Background & Aims

Along with generalized musculoskeletal pain, cognitive dysfunction is widely reported in fibromyalgia patients, including problems with memory and attention. Studies have found deficits in executive function in this group, particularly affecting inhibitory control and working memory [1]. Several cognitive tasks have been proposed to evaluate the executive domains. In particular, change detection (CD) tasks have been proposed to evaluate the storage capacity of working memory. On the other hand, n-back tasks have been used to evaluate not only working memory capacity, but also the maintenance and manipulation of the stored information [2]. In this study, we propose to use CD and n-back tasks to quantitatively evaluate cognitive impairment reported by fibromyalgia patients.

Methods

Sixteen fibromyalgia patients and 15 healthy controls participated in a single experimental session which consisted of 10 blocks of a CD task and 5 blocks of an n-back task, presented on a computer screen. For the CD task, an arrow indicating the side of the screen to memorize appeared for 1100 ms, followed by coloured squares for 250 ms. After a retention interval of 1300 ms, a new array of coloured squares appeared, in which the volunteer had to decide whether it matched the one presented earlier or not . The task had three levels of cognitive load (2, 4 and 6 squares) and each block consisted of 10 trials per level. For the n-back task, each block consisted of 62 consecutive letters. The volunteer had to decide if the current letter matched the letter presented 2 positions back in the sequence (2-back). The outcomes for the CD task were the hit rate (HR) and reaction time (RT), and for the n-back task were the HR, the false alarm rate (FA) and the RT.

Results

For the CD task, the HR for controls was 93.3±4.27% when the task involved 2 squares, 87.4±6.16% for 4 squares and 79.4±6.73% for 6 squares. For patients, the HR was 86.5±15% for 2 coloured squares, 76.2±11.6% for 4 squares and 71.7±10.3% for 6 squares. The statistical analysis revealed significant differences between the different memory loads (p<0.001 for all pairwise comparisons), and between groups (p=0.014). The RTs were 1053 [368] ms for 2, 1304 [461] ms for 4 and 1448 [642] ms for 6 squares. For controls, RT was 857 [213] ms for 2, 955 [259] ms for 4 and 1054 [212] ms for 6 squares. By fitting a generalized mixed model, we found a significant main effect for cognitive load (p<0.001). For the n-back task, the mean HR was 86.4±12.3% for controls and 78.5±21.7% for patients. The FA rate was 7.9±6.11% for controls and 12.1±9.52% for patients. Finally, the RT was 561[174] ms for controls and 594[104] ms for patients. No significant differences were observed in these variables.

Conclusions

The study employed two cognitive tests, namely CD and n-back task, to assess potential differences in working memory between healthy volunteers and fibromyalgia patients. The CD task revealed differences in hit rates between the different cognitive loads and between groups. The effect size (~9%) was consistent across cognitive loads and we did not observe a significant interaction, implying that the difference between groups is independent of the cognitive load. On the other hand, we did not observe significant differences on the behavioral measures for the n-back task between groups. Even though the hit rate in the n-back task presented a similar effect size compared to the CD task, the variability was twice as large. With clinical applications in mind, these results support the use of CD tasks for quantitative assessment of fibrofog.

References

[1]T. Bell et al., “Meta-analysis of cognitive performance in fibromyalgia,” J. Clin. Exp. Neuropsychol., vol. 40, no. 7, pp. 698–714, Aug. 2018, doi: 10.1080/13803395.2017.1422699.
[2]M. A. Shalchy, V. Pergher, A. Pahor, M. M. Van Hulle, and A. R. Seitz, “N-Back Related ERPs Depend on Stimulus Type, Task Structure, Pre-processing, and Lab Factors,” Front. Hum. Neurosci., vol. 14, p. 549966, Oct. 2020, doi: 10.3389/fnhum.2020.549966.

Presenting Author

Elizabeth Young

Poster Authors

Elizabeth Young

MSc

National Scientific and Technical Research Council (CONICET)

Lead Author

E-mail

Christian Mista

PhD

Institute for Research and Development in Bioengineering and Bioinformatics (IBB) CONICET-UNER

Lead Author

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Diego Arévalo

MSc Biomed Eng)

Institute for Research and Development in Bioengineering and Bioinformatics (IBB) CONICET-UNER

Lead Author

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Daiana Piccard

National University of Entre Ríos- Faculty of Engineering

Lead Author

E-mail

Yanina Atum

PhD

National University of Entre Ríos- Faculty of Engineering

Lead Author

E-mail

Jose Alberto Biurrun Manresa

National Scientific and Technical Research Council (CONICET)

Lead Author

E-mail

Topics

  • Specific Pain Conditions/Pain in Specific Populations: Fibromyalgia