Pain and left-right discrimination; more complicated than ...€¦ · Correspondence:...
1
Correspondence: [email protected] Pain and left-right discrimination; more complicated than we thought? Nichole Phillips 1 , Jamie Mannion 1 , Scott McLaren 2 and Robert Moran 1 1 Healthcare Network, Unitec Institute of Technology, Auckland 2 Greenwood Medical Centre, Epsom, Auckland Our results were not consistent with previous left-right discrimination response latency findings in acute experimental pain and do not support the ‘attentional bias’ hypothesis currently thought to underpin this effect. Instead, significant changes in mean response latency overall were deferred to the post-pain discrimination tasks. It is currently not clear why acute experimental pain did not result in immediate response latency changes. Across all pain condition (pre-, during- and post-), reaction times for left hand images were slower when the right hand was (due to be) affected by pain. The reverse, slower reaction times for right hand images during all left hand pain conditions, did not occur. General asymmetrical hemispheric function may therefore affect left-right discrimination as a pre-existing characteristic. A potential limitation of the current study was that the non-injected hand acted as the response hand. Future studies employing the current paradigm may benefit from verbal response methods. This format may eliminate the potential confounding factors of hand dominance when inputting responses. DISCUSSION AND CONCLUSION RESULTS • Changes in mean response latency were not seen until the post-pain condition which was significantly faster overall compared to the during-pain condition (p = 0.036). • Overall, participants responded slower to images of left hands than right hands for all images, in all pain conditions and all pain locations (p = 0.004). • However, when separated into pain locations, this difference only related to a right-hand pain location regardless of pain condition (p = 0.005). 1 Moseley, G. L., et al. (2005). Experimental hand pain delays recognition of the contralateral hand-evidence that acute and chronic pain have opposite effects on information processing? Brain Research, 25(1), 188-194. 2 Hudson, M. L. et al. (2006). Expectation of pain replicates the effect of pain in a hand laterality recognition task: Bias in information processing toward the painful side? European Journal of Pain, 10(3), 219-224. 3 Coslett, H. B., et al. (2010a). Mental motor imagery and chronic pain: the foot laterality task. Journal of the International Neuropsychological Society, 16(4), 603-612. 4 Coslett, H. B., et al. (2010b). Mental motor imagery indexes pain: the hand laterality task. European Journal of Pain, 14(10), 1007-1013. doi: 10.1016/j.ejpain.2010.04.001 5 Elsig, S., et al. (2014). Sensorimotor tests, such as movement control and laterality judgment accuracy, in persons with recurrent neck pain and controls. A case-control study. Man Ther, 19(6), 555-561 REFERENCES This research was funded by a Todd Foundation Awards for Excellence (Institutes of Technology and Polytechnics). ACKNOWLEDGEMENTS & FUNDING Left-right discrimination judgements are thought to activate the same neural processes as actual movement of the limb. Studies show that acute experimental hand pain delays judgement response latency to images of the non-painful hand. 1,2 This latency delay has been proposed to be underpinned by an ‘attentional bias’ which is generated as the brain allocates more cortical processing towards the painful limb. 1 In comparison, chronic limb pain patients show delayed judgement latency to images that correspond to the affected side, thought to be due to a deficit in sensorimotor integration of the virtual body. 3,4 In order to further investigate potential clinical utility of this phenomenon as a biomarker for transition to chronic pain, 5 more detailed study is needed. AIM: To investigate the response latency for left-right discrimination judgements during acute experimental hand pain. INTRODUCTION 22 RIGHT-HANDED PARTICIPANTS Exclusion criteria: • pain/related conditions • pain catastrophizing • analgesia use • upper limb trauma/conditions • visual impairment • dyslexia Repeated measures cross-over study: • Left-right discrimination judgement task of the hand (see Figure 1) • 3 conditions; before, during and after an experimental pain stimulus • 0.4ml intramuscular 5% NaCl injection delivered to L)/R) thenar eminences (see Figure 2) Dependent measures: • Response latency using custom software application (s, button press) (see Figure 3) • Pain intensity rating (Visual Analog Scale; not reported here) (see Figure 4) METHODS Figure 4 Figure 1 Figure 3 Figure 2
Transcript of Pain and left-right discrimination; more complicated than ...€¦ · Correspondence:...
