205 research outputs found
Parallel activation of field CA2 and dentate gyrus by synaptically elicited perforant path volleys.
No full textPrevious studies showed that dorsal psalterium (PSD) volleys to the entorhinal cortex (ENT) activated in layer II perforant path neurons projecting to the dentate gyrus. The discharge of layer II neurons was followed by the sequential activation of the dentate gyrus (DG), field CA3, field CA1. The aim of the present study was to ascertain whether in this experimental model field, CA2, a largely ignored sector, is activated either directly by perforant path volleys and/or indirectly by recurrent hippocampal projections. Field potentials evoked by single-shock PSD stimulation were recorded in anesthetized guinea pigs from ENT, DG, fields CA2, CA1, and CA3. Current source-density (CSD) analysis was used to localize the input/s to field CA2. The results showed the presence in field CA2 of an early population spike superimposed on a slow wave (early response) and of a late and smaller population spike, superimposed on a slow wave (late response). CSD analysis during the early CA2 response showed a current sink in stratum lacunosum-moleculare, followed by a sink moving from stratum radiatum to stratum pyramidale, suggesting that this response represented the activation and discharge of CA2 pyramidal neurons, mediated by perforant path fibers to this field. CSD analysis during the late response showed a current sink in middle stratum radiatum of CA2 followed by a sink moving from inner stratum radiatum to stratum pyramidale, suggesting that this response was mediated by Schaffer collaterals from field CA3. No early population spike was evoked in CA3. However, an early current sink of small magnitude was evoked in stratum lacunosum-moleculare of CA3, suggesting the presence of synaptic currents mediated by perforant path fibers to this field. The results provide novel information about the perforant path system, by showing that dorsal psalterium volleys to the entorhinal cortex activate perforant path neurons that evoke the parallel discharge of granule cells and CA2 pyramidal neurons and depolarization, but no discharge of CA3 pyramidal neurons. Consequently, field CA2 may mediate the direct transfer of ENT signals to hippocampal and extrahippocampal structures in parallel with the DG-CA3-CA1 system and may provide a security factor in situations in which the latter is disrupted
Topographic activation of the medial entorhinal cortex by presubicular commissural projections.
No full textPrevious investigations have shown that presubicular commissural fibers traveling in the caudal part of the dorsal hippocampal commissure (PSD) selectively activated the dorsalmost portion of the entorhinal cortex (EC), where they discharged perforant path neurons to the dorsal dentate gyrus. The dentate activation was followed by that of the dorsal hippocampus. The aim of the present study was to ascertain whether presubiculum commissural projections traveling in the PSD can also activate ventral levels of the EC and, if so, whether this activation is followed by that of the dentate gyrus-hippocampal. system in the ventral hippocampus. The experiments were carried out in adult, anesthetized guinea pigs by field potential analysis. The results showed that presubicular fibers traveling at different PSD loci selectively activated specific EC portions, with caudal fibers activating only the dorsal EC and more rostral fibers activating ventral EC points. The region activated by PSD projections corresponded to the medial EC. Current source-density (CSD) analysis revealed that at both dorsal and ventral EC levels excitatory synaptic potentials followed by neuron discharge were generated in layer II, site of origin of the perforant path to the dentate gyrus. Activation of either dorsal or ventral levels of the EC was followed by activation of the dentate gyrus-hippocampal system in corresponding hippocampal segments. The results provide physiological evidence that the commissural presubicular projections activate the EC in a topographic manner. The massive activation of perforant path neurons at all EC levels suggests that presubicular signals may strongly influence the functions played by the EC-dentate-hippocampal system
Input-output relations in the entorhinal cortex-dentate-hippocampal system: evidence for a non-linear transfer of signals.
No full textIn the current study we analyzed the input-output relations in the entorhinal-dentate-hippocampal system, a major network involved in long-term memory. In anesthetized guinea pigs, the system was driven by activation of perforant path neurons in the entorhinal cortex (ENT), via presubicular fibers directly stimulated in the dorsal psalterium. Perforant path neuron discharge activated in parallel the dentate gyrus (DG) and hippocampal field CA2. Whereas the output from the DG activated hippocampal field CA3, the output from the sole field CA2 was sufficient for activation of field CA1. Signals from field CA3 operated in concert with CA2, likely contributing to discharge field CA1. These findings indicate the existence of two in parallel disynaptic systems: an ENT-CA2-CA1 and an ENT-DG-CA3 system. The convergence of the latter with the former gives origin the classical trisynaptic circuit, the ENT-DG-CA3-CA1 system. The input-output relations between the population excitatory postsynaptic potentials (pEPSP) evoked in the DG, CA3, CA2 and CA1 and the population spike (PS) evoked in the structure upstream (the input) were described by smooth sigmoid curves. In contrast, the input-output relations of the PS versus the pEPSP within each structure were described by steep sigmoid curves. The net input-output functions of the DG (ENT-DG system), field CA2 (ENT-CA2 system), field CA3 (ENT-DG-CA3 system) and field CA1 (ENT-CA2-CA1&ENT-DG-CA3-CA1 system) were described by sigmoid curves. While the DG and field CA2 exhibited steep sigmoids, fields CA3 and CA1 had less steep sigmoid functions. The present study demonstrates that all structures downstream to the ENT operate according to sigmoid input-output functions, characterized by specific parameters. These different behaviors may contribute to different memory processes. We additionally demonstrate that field CA1 can be activated by field CA2, independently from field CA3. This functional dissociation between CA3 and CA1 may subserve specific roles of each field in memory encoding/retrieval
Tiziana Andina, Ontologia sociale. Transgenerazionalità, potere, giustizia
No full text§ 1. The main idea expressed in Tiziana Andina’s Ontologia sociale. Transgenerazionalità, potere, giustizia is that some social actions are identified and structured by the fundamental property of transgenerationality, i.e. the ability to significantly affect the interests not only of the present generation, but also of future ones (p. 85, Eng. tr. pp. 77-78). From an ontological point of view – which the author addresses in the first two chapters of the four that make up the book – transgene..
