title: Parallel spinal pathways generate the middle-latency N1 and the late P2 components of the laser evoked potentials.
abstract: OBJECTIVE
  To investigate the possible presence of multiple spino-thalamic pathways with different conduction velocities (CVs) in the human spinal cord.
  
  
  METHODS
  Laser evoked potentials (LEPs) were recorded in 10 healthy subjects after stimulation of the dorsal midline at four vertebral level: C5, T2, T6, and T10. This method allowed us to minimize the influence of the conduction in the peripheral fibers and to calculate the spinal CV in two different ways: (1) the reciprocal of the slope of the regression line was obtained from the latencies of the different LEP components, and (2) the distance between C5 and T10 was divided by the latency difference of the responses at the two sites. In particular, we considered the middle-latency N1 potential (latencies of around 135, 150, 157, and 171 ms after stimulation at C5, T2, T6, and T10 levels, respectively), which is generated in the second somatosensory (SII) area, and the late P2 response (latencies of around 336, 344, 346, and 362 ms after stimulation at C5, T2, T6, and T10 levels, respectively), which is generated in the anterior cingulate cortex (ACC).
  
  
  RESULTS
  The calculated CV of the spinal fibers generating the N1 potential (around 9 m/s) was significantly different (P<0.05) from the one of the pathway producing the P2 response (around 13 m/s).
  
  
  CONCLUSIONS
  Our results suggest that the N1 and the P2 LEP components are generated by two parallel spinal pathways.
  
  
  CONCLUSIONS
  Both the N1 and P2 potentials should be recorded in the clinical routine since a dissociated abnormality of either response may be found in lesions of the nociceptive system not only in the brain, but also at spinal cord level.
authors: Divisione di Neurologia, Ospedale Pediatrico Bambino Gesù, IRCCS, Roma, Italy. m.valeriani@tiscali.it
authors: Massimiliano
authors: M
authors: Valeriani
authors: Domenica
authors: D
authors: Le Pera
authors: Domenico
authors: D
authors: Restuccia
authors: Liala
authors: L
authors: de Armas
authors: Roberto
authors: R
authors: Miliucci
authors: Viviana
authors: V
authors: Betti
authors: Federico
authors: F
authors: Vigevano
authors: Pietro
authors: P
authors: Tonali
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D007834:Lasers; D008297:Male; D009412:Nerve Fibers / Q000502:physiology; D009431:Neural Conduction / Q000502:physiology; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D012879:Skin Physiological Phenomena; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*; D013133:Spinothalamic Tracts / Q000166:cytology / Q000502:physiology*