Correspondence: [email protected]
Pain and left-right discrimination; more complicated than we thought? Nichole Phillips1, Jamie Mannion1, Scott McLaren2 and Robert Moran1
1 Healthcare Network, Unitec Institute of Technology, Auckland 2 Greenwood Medical Centre, Epsom, Auckland
Our results were not consistent with previous left-right discrimination response latency � ndings in acute experimental pain and do not support the ‘attentional bias’ hypothesis currently thought to underpin this e� ect.
Instead, signi� cant changes in mean response latency overall were deferred to the post-pain discrimination tasks. It is currently not clear why acute experimental pain did not result in immediate response latency changes.
Across all pain condition (pre-, during- and post-), reaction times for left hand images were slower when the right hand was (due to be) a� ected by pain. The reverse, slower reaction times for right hand images during all left hand pain conditions, did not occur. General asymmetrical hemispheric function may therefore a� ect left-right discrimination as a pre-existing characteristic.
A potential limitation of the current study was that the non-injected hand acted as the response hand. Future studies employing the current paradigm may bene� t from verbal response methods. This format may eliminate the potential confounding factors of hand dominance when inputting responses.
DISCUSSION AND CONCLUSION
RESULTS• Changes in mean response latency were not seen until the post-pain condition which was signi� cantly
faster overall compared to the during-pain condition (p = 0.036).
• Overall, participants responded slower to images of left hands than right hands for all images, in all pain conditions and all pain locations (p = 0.004).
• However, when separated into pain locations, this di� erence only related to a right-hand pain location regardless of pain condition (p = 0.005).
1 Moseley, G. L., et al. (2005). Experimental hand pain delays recognition of the contralateral hand-evidence that acute and chronic pain have opposite e� ects on information processing? Brain Research, 25(1), 188-194.
2 Hudson, M. L. et al. (2006). Expectation of pain replicates the e� ect of pain in a hand laterality recognition task: Bias in information processing toward the painful side? European Journal of Pain, 10(3), 219-224.
3 Coslett, H. B., et al. (2010a). Mental motor imagery and chronic pain: the foot laterality task. Journal of the International Neuropsychological Society, 16(4), 603-612.
4 Coslett, H. B., et al. (2010b). Mental motor imagery indexes pain: the hand laterality task. European Journal of Pain, 14(10), 1007-1013. doi: 10.1016/j.ejpain.2010.04.001
5 Elsig, S., et al. (2014). Sensorimotor tests, such as movement control and laterality judgment accuracy, in persons with recurrent neck pain and controls. A case-control study. Man Ther, 19(6), 555-561
REFERENCES
This research was funded by a Todd Foundation Awards for Excellence (Institutes of Technology and Polytechnics).
ACKNOWLEDGEMENTS& FUNDING
Left-right discrimination judgements are thought to activate the same neural processes as actual movement of the limb. Studies show that acute experimental hand pain delays judgement response latency to images of the non-painful hand.1,2 This latency delay has been proposed to be underpinned by an ‘attentional bias’ which is generated as the brain allocates more cortical processing towards the painful limb.1 In comparison, chronic limb pain patients show delayed judgement latency to images that correspond to the a� ected side, thought to be due to a de� cit in sensorimotor integration of the virtual body.3,4 In order to further investigate potential clinical utility of this phenomenon as a biomarker for transition to chronic pain,5 more detailed study is needed.
AIM: To investigate the response latency for left-right discrimination judgements during acute experimental hand pain.
INTRODUCTION
22 RIGHT-HANDED PARTICIPANTS Exclusion criteria:• pain/related conditions• pain catastrophizing• analgesia use • upper limb trauma/conditions• visual impairment• dyslexia
Repeated measures cross-over study:• Left-right discrimination judgement task of the hand
(see Figure 1)• 3 conditions; before, during and after an
experimental pain stimulus • 0.4ml intramuscular 5% NaCl injection delivered to
L)/R) thenar eminences (see Figure 2) Dependent measures:• Response latency using custom software application
(s, button press) (see Figure 3)• Pain intensity rating (Visual Analog Scale; not
reported here) (see Figure 4)
METHODS
Figure 4
Figure 1
Figure 3Figure 2
