Transcript Document

www.medicine.manchester.ac.uk
www.hop.man.ac.uk/painresearch
133000
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.
Results
Amplitude (mV)
-3
Condition
5
0
-5
Unpleasantness
without noise
-20
-25
Localisation without noise
**
-30
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).
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 GFP
(N2) and P430-Cz (P2) LEP peaks (Fig. 2).
Adjusted latency (ms)
T7
3
3
4
Cz
0.5
0
-100
100
300
500
700
900
1100
1300
1500
Latency (ms)
-7
Localisation without noise
P430-Cz
*
12
Distraction
-10
10
-8
8
-6
-4
500
1000
1500
-2
0
4
2
0
Localisation
Unpleasantness
+4.4
2
+3.8
Latency (ms)
+3.1
+2.5
6
+1.9
+1.3
8
N310-T7
+0.6
0
-0.6
12
-1.3
FCz
-1.9
-4
-2.5
0
500
1000
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)
(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 eventrelated potentials following CO2 laser stimulation in man. Exp
Brain Res 127, pp. 131–140.
-3.8
-4.4
2
310.00 ms
4
-5.0
-4
Latency (ms)
6
-2 0
-500
8
-4
500
1000
1500
-2
-500
0
10
12
2
+5.0
P430-Cz
+2.5
500
1000
Latency (ms)
+3.8
+3.1
1500
+1.9
0
+1.3
2
+0.6
0
Latency (ms)
-0.6
6
-1.3
-1.9
-2.5
-3.1
-3.8
-4.4
-5.0
Fig. 2.
Grand average LEPs, global field power (GFP) plot and topographic
maps for all subjects and all conditions (n =18).
 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
6
8
Loc Control
10
Loc Distract
12
0
500
0
4
+4.4
Cz
-4
4
References
(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
-3.1
1500
0
-2
This work was supported by the Arthritis Research
Campaign (UK).
Unpleasantness
Condition
+5.0
0
4
Acknowledgments
(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.
6
Condition
-2
10
-500
-6
Control
-4
-2
-5
N310-T7
-12
Localisation
-500
-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).
T7
-500
-3
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
Amplitude (mV)
1
-300
-2
FCz
2
1.5
-500
-1
#
Unpleasantness without noise
2.5
430.00 ms
 Pain Unpleasantness ratings were reduced by 11 
14.9% in the Distraction condition.
1500
Amplitude (mV)
-15
8
the
500
1
-10
12
 The mean unpleasantness rating during
Unpleasantness Control condition was 4.9  1.2.
-2
-1
-100
0
-500
2
10
Behavioural results
0
N310-T7 Peak Amplitude (mV)
10
#
-4
Condition
N310-T7
-5
1000
1500
Latency (ms)
2
Amplitude (mV)
 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.
 Only pain unpleasantness ratings were significantly reduced
by distraction (**p<0.01) (Fig. 1), confirming previous results 1.
Amplitude (mV)
 18 right handed healthy volunteers
 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 P430Cz 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.
Amplitude (mV)
Methods
 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
 The topography of this peak suggests a source in
somatosensory cortices. This supports evidence that the
2,3,4
somatosensory cortex processes pain localisation
.
Amplitude (mV)
Aim
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.
Summary & Conclusions
 The ability to localise pain was reduced by 0.8  6.9 % in the
Distraction condition
Amplitude (mV)
 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
1
reduced by distraction .
 This study investigates the effects of distraction on
these aspects of pain and the different components of
LEPs.
11 subjects who showed a contralateral maximum at 310ms,
2
confirming previous results .
Amplitude (mV)
Pain is composed of 3 components: sensorydiscriminative, affective-motivational and cognitiveevaluative.
 The mean percentage of correct responses during the pain
Localisation Control condition was 86.4  6.7 %
% change
Introduction
(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.
4
6
8
Unp Control
Unp Distract
10
12
*
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).
 This was due to a reduction in P430-Cz peak amplitude with
distraction only during the Unpleasantness task (Fig. 5)
(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