bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrical responses reveal the temporal dynamics of brain events during involuntary attention switching
Authors: Escera Carles , Yago Elena , Alho Kimmo 
Published: March 2003

AbstractSurviving in the natural environment requires the rapid switching of attention among potentially relevant stimuli. We studied electrophysiologically the involuntary switching time in humans performing a task designed to study brain mechanisms of involuntary attention and distraction (C. Escera et al., 1998, J. Cogn. Neurosci., 10, 590–604). Ten subjects were instructed to discriminate visual stimuli preceded by a task‐irrelevant sound, this being either a repetitive tone (P = 0.8) or a distracting sound, i.e. a slightly higher deviant tone (P = 0.1) or an environmental novel sound (P = 0.1). In different conditions, the sounds preceded the visual stimuli by 245 or 355 ms. Deviant tones and novel sounds prolonged reaction times significantly to subsequent visual stimuli by 7.4 (P < 0.02) and 15.2 ms (P < 0.003), respectively. In addition to a mismatch negativity (MMN) and a positive‐polarity, 320‐ms latency, P3a event‐related potential associated, respectively, with detection of the distracting sound and the subsequent orienting of attention to it, a late frontal negative deflection was observed in distracting trials. The peak latency of this brain response from sound onset was 580 ms in the 245‐ms condition and 115 ms longer in the 355‐ms condition (P < 0.001), peaking consequently at 340 ms from visual stimulus onset, irrespective of the onset of the distracting sound. We suggest that this late frontal negative response may signal over the scalp the process of reallocating attention back to the original task after momentary distraction, and therefore that recovering from distraction may take a similar shifting time as orienting attention involuntarily towards unexpected novelty.
High expression and anterograde axonal transport of aminoterminal sonic hedgehog in the adult hamster brain
Authors: Traiffort Elisabeth , Moya Kenneth L. , Faure Hélène , Hässig Raymonde , Ruat Martial 
Published: March 2003

AbstractSonic hedgehog (SHH) is considered to play an important role in tissue induction and patterning during development, particularly in determining neuronal cell fate in the ventral neural tube and in the embryonic forebrain. SHH precursor is autoproteolytically cleaved to an aminoterminal fragment (SHHN) which retains all known SHH biological activities. Here, we demonstrate the expression of a 22‐kDa SHHN immunoreactive peptide in developing and adult hamster brain regions using a rabbit antiserum directed against a mouse SHHN fragment. Interestingly, SHHN was developmentally regulated with the highest expression observed in the adult brain, was resistant to Triton X‐100 solubilization at 4 °C and partitioned with the raft component ganglioside GM1 during density gradient centrifugation. In rat brain, Shh transcripts were identified by double in situ hybridization in GABAergic neurons located in various basal forebrain nuclei including globus pallidus, ventral pallidum, medial septum‐diagonal band complex, magnocellular preoptic nucleus and in cerebellar Purkinje cells as well as in motoneurons of several cranial nerve nuclei and of the spinal cord. We show that radiolabelled SHHN peptides are synthesized in the adult hamster retina and are transported axonally along the optic nerve to the superior colliculus in vivo. Our data indicate that SHHN is associated with cholesterol rich raft‐like microdomains and anterogradely transported in the adult brain, and suggest that the roles of this extracellular protein are more diverse than originally thought.
The psychoactive ingredient of marijuana induces behavioural sensitization
Authors: Rubino Tiziana , Viganò Daniela , Massi Paola , Parolaro Daniela 
Published: March 2003

SummaryHere we describe, for the first time, the occurrence of behavioural sensitization after chronic exposure to Δ9‐tetrahydrocannabinol. Rats were treated twice a day, for five days, with increasing doses (5, 10, 20, 40, 40 mg/kg i.p.) of Δ9‐tetrahydrocannabinol or its vehicle and after 20 days of withdrawal, animals were challenged with 5 mg/kg (i.p.) of the drug and their behaviour was assessed. Contrary to the motor inhibition induced in control rats, challenge with Δ9‐tetrahydrocannabinol in pre‐exposed animals elicited a complex behavioural syndrome mainly characterized by oral stereotyped items. Due to the relevance of behavioural sensitization in drug‐seeking behaviour that persists long after discontinuation of drug use, our findings suggest that cannabinoids could trigger neurobiological alteration not dissimilar from those observed with more harmful abused drugs.
Homeostatic plasticity induced by chronic block of AMPA/kainate receptors modulates the generation of rhythmic bursting in rat spinal cord organotypic cultures
Authors: Galante Micaela , Avossa Daniela , Rosato‐Siri Marcelo , Ballerini Laura 
Published: March 2003

