bluuebunny/crossref_metadata_2025_split huggingface dataset:
Directional responses of visual wulst neurones to grating and plaid patterns in the awake owl
Authors: Baron Jerome , Pinto Lucas , Dias Marcelo Oliveira , Lima Bruss , Neuenschwander Sergio 
Published: September 2007

AbstractThe avian retinothalamofugal pathway reaches the telencephalon in an area known as visual wulst. A close functional analogy between this area and the early visual cortex of mammals has been established in owls. The goal of the present study was to assess quantitatively the directional selectivity and motion integration capability of visual wulst neurones, aspects that have not been previously investigated. We recorded extracellularly from a total of 101 cells in awake burrowing owls. From this sample, 88% of the units exhibited modulated directional responses to sinusoidal gratings, with a mean direction index of 0.74 ± 0.03 and tuning bandwidth of 28 ± 1.16°. A direction index higher than 0.5 was observed in 66% of the cells, thereby qualifying them as direction selective. Motion integration was tested with moving plaids, made by adding two sinusoidal gratings of different orientations. We found that 80% of direction‐selective cells responded optimally to the motion direction of the component gratings, whereas none responded to the global motion of plaids, whose direction was intermediate to that of the gratings. The remaining 20% were unclassifiable. The strength of component motion selectivity rapidly increased over a 200 ms period following stimulus onset, maintaining a relatively sustained profile thereafter. Overall, our data suggest that, as in the mammalian primary visual cortex, the visual wulst neurones of owls signal the local orientated features of a moving object. How and where these potentially ambiguous signals are integrated in the owl brain might be important for understanding the mechanisms underlying global motion perception.
Detecting modulated signals in modulated noise: (II) neural thresholds in the songbird forebrain
Authors: Bee Mark A. , Buschermöhle Michael , Klump Georg M. 
Published: September 2007

AbstractSounds in the real world fluctuate in amplitude. The vertebrate auditory system exploits patterns of amplitude fluctuations to improve signal detection in noise. One experimental paradigm demonstrating these general effects has been used in psychophysical studies of ‘comodulation detection difference’ (CDD). The CDD effect refers to the fact that thresholds for detecting a modulated, narrowband noise signal are lower when the envelopes of flanking bands of modulated noise are comodulated with each other, but fluctuate independently of the signal compared with conditions in which the envelopes of the signal and flanking bands are all comodulated. Here, we report results from a study of the neural correlates of CDD in European starlings (Sturnus vulgaris). We manipulated: (i) the envelope correlations between a narrowband noise signal and a masker comprised of six flanking bands of noise; (ii) the signal onset delay relative to masker onset; (iii) signal duration; and (iv) masker spectrum level. Masked detection thresholds were determined from neural responses using signal detection theory. Across conditions, the magnitude of neural CDD ranged between 2 and 8 dB, which is similar to that reported in a companion psychophysical study of starlings [U. Langemann & G.M. Klump (2007) Eur. J. Neurosci., 26, 1969–1978]. We found little evidence to suggest that neural CDD resulted from the across‐channel processing of auditory grouping cues related to common envelope fluctuations and synchronous onsets between the signal and flanking bands. We discuss a within‐channel model of peripheral processing that explains many of our results.
Overexpression of APP provides neuroprotection in the absence of functional benefit following middle cerebral artery occlusion in rats
Authors: Clarke Jared , Thornell Anders , Corbett Dale , Soininen Hilkka , Hiltunen Mikko , Jolkkonen Jukka 
Published: September 2007

