Laser-evoked potentials in human pain

In Part I, this Focus article describes characteristics of laser-evoked brain potentials (LEPs) in human pain and examines some of the methodological inconsistencies. Evidence both cautioning and supporting the use of LEPs is contrasted. A host of neurological mechanisms clearly illustrates the relation of LEPs and pain processing: Lasers elicit selectively the cutaneous receptors of thin afferent fibers, the anterolateral spinal tract, and the lateral tracts of the brainstem. Implication for clinical use is briefly suggested. We raise three contending issues: (1) measurement standard, (2) association and dissociation of the LEP amplitude and pain, and (3) dynamic spatiotemporal specificity of LEPs. We conclude that LEPs may reflect nociceptive processing but may not be the entire pain experience. We emphasize the proper use of LEPs in understanding the mechanisms of nociceptive activation in pain experience. To achieve this, we address the technological advance required in studying the dynamic spatiotemporal specificity of LEPs and human pain.