N. Forss, R. Hari, E. Kirveskari, M. Pohja, T. Raij, and N. Vartiainen
Collaborators:
Helsinki University Central Hospital
Charles University, Prague, Czech Republic
One serious problem in experimental pain research is stimulus nonselectivity. With small modifications to the intensity and area of stimulation with a thullium laser, we have recently been able to selectively stimulate the two nociceptive fibre systems, A_- and C-fibres; the corresponding responses in the secondary somatosensory cortex SII peaked at 150-200 ms and at 800-850 ms. Such a reliable temporospatial differentiation of cortical responses to "first" and "second" pain offers an unique tool for further basic research as well as for clinical assesment of patients with chronic pain.
We are also interested in the connection between pain and motor activation. Our preliminary data indicate that noxious stimuli may automatically activate the motor cortex, an apparenly useful phenomenon in acute pain but a source of a vicious cycle during chronic (tension) pain. We have studied the pain-motor cortex connection in healthy subjects by monitoring the reactivity of the 20-Hz motor-cortex rhythms.