AbstractCerebral ischaemia leads to a transient accumulation of β‐amyloid precursor protein (APP) and β‐amyloid (Aβ) peptides adjacent to the ischaemic lesion. There is conflicting evidence that APP/Aβ fragments may either enhance neuronal plasticity or be neurotoxic. The aim of the current study was to assess the effect of overexpression of human APP in rats on functional recovery following cerebral ischaemia. Adult APP‐overexpressing (hAPP695 Tg) rats subjected to transient middle cerebral artery occlusion (MCAO) had significantly smaller infarct volumes than non‐transgenic littermates, yet did not perform better on a series of sensorimotor or learning tests during a 6‐month follow‐up period. In fact, transgenic animals were found to be significantly more impaired in both the beam‐walking and Morris water maze tests following MCAO. Immunohistochemistry showed human Aβ‐positive staining in the cortex and hippocampus of APP transgenic rats. The present data suggest that while overexpression of APP in rats may provide some histological neuroprotection in the event of cerebral ischaemia, this does not translate into significant functional recovery.
Group S8A serine proteases, including a novel enzyme cadeprin, induce long‐lasting, metabotropic glutamate receptor‐dependent synaptic depression in rat hippocampal slices
Authors: MacGregor Duncan G. , Mallon Andrew P. , Harvey Alan. L. , Young Louise , Nimmo Hugh G. , Stone Trevor W. 
Published: September 2007

AbstractLong‐term potentiation and long‐term depression (LTD) are forms of synaptic plasticity in the central nervous system. We now report that a group of chymotrypsin‐like serine proteases, especially members of the S8A subfamily, induce LTD of evoked potentials in rat hippocampal slices. The proteolytic activity of these enzymes is required for the induction of LTD, as serine protease inhibitors prevent the effect. The depression is partly mediated by the suppression of transmitter release from glutamatergic terminals but also involves an elevation of action potential threshold with no change of post‐synaptic membrane potential or input resistance. We have also isolated a novel and more potent related enzyme, cadeprin, fromAspergillus. The LTD produced by all of these proteases is not dependent on receptors for several transmitter systems, includingN‐methyl‐d‐aspartate or adenosine receptors, but is prevented by blocking group I metabotropic glutamate receptors. The activity of cadeprin, subtilisin and other S8A serine proteases may shed light on the mechanisms of LTD and a related endogenous molecule could have a physiological or pathological role as a modulator of synaptic plasticity in the mammalian hippocampus.
Synchronous oscillations and phase reorganization in the basal ganglia during akinesia induced by high‐dose haloperidol
Authors: Burkhardt John M. , Constantinidis Christos , Anstrom Kristin K. , Roberts David C. S. , Woodward Donald J. 
Published: September 2007

AbstractMovement disorders such as tremor and akinesia observed in Parkinson's disease have been attributed to dopamine (DA) depletion in the basal ganglia. The changes in subcortical neuronal discharge patterns that follow DA depletion have been a matter of much discussion. Here, we implanted rats with chronic recording electrodes bilaterally in the striatum (CPu) and external globus pallidus (GPe), and induced both acute and repeated DA blockade by administration of high‐dose haloperidol. Recordings were made in baseline states, as well as before and after haloperidol injections, which rendered rats akinetic. The immediate physiological effect of pharmacological DA blockade was the development of prominent oscillatory firing in the 6–8 Hz range in both CPu and GPe. Importantly, this oscillatory pattern was not accompanied by consistent changes in the firing rate of either CPu or GPe neurons. Cross‐correlation analysis further indicated that neurons within the CPu and GPe fired synchronously after DA blockade. Furthermore, although phase lags between neuronal discharges in the GPe and CPu were uniformly distributed prior to haloperidol administration, CPu significantly lagged GPe discharges after repeated DA blockade. Our results demonstrate that acute DA blockade is sufficient to produce synchronous oscillatory activity across basal ganglia neuron populations, and that prolonged DA blockade results in phase lag changes in pallidostriatal synchrony.
Dopamine lesion‐induced changes in subthalamic nucleus activity are not associated with alterations in firing rate or pattern in layer V neurons of the anterior cingulate cortex in anesthetized rats
Authors: Parr‐Brownlie Louise C. , Poloskey Stacey L. , Flanagan Kalynda K. , Eisenhofer Graeme , Bergstrom Debra A. , Walters Judith R. 
Published: September 2007

