Cognitive fatigue and cortical-striatal network in old age

Figures

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  Figure 1. Cognitively demanding tasks used to induce CF. (A) The experimental paradigm included two cognitively fatiguing tasks during fMRI scanning, in a random order, across subjects. (B) Dual-1 back task was a letter-location task. (C) The Color-word Stroop task consisted of congruent and incongruent conditions on color.

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  Figure 2. CF profile for the entire sample. (A) The distribution of CF change (post-pre) induced by cognitive tasks during fMRI scanning. According to different perceived fatigue, two groups were selected: low-CF subgroup (12 subjects with CF change ≤ 0, shown in blue) and high-CF subgroup (14 subjects with CF change ≥ 1, shown in red). In addition, there were 20 subjects outside the high- or low-CF subgroups (shown in grey). (B) The VAS fatigue score before and after performing cognitive tasks for each group, showing significant difference between high- and low-CF subgroup. (C) The IIVRT in Block1 and Block6 for each group showed the performance change with time by CF subgroups. There were significant different trends in IIVRT change between high- and low-CF subgroup. (D) Higher CF was significantly associated with larger IIVRT change (worse cognitive performance). Note: CF, cognitive fatigue; IIVRT, intra-individual variability of reaction time. low-CF subgroup: blue; high-CF subgroup: red; others: gray.

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  Figure 3. The interaction effects of CF subgroup and task block on left and right cortical-striatal network connectivity. For the left cortical-striatal network, there were significant differences of connectivity change in L SFG, R ACC, L PCC and R Cuneus. For the right cortical-striatal network, there were significant differences of connectivity change in L MFG, L MFG2, L MedFG and L OG. During the fatiguing tasks, the connectivity strength of cortical-striatal network increased in low-CF group, while deceased in high-CF group. Note: L, left; R, right; SFG, superior frontal gyrus; ACC, anterior cingulate cortex; PCC, posterior cingulate cortex; MedFG, medial frontal gyrus, MFG, middle frontal gyrus; OG, occipital gyrus. CF, cognitive fatigue.

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  Figure 4. Correlations between connectivity change and CF in the entire sample. In the cortical-striatal network, the partial correlation analysis showed CF change was significantly correlated with the anterior regions, including L SFG, R ACC, L MFG, LMFG2 and L MedFG. The CF change showed negative correlation trend with the posterior regions but not significant, including L PCC, R Cuneus and L OG. Note: L, left; R, right; SFG, superior frontal gyrus; ACC, anterior cingulate cortex; PCC, posterior cingulate cortex; MedFG, medial frontal gyrus, MFG, middle frontal gyrus; OG, occipital gyrus. p values here are FDR-corrected across all regions. CF, cognitive fatigue; IIVRT, intra-individual variability of reaction time.

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  Figure 5. Relationships between the anterior and posterior cortical-striatal network functional connectivity and CF. (A) During the cognitively fatiguing tasks, both of the anterior and posterior network showed significant interaction effects between subgroup (high- vs. low-CF) and block (1 vs. 6), that connectivity strength increased in low-CF group while decreased in high-CF group (B) Although CF was negatively associated with change of anterior or posterior connectivity, the negative relationship was more robust in anterior cortical-striatal network. Note: CF, cognitive fatigue; IIVRT, intra-individual variability of reaction time.

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  Figure 6. Moderation analysis of relationship between PAS and cognitive function. There was a significant interacting effect between CF and PAS in predicting task performance, showing greater PAS was related to better cognitive performance (smaller IIVRT) in the low-CF subgroup while worse cognitive performance (larger IIVRT) in the high-CF subgroup. Consistently, CF also significantly interacted with PAS in predicting executive function. Note: CF, cognitive fatigue; IIVRT, intra-individual variability of reaction time. PAS, posterior-anterior shifting.