EEG and laser stimulation as tools for pain research.

Laser heat stimulators selectively activate Adelta and C-nociceptors in the superficial layers of the skin. Their high power output produces steep heating ramps, which improve synchronization of afferent volleys and therefore allow the recording of time-locked events, such as laser-evoked brain potentials. Study of the electrical brain activity evoked by Adelta- and C-nociceptor afferent volleys revealed the existence of an extensive, sequentially activated, cortical network. These electrophysiological responses are modulated by stimulus-driven and, even more extensively, top-down processes. The specificity and validity of these components for pain research are currently under intense scrutiny.