AbstractDysfunctional activity in the subthalamic nucleus (STN) is thought to underlie movement deficits of patients with Parkinson's disease. Alterations in STN firing patterns are also evident in the anesthetized rat model of Parkinson's disease, where studies show that loss of striatal dopamine and concomitant changes in the indirect pathway are associated with bursty and oscillatory firing patterns in STN output. However, the extent to which alterations in cortical activity contribute to changes in STN activity is unclear. As pyramidal neurons in the cingulate cortex project directly to the STN, cingulate output was assessed after dopamine lesion by simultaneously recording single‐unit and local field potential (LFP) activities in STN and anterior cingulate cortex in control, dopamine‐lesioned and non‐lesioned hemispheres of urethane‐anesthetized rats. Correlated oscillations were observed in cross‐correlograms of spike trains from STN and cingulate layer V neurons with broad waveforms indicative of pyramidal neurons. One−2 weeks after dopamine cell lesion, firing rate, incidence of bursty and 0.3–2.5 Hz oscillatory activity of neurons and LFP power in the STN all increased significantly. In contrast, firing rate, incidence of bursty and 0.3–2.5 Hz oscillatory activity of cingulate layer V putative pyramidal neurons and power in cingulate LFPs did not differ significantly between dopamine‐lesioned, non‐lesioned or control hemispheres, despite significant loss of dopamine in the lesioned cingulate cortex. Data show that alterations in STN activity in the dopamine‐lesioned hemisphere are not associated with alterations in neuronal activity in layer V of the anterior cingulate cortex in anesthetized rats.
Spatial and temporal analysis of fMRI data on word and sentence reading
Authors: Haller Sven , Klarhoefer Markus , Schwarzbach Jens , Radue Ernst W. , Indefrey Peter 
Published: September 2007

AbstractWritten language comprehension at the word and the sentence level was analysed by the combination of spatial and temporal analysis of functional magnetic resonance imaging (fMRI). Spatial analysis was performed via general linear modelling (GLM). Concerning the temporal analysis, local differences in neurovascular coupling may confound a direct comparison of blood oxygenation level‐dependent (BOLD) response estimates between regions. To avoid this problem, we parametrically varied linguistic task demands and compared only task‐induced within‐region BOLD response differences across areas. We reasoned that, in a hierarchical processing system, increasing task demands at lower processing levels induce delayed onset of higher‐level processes in corresponding areas. The flow of activation is thus reflected in the size of task‐induced delay increases. We estimated BOLD response delay and duration for each voxel and each participant by fitting a model function to the event‐related average BOLD response. The GLM showed increasing activations with increasing linguistic demands dominantly in the left inferior frontal gyrus (IFG) and the left superior temporal gyrus (STG). The combination of spatial and temporal analysis allowed a functional differentiation of IFG subregions involved in written language comprehension. Ventral IFG region (BA 47) and STG subserve earlier processing stages than two dorsal IFG regions (BA 44 and 45). This is in accordance with the assumed early lexical semantic and late syntactic processing of these regions and illustrates the complementary information provided by spatial and temporal fMRI data analysis of the same data set.
Overexpression of neurotrophin‐3 enhances the mechanical response properties of slowly adapting type 1 afferents and myelinated nociceptors
Authors: McIlwrath Sabrina L. , Lawson Jeffrey J. , Anderson Collene E. , Albers Kathryn M. , Koerber H. Richard 
Published: September 2007

AbstractConstitutive overexpression of neurotrophin‐3 (NT3) in murine skin results in an increased number of sensory neurons within the dorsal root ganglia, an increase of myelinated axons in cutaneous nerves, hyperinnervation of the skin, and an increased number of Merkel cells found in flank skin. Here we used a saphenous skin/nerve preparation to determine if these anatomical changes affect the functional response characteristics of cutaneous sensory neurons. Overexpression of NT3 significantly increased the responses of slowly adapting type 1 (SA1) low‐threshold mechanoreceptors and Aδ high‐threshold mechanoreceptors to suprathreshold mechanical stimulation. It also resulted in significantly faster conduction velocities of SA1 fibers. In contrast to earlier findings in flank skin, no differences were noted in the numbers of Merkel cells in the touch domes in hindlimb skin of NT3‐overexpressing mice. In addition, the number of dermal Merkel cells, located around hair follicles on the dorsum of the foot, was reduced by 55%. The increase in mechanical sensitivity was found to correlate with significant increases in the expression of acid‐sensing ion channels (ASIC) 1 and 3. Additional experiments using intracellular recordings and staining procedures confirmed that at least some cutaneous myelinated nociceptors and SA1 mechanoreceptors stained positively for both trkC and ASIC3. These results indicate that cutaneous NT3 overexpression alters the response properties of specific cutaneous sensory neurons, and that these changes may be due to the modulation of putative mechanosensitive ion channels.
Serotonin transporter deficiency in rats improves inhibitory control but not behavioural flexibility
Authors: Homberg Judith R. , Pattij Tommy , Janssen Mieke C. W. , Ronken Eric , De Boer Sietse F. , Schoffelmeer Anton N. M. , Cuppen Edwin 
Published: September 2007

