bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dopaminergic Modulation of Working Memory for Spatial but Not Object Cues in Normal Humans
Authors: Luciana Monica , Collins Paul F. 
Published: February 2008

Abstract
It appears that functionally segregated visual pathways exist in the primate brain for the processing of visuospatial versus nonspatial information. Functional segregation has been demonstrated for the early associative processing of sensory information but may also exist at higher levels of cognitive analysis. Namely, connections between the dorsal visual system and dorsolateral prefrontal cortex (PFC) appear to mediate spatial working memory, which is modulated by dopamine receptor fields in the principal sulcal region of the PFC. It is speculated that nonspatial working memory may be modulated within connections between ventral visual processing regions and the inferior convexity of the PFC. Whether dopamine facilitates nonspatial memory through connections between the ventral visual system and ventral PFC has not been examined. In this study, normal humans completed spatial and nonspatial working memory tasks under pharmacological challenges with a dopamine receptor agonist (bromocriptine) and antagonist (haloperidol) in a double-blind placebcxontrolled repeated measures design. Findings indicated facilitation of spatial delayed working memory functions by bromocriptine and impairment of spatial working memory functions by haloperidol. Neither drug was effective in manipulating nonspatial memory performance. Control tasks were included to measure drug effects on basic sensorimotor and attentional processes. Findings suggest that separate processing mechanisms for remembering “What” versus “Where” an object is may exist at structural, but also neurochemical, levels in the human brain.
Mental Rotation Studied by Functional Magnetic Resonance Imaging at High Field (4 Tesla): Performance and Cortical Activation
Authors: Tagaris Georgios A. , Kim Seong-Gi , Strupp John P. , Andersen Peter , Uğurbil Kamil , Georgopoulos Apostolos P. 
Published: February 2008

Abstract
We studied the performance and cortical activation patterns during a mental rotation task (Shepard & Metzler, 1971) using functional magnetic resonance imaging (fMlU) at high field (4 Tesla). Twenty-four human subjects were imaged (fMRI group), whereas six additional subjects performed the task without being imaged (control group). All subjects were shown pairs of perspective drawings of 31, objects and asked to judge whether they were the same or mirror images. The measures of performance examined included (1) the percentage of errors, (2) the speed of performance, calculated as the inverse of the average response time, and (3) the rate of rotation for those object pairs correctly identified as “same.” We found the following: (1) Subjects in the fMRI group performed well outside and inside the magnet, and, in the latter case, before and during data acquisition. Moreover, performance over time improved in the same manner as in the control group. These findings indicate that exposure to high magnetic fields does not impair performance in mental rotation. (2) Functional activation data were analyzed from 16 subjects of the fMRI goup. Several cortical areas were activated during task performance. The relations between the measures of performance above and the magnitude of activation of specific cortical areas were investigated by anatomically demarcating these areas of interest and calculating a normalized activation for each one of them. (3) We used the multivariate technique of hierarchical tree modeling to determine functional clustering among areas of interest and performance measures. Two main branches were distinguished: One comprised areas in the right hemisphere and the extrastriate and superior parietal lobules bilaterally, whereas the other comprised areas of the left hemisphere and the frontal pole bilaterally; all three performance measures above clustered with the former branch. Specifically, performance outcome (“percentage of errors”) clustered with the parieto-occipital subcluster, whereas both the speed of performance and the rate of mental rotation clustered with the right precentral gyms. We conclude that the mental rotation paradigm used involves the cooperative interaction of functional groups of cortical areas of which some are probably more specifically associated with performance, whereas others may serve a more general function within the task constraints.
The Neural Substrate for Concrete, Abstract, and Emotional Word Lexica A Positron Emission Tomography Study
Authors: Beauregard Mario , Chertkow H. , Bub D. , Murtha S. , Dixon R. , Evans A. 
Published: February 2008

