243 research outputs found
Gandolfi, Silvana
No full textA brief description of the main characteristics of the works for children of the Italian author Silvana Gandolfi, the themes she privileges, her way of portraying children, the influence of Oriental culture and philosophy upon her writing
La Liguria bizantina dopo un settantennio di ricerche: dati acquisiti e prospettive future
No full textQuadro complessivo sulle conoscenze relative alla dominazione bizantina sulla Liguria costiera, alla luce dei dati archeologici
High-pass filtering and dynamic gain regulation enhance vertical bursts transmission along the mossy fiber pathway of cerebellum
No full textSignal elaboration in the cerebellum mossy fiber input pathway presents controversial aspects, especially concerning gain regulation and the spot-like (rather than beam-like) appearance of granular-to-molecular layer transmission. By using voltage-sensitive dye (VSD) imaging in rat cerebellar slices (Mapelli et al., 2010), we found that mossy fiber bursts optimally excited the granular layer above ~50 Hz and the overlaying molecular layer above ~100 Hz, thus generating a cascade of high-pass filters. NMDA receptors enhanced transmission in the granular, while GABA-A receptors depressed transmission in both the granular and molecular layer. Burst transmission gain was controlled through a dynamic frequency-dependent involvement of these receptors. Moreover, while high-frequency transmission was enhanced along vertical lines connecting the granular to molecular layer, no high-frequency enhancement was observed along the parallel fiber axis in the molecular layer. This was probably due to the stronger effect of Purkinje cell GABA-A receptor-mediated inhibition occurring along the parallel fibers than along the granule cell axon ascending branch. The consequent amplification of burst responses along vertical transmission lines could explain the spot-like activation of Purkinje cells observed following punctuate stimulation in vivo
Long-Term Spatiotemporal Reconfiguration of Neuronal Activity Revealed by Voltage-Sensitive Dye Imaging in the Cerebellar Granular Layer
No full textUnderstanding the spatiotemporal organization of long-term synaptic plasticity in neuronal networks demands techniques capable of monitoring changes in synaptic responsiveness over extended multineuronal structures. Among these techniques, voltage-sensitive dye imaging (VSD imaging) is of particular interest due to its good spatial resolution. However, improvements of the technique are needed in order to overcome limits imposed by its low signal-to-noise ratio. Here, we show that VSD imaging can detect long-term potentiation (LTP) and long-term depression (LTD) in acute cerebellar slices. Combined VSD imaging and patch-clamp recordings revealed that the most excited regions were predominantly associated with granule cells (GrCs) generating EPSP-spike complexes, while poorly responding regions were associated with GrCs generating EPSPs only. The correspondence with cellular changes occurring during LTP and LTD was highlighted by a vector representation obtained by combining amplitude with time-to-peak of VSD signals. This showed that LTP occurred in the most excited regions lying in the core of activated areas and increased the number of EPSP-spike complexes, while LTD occurred in the less excited regions lying in the surround. VSD imaging appears to be an efficient tool for investigating how synaptic plasticity contributes to the reorganization of multineuronal activity in neuronal circuits
Combinatorial responses controlled by synaptic inhibition in the cerebellum granular layer
No full textThe granular layer of cerebellum has been long hypothesized to perform combinatorial operations on incoming signals. Although this assumption is at the basis of main computational theories of cerebellum, it has never been assessed experimentally. Here, by applying high-resolution voltage-sensitive dye imaging techniques, we show that simultaneous activation of two partially overlapping mossy fiber bundles (either with single pulses or high-frequency bursts) can cause combined excitation and combined inhibition, which are compatible with the concepts of coincidence detection and spatial pattern separation predicted by theory. Combined excitation appeared as an area in which the combination of two inputs is greater than the arithmetic sum of the individual inputs and was enhanced by gamma-aminobutyric acid type A (GABA(A)) receptor blockers. Combined inhibition was manifest as an area where two inputs combined resulted in a reduction to less than half of the activity evoked from either one of the two inputs alone and was prevented by GABA(A) receptor blockers. The combinatorial responses occupied small granular layer regions (approximately 30 microm diameter), with combined inhibition being interspersed among extended areas of combined excitation. Moreover, the combinatorial effects lasted for tens of milliseconds and combined inhibition occurred only after termination of the stimuli. These combinatorial operations, if engaged by natural input patterns in vivo, may be important to influence incoming impulses organizing spatiotemporal spike sequences to be relayed to Purkinje cell