AbstractImpulsivity and aggression have been suggested to inversely correlate with central serotonin (5‐HT) levels in a trait‐like manner. However, this relationship is far from straightforward. In the present study we addressed the effect of lifelong reduced or absent serotonin transporter (SERT) function, which is associated with constitutively increased extracellular 5‐HT levels, on impulsivity and aggression. We used unique SERT knockout rats in a resident–intruder test, five‐choice serial reaction time task and serial reversal learning task to assay aggression, inhibitory control and behavioural flexibility, respectively. Homozygous SERT knockout rats (SERT –/–) displayed reduced aggression and improved inhibitory control, but unchanged behavioural flexibility. The behavioural phenotype of heterozygous SERT knockout rats (SERT +/–) was not different from that of wild‐type controls in any of the behavioural paradigms. We determined monoamine (metabolite) tissue levels in the medial prefrontal cortex, orbitofrontal cortex, lateral hypothalamus, raphe nuclei and cerebrospinal fluid, and found that the 5‐HT levels, but not other monoamine tissue levels, were reduced in SERT –/–rats. In addition, the 5‐hydroxyindoleacetic acid (5‐HIAA)/5‐HT ratio in cerebrospinal fluid was increased in these rats. In conclusion, our data show that the absence of the SERT affects aggression and inhibitory control, but not behavioural flexibility, characteristics that may reflect the trait‐like consequences of constitutive changes in central 5‐HT levels.
Understanding the Truth about Subjectivity
Authors: Rowley Martin , Robinson Elizabeth J. 
Published: September 2007

AbstractResults of two experiments show children's understanding of diversity in personal preference is incomplete. Despite acknowledging diversity, in Experiment 1 (N = 108), six‐ and eight‐year‐old children were less likely than adults to see preference as a legitimate basis for personal tastes and more likely to say a single truth could be found about a matter of taste. In Experiment 2 (N = 96), seven‐ and nine‐year‐olds were less likely than 11‐ and 13‐year‐olds to say a dispute about a matter of preference might not be resolved. These data suggest that acceptance of the possibility of diversity does not indicate an adult‐like understanding of subjectivity. An understanding of the relative emphasis placed on objective and subjective factors in different contexts continues to develop into adolescence.
Capital Structure and Assets: Effects of an Implicit Collateral
Authors: Riis Flor Christian 
Published: September 2007

Abstract This paper analyses a firm's capital structure choice when assets have outside value. Valuable assets implicitly provide a collateral and increase tax shield exploitation. The key feature in this paper is asset value uncertainty, implying that it is unknown ex ante whether the equity holders ex post optimally sell the assets or re‐optimise the capital structure. Ex ante, more uncertain asset value decreases leverage, but not firm value, and selling the assets becomes less likely. Firms should tend to invest in assets whose value is less correlated to changes in earnings and, in addition, asset sales are less likely when this correlation is low.
An Empirical Analysis of the Pricing of Bank Issued Options versus Options Exchange Options
Authors: Horst Jenke ter , Veld Chris 
Published: September 2007

