bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activity and Calcium-Dependent Mechanisms Maintain Reliable Interneuron Synaptic Transmission in a Rhythmic Neural Network
Authors: Parker David 
Published: April 2018

Inputs from glutamatergic excitatory interneurons (EIN) to motor neurons in the lamprey spinal cord locomotor network exhibit activity-dependent depression during spike trains. The mechanism underlying this depression has been examined here, and its relevance to transmitter release during rhythmic activity has been investigated.The depression of EIN inputs was greater after larger initial EPSPs and reduced in low-calcium Ringer's solution, effects that are consistent with depression caused by depletion of releasable transmitter stores. However, the depression was greater at lower stimulation frequencies and could be reversed by increasing the stimulation frequency. In addition, high-calcium Ringer's solution and the slow intracellular calcium chelator EGTA-AM, which both failed to affect the amplitude of low frequency-evoked EPSPs, reduced and increased the depression, respectively. These results are inconsistent with a simple depletion mechanism but suggest that ongoing activity and calcium-dependent mechanisms oppose depletion.The network relevance of this mechanism was examined using physiologically relevant bursts to simulate EIN spiking during rhythmic activity. Although considerably more EPSPs were evoked than during spike trains, burst-evoked EPSPs did not depress. However, single EPSPs evoked at the interburst interval depressed, and burst transmission was disrupted by EGTA-AM, again suggesting the involvement of activity and calcium-dependent mechanisms. By responding to the calcium changes evoked by increased interneuron activity, this mechanism can monitor transmitter requirements caused by EIN spiking, allowing reliable transmission across different patterns of network activity. However, not all types of spinal interneurons exhibit reliable burst transmission, suggesting specificity of this mechanism to a subset of neurons.
A Positron Emission Tomographic Study of Auditory Localization in the Congenitally Blind
Authors: Weeks Robert , Horwitz Barry , Aziz-Sultan Ali , Tian Biao , Wessinger C. Mark , Cohen Leonardo G. , Hallett Mark , Rauschecker Josef P. 
Published: April 2018

We have used positron emission tomography (PET) to measure regional cerebral blood flow (rCBF) in sighted and congenitally blind subjects performing auditory localization tasks. During scanning, the spectral and binaural cues of localized sound were reproduced by a sound system and delivered via headphones. During tasks that required auditory localization both the sighted and blind subjects strongly activated posterior parietal areas. In addition, the blind subjects activated association areas in the right occipital cortex, the foci of which were similar to areas previously identified in visual location and motion detection experiments in sighted subjects. The blind subjects, therefore, demonstrated visual to auditory cross-modal plasticity with auditory localization activating occipital association areas originally intended for dorsal-stream visual processing.To determine the functional connectivity of pre-selected brain regions in primary and non-primary auditory and posterior parietal cortex in the two cohorts, we performed an inter-regional correlation analysis on the rCBF data set. During auditory localization in the blind subjects, rCBF activity in the right posterior parietal cortex was positively correlated with that in the right occipital region, whereas in sighted subjects correlations were generally negative. There were no significant positive occipital correlations in either cohort when reference regions in temporal or left parietal cortex were chosen. This indicates that in congenitally blind subjects the right occipital cortex participates in a functional network for auditory localization and that occipital activity is more likely to arise from connections with posterior parietal cortex.
Columnar Organization of Dendrites and Axons of Single and Synaptically Coupled Excitatory Spiny Neurons in Layer 4 of the Rat Barrel Cortex
Authors: Lübke Joachim , Egger Veronica , Sakmann Bert , Feldmeyer Dirk 
Published: April 2018