Abstract
Viewing of single words produces a cognitively complex mental state in which anticipation, emotional responses, visual perceptual analysis, and activation of orthographic representations are all occurring. Previous PET studies have produced conflicting results, perhaps due to the conflation of these separate processes or the presence of subtle differences in stimulus material and methodology. A PET study of 10 normal individuals was carried out using the bolus H2 15O intravenous injection technique to examine components of processing of passively viewed words. Subjects viewed blocks of random-letter strings or abstract, concrete, or emotional words (words with positive or negative emotional salience). Baseline conditions were either passive viewing of plus signs or an anticipatory state (viewing plus signs after being warned to expect words or random letters to appear imminently). All words (and to a lesser extent the random letters) produced robust activation of cerebral blood flow in the left posterior temporal lobe, in addition to bilateral occipital activation. Furthermore, emotional words produced activation in orbital and midline frontal structures. Further activation in the left orbital frontal gyrus, the left inferior temporal gyrus, the left caudate nucleus, the anterior cingulate, and the cerebellum could be ascribed to the anticipatory state. This pattern of activity suggests that the occipital regions are recruited for visual-perceptual analysis of words, and the left temporal lobe represents the neural substrate for the orthographic lexicon. In addition, emotionally relevant material produces further processing in limbic brain structures of the frontal lobes. Detailed analysis of the task therefore substantially clarifies the neuroanatomic basis of single-word processing.
What Is Special about Face Recognition? Nineteen Experiments on a Person with Visual Object Agnosia and Dyslexia but Normal Face Recognition
Authors: Moscovitch Morris , Winocur Gordon , Behrmann Marlene 
Published: February 2008

Abstract
In order to study face recognition in relative isolation from visual processes that may also contribute to object recognition and reading, we investigated CK, a man with normal face recognition but with object agnosia and dyslexia caused by a closed-head injury. We administered recognition tests of up right faces, of family resemblance, of age-transformed faces, of caricatures, of cartoons, of inverted faces, and of face features, of disguised faces, of perceptually degraded faces, of fractured faces, of faces parts, and of faces whose parts were made of objects. We compared CK's performance with that of at least 12 control participants. We found that CK performed as well as controls as long as the face was upright and retained the configurational integrity among the internal facial features, the eyes, nose, and mouth. This held regardless of whether the face was disguised or degraded and whether the face was represented as a photo, a caricature, a cartoon, or a face composed of objects. In the last case, CK perceived the face but, unlike controls, was rarely aware that it was composed of objects. When the face, or just the internal features, were inverted or when the configurational gestalt was broken by fracturing the face or misaligning the top and bottom halves, CK's performance suffered far more than that of controls. We conclude that face recognition normally depends on two systems: (1) a holistic, face-specific system that is dependent on orientationspecific coding of second-order relational features (internal), which is intact in CK and (2) a part-based object-recognition system, which is damaged in CK and which contributes to face recognition when the face stimulus does not satisfy the domain-specific conditions needed to activate the face system.
On the Different Processing of Wholes and Parts: A Psychophysiological Analysis
Authors: Han Shihui , Fan Silu , Chen Lin , Zhuo Yan 
Published: February 2008

Abstract
The global precedence hypothesis (Navon, 1977) assumes that the processing of the global level of a hierarchical pattern precedes that of the local level. To explore further the nature of global and local processing of compound stimuli, we recorded the event-related brain potentials (ERPs) associated with ident@ing the global and local levels of nonlinguistic compound stimuli in a selective attention task. Wile subjects' behavioral responses were similar to those observed by Navon (1977), the analyses of ERP data showed that identification of the local level elicited longer N2 and P3 peak latencies with enhanced N2 and decreased P3 amplitudes relative to the identification of the global level. The inconsistency between the global and local levels made N2 and P3 amplitudes more negative with longer peak latencies. This interference effect on N2 and P3 amplitude and P3 latency was stronger on the local level than on the global level. The modulation of N2 by the consistency of the global and local levels observed in this and the previous (Heinze, Muente, et al., 1994) study suggests that the interference effect may be mediated by the early perceptual processing. Moreover, we found that the amplitude of an early posterior P1 component was modulated by attention to the global and local levels, being larger to the local target than to the global one. This PI effect gives no support to the notion that the variation of attentional spotlight determines the global precedence effect.
Semantic Repetition Priming for Verbal and Pictorial Knowledge: A Functional MRI Study of Left Inferior Prefrontal Cortex
Authors: Wagner Anthony D. , Desmond John E. , Demb Jonathan B. , Glover Gary H. , Gabrieli John D. E. 
Published: February 2008

