PMID- 20592123
OWN - NLM
STAT- MEDLINE
DCOM- 20110830
LR  - 20101005
IS  - 1522-1598 (Electronic)
IS  - 0022-3077 (Linking)
VI  - 104
IP  - 4
DP  - 2010 Oct
TI  - Stimulus novelty, and not neural refractoriness, explains the repetition 
      suppression of laser-evoked potentials.
PG  - 2116-24
LID - 10.1152/jn.01088.2009 [doi]
AB  - Brief radiant laser pulses selectively activate skin nociceptors and elicit 
      transient brain responses (laser-evoked potentials [LEPs]). When LEPs are 
      elicited by pairs of stimuli (S1-S2) delivered at different interstimulus 
      intervals (ISIs), the S2-LEP is strongly reduced at short ISIs (250 ms) and 
      progressively recovers at longer ISIs (2,000 ms). This finding has been 
      interpreted in terms of order of arrival of nociceptive volleys and 
      refractoriness of neural generators of LEPs. However, an alternative explanation 
      is the modulation of another experimental factor: the novelty of the eliciting 
      stimulus. To test this alternative hypothesis, we recorded LEPs elicited by pairs 
      of nociceptive stimuli delivered at four ISIs (250, 500, 1,000, 2,000 ms), using 
      two different conditions. In the constant condition, the ISI was identical across 
      the trials of each block, whereas in the variable condition, the ISI was varied 
      randomly across trials and single-stimulus trials were intermixed with paired 
      trials. Therefore the time of occurrence of S2 was both less novel and more 
      predictable in the constant than in the variable condition. In the constant 
      condition, we observed a significant ISI-dependent suppression of the biphasic 
      negative-positive wave (N2-P2) complex of the S2-LEP. In contrast, in the 
      variable condition, the S2-LEP was completely unaffected by stimulus repetition. 
      The pain ratings elicited by S2 were not different in the two conditions. These 
      results indicate that the repetition-suppression of the S2-LEP is not due to 
      refractoriness in nociceptive afferent pathways, but to a modulation of novelty 
      and/or temporal predictability of the eliciting stimulus. This provides further 
      support to the notion that stimulus saliency constitutes a crucial determinant of 
      LEP magnitude and that a significant fraction of the brain activity time-locked 
      to a brief and transient sensory stimulus is not directly related to the quality 
      and the intensity of the corresponding sensation, but to bottom-up attentional 
      processes.
FAU - Wang, A L
AU  - Wang AL
AD  - Department of Neuroscience, Physiology and Pharmacology, University College 
      London, London, UK.
FAU - Mouraux, A
AU  - Mouraux A
FAU - Liang, M
AU  - Liang M
FAU - Iannetti, G D
AU  - Iannetti GD
LA  - eng
GR  - Biotechnology and Biological Sciences Research Council/United Kingdom
PT  - Comparative Study
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20100630
PL  - United States
TA  - J Neurophysiol
JT  - Journal of neurophysiology
JID - 0375404
SB  - IM
MH  - Adult
MH  - Electroencephalography/methods
MH  - Evoked Potentials, Somatosensory/*physiology
MH  - Female
MH  - Humans
MH  - *Lasers
MH  - Male
MH  - Middle Aged
MH  - Neurons/physiology
MH  - Nociceptors/*physiology
MH  - Refractory Period, Electrophysiological/*physiology
MH  - Time Factors
MH  - Young Adult
EDAT- 2010/07/02 06:00
MHDA- 2011/08/31 06:00
CRDT- 2010/07/02 06:00
PHST- 2010/07/02 06:00 [entrez]
PHST- 2010/07/02 06:00 [pubmed]
PHST- 2011/08/31 06:00 [medline]
AID - jn.01088.2009 [pii]
AID - 10.1152/jn.01088.2009 [doi]
PST - ppublish
SO  - J Neurophysiol. 2010 Oct;104(4):2116-24. doi: 10.1152/jn.01088.2009. Epub 2010 
      Jun 30.