bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamics of narrow‐band EEG phase effects in the passive auditory oddball task
Authors: Barry Robert J. , Rushby Jacqueline A. , Smith Janette L. , Clarke Adam R. , Croft Rodney J. 
Published: July 2006

AbstractEvidence suggests that the component frequencies of the electroencephalogram (EEG) are dynamically adjusted to provide particular brain states at stimulus occurrence, and that these facilitate cortical processing of the stimulus. We examined relationships between stimulus intensity, the phase of narrow‐band EEG activity at stimulus onset, and the resultant event‐related potentials (ERPs) in a passive auditory oddball task, using a novel conceptualization of orthogonal phase effects (cortical negativity vs. positivity, negative driving vs. positive driving, waxing vs. waning). EEG responses to the standard stimuli (50 vs. 80 dB, varied between subjects) were analysed. Prestimulus narrow‐band EEG activity (in 1‐Hz bands from 1 to 13 Hz) at Cz was assessed for each trial by digital filtering. For each frequency, the cycle at stimulus onset was used to sort trials into four phases, for which ERPs were derived from both the filtered and unfiltered EEG activity at Fz, Cz and Pz. Preferred brain states at various frequencies were indicated by 16–34% differential occurrence within the orthogonal phase dimensions explored. The preferred states were associated with smaller N1, N2 and N3, larger P2 and P3, shorter N1, P2, N2 and P3 latencies, and some intensity effects. These effects reflected the operation of three separate phase‐influenced mechanisms, involving anticipatory potentials and prestimulus/poststimulus amplitudes in various EEG frequencies. Results indicate that, even in paradigms with a slightly varying interstimulus interval, brain dynamics provide preferred brain states at the moment of stimulus presentation, which differentially affect the EEG correlates of stimulus processing.
Cholinergic modulation of response properties and orientation tuning of neurons in primary visual cortex of anaesthetized Marmoset monkeys
Authors: Zinke W. , Roberts M. J. , Guo K. , McDonald J. S. , Robertson R. , Thiele A. 
Published: July 2006

AbstractCortical processing is strongly influenced by the actions of neuromodulators such as acetylcholine (ACh). Early studies in anaesthetized cats argued that acetylcholine can cause a sharpening of orientation tuning functions and an improvement of the signal‐to‐noise ratio (SNR) of neuronal responses in primary visual cortex (V1). Recent in vitro studies have demonstrated that acetylcholine reduces the efficacy of feedback and intracortical connections via the activation of muscarinic receptors, and increases the efficacy of feed‐forward connections via the activation of nicotinic receptors. If orientation tuning is mediated or enhanced by intracortical connections, high levels of acetylcholine should diminish orientation tuning. Here we investigate the effects of acetylcholine on orientation tuning and neuronal responsiveness in anaesthetized marmoset monkeys. We found that acetylcholine caused a broadening of the orientation tuning in the majority of cells, while tuning functions became sharper in only a minority of cells. Moreover, acetylcholine generally facilitated neuronal responses, but neither improved signal‐to‐noise ratio, nor reduced trial‐to‐trial firing rate variance systematically. Acetylcholine did however, reduce variability of spike occurrences within spike trains. We discuss these findings in the context of dynamic control of feed‐forward and lateral/feedback connectivity by acetylcholine.
Expression of Drosophila BarH1‐H2 homeoproteins in developing dopaminergic cells and segmental nerve a (SNa) motoneurons
Authors: Garces Alain , Bogdanik Laurent , Thor Stefan , Carroll Patrick 
Published: July 2006

