Title |
Thermal Detection Thresholds of Aδ- and C-Fibre Afferents Activated by Brief CO2 Laser Pulses Applied onto the Human Hairy Skin
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Published in |
PLOS ONE, April 2012
|
DOI | 10.1371/journal.pone.0035817 |
Pubmed ID | |
Authors |
Maxim Churyukanov, Léon Plaghki, Valéry Legrain, André Mouraux |
Abstract |
Brief high-power laser pulses applied onto the hairy skin of the distal end of a limb generate a double sensation related to the activation of Aδ- and C-fibres, referred to as first and second pain. However, neurophysiological and behavioural responses related to the activation of C-fibres can be studied reliably only if the concomitant activation of Aδ-fibres is avoided. Here, using a novel CO(2) laser stimulator able to deliver constant-temperature heat pulses through a feedback regulation of laser power by an online measurement of skin temperature at target site, combined with an adaptive staircase algorithm using reaction-time to distinguish between responses triggered by Aδ- and C-fibre input, we show that it is possible to estimate robustly and independently the thermal detection thresholds of Aδ-fibres (46.9±1.7°C) and C-fibres (39.8±1.7°C). Furthermore, we show that both thresholds are dependent on the skin temperature preceding and/or surrounding the test stimulus, indicating that the Aδ- and C-fibre afferents triggering the behavioural responses to brief laser pulses behave, at least partially, as detectors of a change in skin temperature rather than as pure level detectors. Most importantly, our results show that the difference in threshold between Aδ- and C-fibre afferents activated by brief laser pulses can be exploited to activate C-fibres selectively and reliably, provided that the rise in skin temperature generated by the laser stimulator is well-controlled. Our approach could constitute a tool to explore, in humans, the physiological and pathophysiological mechanisms involved in processing C- and Aδ-fibre input, respectively. |
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Researcher | 16 | 15% |
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Student > Bachelor | 10 | 9% |
Professor | 7 | 6% |
Other | 20 | 18% |
Unknown | 15 | 14% |
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Engineering | 18 | 16% |
Medicine and Dentistry | 16 | 15% |
Agricultural and Biological Sciences | 12 | 11% |
Psychology | 5 | 5% |
Other | 10 | 9% |
Unknown | 22 | 20% |