AbstractGeneration of spontaneous rhythmic activity is a distinct feature of developing spinal networks. We report that rat embryo organotypic spinal cultures contain the basic circuits responsible for pattern generation. In this preparation rhythmic activity can be recorded from ventral interneurons and is developmentally regulated. When chronically grown in the presence of an AMPA/kainate receptor blocker, this circuit expresses long‐term plasticity consisting largely of increased frequency of fast synaptic activity and reduction in slow GABAergic events. We examined whether, once this form of homeostatic plasticity is established, the network could still exhibit rhythmicity with properties similar to controls. Control or chronically treated ventral interneurons spontaneously generated (with similar probability) irregular, network‐driven bursts over a background of ongoing synaptic activity. In control cultures increasing network excitability by strychnine plus bicuculline, or by raising [K+]o, induced rapid‐onset, regular rhythmic bursts. In treated cultures the same pharmacological block of Cl–‐mediated transmission or high‐K+ application also induced regular patterned activity, although significantly faster and, in the case of high K+, characterized by slow onset due to postsynaptic current summation. Enhancing GABAergic transmission by pentobarbital surprisingly accelerated the high‐K+ rhythm of control cells (though depressing background activity), whereas it slowed it down in chronically treated cells. This contrasting effect of pentobarbital suggests that, to preserve bursting ability, chronic slices developed a distinct GABAergic inhibitory control on over‐expressed bursting circuits. Conversely, in control slices GABAergic transmission depressed spontaneous activity but it facilitated bursting frequency. Thus, even after homeostatic rearrangement, developing mammalian spinal networks still generate rhythmic activity.
Temporal characterization of memory retrieval processes: an fMRI study of the ‘tip of the tongue’ phenomenon
Authors: Kikyo Hideyuki , Ohki Kenichi , Sekihara Kensuke 
Published: March 2003

Abstract‘Tip of the tongue’ (TOT) is a natural phenomenon in which people cannot retrieve a target word immediately, even though they feel confident that they know the target. This provides us an opportunity to understand the human memory system, because cognitive components of memory retrieval such as retrieval effort and successful retrieval are temporally dissociated from each other during the TOT states. The purpose of the present study was to reveal the neural correlates of the cognitive components of the retrieval process by separating cognitive phases of the TOT phenomenon using event‐related functional magnetic resonance imaging with multiple regression analysis. We demonstrated that the left dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex were activated at the time of successful retrieval, and the left DLPFC also showed activation when the subjects successfully retrieved the target names as compared to when they gave up. This result suggests that the left DLPFC is specific to the successful retrieval process. During the TOT state, a number of regions were activated, and this suggests that widely distributed brain regions are engaged when people make a hard effort to retrieve a proper name in the TOT state. Our new approach employing temporal resolution of the TOT phenomenon may contribute to the understanding of the mechanisms of the human memory system.
Striatal projections from the cat visual thalamus
Authors: Harting John K. , Updyke Bruce V. , Van Lieshout David P. 
Published: March 2003

AbstractAnterograde transport methods reveal an extensive thalamostriate projection from the extrageniculate visual thalamus. These projections distribute to approximately the same regions of the striatum innervated by the corticostriate projections from over a dozen higher visual cortical areas [visual‐recipient sector; Updyke, B.V. (1993) J. Comp. Neurol., 327, 159–193.]. Like their cortical counterparts, the thalamostriate projections to the caudate distribute in a patchy manner that suggests potential overlap or intermingling spatial relationships between the two major afferents. All of the visually related thalamic nuclei projecting to the striatum receive ascending signals from the superior colliculus, suggesting that the constraints placed upon tectal processing by striatonigral control have important consequences for central perceptuomotor processing at the striatal and cortical levels.
Caspase inhibitors increase short‐term survival of progenitor‐cell progeny in the adult rat dentate gyrus following status epilepticus
Authors: Ekdahl Christine T. , Mohapel Paul , Elmér Eskil , Lindvall Olle 
Published: March 2003

