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Cortical activation changes during repeated laser stimulation: a magnetoencephalographic study.

Stancak A, Alghamdi J, Nurmikko TJ - PLoS ONE (2011)

Bottom Line: The pain resulting from repetitive warm stimuli is mediated by summated C fibre responses.The neuromagnetic fields were modelled by five equivalent source dipoles located in the occipital cortex, cerebellum, posterior cingulate cortex, and left and right operculo-insular cortex.The amplitude increases of the late component of the contralateral operculo-insular source dipole correlated with the subjects' numerical ratings of warmth and pain.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Psychology, Institute of Psychology, Health, and Society, University of Liverpool, Liverpool, United Kingdom. a.stancak@liverpool.ac.uk

ABSTRACT
Repeated warm laser stimuli produce a progressive increase of the sensation of warmth and heat and eventually that of a burning pain. The pain resulting from repetitive warm stimuli is mediated by summated C fibre responses. To shed more light on the cortical changes associated with pain during repeated subnoxious warm stimulation, we analysed magnetoencephalographic (MEG) evoked fields in eleven subjects during application of repetitive warm laser stimuli to the dorsum of the right hand. One set of stimuli encompassed 10 laser pulses occurring at 2.5 s intervals. Parameters of laser stimulation were optimised to elicit a pleasant warm sensation upon a single stimulus with a rise of skin temperature after repeated stimulation not exceeding the threshold of C mechano-heat fibres. Subjects reported a progressive increase of the intensity of heat and burning pain during repeated laser stimulation in spite of only mild (4.8°C) increase of skin temperature from the first stimulus to the tenth stimulus. The mean reaction time, evaluated in six subjects, was 1.33 s, confirming involvement of C fibres. The neuromagnetic fields were modelled by five equivalent source dipoles located in the occipital cortex, cerebellum, posterior cingulate cortex, and left and right operculo-insular cortex. The only component showing statistically significant changes during repetitive laser stimulation was the late component of the contralateral operculo-insular source peaking at 1.05 s after stimulus onset. The amplitude increases of the late component of the contralateral operculo-insular source dipole correlated with the subjects' numerical ratings of warmth and pain. Results point to a pivotal role of the contralateral operculo-insular region in processing of C-fibre mediated pain during repeated subnoxious laser stimulation.

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Related in: MedlinePlus

Temperature changes during repeated laser stimulation.A. Mean temperature values preceding the first laser stimulus (labelelled “0”) and following each of 10 laser stimuli. B. Trial-by-trial baseline temperature values. The vertical vertical bars represent the standard deviations.
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pone-0019744-g006: Temperature changes during repeated laser stimulation.A. Mean temperature values preceding the first laser stimulus (labelelled “0”) and following each of 10 laser stimuli. B. Trial-by-trial baseline temperature values. The vertical vertical bars represent the standard deviations.

Mentions: Figure 6A shows the mean temperature changes prior to the first laser stimulus and after each of 10 laser stimuli. The skin temperature gradually increased from the mean value of 32.3±1.4°C at baseline to 37.1±1.7°C that was recorded after the last laser stimulus. The increase of temperature from stimulus 1 to stimulus 10 was statistically significant according to one-way repeated measures ANOVA (F(9,36) = 351.5, P<0.0001, Greenhouse Geisser ε = 0.111).


Cortical activation changes during repeated laser stimulation: a magnetoencephalographic study.

Stancak A, Alghamdi J, Nurmikko TJ - PLoS ONE (2011)

Temperature changes during repeated laser stimulation.A. Mean temperature values preceding the first laser stimulus (labelelled “0”) and following each of 10 laser stimuli. B. Trial-by-trial baseline temperature values. The vertical vertical bars represent the standard deviations.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3091873&req=5

pone-0019744-g006: Temperature changes during repeated laser stimulation.A. Mean temperature values preceding the first laser stimulus (labelelled “0”) and following each of 10 laser stimuli. B. Trial-by-trial baseline temperature values. The vertical vertical bars represent the standard deviations.
Mentions: Figure 6A shows the mean temperature changes prior to the first laser stimulus and after each of 10 laser stimuli. The skin temperature gradually increased from the mean value of 32.3±1.4°C at baseline to 37.1±1.7°C that was recorded after the last laser stimulus. The increase of temperature from stimulus 1 to stimulus 10 was statistically significant according to one-way repeated measures ANOVA (F(9,36) = 351.5, P<0.0001, Greenhouse Geisser ε = 0.111).

Bottom Line: The pain resulting from repetitive warm stimuli is mediated by summated C fibre responses.The neuromagnetic fields were modelled by five equivalent source dipoles located in the occipital cortex, cerebellum, posterior cingulate cortex, and left and right operculo-insular cortex.The amplitude increases of the late component of the contralateral operculo-insular source dipole correlated with the subjects' numerical ratings of warmth and pain.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Psychology, Institute of Psychology, Health, and Society, University of Liverpool, Liverpool, United Kingdom. a.stancak@liverpool.ac.uk

ABSTRACT
Repeated warm laser stimuli produce a progressive increase of the sensation of warmth and heat and eventually that of a burning pain. The pain resulting from repetitive warm stimuli is mediated by summated C fibre responses. To shed more light on the cortical changes associated with pain during repeated subnoxious warm stimulation, we analysed magnetoencephalographic (MEG) evoked fields in eleven subjects during application of repetitive warm laser stimuli to the dorsum of the right hand. One set of stimuli encompassed 10 laser pulses occurring at 2.5 s intervals. Parameters of laser stimulation were optimised to elicit a pleasant warm sensation upon a single stimulus with a rise of skin temperature after repeated stimulation not exceeding the threshold of C mechano-heat fibres. Subjects reported a progressive increase of the intensity of heat and burning pain during repeated laser stimulation in spite of only mild (4.8°C) increase of skin temperature from the first stimulus to the tenth stimulus. The mean reaction time, evaluated in six subjects, was 1.33 s, confirming involvement of C fibres. The neuromagnetic fields were modelled by five equivalent source dipoles located in the occipital cortex, cerebellum, posterior cingulate cortex, and left and right operculo-insular cortex. The only component showing statistically significant changes during repetitive laser stimulation was the late component of the contralateral operculo-insular source peaking at 1.05 s after stimulus onset. The amplitude increases of the late component of the contralateral operculo-insular source dipole correlated with the subjects' numerical ratings of warmth and pain. Results point to a pivotal role of the contralateral operculo-insular region in processing of C-fibre mediated pain during repeated subnoxious laser stimulation.

Show MeSH
Related in: MedlinePlus