Antitumor activity of imatinib mesylate in neuroblastoma xenografts
No full textImatinib mesylate has antitumor activity in vitro and in vivo against neuroblastoma cell lines and xenografts characterized by a different expression of receptor tyrosine kinases. In this article, we report that imatinib tumor concentration can be independent of the administered dose and does not correlate with the antitumor effect. In xenografts, high-dose administration does not improve imatinib efficacy. In conclusion, there is no clear-cut correlation between the levels of expression for imatinib-responsive targets and the in vitro and in vivo sensitivity. This further suggests that in neuroblastoma the antitumor activity of imatinib may involve the inhibition of other tyrosine kinases and/or pathways
Il caso (azda) Posledná večera: libertà d’espressione e verità religiosa nel processo di democratizzazione slovacco
No full textThe article explores, through the case of Martin Kasarda’s novel (azda) Posledná večera (1991) and the ensuing controversy and complaints of public insult against the author and the publishers by some members of the Slovak Parliament, the article explores the difficult process of democratization in Slovakia during the period following the end of the Czechoslovak Socialist Republic. The author focuses on the clashes between two fundamental civic rights such as freedom of speech and freedom of religion, and between culture and politics. The article compares the Slovak case with other contemporary situations such as complaints against Martin Scorsese’s film The Last Temptation of Christ and the issue of Salman Rushdie’s The Satanic Verses.<br/
From the more iconic to the less iconic linguistic form: morphological syntagms in Pāṇini
No full textStarting from Kastovsky’s definition of “morphological syntagm”, the author tries to understand whether any similarity exists between complex word forms (such as compounds and secondary derivatives) and the matching source-phrases which should be taken into
account in the relevant formation-rules according to Pāṇini’s teaching. Thus, A 2.1.1 is
interpreted and tested in a fresh manner, leading to the outline of a a scalar pattern of
iconicity which encompasses the several outputs of the provisions it governs
Relazioni tra una multifunzione e la sua frontiera
No full textDenote by "frF" the multivalued mapping defined as the boundary of F. In the paper, in the setting T topological space and X is a topological linear space, the author studies the connection existing between the lower [respectively, upper] semicontinuity of the multivalued mapping F, and the lower [respectively, upper] semicontinuity of "frF". This paper can be seen as an extension of a previous work by the author and F. Papalini
Presentazione
No full textIn veste di curatrice della pubblicazione, l'autrice introduce i contributi contenuti nel numero 1/2017 del Semestrale di Studi e Ricerche di Geografia, dedicato alla relazione tra tecnologie digitali e geografia.The author introduces the contributions of the 1/2017 issue of the "Semestrale di Studi e Ricerche di Geografia", focused on the relationship between digital technologies and geography
Impact of scientific production of Italian scientists in exercises and sport sciences by measuring the author-weighted h-index
No full textThis study aimed to measure the consistency of the impact of scientific production, weighted by authorship, of Italian scientists in two academic disciplines (AD) of Exercise and Sports Sciences (ESS) from 2017 to 2022, with a specific focus on the subfield "Sport Sciences", using topic-specific keywords. Through the Scopus database, the scientific products of Italian ESS scientists associated with each keyword were identified. Subsequently, total and relative metric parameters from 2017 to 2022 were collected, including the total and relative number of citations. To evaluate the impact of the publications, the total and relative h-index were calculated, and weighted by considering different categories of authorship. Specific weights were attributed to each category: single author, first author, last author and co-author, following the classifications already in use on Scopus for each author. The trends of total and relative metrics, including citations and h-index, from 2017 to 2022 were analyzed using Spearman's correlation. Non-parametric linear regression analysis was used for the predictive analysis of these trends. Among the 83 identified ESS scientists, a detailed analysis revealed that 31.3% were full professors, 42.1% associate professors, and 26.6% researchers. Less than half of these scientists were directly affiliated with ESS. Despite minority representation, significant positive correlations emerge between total and relative citations from 2017 to 2022 (r = 0.687) and between the weighted total h-index and the weighted relative h-index (r = 0.965). Significant trends emerge in the metric parameters of the same scientists when analyzed separately by AD. The regression results indicate that variations in total citations and the weighted total and relative h-index can predict or explain the observed changes in 2017-2022 (p < 0.05). This result suggests that the production and impact of research in the field of ESS follow the same general trend as production and impact in the specific subfield
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