Cortical columns are the functional units of the neocortex that are particularly prominent in the “barrel” field of the somatosensory cortex. Here we describe the morphology of two classes of synaptically coupled excitatory neurons in layer 4 of the barrel cortex, spiny stellate, and star pyramidal cells, respectively. Within a single barrel, their somata tend to be organized in clusters. The dendritic arbors are largely confined to layer 4, except for the distal part of the apical dendrite of star pyramidal neurons that extends into layer 2/3. In contrast, the axon of both types of neurons spans the cortex from layer 1 to layer 6. The most prominent axonal projections are those to layers 4 and 2/3 where they are largely restricted to a single cortical column. In layers 5 and 6, a small fraction of axon collaterals projects also across cortical columns. Consistent with the dense axonal projection to layers 4 and 2/3, the total number and density of boutons per unit axonal length was also highest there. Electron microscopy combined with GABA postimmunogold labeling revealed that most (>90%) of the synaptic contacts were established on dendritic spines and shafts of excitatory neurons in layers 4 and 2/3.The largely columnar organization of dendrites and axons of both cell types, combined with the preferential and dense projections within cortical layers 4 and 2/3, suggests that spiny stellate and star pyramidal neurons of layer 4 serve to amplify thalamic input and relay excitation vertically within a single cortical column.
Activity-Dependent Regulation of Substance P Expression and Topographic Map Maintenance by a Cholinergic Pathway
Authors: Tu Shichun , Butt Christopher M. , Pauly James R. , Debski Elizabeth A. 
Published: April 2018

We have assessed the role of activity in the adult frog visual system in modulating two aspects of neuronal plasticity: neurotransmitter expression and topographic map maintenance. Chronic treatment of one tectal lobe with the non-NMDA receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione decreased the percentage of substance P-like immunoreactive (SP-IR) tectal cells in the untreated lobe while disrupting topographic map formation in the treated one. Treatment with the NMDA receptor antagonistd-(−)-2-amino-5-phosphonovaleric acid (d-AP-5) disrupted the topographic map but had no affect on SP-IR cells. These results indicate that maintenance of the topographic map is dependent on direct input from the glutamatergic retinal ganglion cells, whereas substance P (SP) expression is being regulated by a pathway that relays activity from one tectal lobe to the other. Such a pathway is provided by the cholinergic nucleus isthmi, which is reciprocally connected to the ipsilateral tectum and sends a projection to the contralateral one.Mecamylamine and atropine, antagonists of nicotinic and muscarinic receptors, respectively, were used together to block all cholinergic activity or alone to block receptor subclass activity. All three treatments decreased SP expression and disrupted the topographic map in the treated tectal lobe. We conclude that both SP expression and topographic map maintenance in the adult optic tectum are activity-dependent processes. Although our results are consistent with the maintenance of the topographic map through an NMDA receptor-based mechanism, they suggest that SP expression is regulated by a cholinergic interaction that depends on retinal ganglion cell input only for its activation.
The Midbrain Precommand Nucleus of the Mormyrid Electromotor Network
Authors: von der Emde Gerhard , Sena Leonel Gómez , Niso Rafaella , Grant Kirsty 
Published: April 2018

The functional role of the midbrain precommand nucleus (PCN) of the electromotor system was explored in the weakly electric mormyrid fishGnathonemus petersii, using extracellular recording of field potentials, single unit activity, and microstimulationin vivo.Electromotor-related field potentials in PCN are linked in a one-to-one manner and with a fixed time relationship to the electric organ discharge (EOD) command cycle, but occur later than EOD command activity in the medulla. It is suggested that PCN electromotor-related field potentials arise from two sources: (1) antidromically, by backpropagation across electrotonic synapses between PCN axons and command nucleus neurons, and (2) as corollary discharge-driven feedback arriving from the command nucleus indirectly, via multisynaptic pathways.PCN neurons can be activated by electrosensory input, but this does not necessarily activate the whole motor command chain. Microstimulation of PCN modulates the endogenous pattern of electromotor command in a way that can mimic the structure of certain stereotyped behavioral patterns. PCN activity is regulated, and to a certain extent synchronized, by corollary discharge feedback inhibition. However, PCN does not generally function as a synchronized pacemaker driving the electromotor command chain. We propose that PCN neurons integrate information of various origins and individually relay this to the command nucleus in the medulla. Some may also have intrinsic, although normally nonsynchronized, pacemaker properties. This descending activity, integrated in the electromotor command nucleus, will play an important modulatory role in the central pattern generator decision process.
Differential Postnatal Development of Catecholamine and Serotonin Inputs to Identified Neurons in Prefrontal Cortex of Rhesus Monkey
Authors: Lambe Evelyn K. , Krimer Leonid S. , Goldman-Rakic Patricia S. 
Published: April 2018