Abstract Barh1/h2 genes encode two related homeobox transcription factors (B‐H1 and B‐H2) previously shown to play essential roles in the formation and specification of the distal leg segments and in retinal neurogenesis. Here we describe the restricted expression pattern of the B‐H1/‐H2 homeoprotein within the embryonic ventral nerve cord of Drosophila. We show that B‐H1/‐H2 are specifically expressed in a subset of dopaminergic neurons, namely the unpaired ventral midline dopaminergic neuron, and in a subpopulation of laterally projecting motoneurons, i.e. the five motoneurons forming the segmental nerve a (SNa) branch. Using the GAL4–UAS system we show that B‐H1/‐H2Gal4 in combination with a membrane‐targeted enhanced green fluorescent protein reporter line provides a powerful genetic tool reproducibly to label SNa motoneuron projections and terminals at the periphery, and their dendritic tree in the ventral nerve cord. Thus, the highly restricted expression pattern of the B‐H1/‐H2 homeoproteins and notably the related Gal4 driver represent powerful genetic tools to identify and study genes that control axon guidance, synaptogenesis or dendritic arborization within a small subpopulation of motoneurons identifiable from embryogenesis to late larval stages.
Substantia nigra pars compacta is critical to both the acquisition and expression of learned orienting of rats
Authors: El‐Amamy Heather , Holland Peter C. 
Published: July 2006

AbstractNovel events produce characteristic orienting responses (ORs), which typically habituate rapidly with repeated stimulus presentation. However, they may re‐emerge if those stimuli become predictors of biologically significant events. This acquisition of conditioned ORs may reflect a broader range of enhancements in top‐down attentional processing of cues that predict important consequences. Previous research from this laboratory showed that a neural circuit that includes the amygdala central nucleus (CeA), substantia nigra pars compacta (SNc) and dorsolateral striatum (DLS) is essential for the learning and expression of one example of conditioned orienting, the rearing of rats to visual stimuli paired with food. Other studies showed that the CeA is critical to the acquisition of these conditioned ORs, but not their expression, and that normal DLS function is required for the expression of previously acquired conditioned ORs, but not for learning itself. The experiments reported here considered the roles of the SNc in conditioned orienting by examining the effects of transient inactivation of the SNc during the acquisition of new associations and during the expression of previous learning. SNc function was critical to both the acquisition and expression of conditioned ORs but not to the display of unconditioned ORs or the learning and expression of conditioned responses directed to the food source. Together with our previous findings, these results suggest that the SNc is trained by the CeA during learning and maintains acquired information so that it may modulate DLS sensory‐motor function at the time of action.
The cytoplasmic domain of NrCAM binds to PDZ domains of synapse‐associated proteins SAP90/PSD95 and SAP97
Authors: Dirks Petra , Thomas Uli , Montag Dirk 
Published: July 2006

AbstractNrCAM, a member of the L1 family of cell adhesion molecules, serves important functions during the development of the nervous system, e.g. in adhesion‐dependent processes such as neurite outgrowth and axonal pathfinding. Complex homo‐ and heterophilic binding and several extracellular ligands of NrCAM have been described, but less is known about intracellular interaction partners. The cytoplasmic carboxy‐terminus of NrCAM contains a typical sequence motif for binding to PDZ domains, making interactions with PDZ domain‐containing scaffolding proteins quite conceivable. In this study, we identified specific interactions of the intracellular domain of NrCAM with class I PDZ domains of the membrane‐associated guanylate kinases SAP90/PSD95 and SAP97. In contrast to NrCAM, the intracellular domains of the other mammalian L1 family molecules, e.g. L1, CHL1 and Neurofascin, did not interact with these PDZ domains. In transfected COS‐7 cells, NrCAM‐mediated recruitment of SAP97 to the plasma membrane was dependent on the PDZ binding motif. We show that NrCAM and SAP97 are colocalized, e.g. within photoreceptor terminals of the mammalian retina. In summary, our results confirm a functional PDZ domain binding motif at the carboxy‐terminus of NrCAM and support potential functions of NrCAM during the assembly of highly organized protein complexes at the cell membrane.
Repeated withdrawal from ethanol spares contextual fear conditioning and spatial learning but impairs negative patterning and induces over‐responding: evidence for effect on frontal cortical but not hippocampal function?
Authors: Borlikova Gilyana G. , Elbers Nicoliene A. , Stephens David N. 
Published: July 2006

