Differential effects on the laser evoked potential of selectively attending to pain localisation versus pain unpleasantness.
OBJECTIVE
To determine the effects on the laser evoked potential (LEP) of selectively attending to affective (unpleasantness) versus sensory-discriminative (localisation) components of pain.


METHODS
LEPs, elicited by painful CO2 laser stimulation of two areas of the right forearm, were recorded from 62 electrodes in 21 healthy volunteers, during three tasks that were matched for generalised attention: Localisation (report stimulus location), Unpleasantness (report stimulus unpleasantness), Control (report pain detection). LEP components are named by polarity, latency, and electrode.


RESULTS
N300-T7 peak amplitude was significantly greater during Localisation than Unpleasantness. The difference in N300-T7 amplitude between Localisation and Control approached significance, suggesting an increased amplitude in Localisation compared with Control, rather than a reduced amplitude in Unpleasantness. Peak amplitude, latency, and topography of N300-FCz, P450, P600-800 (early P3) and P800-1000 (late P3) did not differ significantly between tasks.


CONCLUSIONS
These results suggest that the N300-T7 LEP peak reflects the activity of cerebral generators involved in the localisation of pain. The topography of N300-T7 is consistent with a source in contralateral secondary somatosensory cortex/insula and maybe primary somatosensory cortex.


CONCLUSIONS
This study confirms a role of the lateral pain system in the localisation of pain, and distinguishes it from stimulus novelty or attention.
Bentley
D E
DE
Human Pain Research Group, University of Manchester Rheumatic Diseases Centre, Clinical Sciences Building, Hope Hospital, Salford M6 8HD, UK. deborah.bentley@man.ac.uk
Watson
A
A
Treede
R-D
RD
Barrett
G
G
Youell
P D
PD
Kulkarni
B
B
Jones
A K P
AK
D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D007834:Lasers / Q000009:adverse effects*; D008297:Male; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods*; D011930:Reaction Time / Q000502:physiology