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Post-stroke memory dysfunction (PMD) is one of the most common forms of cognitive impairment among stroke survivors. However, only a limited number of studies have directly investigated the neural mechanisms associated with memory decline. The aim of the present study was to identify dynamic changes in the functional organization of the default mode network (DMN) and the dorsal attention network of patients with PMD. A total of 27 patients with PMD who experienced a stroke in the right hemisphere were enrolled in the current study, along with 27 healthy control subjects matched by age, sex, and educational level. A behavioral examination and functional magnetic resonance imaging scan were performed. The data were analyzed using an independent component analysis method. The results revealed a significantly increased functional connectivity between the DMN and prefrontal cortex (left middle/inferior frontal and left precentral gyri), temporal regions (left superior temporal gyrus), and bilateral and posterior cingulate gyri/precuneus (P<0.001). There was also a significantly decreased functional connectivity between the DMN and right middle temporal gyrus, left uvula, and right inferior parietal lobule, and between the dorsal attention network and prefrontal cortex (left precentral/inferior and right inferior/middle frontal gyri), right inferior parietal gyrus, and right insula (P<0.001). These results suggest that the stroke affected both the lesioned and contralesional hemispheres. The prefrontal cortex, temporal regions, insula, and posterior cingulate gyrus/precuneus serve a crucial role in memory processing. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate the effect of electroacupuncture (EA) on cognitive deficits, and the underlying mechanism following cerebral ischemia-reperfusion (I/R) via the calmodulin (CaM)-calmodulin-dependent protein kinase type IV (CaMKIV)-cyclic adenosine monophosphate response elements binding protein (CREB) intracellular signaling pathway in the hippocampus. In total, 45 adult female Sprague-Dawley rats were randomly divided into three groups, namely the sham group, the middle cerebral artery occlusion (MCAO) group and the MCAO + EA group. Rats in the MCAO and MCAO + EA groups were modeled for post-stroke cognitive impairment. EA was performed at the Baihui and Shenting acupuncture points for 30 min/day for one week in the MCAO + EA group. Behavioral testing was analyzed using a step-down apparatus, while 2,3,5-triphenyl tetrazolium chloride was used to detect the infarct volume and lesion size. In addition, CaM activity was assessed by cyclic nucleotide-dependent phosphodiesterase analysis, and the protein expression levels of CaM, CaMKIV, phosphorylated (p)-CaMKIV, CREB and p-CREB were analyzed by western blot analysis. The cerebral I/R injured rat model in the MCAO group was established successfully with regard to the infarct volume and neuronal lesion size, as compared with the sham group. EA was demonstrated to effectively improve the cognitive ability, as measured by the step-down apparatus test, and decrease the infarct volume when compared with the MCAO group (P<0.05). The step-down apparatus test for the EA-treated rats revealed improved learning and reduced memory impairment when compared with the MCAO group. Furthermore, CaM activity and CaM protein expression levels in the MCAO + EA group were lower compared with those in the MCAO group (P<0.05). By contrast, the protein expression levels of CaMKIV, p-CaMKIV, CREB and p-CREB were significantly reduced in the MCAO group when compared with the sham group (P<0.05), although the expression levels increased following EA treatment when compared with the MCAO group (P<0.05). Therefore, cognitive repair benefited from EA, and the main intracellular signaling pathway in the hippocampus was mediated by CaM-CaMKIV-CREB. EA effectively inhibited the expression and activity of CaM, while further enhancing the expression of CaMKIV and CREB, and their associated phosphorylated functions. [ABSTRACT FROM AUTHOR]