AbstractRepeated exposure of rats to withdrawal from chronic ethanol reduces hippocampal long‐term potentiation and gives rise to epileptiform‐like activity in hippocampus. We investigated whether such withdrawal experience also affects learning in tasks thought to be sensitive to hippocampal damage. Rats fed an ethanol‐containing diet for 24 days with two intermediate 3‐day withdrawal episodes, resulting in intakes of 13–14 g/kg ethanol per day, showed impaired negative patterning discrimination compared with controls and animals that had continuous 24‐day ethanol treatment, but did not differ from these animals in the degree of contextual freezing 24 h after training or in spatial learning in the Barnes maze. Repeatedly withdrawn animals also showed increased numbers of responses in the period immediately before reinforcement became available in an operant task employing a fixed‐interval schedule although overall temporal organization of responding was unimpaired. Thus, in our model of repeated withdrawal from ethanol, previously observed changes in hippocampal function did not manifest at the behavioural level in the tests employed. The deficit seen after repeated withdrawal in the negative patterning discrimination and over‐responding in the fixed‐interval paradigm might be related to the changes in the functioning of the cortex after withdrawal.
The septal EEG suggests a distributed organization of the pacemaker of hippocampal theta in the rat
Authors: Nerad Ludek , McNaughton Neil 
Published: July 2006

AbstractIndividual neurons in the medial septum and diagonal band fire in phase with, and appear to act as a ‘pacemaker’ of, the hippocampal theta rhythm. We investigated the relationships of periodic EEG both among various parts of the septum and with dorsal hippocampal theta recorded concurrently in freely moving rats. Most septal sites showed theta rhythm concurrent with hippocampal theta during locomotion. However, periods with theta at hippocampal but not septal sites were more frequent than the reverse. Theta waves in different parts of the septum were synchronized with each other but medial septal sites showed less frequent theta than other sites. The phase delays between medial and lateral septal sites were < 10 ms, suggesting that the hippocampus does not act as a simple relay between the two. Spectral analysis revealed periods (> 5 s) of theta at hippocampal sites co‐occurring with rhythms at multiple septal sites that were slower than theta. Even slower were the ‘slow septal waves’ (mean 2.7 Hz), which were present in the absence of locomotion and did not ‘drive’ the hippocampus. Our data suggest that the pacemaker of hippocampal theta may best be thought of as a set of functionally differentiated components rather than as a single homogenous unit.
Net influx of plasma 6‐[18F]fluoro‐l‐DOPA (FDOPA) to the ventral striatum correlates with prefrontal processing of affective stimuli
Authors: Siessmeier Thomas , Kienast Thorsten , Wrase Jana , Larsen Jennifer Lynne , Braus Dieter F. , Smolka Michael N. , Buchholz Hans Georg , Schreckenberger Mathias , Rösch Frank , Cumming Paul , Mann Karl , Bartenstein Peter , Heinz Andreas 
Published: July 2006

AbstractDopaminergic neurotransmission in the ventral and dorsal striatum interact with central processing of rewarding and reward‐indicating stimuli, and may affect frontocortical–striatal–thalamic circuits regulating goal‐directed behaviour. Thirteen healthy male volunteers were investigated with multimodal imaging, using the radioligand 6‐[18F]fluoro‐l‐DOPA (FDOPA) for positron emission tomography (PET) measurements of dopamine synthesis capacity, and also functional magnetic resonance imaging (fMRI) in a cognitive activation paradigm. We calculated the correlation between FDOPA net blood–brain influx (; ml/g/min) in the ventral and associative dorsal striatum and BOLD signal changes elicited by standardized affectively positive, negative and neutral visual stimuli. The magnitude of in the ventral striatum was positively correlated with BOLD signal increases in the left anterior cingulate cortex and right insular operculum elicited by positive vs. neutral stimuli, but not negative vs. neutral stimuli. In the dorsal striatum, the magnitude of was positively correlated with processing of positive and negative stimuli in the left dorsolateral prefrontal cortex. These findings suggest that dopamine synthesis capacity in the ventral striatum correlates with the attentional processing of rewarding positive stimuli in the anterior cingulate cortex of healthy subjects. Dopaminergic neurotransmission in the associative dorsal striatum has been associated previously with habit learning. The observed correlation between dopamine synthesis capacity in the dorsal striatum and BOLD signal changes in the dorsolateral prefrontal cortex suggests dopaminergic modulation of processing of emotional stimuli in brain areas associated with motor planning and executive behaviour control.
Effects of human–carnivore conflict on tiger (Panthera tigris) and prey populations in Lao PDR
Authors: Johnson A. , Vongkhamheng C. , Hedemark M. , Saithongdam T. 
Published: July 2006