Abstract
Functional neuroimaging studies of single-word processing have demonstrated decreased activation in left inferior prefrontal cortex (LIPC) during repeated semantic processing relative to initial semantic processing. This item-specific memory effect occurs under implicit test instructions and represents word-toword semantic repetition priming. The present study examined the stimulus generality of LIPC function by measuring prefrontal cortical activation during repeated relative to initial semantic processing of words (word-to-word semantic repetition priming) and of pictures (picture-to-picture semantic repetition priming). For both words and pictures, LIPC activation decreased with repetition, suggesting that this area subserves semantic analysis of stimuli regardless of perceptual form. Decreased activation was greater in extent for words than for pictures. The LIPC area may act as a semantic executive system that mediates on-line retrieval of long-term conceptual knowledge necessary for guiding task performance.
Localization of Auditory Evoked Potentials Related to Selective Intermodal Attention
Authors: Dien Joseph , Tucker Don M. , Potts Geoff , Hartry-Speiser Ann 
Published: February 2008

Abstract
A long-standing question in attention research is the extent to which selection involves gates in the sensory stream and the extent to which they involve added secondary processes. Intermodal attention paradigms are useful for examining this issue since different modalities involve readily distinguished cortical regions. Evoked potential studies have identified an attention-related frontal negativity labeled the Nd in auditory attention studies. It has been suggested that it arises from modulation of the auditory cortex (compatible with gating mechanisms) or of the frontal cortex (compatible with secondary processes such as short-term memory buffers). Efforts to localize the Nd have been impaired by the finding that the Nd comprises multiple components. Some novel procedures utilizing principal components analysis, in conjunction with high-density 64-channel recordings, were used to address this issue. Results suggest that the major source of the early Nd (the portion of most interest) resides in the frontal cortex, supporting the secondary process view for this particular mechanism.
Coordinate Frame for Pattern Recognition in Unilateral Spatial Neglect
Authors: Pavlovskaya Marina , Glass Itzhak , Soroker Nachum , Blum Baruch , Groswasser Zeev 
Published: February 2008

Abstract
The present research examines the effect of spatial (object-centered) attentional constraints on pattern recognition. Four normal subjects and two right-hemisphere-damaged patients with left visual neglect participated in the study. Small, letterlike, prelearned patterns served as stimuli. Short exposure time prevented overt scanpaths during stimulus presentation. Attention was attracted to a central (midsagittal) hation point by precuing this location prior to each stimulus presentation. Minute (up to 1.5° of visual angle) rightward and leftward stimulus shifts caused attention to be allocated each time to a different location on the object space, while remaining in a fixed central position in viewercentered coordinates. The task was to decide which of several prelearned patterns was presented in each trial. In the normal subjects, best performance was achieved when the luminance centroid (LC; derived from the analysis of low-spatial frequencies in the object space) of each pattern coincided with the spatial position of the precue. In contrast, the patients with neglect showed optimal recognition performance when precuing attracted attention to locations within the object space, to the left of the LC. The normal performance suggests that the LC may serve as a center of gravity for attention allocation during pattern recognition. This point seems to be the target location where focal attention is normally directed, following a primary global analysis based on the low spatial frequencies. Thus, the LC of a simple pattern may serve as the origin point for an object-centered-coordiate-frame (OCCF), dividing it into right and left. This, in turn, serves to create a prototype description of the pattern, in its own coordinates, in memory, to be addressed during subsequent recognition tasks. The best match of the percept with the stored description may explain the observed advantage of allocating attention to the LC. The performance of the brain- damaged patients can be explained in terms of neglect operating in the OCCE
Glacier Changes and Regional Climate: A Mass and Energy Balance Approach*
Authors: Rupper Summer , Roe Gerard 
Published: February 2008

