A bioadaptive approach for experimental pain research in humans using laser-evoked brain potentials

In order to find an experimental approach counteracting habituation in experimental pain research using short infrared laser stimulation in humans we developed a bioadaptive method based on subject's report on painfulness of stimulation (pain report; PR). After determination of the initial relationship between the energy of the laser stimulus and the corresponding PRs, the approach continuously adjusts the intensity of noxious stimuli so that PR is kept constant across time. Each difference between the PR evoked by the actual laser stimulus and the desired PR leads to an increase or decrease of the laser output energy value for the next stimulation with the desired PR proportional to the PR difference as well as to the slope of the initial correlation function between laser energy and corresponding PRs. This method has been applied in a study with nine volunteers. Results show that the approach leads to a constant PR by increasing the laser output energy by 0.01 mJ/s per mm2 on the average. Furthermore, an analysis of the laser-evoked brain potentials (LEPs) recorded from Cz was performed for the first and second half of stimuli. However, no significant changes in latencies or amplitudes of the main LEP components recorded at 210 ms (N210) and 350 ms (P350) were found. The method seems to be useful for different approaches in experimental and clinical pain research.

[1]  L. Plaghki,et al.  Direct isolation of ultra-late (C-fibre) evoked brain potentials by CO2 laser stimulation of tiny cutaneous surface areas in man , 1996, Neuroscience Letters.

[2]  K L Casey,et al.  Variability of laser-evoked potentials: attention, arousal and lateralized differences. , 1993, Electroencephalography and clinical neurophysiology.

[3]  J. Spiegel,et al.  Laser-evoked potentials after painful hand and foot stimulation in humans: evidence for generation of the middle-latency component in the secondary somatosensory cortex , 1996, Neuroscience Letters.

[4]  C. Braun,et al.  Somatosensory event-related potentials to painful and non-painful stimuli: effects of attention , 1989, Pain.

[5]  R. Treede,et al.  Laser-evoked cerebral potentials in the assessment of cutaneous pain sensitivity in normal subjects and patients. , 1991, Revue neurologique.

[6]  Christoph Braun,et al.  Habituation of subjective ratings and event-related potentials to painful intracutaneous electrical stimulation of the skin , 1987 .

[7]  B. Bromm,et al.  Laser evoked brain potentials in response to painful trigeminal nerve activation. , 1995, The International journal of neuroscience.

[8]  Burkhart Bromm,et al.  Response plasticity of pain evoked reactions in man , 1982, Physiology & Behavior.

[9]  H. Sauer,et al.  Internal consistency of dipole localizations for the human movement-evoked magnetic field component 1 (MEF 1) , 1996, Neuroscience Letters.

[10]  R. Treede,et al.  Equivalent electrical source analysis of pain-related somatosensory evoked potentials elicited by a CO2 laser. , 1993, Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society.

[11]  A. M. Purves,et al.  Time-shifted averaging for laser evoked potentials. , 1993, Electroencephalography and clinical neurophysiology.