AbstractUnique to South‐east Asia, Lao People's Democratic Republic contains extensive habitat for tigers and their prey within a multiple‐use protected area system covering 13% of the country. Although human population density is the lowest in the region, the impact of human occurrence in protected areas on tiger Panthera tigris and prey populations was unknown. We examined the effects of human–carnivore conflict on tiger and prey abundance and distribution in the Nam Et‐Phou Louey National Protected Area on the Lao–Vietnam border. We conducted intensive camera‐trap sampling of large carnivores and prey at varying levels of human population and monitored carnivore depredation of livestock across the protected area. The relative abundance of large ungulates was low throughout whereas that of small prey was significantly higher where human density was lower. The estimated tiger density for the sample area ranged from 0.2 to 0.7 per 100 km2. Tiger abundance was significantly lower where human population and disturbance were greater. Three factors, commercial poaching associated with livestock grazing followed by prey depletion and competition between large carnivores, are likely responsible for tiger abundance and distribution. Maintaining tigers in the country's protected areas will be dependent on the spatial separation of large carnivores and humans by modifying livestock husbandry practices and enforcing zoning.
Influence of anthropogenic disturbance on bird communities in a tropical dry forest: role of vegetation structure
Authors: Shahabuddin G. , Kumar R. 
Published: July 2006

AbstractA study was carried out in Sariska Tiger Reserve in India to investigate the effects of anthropogenic disturbance caused by biomass extraction on the bird communities of tropical dry forests. The study was based on comparisons of the avifaunal community as well as vegetation structure between strictly protected (‘undisturbed’) and intensively used (‘disturbed’) sites that were demarcated a priori on the basis of disturbance indicators. There was no significant difference in the number of recorded species and bird abundance between disturbed and undisturbed sites. However, bird species diversity was significantly lower in disturbed sites. Bird species composition was found to differ significantly between disturbed and undisturbed sites and was associated with the measured disturbance indicators. Changes in bird species composition occurred because of seven of 26 locally abundant bird species (26.9%) responding significantly to the disturbance regime. All the affected bird species are primarily insectivorous. Bird species composition was significantly related to six vegetation structural variables, including two that were significantly altered by disturbance. Changes in vegetation structure accounted for all the changes in bird species composition caused by disturbance. However, vegetation structure had additional effects on bird species composition besides those caused simply by disturbance. Thus, our study indicates that forest use in the form of chronic biomass extraction can have significant effects upon bird diversity and species composition of tropical dry forest. There is a need to retain a proportion of natural ecosystems as inviolate if the full complement of biodiversity is to be conserved.
Critical habitat during the transition from maternal provisioning in freshwater fish, with emphasis on Atlantic salmon (Salmo salar) and brown trout (Salmo trutta)
Authors: Armstrong J. D. , Nislow K. H. 
Published: July 2006

AbstractIn freshwater fish, the transition from dependence on maternal yolk reserves to independent foraging can be an early critical period, with survival during this stage having a strong influence on population abundance and cohort strength. Information concerning Atlantic salmonSalmo salarand brown troutSalmo truttaas model species is reviewed to show how population dynamics are influenced by habitat use during the transitional stage and illustrate the role of maternal provisioning along with density‐dependent and ‐independent factors. The allocation of resources in yolk and timing and position of spawning strongly influence the biotic and abiotic environments of juveniles and their subsequent performance. Vulnerability to predators, adverse environmental conditions and restricted conditions over which they can successfully forage result in specific habitat requirements for newly independent juveniles. The availability of slow‐flowing habitats at stream margins during the first month of independence is crucial. Alteration of natural flow regimes and physical habitat structure, associated with a wide range of anthropogenic influences, can have significant deleterious effects on the availability of critical juvenile habitat. A model combining habitat structure and the relationship between density‐dependent and ‐independent mortality is presented to explore the range of conditions under which the transitional period would have a strong influence on population abundance. This model provides a framework for establishing thresholds or optima for habitat availability that will favour sufficient recruitment out of the transitional stage. Using the modelling framework, managers can make informed decisions on the utility and cost effectiveness of fisheries and habitat management activities designed to increase juvenile survival during the transition to independence. A range of management options is outlined for improving habitat quality and increasing juvenile survival during the transitional period, including restoration of structural complexity, provision of suitable flow regimes, and tailoring stocking and reintroduction strategies to mimic natural dynamics.
Habitat selection and habitat‐specific survival of fledgling ovenbirds (Seiurus aurocapilla)
Authors: King D. I. , Degraaf R. M. , Smith M.‐L. , Buonaccorsi J. P. 
Published: July 2006

