Modulation of auditory sensory memory by chronic clinical pain and acute experimental pain: a mismatch negativity study

Pain, especially chronic pain, can lead to cognitive deficits. Mismatch negativity (MMN) is a change-specific component of the auditory event-related brain potential (ERP) that is thought to provide a unique window into sensory memory processes. The present study was designed to determine how chronic and acute pain affects auditory sensory memory. In experiment 1, MMNs elicited by standard and deviant auditory stimuli at short and long inter-stimulus intervals (ISIs) were compared between trigeminal neuralgia (TN) patients and demographically matched healthy controls (HCs). The TN patients were found to have stronger attenuation of the MMN at longer ISIs than HCs. Correlation analysis revealed a significant positive correlation between the sensory subscale of McGill Pain Questionnaire and MMN amplitude reduction across ISI conditions. In experiment 2, MMNs recorded before, during, and after the cold pressor test were compared in healthy subjects. MMN amplitude was significantly reduced during pain exposure and recovered immediately thereafter. These results suggest that both chronic pain and acute pain can interfere with automatic change detection processes in the brain. This study provides the first evidence that chronic pain patients have a faster auditory memory trace decay than HCs.

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

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.

Disruption of Attention and Working Memory Traces in Individuals with Chronic Pain

BACKGROUND

Research has found that chronic pain disrupts attention and that this disruption can lead to significant functional impairment and decreased quality of life. We conducted the present study to examine how attention and memory are disrupted by chronic pain.

METHODS

Computerized tests of working memory were given to participants with chronic pain along with a neuropsychological test of attention before and after procedures resulting in analgesia.

RESULTS

Two-thirds of participants with chronic pain had scores in the clinically impaired range on attentional tasks. These results were independent of age, education level, sleep disruption, and pain relief. Medication use was also recorded and is reported to account for potential effects of medication on task performance. Those participants with the highest level of impairment had significantly greater difficulties in maintaining a memory trace during a challenging test of working memory.

CONCLUSIONS

These findings point to a specific cognitive mechanism, the maintenance of the memory trace, that is affected by chronic pain during task performance. Cognitive function was not improved by short-term local analgesia.