Performance-dependent inhibition of pain by an executive working memory task

Abstract

It is widely assumed that distraction reduces pain. Similarly, it is assumed that pain distracts from concurrent, unrelated cognitive processing, reducing performance on difficult tasks. Taken together, these assumptions suggest pain processing and cognitive function engage an overlapping set of domain-general, capacity-limited mental resources. However, experimental tests of this proposal have yielded mixed results, leading to alternative proposals that challenge the common model of a bidirectional relationship between concurrent pain and task performance. We tested these contrasting positions using a novel concurrent pain and executive working memory paradigm. Both task difficulty and nociceptive stimulus intensity were individually calibrated for each participant. Participants reported less pain during the working memory task than a visually matched control condition. Conversely, increasing levels of heat incrementally reduced task performance. Path analyses showed that variations in pain completely mediated this effect, and that even within a given heat level, trial-by-trial fluctuations in pain predicted decrements in performance. In sum, these findings argue that overlapping cognitive resources play a role in both pain processing and executive working memory. Future studies could use this paradigm to understand more precisely which components of executive function or other cognitive resources contribute to the experience of pain.

Fig. 1

Conceptual model of the relationship between pain and performance. Three general hypotheses can be tested to evaluate this model: I. Pain ratings or other indices of pain experience are reduced by unrelated, concurrent, cognitive demand; II. cognitive performance is reduced by concurrent pain; III. A negative relationship exists between trial-by-trial fluctuations of performance and pain, even within a given heat level.

Fig. 2

Timeline of single trial.

Fig. 3

The effect of task demand on pain. Error bars reflect within-subject standard error computed using pooled variance from the Participant × Performance and Participant × Performance × Heat Level interactions [47].

Fig. 4

The effect of heat level on performance. Error bars reflect within-subject standard error of the Participant × Heat Level interaction. The mean within-subject standard deviations of A were .14, .14, and .16 for low, medium, and high levels of heat, respectively.

Fig. 5

The relationship between pain and performance. For visualization, performance data were binned into quintiles based on pain ratings.

Fig. 6

Summary of mediation results for Working Memory Load trials. A first mediation analysis assessed whether Pain (M₁) mediated the relationship between Heat level (X₁) and Performance (Y₁): a₁: the relationship between Heat Level and Pain; b₁: the relationship between Pain and Performance, controlling for Heat Level; c₁: the observed relationship between Heat level and Performance; c′₁: the relationship between Heat Level and Performance, controlling for a₁ and b₁. A second mediation analysis assessed whether trial-by-trial fluctuations in Performance (M₂) mediated the relationship between Heat Level (X₂) and Pain (Y₂): a₂: the relationship between Heat Level and Performance; b₂: the relationship between Performance and Pain, controlling for Heat Level; c₂: the observed relationship between Heat Level and Pain; c′₂: the relationship between Heat Level and Pain, controlling for a₂ and b₂. * p< .05. **p< .001.