Rapid deterioration of pain sensory-discriminative information in short-term memory.
The assessment of pain and analgesic efficacy sometimes relies on the retrospective evaluation of pain felt in the immediate, recent or distant past, yet we have a very limited understanding of the processes involved in the encoding, maintenance and intentional retrieval of pain. We examine the properties of the short-term memory of thermal and pain sensation intensity with a delayed-discrimination task using pairs of heat pain, warm and cool stimulation in healthy volunteers. Performance decreased as a function of the inter-stimulus interval (ISI), indicating a robust deterioration of sensory information over the test period of 4-14 s. As expected, performance also decreased with smaller temperature differences (Delta-T) and shorter stimulus durations (6-2 s). The relation between performance and Delta-T was adequately described by a power function, the exponent of which increased linearly with longer ISI. Importantly, performance declined steadily with increasing ISI (from 6 to 14 s)--but only for pairs of heat pain stimuli that were relatively difficult to discriminate (Delta-T < or = 1.0 degree C; perceptual difference < or = 32/100 pain rating units) while no deterioration in performance was observed for the largest temperature difference tested (Delta T = 1.5 degrees C; perceptual difference of 50 units). These results are consistent with the possibility that short-term memory for pain and temperature sensation intensity relies on a transient analog representation that is quickly degraded and transformed into a more resistant but less precise categorical format. This implies that retrospective pain ratings obtained even after very short delays may be rather inaccurate but relatively reliable.
Rainville
Pierre
P
Département de Stomatologie, Faculté de Médecine Dentaire, Université de Montréal, CP 6128, Succursale Centre-ville, Montréal, Que. H3C 3J7, Canada Centre de recherche en sciences neurologique (CRSN), Université de Montréal, CP 6128, Succursale Centre-ville,Montréal, Que. H3C 3J7, Canada Groupe de recherche en neuropsychologie et cognition (GRENEC), Université de Montréal, CP 6128, Succursale Centre-ville, Montréal, Que. H3C 3J7, Canada Groupe de recherche sur le système nerveux central (GRSNC), Université de Montréal, CP 6128, Succursale Centre-ville, Montréal, Que. H3C 3J7, Canada.
Doucet
Jean-Charles
JC
Fortin
Marie-Chantale
MC
Duncan
Gary H
GH
D000704:Analysis of Variance; D004192:Discrimination, Psychological / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D010146:Pain / Q000503:physiopathology* / Q000523:psychology; D010147:Pain Measurement / Q000379:methods*; D013997:Time Factors