AbstractThe dentate gyrus (DG) is one of the few regions in the brain that continues to produce new neurons throughout adulthood. Seizures not only increase neurogenesis, but also lead to death of DG neurons. We investigated the relationship between cell death and neurogenesis following seizures in the DG of adult rats by blocking caspases, which are key components of apoptotic cell death. Multiple intracerebroventricular infusions of caspase inhibitors (pancaspase inhibitor zVADfmk, and caspase 3 and 9 inhibitor) prior to, just after, 1 day after, and 1 week following 2 h of lithium–pilocarpine‐induced status epilepticus reduced the number of terminal deoxynucleotidyl transferase‐mediated fluorescein‐dUTP nick‐end labelled (TUNEL) cells and increased the number of bromodeoxyuridine (BrdU) ‐stained proliferated cells in the subgranular zone at 1 week. The caspase inhibitor‐treated group did not differ from control at 2 days or 5 weeks following the epileptic insult. Our findings suggest that caspases modulate seizure‐induced neurogenesis in the DG, probably by regulating apoptosis of newly born neurons, and that this action can be suppressed transiently by caspase inhibitors. Furthermore, although previous studies have indicated that increased neuronal death can trigger neurogenesis, we show here that reduction in apoptotic death may be associated with increased neurogenesis.
ATP stimulation of P2X7 receptors activates three different ionic conductances on cultured mouse Schwann cells
Authors: Colomar Aurore , Amédée Thierry 
Published: March 2003

AbstractExtracellular ATP, by acting on P2 purinergic receptors, is a potent mediator of cell‐to‐cell communication both within and between the nervous and the immune systems. We show here by patch‐clamp recording, fluorescent dye uptake and immunocytochemistry that, in cultured mouse Schwann cells, ATP activates a P2X7 receptor associated with three different ionic conductances. In control conditions, ATP activated an inward current (IATP) with a low potency (EC50, 7.2 mm). Replacing ATP either by the ATP analogue 2′,3′‐O‐(4‐benzoyl‐4‐benzoyl)‐ATP (BzATP) or by the tetraacidic form ATP4– potentiated the inward current (ATP4– EC50, 375 µm). ATP and BzATP currents were strongly reduced by periodate oxidized ATP (oATP), an antagonist of P2X7 receptors. IATP was a mixed current composed of a nonselective cationic conductance, a cationic conductance selective for K+ and an anionic conductance selective for Cl–. The activation of the K+ conductance was dependent on an influx of Ca2+, and was blocked by charybdotoxin (ChTX) and tetraethylammonium (TEA), two potent antagonists of large conductance Ca2+‐activated K+ channels (BK channels). The activation of the Cl– conductance was insensitive to Ca2+ but required the presence of K+. Total removal of K+ blocked both the Ca 2+‐activated K+ conductance and the Cl– conductance, unveiling the P2X7 nonselective cationic conductance. The P2X7 receptor was localized by immunocytochemistry using a polyclonal antibody, anti‐P2X7, whilst its expression and functionality were both detected by the uptake of Lucifer Yellow. This receptor could regulate the synthesis and the release of cytokines by Schwann cells during pathophysiological events.
Immobilized amyloid precursor protein constructs: a tool for the in vitro screening of glial cell reactivity
Authors: Von Bernhardi Rommy , Ramírez Gigliola , Matile Hugues , Döbeli Heinz 
Published: March 2003

