Formalin-induced pain prolongs sub- to supra-second time estimation in rats

Xinhe Liu; Ning Wang; Jinyan Wang; Fei Luo

doi:10.7717/peerj.11002

Formalin-induced pain prolongs sub- to supra-second time estimation in rats

PeerJ. 2021 Mar 2:9:e11002. doi: 10.7717/peerj.11002. eCollection 2021.

Authors

Xinhe Liu^{1

2}, Ning Wang^{1

2}, Jinyan Wang^{1

2}, Fei Luo^{1

2}

Affiliations

¹ CAS Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing, China.
² Department of Psychology, University of Chinese Academy of Sciences, Beijing, China.

Abstract

Background: Temporal estimation can be influenced by pain, which is a complex psychological and physiological phenomenon. However, the time range in which perception is most sensitive to pain remains unclear.

Methods: In the present study, we explored the effects of acute inflammatory pain on time perception in the sub- to supra-second (0.6-2.4-s) and supra-second (2-8-s) ranges in rats. Plantar formalin injection was used to induce acute inflammatory pain, and a temporal bisection task was used to measure time perception. Task test sessions were held for five consecutive days (one per day): the day before injection (baseline), immediately after injection, and the three post-injection days. The point of subjective equality (PSE, which reflects the subjective duration) and Weber fraction (which reflects temporal sensitivity) were calculated and analysed.

Results: In the 0.6-2.4-s range, the PSE was significantly lower, indicating prolonged subjective duration, in the formalin group relative to the saline group (p = 0.049) immediately after injection. Formalin-induced pain also tended to lengthened time perception in the 0.6-2.4-s range on post-injection days 2 (p = 0.06) and 3 (p = 0.054). In the 2-8-s range, formalin injection did not affect the PSE or Weber fraction.

Conclusions: The enhanced effect of pain on temporal perception in the sub- to supra-second range is observed in this study and this effect is attenuated with the prolongation of estimated time, even in rats.

Keywords: Formalin-induced pain; Temporal bisection task; Temporal range; Time perception.

Grants and funding

This work was supported by NNSF (National Natural Science Foundation of China) grants to Ning Wang (31671140), Jin-Yan Wang (31271092), and Fei Luo (31970926), grants from CAS Key Laboratory of Mental Health, Institute of Psychology (KLMH 2014G01, KLMH2016K02), and a grant from the initiation fund of the CAS/SAFEA International Partnership Program for Creative Research Teams (Y2CX131003). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.