Previous study has proved the specific role of prefrontal-parietal network in the rapid goal-directed chunking (RGDC), which could dissociate the prefrontal activity from the working memory demand or encoding difficulty. However, it remains unknown how the prefrontal and parietal cortices collaborate to accomplish RGDC. A novel experiment design using Chinese characters as materials wad conduced with eighteen undergraduate students (9 females, mean age = 22.4 years) while recoding electroencephalogram (EEG). The radical-level chunking, accomplished in a timely stringent way, made a strict contrast with the stroke-level chunking whose cognitive brain processing were far less coherent due to the irregular and unpredictable chunking procedure. Comparing to the stoke-level chunking, RGDC like radical-level chunking showed an early increase of gamma band synchronization over parietal and occipital cortices, followed by enhanced power in the beta-gamma band (25-38 Hz) over frontal areas in the regular versus irregular chunking conditions. We suggest that the posterior rhythmic activities in the gamma band may underlie the processes that are directly associated with perceptual manipulations of chunking, while the subsequent beta-gamma activation over frontal area appears to reflect the reinforcement of the selected rules over alternative options, which would differentiate goal-directed chunking from chunking processes accomplished in a more implicit manner.
Background Pharmacological and conventional non-pharmacological treatments are only moderately effective in treating generalised anxiety disorder (GAD). Recently, repetitive transcranial magnetic stimulation (rTMS) has attracted interest because of its potential therapeutic value. Aim To investigate the efficacy and safety of rTMS treatment for GAD. Methods Literature studies published in English or Chinese were screened in 10 electronic databases up to 5 December 2018. The included studies’ bias risk was assessed using Cochrane risk of bias assessment tool. Meta-analysis was performed to compute the standardised mean difference (SMD) and risk ratio (RR) along with its 95% CIs through using RevMan V.5.3. Heterogeneity was inspected by I 2 and the χ 2 test. We performed subgroup analysis and meta-regression to investigate heterogeneity. We used funnel plot to assess publication bias. We used the GRADE approach to assess the whole quality of evidence. Results Twenty-one studies, with a total sample size of 1481, were analysed. The risk of bias in most studies included is moderate, the majority of which are lacking of blinding methods of treatment allocation. The treatment had beneficial effects in the rTMS group compared with the control group in mean anxiety score (SMD=−0.68; 95% CI −0.89 to −0.46). None of the 21 studies included here reported severe adverse events. As for dropout rates, there are no statistically significant differences between the two groups (RR 1.14, 95% CI 0.72 to 1.82) or adverse events (RR 0.95, 95% CI 0.77 to 1.18). No particular influence on the heterogeneity of any variable was observed. The risk of publication bias was low. According to the GRADE approach, the evidence levels of primary outcome (treatment effects) and secondary outcomes (acceptability and safety) were rated as ‘medium’. Conclusion The use of rTMS combined with medication treatment may have a significant positive anti-anxiety effect on patients with GAD. However, we should interpret the results cautiously due to the relatively high heterogeneity of the meta-analysis. Future high-quality clinical trials are needed to confirm our results.
Background: Mild cognitive impairment (MCI) is an early stage of Alzheimer's disease. Repetitive transcranial magnetic stimulation (rTMS) has been widely employed in MCI research. However, there is no reliable systematic evidence regarding the effects of rTMS on MCI. The aim of this review was to evaluate the efficacy and safety of rTMS in the treatment of MCI. Methods: A comprehensive literature search of nine electronic databases was performed to identify articles published in English or Chinese before June 20, 2019. The identified articles were screened, data were extracted, and the methodological quality of the included trials was assessed. The meta-analysis was performed using the RevMan 5.3 software. We used the GRADE approach to rate the quality of the evidence. Results: Nine studies comprising 369 patients were included. The meta-analysis showed that rTMS may significantly improve global cognitive function (standardized mean difference [SMD] 2.09, 95% confidence interval [CI] 0.94 to 3.24, p = 0.0004, seven studies, n = 296; low-quality evidence) and memory (SMD 0.44, 95% CI 0.16 to 0.72, p = 0.002, six studies, n = 204; moderate-quality evidence). However, there was no significant improvement in executive function and attention ( p > 0.05). Subgroup analyses revealed the following: (1) rTMS targeting the left hemisphere significantly enhanced global cognitive function, while rTMS targeting the bilateral hemispheres significantly enhanced global cognitive function and memory; (2) high-frequency rTMS significantly enhanced global cognitive function and memory; and (3) a high number of treatments ≥20 times could improve global cognitive function and memory. There was no significant difference in dropout rate ( p > 0.05) between the rTMS and control groups. However, patients who received rTMS had a higher rate of mild adverse effects (risk ratio 2.03, 95% CI 1.16 to 3.52, p = 0.01, seven studies, n = 317; moderate-quality evidence). Conclusions: rTMS appears to improve global cognitive function and memory in patients with MCI and may have good acceptability and mild adverse effects. Nevertheless, these results should be interpreted cautiously due to the relatively small number of trials, particularly for low-frequency rTMS.
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