AbstractAstrocytes and microglia are closely associated with amyloid plaques in Alzheimer's disease (AD). Microglia constitute the first barrier surrounding plaques, although they seem to be unable to remove them efficiently. We evaluated the reaction of microglial cells from neonatal rats and mice to plaque mimetics. The C‐terminal part of the amyloid precursor protein (APP) or amyloid peptide (Aβ) was immobilized to either 60‐µm or 2.8‐µm beads and incubated with microglial cells. Beads of 60 µm, having approximately the size of senile plaques, were not phagocytosed, in contrast to 2.8‐µm beads, which were phagocytosed by microglia but not by astrocytes. Once taken up by the cells, proteins immobilized to the beads were degraded rapidly, as confirmed by mass spectrometry and immunofluorescence with an antibody against β‐amyloid. On the other hand, no protein degradation was observed with 60‐µm beads. Also, probably as a reaction to its incapability to phagocytose the beads, glia organized around the beads and started to proliferate. Cell proliferation was more pronounced when the beads contained the Aβ epitope compared with the beads with an inert surface. This in vitro effect could be exploited to set up a screening assay for compounds that ameliorate the adverse reaction of microglia supposed to contribute to the pathogenesis of AD.
Strain differences in the behavioural outcome of neonatal ventral hippocampal lesions are determined by the postnatal environment and not genetic factors
Authors: Wood Graham K. , Marcotte Eric R. , Quirion Remi , Srivastava Lalit K. 
Published: March 2003

AbstractIt has been demonstrated that not only do rats neonatally lesioned in the ventral hippocampus (VH) develop behavioural hypersensitivity to amphetamine postpubertally, but also that the expression of the sensitivity is strain specific. For example, excitotoxic VH lesions at postnatal day (PD) 7 lead to significant increases in amphetamine‐induced locomotion in postpubertal Fischer rats, but not in Lewis rats. However, as it is likely that the effect of strain differences are due to a combination of genetics and environment, we examined the contributions of the environment of the pups in determining the behavioural outcome following neonatal VH lesions. Fisher and Lewis rat pups were cross‐fostered at birth, and then at PD7 lesioned bilaterally in the VH with ibotenic acid. anova analysis of postpubertal amphetamine‐induced locomotor data revealed a significant effect of the strain of the dams raising the pups but no effect of the strain of the pup. In addition, a post hoc analysis revealed that lesioned Fisher or Lewis rats raised by Fisher, but not those raised by Lewis, dams demonstrated amphetamine‐induced hyperlocomotion relative to nonlesioned controls. Observations of the maternal behaviour of Fischer and Lewis dams revealed significant differences in the frequency of arched‐back nursing between the two strains. Interestingly, a correlation of the frequency of arched back nursing vs novelty‐ or amphetamine‐induced locomotion revealed that the lesioned rats were significantly more affected by increases in arched‐back nursing compared to the controls. The results suggest that the genetic background of the pups does not significantly affect the behavioural outcome following neonatal VH lesions; however, the results do suggest an important role of early environmental variables on the behavioural outcome of neonatal VH lesions.
Detection of animals in natural images using far peripheral vision
Authors: Thorpe Simon J. , Gegenfurtner Karl R. , Fabre‐Thorpe Michèle , Bülthoff Heinrich H. 
Published: March 2003

AbstractIt is generally believed that the acuity of the peripheral visual field is too poor to allow accurate object recognition and, that to be identified, most objects need to be brought into foveal vision by using saccadic eye movements. However, most measures of form vision in the periphery have been done at eccentricities below 10° and have used relatively artificial stimuli such as letters, digits and compound Gabor patterns. Little is known about how such data would apply in the case of more naturalistic stimuli. Here humans were required to categorize briefly flashed (28 ms) unmasked photographs of natural scenes (39° high, and 26° across) on the basis of whether or not they contained an animal. The photographs appeared randomly in nine locations across virtually the entire extent of the horizontal visual field. Accuracy was 93.3% for central vision and decreased almost linearly with increasing eccentricity (89.8% at 13°, 76.1% at 44.5° and 71.2% at 57.5°). Even at the most extreme eccentricity, where the images were centred at 70.5°, subjects scored 60.5% correct. No evidence was found for hemispheric specialization. This level of performance was achieved despite the fact that the position of the image was unpredictable, ruling out the use of precued attention to target locations. The results demonstrate that even high‐level visual tasks involving object vision can be performed using the relatively coarse information provided by the peripheral retina.
Effect of vasopressin on the input–output properties of rat facial motoneurons
Authors: Pierson Patricia , Tribollet Eliane , Raggenbass Mario 
Published: March 2003