The monoaminergic innervation of cerebral cortex has long been implicated in its development. Methods now exist to examine catecholamine and serotonin inputs to identified neurons in the cerebral cortex. We have quantified such inputs on pyramidal and nonpyramidal cells in prefrontal cortex of rhesus monkeys ranging in age from 2 weeks to 10 years. Individual layer III neurons were filled with Lucifer yellow and double-immunostained with axons containing either tyrosine hydroxylase (TH) or 5-hydroxytryptamine (5-HT). The filled cells were reconstructed, and putative appositions between the axons and dendritic spines and shafts were quantified at high magnification using light microscopy.The density of catecholamine appositions on pyramidal neurons matures slowly, reaching only half the adult level by 6 months of age and thereafter rising gradually to adult levels by 2 years of age. By contrast, the density of serotonin appositions on pyramidal cells reaches the adult level before the second week after birth. The average adult pyramidal neuron in layer III of area 9m receives three times stronger input from catecholaminergic than from serotoninergic axons. The overall density of both inputs to interneurons does not appear to change during postnatal development. Selective changes in the TH innervation of pyramidal cells against a backdrop of constant TH innervation of interneurons suggest that the balance between excitation and inhibition may change developmentally in the prefrontal cortex. By contrast, 5-HT innervation of both types of neurons remains relatively constant over the age range studied.
Thalamic Reticular Nucleus Activation Reflects Attentional Gating during Classical Conditioning
Authors: McAlonan Kerry , Brown Verity J. , Bowman Eric M. 
Published: April 2018

All senses, except olfaction, are routed through the thalamus to cerebral cortex. Thus, the thalamus is often referred to as the sensory gateway to cortex. Located between thalamus and cortex is a thin lamina of neurons called the thalamic reticular nucleus, which may function as an attentional gate. The phenomenon of blocking in classical conditioning provides an opportunity to test whether an attended stimulus activates the thalamic reticular nucleus more than an unattended stimulus: when a second stimulus is presented together with a previously conditioned stimulus, conditioned responding to the second stimulus is inhibited.Different groups of rats were given conditioning sessions with a single stimulus, a light or a tone, and then given conditioning sessions with compound (light and tone) stimuli. Blocking was confirmed using probe trials of single stimulus presentations. After a final test session of compound stimulus presentations, the brains were processed for the presence of Fos protein. Here we show that Fos-positive neurons were more numerous in the sector of the thalamic reticular nucleus associated with the attended conditioned stimulus than in the sector associated with the unattended stimulus. Thus, we provide evidence for an involvement of the thalamic reticular nucleus in selective attention.
Long-Range Temporal Correlations and Scaling Behavior in Human Brain Oscillations
Authors: Linkenkaer-Hansen Klaus , Nikouline Vadim V. , Palva J. Matias , Ilmoniemi Risto J. 
Published: April 2018

The human brain spontaneously generates neural oscillations with a large variability in frequency, amplitude, duration, and recurrence. Little, however, is known about the long-term spatiotemporal structure of the complex patterns of ongoing activity. A central unresolved issue is whether fluctuations in oscillatory activity reflect a memory of the dynamics of the system for more than a few seconds.We investigated the temporal correlations of network oscillations in the normal human brain at time scales ranging from a few seconds to several minutes. Ongoing activity during eyes-open and eyes-closed conditions was recorded with simultaneous magnetoencephalography and electroencephalography. Here we show that amplitude fluctuations of 10 and 20 Hz oscillations are correlated over thousands of oscillation cycles. Our analyses also indicated that these amplitude fluctuations obey power-law scaling behavior. The scaling exponents were highly invariant across subjects. We propose that the large variability, the long-range correlations, and the power-law scaling behavior of spontaneous oscillations find a unifying explanation within the theory of self-organized criticality, which offers a general mechanism for the emergence of correlations and complex dynamics in stochastic multiunit systems. The demonstrated scaling laws pose novel quantitative constraints on computational models of network oscillations. We argue that critical-state dynamics of spontaneous oscillations may lend neural networks capable of quick reorganization during processing demands.
Synaptic Currents Generating the Inhibitory Surround of Ganglion Cells in the Mammalian Retina
Authors: Flores-Herr Nicolas , Protti Dario A. , Wässle Heinz 
Published: April 2018