Abstract Since 1998, large investment banks have become active as issuers of options, generally referred to as call warrants or bank‐issued options. This has led to an interesting situation in the Netherlands, where simultaneously call warrants are traded on the stock exchange, and long‐term call options are traded on the options exchange. Both entitle their holders to buy shares of common stock. We start with a direct comparison between call warrants and call options, written on the same stock and with the same exercise price, but where the call option has a longer time to maturity. In 13 out of 16 cases we find that the call warrants are priced higher, which is a clear violation of basic option pricing rules. In the second part of the analysis we use option pricing models to compare the pricing of call warrants and call options. If implied standard deviations from options are used to price the call warrants, we find that the call warrants are strongly overpriced during the first five trading days. The average overpricing is between 25 and 30%. Only a small part of the overpricing can be explained by rational arguments such as transaction costs. We suggest that the overvaluation can be explained by a combination of an active financial marketing by the banks and the framing effect.
Have European Stocks become More Volatile? An Empirical Investigation of Idiosyncratic and Market Risk in the Euro Area
Authors: Kearney Colm , Potì Valerio 
Published: September 2007

Abstract We examine the dynamics of idiosyncratic risk, market risk and return correlations in European equity markets using weekly observations from 3515 stocks listed in the 12 euro area stock markets over the period 1974–2004. Similarly to

Campbell et al. (2001)

, we find a rise in idiosyncratic volatility, implying that it now takes more stocks to diversify away idiosyncratic risk. Contrary to the US, however, market risk is trended upwards in Europe and correlations are not trended downwards. Both the volatility and correlation measures are pro‐cyclical, and they rise during times of low market returns. Market and average idiosyncratic volatility jointly predict market wide returns, and the latter impact upon both market and idiosyncratic volatility. This has asset pricing and risk management implications.
Academics on Non‐Standard Contracts in UK Universities: Portfolio Work, Choice and Compulsion
Authors: Brown Donna , Gold Michael 
Published: September 2007

AbstractThis paper analyses the profile and motivation of over 1,300 academics employed on part‐time, fixed term or temporary contracts at 10 post‐1992 UK universities, whom it categorises as ‘non‐standard academics’. Based on a questionnaire survey, it investigates their demographic background, including age, gender and ethnic background, as well as the factors behind acceptance of their current employment status. It reveals that six out of ten chose their status and correspond in some ways to the profile of ‘portfolio worker’ (high level of qualifications, multiple job holding and sense of independence). This tends to correct the perception of them as mainly ‘casual’. However, commitment to their current employment status is less clear, with over one‐third stating that they would accept a permanent job on their current hours. There are, therefore, signs of adaptation to certain forms of non‐standard status (hours) but not to others (impermanence). Such uncertainty illustrates the hazy boundaries between casual and portfolio status.
An Analysis of First Experience Students' Financial Awareness and Attitude to Debt in a Post‐1992 UK University
Authors: Marriott Pru 
Published: September 2007

AbstractWhile students have always found balancing their finances difficult, the current generation are faced with unprecedented debt burdens during and on completion of their studies. Student debt is now an expected outcome of attending university and, apart from the negative consequences it may have on participation in higher education, it may have a detrimental impact on the academic performance and psychological well‐being of students as they strive to fund their education and reduce their debt through part‐time working patterns. However, student debt can be managed better if students possess adequate personal financial awareness, have a responsible attitude to debt and are able to budget carefully. This study attempts to measure the personal financial awareness, attitude to debt and budgeting capabilities of 149 first‐year business school undergraduates using a specially developed test. The mean test score of 34 per cent on the financial awareness section indicates significant gaps in their personal financial knowledge and it appears that they are entering a critical stage of their lives ill‐equipped to cope with the severe cash restrictions they will encounter. This study is a valuable starting point in understanding the financial challenges faced by students in higher education in the UK and highlights how academic institutions can provide support to increase the financial awareness of students so that they can manage better their personal finances while at university.
Scoping the Duals: Structural Challenges of Combining Further and Higher Education in Post‐Secondary Institutions
Authors: Garrod Neil , Macfarlane Bruce 
Published: September 2007

AbstractDual sector universities (or duals) are a growing international phenomenon that cut across the divide that typically exists in post‐secondary education. Duals combine ‘further’ and ‘higher’ education within a single institution providing enhanced opportunities for student transition between post‐secondary sectors. This paper reports the results of an international survey of duals in Australia, Canada, New Zealand, South Africa and the UK. The results indicate that duals operate divergent operational models in managing the structural challenges of cross‐sector education characterised as unitary and binary. Many duals contend that state and provincial government regulation militates against the integration of structures, processes and human resources within a dual sector context.