cortical activation changes during repeated laser stimulation a magnetoencephalographic study皮质激活变化重复magnetoencephalographic研究激光刺激.pdf

Cortical Activation Changes during Repeated Laser Stimulation: A Magnetoencephalographic Study 1,2 3 4 Andrej Stancak *, Jamaan Alghamdi , Turo J. Nurmikko 1 Department of Experimental Psychology, Institute of Psychology, Health, and Society, University of Liverpool, Liverpool, United Kingdom, 2 Third Faculty of Medicine, Charles University Prague, Prague, Czech Republic, 3 Department of Cellular and Molecular Biology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom, 4 Unit of Neuroscience, Pain Research Institute, Institute of Aging and Chronic Disease, University of Liverpool, Liverpool, United Kingdom 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 stimution, 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 (4.8uC) increase of skin temperature from the first stimulus to the tenth stimulus. The mean reaction time, evaluated in six subjects, was 1.33 s