The receptive field (RF) of retinal ganglion cells (RGCs) consists of an excitatory central region, the RF center, and an inhibitory peripheral region, the RF surround. It is still unknown in detail which inhibitory interneurons (horizontal or amacrine cells) and which inhibitory circuits (presynaptic or postsynaptic) generate the RF surround.To study surround inhibition, light-evoked whole-cell currents were recorded from RGCs of the isolated, intact rabbit retina. The RFs were stimulated with light or dark spots of increasing diameters and with annular light stimuli.Direct inhibitory currents could be isolated by voltage clamping ganglion cells close to the Na+/K+reversal potential. They mostly represent an input from GABAergic amacrine cells that contribute to the inhibitory surround of ganglion cells. This direct inhibitory input and its physiological function were also investigated by recording light-evoked action potentials of RGCs in the current-clamp mode and by changing the intracellular Cl−concentration.The excitatory input of the ganglion cells could be isolated by voltage clamping ganglion cells at the Cl−reversal potential. Large light spots and annular light stimuli caused a strong attenuation of the excitatory input. Both GABAAreceptors and GABACreceptors contributed to this inhibition, and picrotoxinin was able to completely block it.Together, these results show that the RF surround of retinal ganglion cells is mediated by a combination of direct inhibitory synapses and presynaptic surround inhibition.
Custodias da terra: A muller rural na obra da irlandesa Alice Taylor
Authors: Estévez-Saá Margarita 
Published: April 2018

A escritora irlandesa Alice Taylor está a adicar a súa producción literaria a reproducir o modo de vida das comunidades rurais do oeste de Irlanda, prestando especial atención á contribución das mulleres, de xeito que a súa obra pode considerarse coma unha testemuña dun modo de vida a piques de extinguirse. O presente traballo reivindica a obra de Alice Taylor, analiza textos representativos dos diferentes xéneros utilizados pola autora (poemas, relatos, novelas e escritos autobiográficos), e tenta buscar unha explicación ao feito de que a a crítica literaria ten descuidado o estudo da aportación dunha autora que, nembargantes, é moi popular entre o público lector.Propoñemos un estudo de textos representativos da súa obra aplicando os conceptos Bergerianos de “autor(a) testemuña” e “memoria histórica”.
La obligación de informar y su compatibilidad con el derecho a la libertad de expresión
Authors: Salgado André Elena 
Published: April 2018

Como es sabido, la publicidad tiene una doble vertiente –informativa y persuasiva- y en cada anuncio puede prevalecer indistintamente una u otra. Sin embargo, con el paso de los años se adivina una tendencia a reforzar la dimensión informativa debido a la convivencia de una serie de normas comunitarias y estatales que regulan el engaño por omisión y establecen obligaciones específicas de información en determinados sectores. Precisamente, la existencia de tales normas nos conduce a un problema de compatibilidad con el derecho a la libertad de expresión. Tras analizar el origen de la tendencia apuntada y la postura de diferentes Tribunales acerca del reconocimiento de protección constitucional a los mensajes de naturaleza publicitaria, se comprueba si la exigencia de un deber de información al anunciante –como límite a la libertad de expresión- puede considerarse una injerencia lícita en el ámbito de protección del citado derecho.
Sulfidogenic activity of sulfate and sulfur reducing bacteria under the influence of metal compounds
Authors: Moroz O. M. , Hnatush S. O. , Tarabas O. V. , Bohoslavets C. I. , Yavorska G. V. , Borsukevych B. M. 
Published: April 2018

