1,354,262 research outputs found
Cholinergic modulation of synaptic transmission and plasticity
No full textThe physiological and cognitive states of the brain are influenced by variations
in the activity of the cholinergic systems. For example, changes in the levels of ACh
have been associated with arousal/sleep cycle, sustained and focal attention. Moreover
interfering with cholinergic transmission affects learning and cellular plasticity.
Despite cholinergic system exerts its action by modifying the extracellular cortical
concentration of acetylcholine (ACh) few investigations have until now tested if and
how variation in ACh concentrations could influence neuronal synaptic efficacy and
plasticity in acute brain preparation. In order to investigate this aspect we have used a
quantitative experimental approach (variations in the levels of cholinergic activity)
rather than a simply qualitative (absence or presence of cholinergic activity) on rodent
visual cortex slices. We found that the extracellular ACh concentration affected in
opposite way cortical synaptic efficacy, producing either an enhancement or an
inhibition of evoked field potentials (FPs) respectively with low or high concentrations
of exogenously applied ACh. The versus of ACh modulatory action was dependent on
the activity of AChE and relayed on specific subtypes of muscarinic acetylcholine
receptors (mAChRs), thus linking the action of ACh to the activation of particular
receptor subtypes. The demonstration of a synaptic-pathway specificity of ACh
modulatory action, suggests that cholinergic release could control, in a dynamic way,
the flow of cortical information. Moreover, we showed that ACh concentration in
cortical tissue contributes to modulate long term changes of synaptic efficacy, such as
LTP or LTD induced by specific patterns of afferent neuronal activity. We found that:
1) in the absence of muscarinic receptors activation LTP is not inducible as shown in
slices treated with atropine, 2)cholinergic action on cortical L TP depends on the
activation of the even (M2, M,i) mAChRs. In addition, the sign of long term change,
whether L TP or LTD, appears to be depend on the endogenous level of ACh; indeed,
we reported that burst stimulation of afferent neurons, in rats with reduced cortical
cholinergic innervation, induces an LTD instead of LTP. These results suggest that the
degree of activation of cholinergic system could control cortical the direction of
synaptic plasticity in visual cortex
When the Family has Other Ideas: A Case Discussion of Shared Decision-Making
No full textClinicians worry that families may request treatments in ways that are not aligned with professional judgment or depart from evidence-based practices. These circumstances may make it challenging to provide a coherent plan of care. Dr. Kuczewski examines some typical cases and explores strategies to cope with such difficult provider-patient relationships.https://digitalcommons.providence.org/ethicsvideos/1051/thumbnail.jp
Who is My Neighbor in Catholic Health Care? Caring for Undocumented Immigrants in Our Community
No full textA variety of challenges have confronted providers over the years in caring for patients who are undocumented immigrants. Dr. Kuczewski considers a variety of issues affecting these patients and how the mission of health care providers, especially those in Catholic health care, can address the needs of our neighbors who are often the victims of widespread unjust treatment.https://digitalcommons.providence.org/ethicsvideos/1053/thumbnail.jp
Nerve growth factor favours long-term depression over long-term potentiation in layer II-III neurones of rat visual cortex
No full textNerve growth factor (NGF) has been shown to regulate plasticity in the visual cortex of monocularly deprived animals. However, to date, few attempts have been made to investigate the role of NGF in synaptic plasticity at the cellular level. In the study reported here we looked at the effects of exogenously applied NGF on synaptic plasticity of layer II-III regular spiking (RS) neurones in visual cortex of 16- to 18-day-old rats. We found that local application of NGF converted high frequency stimulation (HFS)-induced long-term potentiation (LTP) into long-term depression (LTD). We showed that this shift of synaptic plasticity was also obtained with bath application of NGF during HFS. Application of NGF subsequent to HFS left Up unaffected, conferring temporal constraints on NGF efficacy. NGF effects on UP were mediated by TrkA receptors. Indeed, blockade of TrkA by monoclonal antibody prevented NGF from inducing LTD following HFS. Low frequency stimulation (LFS) elicited LTD in RS cells. We found that NGF or blockade of NGF signalling by anti-TrkA antibody did not change the amplitude of the LTD induced by LFS. Thus, the NGF effect is selective for synaptic modifications induced by HFS in RS cells. The present results indicate that NGF may modulate the sign of long-term changes of synaptic efficacy in response to high frequency inputs
Nerve growth factor favours long-term depression over long-term potentiation in layer II-III neurones of rat visual cortex
No full textNerve growth factor (NGF) has been shown to regulate plasticity in the visual cortex of monocularly deprived animals. However, to date, few attempts have been made to investigate the role of NGF in synaptic plasticity at the cellular level. In the study reported here we looked at the effects of exogenously applied NGF on synaptic plasticity of layer II-III regular spiking (RS) neurones in visual cortex of 16- to 18-day-old rats. We found that local application of NGF converted high frequency stimulation (HFS)-induced long-term potentiation (LTP) into long-term depression (LTD). We showed that this shift of synaptic plasticity was also obtained with bath application of NGF during HFS. Application of NGF subsequent to HFS left LTP unaffected, conferring temporal constraints on NGF efficacy. NGF effects on LTP were mediated by TrkA receptors. Indeed, blockade of TrkA by monoclonal antibody prevented NGF from inducing LTD following HFS. Low frequency stimulation (LFS) elicited LTD in RS cells. We found that NGF or blockade of NGF signalling by anti-TrkA antibody did not change the amplitude of the LTD induced by LFS. Thus, the NGF effect is selective for synaptic modifications induced by HFS in RS cells. The present results indicate that NGF may modulate the sign of long-term changes of synaptic efficacy in response to high frequency inputs
Developmental modulation of synaptic transmission by acetylcholine in the primary visual cortex
No full textDespite the evidence that cortical synaptic organization and cognitive functions are influenced by the activity of the cholinergic system during postnatal development, so far no information is available on the effects produced by acetylcholine (ACh) on synaptic transmission. In the present article, we show that the ability of visual cortex slices to respond to ACh depends on postnatal age. In adulthood, ACh exerts mainly a facilitatory action on synaptic transmission, depressing field potential (FP) amplitude only if applied at high concentrations (millimolar range). During early postnatal development, at postnatal day 13 (P13), facilitation by ACh was lacking, with depression of FP observed with concentration of ACh in the micromolar range. The magnitude of ACh facilitatory effects increases with age. The time course of ACh-dependent facilitation overlaps the developmental maturation of acetylcholinesterase (AChE), suggesting a close relationship between ACh action and AChE activity. Thus, age-dependent modification of the cholinergic modulatory action may affect cortical maturation by regulating the magnitude of synaptic transmission. (c) 2006 Elsevier B.V. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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
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