1,720,958 research outputs found
Timed, sustained, attention-demanding performance reorganizes or dampens multiple circadian rhythms.
No full textGritton et al (2009) reported that rats practicing daily a sustained attention task (SAT) at ZT4 exhibit inverted activity patterns, such that the majority of activity as measured by movement occurs during the light phase. This shift was not apparent in animals trained under several other control conditions, including an operantly similar simple reaction task that requires less cognitive vigilance performed at the same time of day. Here we report that the SAT performance also alters circadian running wheel activity at ZT4 in a similar manner. Furthermore, the SAT performance causes phase advances (diurnality) at ZT4, a smaller phase advance at ZT10 and small phase delays at ZT16. Core body temperatures (Tb) are consistent with running wheel records for training at ZT10 and ZT16. However, at ZT4 the Tb is no longer synchronized with running wheel records, and contain elements of both daily training and LD effects. Acetylcholine (ACh) release in the prefrontal cortex, as measured via microdialysis, anticipates and remains entrained for at least 3 days after the last training session at ZT4. Entrainment to the time of daily training also occurs at ZT16, but the anticipatory rise is absent. In contrast, an operant schedule of reinforcement devoid of explicit demands on cognitive processes (FI-9) did not shift activity at ZT4 also did not entrain ACh release. Animals practicing at ZT4 the SAT, but not the FI-9, exhibit dampened food intake, stool output, and corticosterone rhythms in addition to the noted changes in activity rhythms and ACh release. Finally, the per2 rhythm in the colon also had a dampened level of expression. These data suggest that attention-demanding tasks may act to attenuate SCN-control of peripheral oscillators
Optogenetically-evoked cortical cholinergic transients in mice expressing channelrhodopsin-2 (ChR2) in cholinergic neurons.
No full textThe use of enzyme-selective microelectrodes for the real-time amperometric detection of neurotransmitter release has generated new insights in the regulation and function of major neurotransmitter and -modulator systems. We previously demonstrated that transient increases in prefrontal cholinergic activity (scale of seconds) mediate the detection of cues in attention-demanding contexts. This research was designed to determine if the transgenic expression of the photo-sensitive cation channel channelrhodopsin-2 (ChR2) is conducive to electrochemical studies measuring neurotransmitter release in the terminal fields of cholinergic projection neurons. We employed a viral vector to selectively express the ChR2 transgene in cholinergic neurons of the basal forebrain (substantia innominata/nucleus basalis of Meynert). Expression was achieved through the infusion of a DIO-ChR2-YFP construct packaged in an AAV vector into mice expressing the CRE recombinase gene under the control of the ChAT promoter. We employed enzyme-coated microelectrodes and fixed potential amperometry in order to measure the release of acetylcholine evoked by photoactivation of cholinergic neurons. Currents recorded via choline oxidase-coated platinum sites were referenced to adjacent non-coated sites. Light pulses were delivered to the cells expressing ChR2 via a laser diode with a wavelength of 446 nm coupled to a fiber-optic cable (200 μm in diameter) that could be raised or lowered via a micromanipulator on a stereotaxic instrument. Individual light pulses (<1 ms in duration, 5-40 mW as measured at the fiber tip) were insufficient to drive detectable cholinergic transients; however short pulses of light delivered in succession (10-60X) at frequencies greater than 10 Hz resulted in measurable cholinergic signals of 0.5 μM or greater. Electrochemical recordings performed in cortical areas contralateral to the hemisphere expressing ChR2 as well as non-projection ipsilateral regions - such as the striatum - did not yield detectable cholinergic signaling. We conclude that the expression of photoactivated ChR2 can be used to selectively activate cholinergic projections to terminal regions and that this release is detectable using enzyme-selective microelectrodes. Future studies will test the hypothesis that the augmentation of cue evoked cholinergic transients improves attentional task-performance and will yield information about the impact of poorly orchestrated or invalid cholinergic transients on cognitive performance
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Gritton, H. E.
No full textPhotograph from the C.R. Savage Portrait Studio. Name associated with the photograph: H. E. Gritto
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
