Memory and pain: tests of mood congruity and state dependent learning in experimentally induced and clinical pain

Abstract

The associative network theory of memory [2] is outlined along with the concepts of mood congruity and state dependent learning. Two experiments are reported which investigate the occurrence of these effects where memory for pain is concerned. In experiment 1 the performance of 25 chronic pain patients was compared with that of 25 non-patient controls on a test involving both immediate and delayed recall of a mixed list of stimulus words of 3 types: pain-related, negative or neutral. No significant group differences were found in overall rates of immediate recall. As predicted, however, pain patients recalled more pain-related words than non-patient controls ( P < 0.001). On delayed recall the same significant group × word-type interaction was obtained ( P < 0.02), but in addition the non-patient controls recalled significantly more words overall ( P < 0.02). These results provide some evidence for the occurrence of a mood congruity effect. Experiment 2 investigated state dependent learning and mood congruity effects in experimentally induced pain. Twenty volunteer subjects were allocated to 1 of 4 conditions in which a wordlist (as in experiment 1) was presented following either a painful stimulus (cold pressor test) or a non-painful one (warm water) and was then recalled immediately following further exposure to stimulus conditions which were congruent with the original stimulus (warm/warm and cold/cold conditions) or non-congruent (warm/cold and cold/warm conditions). A 3-way split plot ANOVA yielded no significant main effects for group or word-type, but a significant interaction emerged between state at encoding and at recall ( P < 0.04). The results provided some support for the occurrence of a state dependent learning effect but no evidence of a mood congruity effect. It is concluded that mood congruity effects in memory for pain may be more related to the status of being a chronic pain patient than to the state of being in pain.