,R estuccia,D .,Le Pera,D .,Fiaschetti,L.., Tonali,P.and Arendt-N ielsen,L..,2000.U nm asking ofan early laserevoked potentialby a pointlocalisation task. C lin Neurophysiol.111,pp.1927–1933. (5) Bentley,D .E.,Youell,P.D .,and Jones,A.K.P.2002, Anatom ical localization and intra-subjectreproducibility oflaser evoked potential source in cingulate cortex,using a realistic head m odel. C lin Neurophysiol. 113,pp.1351-1356 Introduction Aim Methods Results Sum m ary & C onclusions Acknowledgm ents R eferences Fig.1 % C hange betw een C ontroland D istraction conditions for U npleasantness ratings (U np)and Localisation perform ance (Loc). B lue,Localisation condition;R ed,U npleasantness condition.(**p<0.01) M ean & SD ( n =18). Fig.2. G rand average LEPs,globalfield pow er(G FP)plotand topographic m aps forallsubjects and allconditions ( n =18). Fig 5. U npleasantness D istraction condtion-specific decrease in P430 peak am plitude atelectrode C z.(*p<0.05)( n=18) G roup LEPs atelectrode C z forLocalisation C ontrol(blue)and D istraction (green)conditions (leftfigure)and U npleasantness C ontrol (red)and D istraction (black)conditions (rightfigure). Fig.3. Localisation task-specific Increase ( # p=0.06)in N 310 peak am plitude atelectrode T7. Leftfigure:grouped LEPs ( n = 11). R ightfigure: N 310-T7 peak am plitude. B lue,Localisation C ontroltask;R ed, U npleasantness rating C ontroltask Fig.4 N 310-T7 and P430-C z peak am plitude forC ontrol(C on)and D istraction (D is)conditions forthe U npleasantness ratings task (U np) and Localisation perform ance (Loc)task.(*p<0.05) M ean & SD ( n =18) www.medicine.manchester.a c.uk GFP 0 0.5 1 1.5 2 2.5 3 -500 -300 -100 100 300 500 700 900 1100 1300 1500 Latency (ms) Amplitude (V) 3 1 0 .0 0 m s 430 .0 0 m s T7 Cz FCz T7 -4 -2 0 2 4 6 8 10 12 -500 500 1000 1500 Latency (ms) Amplitude (V) FCz -4 -2 0 2 4 6 8 10 12 -500 0 500 1000 1500 Latency (ms) Amplitude (V) Cz -4 -2 0 2 4 6 8 10 12 -500 500 1000 1500 Latency (ms) Amplitude (V) N310-T7 P430-Cz 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. 133000 -7 -6 -5 -4 -3 -2 -1 0 Condition N310-T7 Peak Amplitude (V) # -5 -4 -3 -2 -1 0 1 2 3 4 -500 -100 500 1500 Adjusted latency (ms) Amplitude (V) N310-T7 # Unpleasantness without noise Localisation without noise Unpleasantness without noise -30 -25 -20 -15 -10 -5 0 5 10 Condition % change ** Localisation without noise N310-T7 P430-Cz 0 2 4 6 8 10 12 Condition Amplitude (V) -12 -10 -8 -6 -4 -2 0 Localisat ion Unpleasantness Condition Amplitude (V) Control Distraction Localisat ion Unpleasantness * Amplitude (V) -4 -2 0 2 4 6 8 10 12 -500 0 500 1000 1500 Latency (ms) Loc Control Loc Distract -4 -2 0 2 4 6 8 10 12 -500 0 500 1000 1500 Latency (ms) Amplitude (V) Unp Control Unp Distract * www.hop.man.ac.uk/ painresearch
medicine.manchester.ac.uk
Jan 31, 2016
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 Presentation
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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)
www.medicine.manchester.ac.uk
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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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