Due to their high content in natural environments, heavy metals exhibit toxic effects on living organisms, which leads to a decrease in the biological diversity and productivity of ecosystems. In niches with low oxidation reducing potential, sulfate and sulfur reducing bacteria carry out the reducing transformation of oxidized sulfur compounds with the formation of significant amounts of hydrogen sulfide. H2S produced by bacteria interacts with metal ions, precipitating them in the form of sulfides. The aim of this work was to investigate the influence of lead, cuprum (II), iron (II) and manganese (II) salts on the production of hydrogen sulfide by bacteria of the Desulfovibrio and Desulfuromonas genera, isolated from Yavorivske Lake, and to evaluate the efficiency of their use for purifying media, enriched with organic compounds, from hydrogen sulfide and heavy metals. The content of heavy metal ions in the water of Yavorivske Lake was determined by the spectrophotometric method. The bacteria were grown for 10 days at 30 °C in the Kravtsov-Sorokin medium under anaerobic conditions. To study the influence of metal ions on bacteria growth and their H2S production, cells were incubated with metal salts (0.5–4.0 mM), washed and grown in media with SO42– or S0. To determine the level of metal ions binding by H2S, produced by bacteria, cells were grown in media with metal compounds (0.5–4.0 mM), SO42– or S0. Biomass was determined by turbidimetric method. In the cultural liquid the content of H2S was determined quantitatively by spectrophotometric method, and qualitatively by the presence of metal cations. The content of metal sulfides in the growth medium was determined by weight method. Sulfate and sulfur-reducing bacteria were resistant to 2.0 mM Pb(NO3)2, 2.5 mM CuCl2, 2.5 mM FeCl2 × 4H2O and 2.0 mM MnCl2 × 4H2O, therefore they are promising for the development of biotechnologies for the purification of water resources contaminated by sulfur and metal compounds. When present in a medium with sulfates or sulfur of 1.0–1.5 mM lead, cuprum (II), iron (II) or manganese (II) ions, they almost completely bind with the H2S produced by bacteria in the form of insoluble sulfides, which confirms the negative results of qualitative reactions to their presence in the cultural liquid.
Biotic links in the fouling community of Odessa Bay (Black Sea)
Authors: Varigin A. Y. 
Published: April 2018

This paper reveals the character of the biotic links between the various organisms that compose the fouling community of Odessa Bay (Black Sea). The fouling community of solid substrates is formed by 62 species of invertebrates and 12 species of macrophytes. The edificator species of the community is the Black Sea mussel Mytilus galloprovincialis Lamarck, 1819. The environment-forming role of the mussel, which is represents the core of the corresponding consortia, was examined. The leading role of sessile organisms in the formation of a superorganismic structure that significantly modifies the properties of the environment was revealed. Together with the mussel, this structure is formed by the bivalve mollusc Mytilaster lineatus (Gmelin, 1791) and the barnacle crustacean Amphibalanus improvisus (Darwin, 1854). The proportion of sessile organisms accounts for 24.6% of the total number of species in the community. In this case, they significantly dominate in relative abundance and biomass (78.9% and 98.8%, respectively). The mussels during the process of growth form complexly organized druses, which are peculiar three-dimensional formations, consisting of mussels of different sizes, fastened together with a substrate by an entire network of strong byssus threads. These formations increase the level of heterogeneity of the substrate and increase the variety of available habitats for other animals. The aggregate of these druses is a kind of sedimentary trap in which particles of nutritive detritus accumulate. The availability of accessible habitats, convenient shelters and food reserves attracts various species of invertebrates to the community. Around the core of the consortia a cluster of organisms formed associated with edificator species. An important role is played by trophic links between different mobile organisms and the phyto-component of the community. The ability of the Black Sea mussel to condition the environment, creating favourable conditions for the development of other organisms, characterizes it as an autogenic ecosystem engineer. Trophic and mediopathic links between the organisms that compose the fouling community go beyond it and extend to the inhabitants of the pelagic environment.