Inhibitory Plasticity: From Molecules to Computation and Beyond
No full textSynaptic plasticity is the cellular and molecular counterpart of learning and memory and, since its first discovery, the analysis of the mechanisms underlying long-term changes of synaptic strength has been almost exclusively focused on excitatory connections. Conversely, inhibition was considered as a fixed controller of circuit excitability. Only recently, inhibitory networks were shown to be finely regulated by a wide number of mechanisms residing in their synaptic connections. Here, we review recent findings on the forms of inhibitory plasticity (IP) that have been discovered and characterized in different brain areas. In particular, we focus our attention on the molecular pathways involved in the induction and expression mechanisms leading to changes in synaptic efficacy, and we discuss, from the computational perspective, how IP can contribute to the emergence of functional properties of brain circuits
Modeling Neurotransmission: Computational Tools to Investigate Neurological Disorders
No full textThe investigation of synaptic functions remains one of the most fascinating challenges in
the field of neuroscience and a large number of experimental methods have been tuned to dissect the
mechanisms taking part in the neurotransmission process. Furthermore, the understanding of the
insights of neurological disorders originating from alterations in neurotransmission often requires the
development of (i) animal models of pathologies, (ii) invasive tools and (iii) targeted pharmacological
approaches. In the last decades, additional tools to explore neurological diseases have been provided
to the scientific community. A wide range of computational models in fact have been developed to
explore the alterations of the mechanisms involved in neurotransmission following the emergence
of neurological pathologies. Here, we review some of the advancements in the development of
computational methods employed to investigate neuronal circuits with a particular focus on the
application to the most diffuse neurological disorders
GAETANO GANDOLFI: Sant'Elena ritrova la Vera Croce; Ritrovamento della Vera Croce
No full textBologna di secondo Settecento e l'Europa. Gaetano Gandolfi con la pala d'altare relativa al "Ritrovamento della vera croce" dimostra ancora a secolo inoltrato quanto la raffigurazione dei misteri sacri potesse essere viva e accostabile. In questo dipinto, documentato anche dal bozzetto, sostanziato dall'impianto grafico correttissimo si sottolinea la novità delle scelte inconsuete, quali la forte preminenza data alla grande croce che si innalza sopra il folto gruppo dei personaggi, accalcati accanto ai tre protagonisti, la regina Elena, il miracolato, il giovane che regge con evidente sforzo il legno benedetto: una lezione che sarà compresa nel secolo successivo dagli artisti più avveduti
Heterosynaptic GABAergic plasticity bidirectionally driven by the activity of pre- and postsynaptic NMDA receptors
No full textDynamic changes of the strength of inhibitory synapses play a crucial role in processing neural information and in balancing network activity. Here, we report that the efficacy of GABAergic connections between Golgi cells and granule cells in the cerebellum is persistently altered by the activity of glutamatergic synapses. This form of plasticity is heterosynaptic and is expressed as an increase (long-term potentiation, LTPGABA) or a decrease (long-term depression, LTDGABA) of neurotransmitter release. LTPGABA is induced by postsynaptic NMDA receptor activation, leading to calcium increase and retrograde diffusion of nitric oxide, whereas LTDGABA depends on presynaptic NMDA receptor opening. The sign of plasticity is determined by the activation state of target granule and Golgi cells during the induction processes. By controlling the timing of spikes emitted by granule cells, this form of bidirectional plasticity provides a dynamic control of the granular layer encoding capacity
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