Atypically larger variability of resource allocation accounts for visual working memory deficits in schizophrenia.

Working memory (WM) deficits have been widely documented in schizophrenia (SZ), and almost all existing studies attributed the deficits to decreased capacity as compared to healthy control (HC) subjects. Recent developments in WM research suggest that other components, such as precision, also mediate behavioral performance. It remains unclear how different WM components jointly contribute to deficits in schizophrenia. We measured the performance of 60 SZ (31 females) and 61 HC (29 females) in a classical delay-estimation visual working memory (VWM) task and evaluated several influential computational models proposed in basic science of VWM to disentangle the effect of various memory components. We show that the model assuming variable precision (VP) across items and trials is the best model to explain the performance of both groups. According to the VP model, SZ exhibited abnormally larger variability of allocating memory resources rather than resources or capacity per se. Finally, individual differences in the resource allocation variability predicted variation of symptom severity in SZ, highlighting its functional relevance to schizophrenic pathology. This finding was further verified using distinct visual features and subject cohorts. These results provide an alternative view instead of the widely accepted decreased-capacity theory and highlight the key role of elevated resource allocation variability in generating atypical VWM behavior in schizophrenia. Our findings also shed new light on the utility of Bayesian observer models to characterize mechanisms of mental deficits in clinical neuroscience.

Effects of Non-invasive Brain Stimulation on Stimulant Craving in Users of Cocaine, Amphetamine, or Methamphetamine: A Systematic Review and Meta-Analysis.

Dopamine system plays a pivotal role in specific kinds of substance use disorders (SUD, i. e., cocaine and methamphetamine use disorders). Many studies addressed whether dopamine-involved craving could be alleviated by non-invasive brain stimulation (NIBS) techniques. Nevertheless, the outcomes were highly inconsistent and the stimulating parameters were highly variable. In the current study, we ran a meta-analysis to identify an overall effect size of NIBS and try to find stimulating parameters of special note. We primarily find 2,530 unduplicated studies in PubMed, Psychology and Behavioral Sciences Collection, PsycARTICLES, PsycINFO, and Google Scholar database involving "Cocaine"/"Amphetamine"/"Methamphetamine" binded with "TMS"/"tDCS"/"non-invasive stimulation" in either field. After visual screening, 26 studies remained. While 16 studies were further excluded due to the lack of data, invalid craving scoring or the absence of sham condition. At last, 16 units of analysis in 12 eligible studies were coded and forwarded to a random-effect analysis. The results showed a large positive main effect of stimulation (Hedge's g = 1.116, CI = [0.597, 1.634]). Further subgroup analysis found that only high-frequency repetitive transcranial magnetic stimulation (rTMS) could elicit a significant decrease in craving, while the outcome of low-frequency stimulation was relatively controversial. Moreover, univariate meta regression revealed that the number of pulses per session could impose negative moderation toward the intervention. No significant moderation effect was found in types of abuse, overall days of stimulation and other variables of stimulating protocol. In conclusion, this meta-analysis offered a persuasive evidence for the feasibility of using NIBS to remit substance addictive behavior directly based on dopamine system. We also give clear methodological guidance that researchers are expected to use high-frequency, sufficiently segmented rTMS to improve the efficacy in future treatments.

Propelling Polysulfide Conversion by Defect-Rich MoS2 Nanosheets for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have tremendous energy density and are cost effective and environmentally compatible, thereby deemed one of the most promising secondary energy storage systems. However, Li-S batteries present sluggish polysulfide intermediate redox kinetics due to the unavoidable "shuttle effect", thus hindering their industrialization and resulting in low sulfur utilization, rapid capacity fading, poor Coulombic efficiency, and anode corrosion. Herein, the present study updates a one-step hydrothermal method to synthesize a highly efficient sulfur host integrating three-dimensional porous graphene aerogel (GA) with uniformly dispersed defect-rich MoS2 nanosheets (200-300 nm) (GA-DR-MoS2). The electrochemical studies reveal that these MoS2 nanosheets with abundant defects could provide strong chemical adsorption for polysulfides, as well as act as an electrocatalyst to markedly accelerate polysulfide redox reactions during the charge/discharge process. The resultant GA-DR-MoS2 composites (70 wt % of sulfur loading) present a high initial discharge capacity of 1429 mAh g-1 at 0.2C, an outstanding cycling stability with a low capacity decay rate of 0.085% per cycle over 500 cycles at 0.2C, and a superior rate performance with an improved capacity from 290 to 581 mAh g-1 at 5C. The presented strategy is effective in achieving high-energy-density Li-S batteries from the point of electrocatalysis and facilitating their practical applications.

Ultradispersed titanium dioxide nanoparticles embedded in a three-dimensional graphene aerogel for high performance sulfur cathodes.

Lithium-sulfur (Li-S) batteries are regarded as one of the most promising energy storage technologies, however, their practical application is greatly limited by a series of sulfur cathode challenges such as the notorious "shuttle effect", low conductivity and large volume change. Here, we develop a facile hydrothermal method for the large scale synthesis of sulfur hosts consisting of three-dimensional graphene aerogel with tiny TiO2 nanoparticles (5-10 nm) uniformly dispersed on the graphene sheet (GA-TiO2). The obtained GA-TiO2 composites have a high surface area of ∼360 m2 g-1 and a hierarchical porous structure, which facilitates the encapsulation of sulfur in the carbon matrix. The resultant GA-TiO2/S composites exhibit a high initial discharge capacity of 810 mA h g-1 with an ultralow capacity fading of 0.054% per cycle over 700 cycles at 2C, and a high rate (5C) performance (396 mA h g-1). Such architecture design paves a new way to synthesize well-defined sulfur hosts to tackle the challenges for high performance Li-S batteries.