Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the brain. Although measurements of GABA levels in vivo in the human brain using edited proton magnetic resonance spectroscopy (1H-MRS) have been established for some time, it is has not been established how regional GABA levels vary with age in the normal human brain. In this study, 49 healthy men and 51 healthy women aged between 20 and 76 years were recruited and J-difference edited spectra were recorded at 3 Tesla to determine the effect of age on GABA levels, and to investigate whether there are regional and gender differences in GABA in mesial frontal and parietal regions. Because the signal detected at 3.02 ppm using these experimental parameters is also expected to contain contributions from both macromolecules (MM) and homocarnosine, in this study the signal is labeled GABA+ rather than GABA. Significant negative correlations were observed between age and GABA+ in both regions studied (GABA+/Cr: frontal region, r = -0.68, p< 0.001, parietal region, r = -0.54, p< 0.001; GABA+/NAA: frontal region, r = -0.58, p< 0.001, parietal region, r = -0.49, p< 0.001). The decrease in GABA+ with age in the frontal region was more rapid in women than men. Evidence of a measureable decline in GABA is important in considering the neurochemical basis of the cognitive decline that is associated with normal aging.
Significance: Functional near-infrared spectroscopy (fNIRS) has been widely used to probe human brain function during task state and resting state. However, the existing analysis toolboxes mainly focus on task activation analysis, few software packages can assist resting-state fNIRS studies. Aim:We aimed to provide a versatile and easy-to-use toolbox to perform analysis for both resting state and task fNIRS.Approach: We developed a MATLAB toolbox called NIRS-KIT that works for both restingstate analysis and task activation detection.Results: NIRS-KIT implements common and necessary processing steps for performing fNIRS data analysis, including data preparation, quality control, preprocessing, individual-level analysis, group-level statistics with several popular statistical models, and multiple comparison correction methods, and finally results visualization. For resting-state fNIRS analysis, functional connectivity analysis, graph theory-based network analysis, and amplitude of low-frequency fluctuations analysis are provided. Additionally, NIRS-KIT also supports activation analysis for task fNIRS.Conclusions: NIRS-KIT offers an open source tool for researchers to analyze resting-state and/ or task fNIRS data in one suite. It contains several key features: (1) good compatibility, supporting multiple fNIRS recording systems, data formats of NIRS-SPM and Homer2, and the shared near-infrared spectroscopy format data format recommended by the fNIRS society; (2) flexibility, supporting customized preprocessing scripts; (3) ease-to-use, allowing processing fNIRS signals in batch manner with user-friendly graphical user interfaces; and (4) feature-packed data viewing and result visualization. We anticipate that this NIRS-KIT will facilitate the development of the fNIRS field.
Purpose This study aims to empirically examine knowledge management practices in China with the purpose to provide a holistic view regarding the current status of knowledge management at both national and organizational levels. Design/methodology/approach Using a survey method, this study collected primary data from organizations across several regions in China. The data were analyzed to detect possible relationships among institutional force, organizational culture and knowledge management process in Chinese organizations. More specifically, to what extent are these relationships moderated by national culture? Findings While knowledge management practices in China were partly influenced by institutional forces, most of the predicted connections between organizational culture and knowledge management were supported. In addition, the dynamic nature of national culture is predominant, that pervasively influencing knowledge management processes and thus contextualization determines how knowledge is being managed in China. Indeed, the ideologies of relationships and trust are key vehicles for knowledge management in the Chinese organizations. Practical implications This study comprehensively reviews existing literature to form an integrative framework, which is under explored in a Chinese context. Such initiative helps scholars and practitioners to gain a full understanding of knowledge management, in general, in the Chinese business environment in particular. Originality/value This paper provides a detailed and empirical insight into the knowledge management practices in Chinese organizations and suggests that knowledge management in a distinctive and yet diverse cultural context should be considered with caution.
This study investigates the influence of individual and information characteristics on university students' information channel selection (that is, search engines, social question & answer sites, online health websites, and social networking sites) of online health information (OHI) for three different types of search tasks (factual, exploratory, and personal experience). Quantitative data were collected via an online questionnaire distributed to students on various postgraduate programs at a large UK university. In total, 291 responses were processed for descriptive statistics, Principal Component Analysis, and Poisson regression. Search engines are the most frequently used among the four channels of information discussed in this study. Credibility, ease of use, style, usefulness, and recommendation are the key factors influencing users' judgments of information characteristics (explaining over 62% of the variance). Poisson regression indicated that individuals' channel experience, age, student status, health status, and triangulation (comparing sources) as well as style, credibility, usefulness, and recommendation are substantive predictors for channel selection of OHI.
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Altered neural dynamics in people who report spontaneous out of body experiences.
Research on brain mechanisms of deviance detection and sensory memory trace formation, best indexed by the mismatch negativity, mainly relied on the investigation of responses elicited by auditory stimuli. However, comparable less research reported the mismatch negativity elicited by somatosensory stimuli. More importantly, little is known on the functional features of mismatch deviant and standard responses across different sensory modalities. To directly compare different sensory modalities, we adopted a crossmodal roving paradigm and collected event-related potentials elicited by auditory, non-nociceptive somatosensory, and nociceptive trains of stimuli, during Active and Passive attentional conditions. We applied a topographical segmentation analysis to cluster successive scalp topographies with quasi-stable landscape of significant differences to extract crossmodal mismatch responses. We obtained three main findings. First, across different sensory modalities and attentional conditions, the formation of a standard sensory trace became robust mainly after the second stimulus repetition. Second, the neural representation of a modality deviant stimulus was influenced by the preceding sensory modality. Third, the mismatch negativity significantly covaried between Active and Passive attentional conditions within the same sensory modality, but not between different sensory modalities. These findings provide robust evidence that, while different modalities share a similar process of standard trace formation, the process of deviance detection is largely modality dependent.
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