Department of Psychiatry, Radboud University Medical Center, Postbus 9101, 6500 HB Nijmegen, The Netherlands; Donders Institute for Brain, Cognition and Behaviour, Radboud University, Postbus 9104, HE Nijmegen, The Netherlands.
Donders Institute for Brain, Cognition and Behaviour, Radboud University, Postbus 9104, HE Nijmegen, The Netherlands; Experimental Psychopathology and Treatment, Behavioural Science Institute Radboud University Nijmegen, Postbus 9104, 6500 HE Nijmegen, The Netherlands.
Brain Behav Immun. 2023 Aug;112:235-245. doi: 10.1016/j.bbi.2023.05.013. Epub 2023 May 29.
Earlier work within the physical domain showed that acute inflammation changes motivational prioritization and effort allocation rather than physical abilities. It is currently unclear whether a similar motivational framework accounts for the mental fatigue and cognitive symptoms of acute sickness. Accordingly, this study aimed to assess the relationship between fatigue, cytokines and mental effort-based decision making during acute systemic inflammation.
Eighty-five participants (41 males; 18-30 years (M = 23.0, SD = 2.4)) performed a mental effort-based decision-making task before, 2 h after, and 5 h after intravenous administration of 1 ng/kg bacterial lipopolysaccharide (LPS) to induce systemic inflammation. Plasma concentrations of cytokines (interleukin (IL)-6, IL-8 and tumor necrosis factor (TNF)) and fatigue levels were assessed at similar timepoints. In the task, participants decided whether they wanted to perform (i.e., 'accepted') arithmetic calculations of varying difficulty (3 levels: easy, medium, hard) in order to obtain rewards (3 levels: 5, 6 or 7 points). Acceptance rates were analyzed using a binomial generalized estimated equation (GEE) approach with effort, reward and time as independent variables. Arithmetic performance was measured per effort level prior to the decisions and included as a covariate. Associations between acceptance rates, fatigue (self-reported) and cytokine concentration levels were analyzed using partial correlation analyses.
Plasma cytokine concentrations and fatigue were increased at 2 h post-LPS compared to baseline and 5 h post-LPS administration. Acceptance rates decreased for medium, but not for easy or hard effort levels at 2 h post-LPS versus baseline and 5 h post-LPS administration, irrespective of reward level. These reductions in acceptance rates occurred despite improved accuracy on the arithmetic calculations itself. Reduced acceptance rates for medium effort were associated with increased fatigue, but not with increased cytokine concentrations.
Fatigue during acute systemic inflammation is associated with alterations in mental effort allocation, similarly as observed previously for physical effort-based choice. Specifically, willingness to exert mental effort depended on effort and not reward information, while task accuracy was preserved. These results extend the motivational account of inflammation to the mental domain and suggest that inflammation may not necessarily affect domain-specific mental abilities, but rather affects domain-general effort-allocation processes.
早期在物理领域的研究表明，急性炎症会改变动机的优先级和努力分配，而不是身体能力。目前尚不清楚类似的动机框架是否可以解释急性疾病的精神疲劳和认知症状。因此，本研究旨在评估疲劳、细胞因子与急性全身性炎症期间基于心理努力的决策之间的关系。
85 名参与者（41 名男性；18-30 岁（M=23.0，SD=2.4））在静脉注射 1ng/kg 细菌脂多糖（LPS）诱导全身性炎症之前、2 小时后和 5 小时后进行了基于心理努力的决策任务。在相似的时间点评估细胞因子（白细胞介素 (IL)-6、IL-8 和肿瘤坏死因子 (TNF))和疲劳水平的血浆浓度。在任务中，参与者决定他们是否愿意（即“接受”）进行不同难度（3 个级别：简单、中等、困难）的算术计算以获得奖励（3 个级别：5、6 或 7 分）。使用二项广义估计方程 (GEE) 分析接受率，努力、奖励和时间作为独立变量。在做出决策之前，根据努力水平测量了算术表现，并将其作为协变量包括在内。使用偏相关分析分析接受率、疲劳（自我报告）和细胞因子浓度水平之间的关系。
与 LPS 给药前和 5 小时后相比，LPS 给药后 2 小时血浆细胞因子浓度和疲劳增加。与 LPS 给药前和 5 小时后相比，接受率在 2 小时后对于中等难度的任务降低，但对于简单或困难难度的任务没有降低，无论奖励水平如何。尽管算术计算本身的准确性提高，但接受率的降低仍发生。对于中等难度的任务，接受率的降低与疲劳增加有关，但与细胞因子浓度增加无关。
急性全身性炎症期间的疲劳与心理努力分配的改变有关，这与之前观察到的物理努力选择类似。具体而言，意愿付出心理努力取决于努力，而不是奖励信息，同时保持任务准确性。这些结果将炎症的动机解释扩展到心理领域，并表明炎症不一定会影响特定于域的心理能力，而是会影响域一般的努力分配过程。
