Abstract
Hemodialysis (HD) is associated with cognitive impairment in patients with end-stage renal disease (ESRD). However, the neural mechanism of spatial working memory (SWM) impairment in HD-ESRD patients remains unclear. We investigated the abnormal alterations in SWM-associated brain activity patterns in HD-ESRD patients using blood oxygen level-dependent functional magnetic resonance imaging (BOLD-fMRI) technique during n-back tasks. Twenty-two HD-ESRD patients and 22 well-matched controls underwent an fMRI scan while undergoing a three-load n-back tasks with different difficulty levels. Cognitive and mental states were assessed using a battery of neuropsychologic tests. The HD-ESRD patients exhibited worse memory abilities than controls. Compared with the control group, the HD-ESRD patient group showed lower accuracy and longer response time under the n-back tasks, especially in the 2-back task. The patterns of brain activation changed under different working memory loads in the HD-ESRD patients, showing decreased activity in the right medial frontal gyrus and inferior frontal gyrus under 0-back and 1-back task, while more decreased activation in the bilateral frontal cortex, parietal lobule, anterior/posterior cingulate cortex and insula cortex under 2-back task. With the increase of task difficulty, the activation degree of the frontal and parietal cortex decreased. More importantly, we found that lower activation in frontal cortex and parietal lobule was associated with worse cognitive function in the HD-ESRD patients. These results demonstrate that the abnormal brain activity patterns of frontal cortex and parietal lobule may reflect the neural mediation of SWM impairment.
Highlights
Cognitive impairment is common in patients with chronic kidney disease (Pi et al 2016), especially those with endstage renal disease (ESRD) who are on hemodialysis (HD) (Chen et al 2015)
Cognitive function was assessed using Montreal Cognitive Assessment (MoCA) for all subjects (Table 2), resulting in HD-ESRD patients showing poorer total scores for MoCA compared with controls (HDESRD patients: 23.67 ± 3.26, Controls: 28.67 ± 0.65, P < 0.01), with statistically significant differences between the two groups on abstractness and memory tests (Ps < 0.05), and visuospatial/executive function, attention, and language tests (Ps < 0.01), but no significant differences were observed for naming and orientation (Ps > 0.05)
Wechsler Memory Scale (WMS) test was used to assess memory function for all subjects (Table 3), HD-ESRD patients had poorer total scores compared with the controls (HD-ESRD patients: 96.9 ± 4.68, Controls: 103.0 ± 5.25, P < 0.01), but no significant differences in personal experience, orientation, or 1 → 100 subtest of mental control and figural memory (Ps > 0.05), while for other subtests there were statistically significant differences between the two groups, especially for associative learning and memory quotient (Ps < 0.01)
Summary
Cognitive impairment is common in patients with chronic kidney disease (Pi et al 2016), especially those with endstage renal disease (ESRD) who are on hemodialysis (HD) (Chen et al 2015). There is growing evidence of cognitive deficits in HD-ESRD patients, including impaired attention, cognitive slowing, impaired executive function, disorientation, memory and language impairment (Hermann et al 2014; Murray et al 2006; Murray 2008). This may affect their later treatment, such as dietary adjustments and drug adherence.
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