AbstractVasopressin can directly excite facial motoneurons in young rats and mice. It acts by generating a persistent inward current, which is Na+‐dependent, tetrodotoxin‐insensitive and voltage‐gated. This peptide‐evoked current is unaffected by Ca++ or K+ channel blockade and is modulated by extracellular divalent cations. In the present work, we determined how vasopressin alters the input–output properties of facial motoneurons. Whole‐cell recordings were obtained from these neurons in the current clamp mode, in brainstem slices of young rats. Repetitive firing was evoked by injecting depolarizing current pulses. Steady‐state frequency–current (f–I) relationships were constructed and the effect of vasopressin on these relationships was studied. We found that vasopressin caused a parallel shift to the left of the cell steady‐state f–I relationship. This effect persisted in the presence of blockers of K+ or Ca++ channels. The peptide effect was distinct from that brought about by Ca++ channel suppression or by apamin, a blocker of the mAHP. These latter manipulations resulted in an increase in the slope of the steady‐state f–I relationship. We conclude that the vasopressin‐induced modification of the input–output properties of facial motoneurons is probably exclusively caused by the sodium‐dependent, voltage‐modulated inward current elicited by the peptide, rather than being due to indirect effects of the peptide on Ca++ channels, K+ channels or Ca++‐dependent K+ channels. Computer simulation, based on a simple model of facial motoneurons, indicates that the introduction of a conductance having the properties of the vasopressin‐dependent conductance can entirely account for the observed peptide‐induced shift of the f–I relationship.
Evaluation of the tetracycline‐ and ecdysone‐inducible systems for expression of neurotransmitter receptors in mammalian cells
Authors: Van Craenenbroeck Kathleen , Vanhoenacker Peter , Leysen Josée E. , Haegeman Guy 
Published: March 2003

AbstractEstablishing a stable cell line that expresses a particular protein of interest is often a laborious and time‐consuming experience. With constitutive expression systems, a gradual loss of the highly expressing clones over a given time span and/or a severe counter‐selection due to toxicity of the expressed protein for the host cell line are major drawbacks. In both cases, inducible expression systems offer a valuable alternative. Over the years, many regulated expression systems have been developed and evaluated. In the present study, we compare the efficiency, the advantages and the drawbacks of a tetracycline‐ and an ecdysone‐inducible system for expression of the reporter protein chloramphenicol acetyltransferase and of different G‐protein‐coupled serotonin (5‐HT) receptors. A high level of expression of different 5‐HT receptors was obtained with the tetracycline‐inducible system. In the cell line L929, which stably expresses the tetracycline‐responsive transactivator, a maximum ligand binding of 20 000 and 9500 fmol/mg protein was measured for the h5‐HT1B and h5‐ht1F receptors, respectively. In the HEK293rtTA cell line, levels of 15 700, 3000, and 9100 fmol bound ligand/mg protein were obtained for the h5‐HT1B, h5‐ht1F and h5‐HT4b receptors, respectively. These high expression levels remained stable for several months of continuous culture. Although the ecdysone‐inducible expression system was useful for tightly regulated expression, the levels were far lower than those obtained with the tetracycline system (e.g. 640 fmol bound ligand/mg protein for the h5‐ht1F receptor in HEK293EcR).
Impairment of binocular vision in the adult cat induces plastic changes in the callosal cortical map
Authors: Watroba Laurent , Buser Pierre , Milleret Chantal 
Published: March 2003

AbstractIn the primary visual cortex of normally reared adult cat, neurons activated through the corpus callosum are almost entirely located at the 17/18 border. They display small receptive fields distributed along the central vertical meridian of the visual field and are orientation selective. Here we demonstrate that a few weeks of monocular deprivation or unilateral convergent strabismus produced in adulthood does not modify the cortical distribution of these neurons, but leads to an increase of their receptive field size mainly toward the ipsilateral hemifield and to a loss of their orientation selectivity. We conclude that manipulation of binocular vision in the adult modifies neither the location of the primary callosal cortical map nor its retinotopy. In contrast, it induces functional plastic changes in this map which lead to a significant widening of the area of visual space signalled through the corpus callosum. These plastic changes are interpreted as the result of the strengthening of normally hidden subthreshold synaptic inputs.