Spatial Working Memory Dysfunction In Minimal Hepatic Encephalopathy: Ethology And BOLD- FMRI Study

Objective: Using ethology and BOLD-fMRI to explore the neural basis of spatial working memory impairment in mild hepatic encephalopathy.Methods: 12 patients with mild hepatic encephalopathy and 12 normal controls were matched for Wechsler Memory scale-Chinese revised (WMS-CR) and brain fMRI scanning of n-back task. The number connection test A (NCT-A) and digit symbol test (DST) were used to select subjects of mild hepatic encephalopathy from the liver cirrhosis. AFNI software was used to analyze fMRI data.Results: In WMS-CR test, the scores of patients with mild hepatic encephalopathy were lower than that of normal controls in the 100â†'1, pictures, regeneration, recognition, touch, understand, association, back number and total memory quotient (P<0.05).In the n-back task, the accuracy and average response time of patients with mild hepatic encephalopathy have no significant difference from the normal control group in the 0-back task(P>0.05);the accuracy of patients with mild hepatic encephalopathy was lower than the control group in the 1-back task, there was significant difference (P<0.01), but the average response time has no significant difference (P>0.05); the accuracy of patients with mild hepatic encephalopathy was lower than the control group, and the average response time was also significantly longer than the control group in the 2-back conditions, there were significant differences (P<0.001).fMRI study found that, the neural network of bilateral prefrontal cortex (PFC), bilateral premotor area (PreMA), supplementary motor area (SMA) and bilateral parietal area (PA) was activated in n-back task. Quantitative analysis of regions of interest (ROIs) found that, all of working memory-related brain regions showed memory load-related load effect in the control group, but only PreMA and PA showed the load effect in patients with mild hepatic encephalopathy, other working memory-related brain regions did not show similar trends. Comparing the groups found that, the activation intensity of working memory-related brain regions of patients with mild hepatic encephalopathy were smaller than the control group in three different Memory loads. Further group analysis showed that, as memory load increased, the activation intensity of working memory-related brain regions of the control group was increasing, and the peak of BOLD signal was rising; but only PreMA and PA showed obvious increase of activation intensity in patients with mild hepatic encephalopathy, other working memory-related brain regions did not show the memory load-related load effect, this was consistent with the result of quantitative analysis of BOLD signal changes of ROIs.Conclusion: These results indicated that patients with mild hepatic encephalopathy had impairment in spatial working memory, and the weakened function of bilateral PFC (BA9/10/46/47), PreMA (BA6), SMA (BA8), and bilateral PA (BA7/40) may be one of the neural mechanisms.