AbstractPatterns of habitat use by some passerines change after the young leave the nest, and thus our understanding of habitat selection derived from counts of singing males earlier in the nesting cycle may not adequately represent the breeding habitat requirements of these species. Post‐fledging changes in habitat use may have important conservation implications if the survival of fledglings is affected by characteristics of the habitat; however, there have been relatively few systematic studies of the post‐fledging ecology of forest passerines and, of these, even fewer have incorporated analyses of the relationship between habitat characteristics and fledgling survival. We studied the post‐fledging habitat selection and survival of ovenbirdsSeiurus aurocapillain northern New Hampshire, USA during two breeding seasons using radio telemetry. Habitat at sites used by radio‐marked fledgling ovenbirds was characterized by fewer large trees and greater vertical structure 0–3 m above ground than ovenbird nest sites. Similarly, habitat at sites used by fledgling ovenbirds was characterized by fewer large trees and greater vertical structure than unused sites. Most (80%) of the 15 mortalities that we observed were due to predation. Nine (70%) of these occurred within the first 3 days of fledging, resulting in a significant drop in survival during this period. Fledgling survival increased significantly with increased vegetation structure. Our observations that fledgling ovenbirds are selective in their habitat use, that they select different habitat features than adult ovenbirds select for nesting and that fledgling survival is positively associated with these habitat features suggest that the use of habitat models based on counts of singing males before fledging does not adequately represent the habitat needs of this species. Conceivably, mortality during the post‐fledging period could limit recruitment to levels insufficient to maintain the viability of ovenbird population even if adequate nesting habitat were available.
Transition to independence by subadult beavers (Castor canadensis) in an unexploited, exponentially growing population
Authors: DeStefano S. , Koenen K. K. G. , Henner C. M. , Strules J. 
Published: July 2006

AbstractWe conducted a 4‐year study of beaversCastor canadensisto compare the movements, survival and habitat of adults established in existing colonies to juveniles dispersing to new sites in a region with high beaver densities along a suburban–rural gradient. Estimates of annual survival were high for adult and juvenile beavers. Of nine known mortalities, seven (78%) were juveniles. Mortalities occurred during spring–summer, and none during fall–winter. There was a trend toward higher‐to‐lower survival along the suburban–rural gradient, respectively. Human‐induced mortality (e.g. trapping and shooting) was higher in rural areas, whereas nonhuman‐induced mortality (e.g. disease, accidents) was higher in suburban areas. Fifteen (14 subadults and one adult) beavers moved from natal colonies to other areas. The average dispersal distance for subadults was 4.5 km (se=1.0) along streams or rivers, or 3.5 km (se=0.7) straight‐line point‐to‐point. Most dispersal movements were made in spring (April–June). In two cases, individual subadults made return movements from their dispersal sites back to their natal colonies. Dispersal sites tended to be in smaller, shallower wetlands or streams and in areas with higher overstorey canopy closure compared with natal colonies. Woody vegetation usually preferred by beavers for food tended to be less common at dispersal sites than at natal colonies. In regions with high densities of beaver, dispersing juveniles are likely to attempt to colonize lower quality sites. High densities of beavers also lead to more human–beaver conflicts and, in Massachusetts, the pest control management options in place during the past decade have been ineffectual at controlling population levels. Alternately, in regions with no beavers or very low densities and where reintroductions are being attempted, the landscape matrix surrounding release sites should include suitable sites for dispersing young to establish colonies.