Abstract
The mass balance of a glacier is a complex consequence of the combination of atmospheric variables that control it. However, the understanding of past, present, and future glacier states is often predicated on very simplified representations of the mass balance–climate relationship. Here, a full surface energy and mass balance (SEMB) model is developed to explore the relationship between glacier equilibrium-line altitudes (ELAs) and climate at a regional scale. This model is applied to central Asia because of the diverse climate regimes and glacier history. The model captures the pattern in ELAs well; the seasonal cycle in energy balance terms are comparable to studies on individual glaciers in central Asia, and the proportionality factor relating melt to temperature is within the range of those reported for individual glaciers within the area. In regions where precipitation is low, ablation at the ELA is dominated by sublimation. Conversely, where precipitation is high, ablation at the ELA is dominated by melt and surface runoff. In turn, the sensitivity of the ELA to changes in climate is strongly tied to the dominant ablation process. In particular, ELAs in melt-dominated regions are most sensitive to interannual variability in air temperature, while ELAs in sublimation-dominated regions are most sensitive to interannual variability in precipitation. Glaciers in sublimation-dominated regions are acutely sensitive to even small changes in atmospheric variables. Finally, changes in clouds are shown to be important in all regions through their influence on the shortwave and longwave radiative fluxes, which dominate the surface energy balance at the ELA.
A Technique for Eliminating Water Returns from Lidar Beach Elevation Surveys
Authors: Yates Marissa L. , Guza R. T. , Gutierrez Roberto , Seymour Richard 
Published: February 2008

Abstract
Airborne light detecting and ranging (lidar) systems can survey hundreds of kilometers of shoreline with high spatial resolution (several elevation estimates per square meter). Sequential surveys yield spatial change maps of beach and dune sand levels. However, lidar data include elevations of the exposed, subaerial beach and, seaward of the waterline, the ocean surface. Here, a simple method is developed to find the waterline and eliminate returns from the ocean surface. A vertical elevation cutoff is used, with the waterline elevation (W) above the known tide level because of the superelevation from wave setup and runup. During each lidar pass, the elevation cutoff (W) is assumed proportional (C) to the offshore significant wave height Hs. Comparison of in situ and lidar surveys on a moderately sloped, dissipative California beach yields C ≈ 0.4, which is qualitatively consistent with existing observations of runup and setup. The calibrated method rejects ocean surface data, while retaining subaerial beach points more than 70 m seaward of the mean high waterline, which is often used as a conservative default waterline.
A Surface Wave Model for Coupling with Numerical Ocean Circulation Models
Authors: Mellor George L. , Donelan Mark A. , Oey Lie-Yauw 
Published: February 2008

AbstractA surface wave model is developed with the intention of coupling it to three-dimensional ocean circulation models. The model is based on a paper by Mellor wherein depth-dependent coupling terms were derived. To be compatible with circulation models and to be numerically economical, this model is simplified compared to popular third-generation models. However, the model does support depth and current refraction, deep and shallow water, and proper coupling with depth-variable currents.The model is demonstrated for several simple scenarios culminating in comparisons of model calculations with buoy data during Hurricane Katrina and with calculations from the model Simulating Waves Nearshore (SWAN); for these calculations, coupling with the ocean was not activated.
Thermodynamic Properties of Mesoscale Convective Systems Observed during BAMEX
Authors: Correia James , Arritt Raymond W. 
Published: February 2008

Abstract
Dropsonde observations from the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX) are used to document the spatiotemporal variability of temperature, moisture, and wind within mesoscale convective systems (MCSs). Onion-type sounding structures are found throughout the stratiform region of MCSs, but the temperature and moisture variability is large. Composite soundings were constructed and statistics of thermodynamic variability were generated within each subregion of the MCS. The calculated air vertical velocity helped identify subsaturated downdrafts. It was found that lapse rates within the cold pool varied markedly throughout the MCS. Layered wet-bulb potential temperature profiles seem to indicate that air within the lowest several kilometers comes from a variety of source regions. It was also found that lapse-rate transitions across the 0°C level were more common than isothermal, melting layers. The authors discuss the implications these findings have and how they can be used to validate future high-resolution numerical simulations of MCSs.
Shape based indexing for faster search of RNA family databases
Authors: Janssen Stefan , Reeder Jens , Giegerich Robert 
Published: February 2008

Abstract

Background
Most non-coding RNA families exert their function by means of a conserved, common secondary structure. The Rfam data base contains more than five hundred structurally annotated RNA families. Unfortunately, searching for new family members using covariance models (CMs) is very time consuming. Filtering approaches that use the sequence conservation to reduce the number of CM searches, are fast, but it is unknown to which sacrifice.

Results
We present a new filtering approach, which exploits the family specific secondary structure and significantly reduces the number of CM searches. The filter eliminates approximately 85% of the queries and discards only 2.6% true positives when evaluating Rfam against itself. First results also capture previously undetected non-coding RNAs in a recent human RNAz screen.

Conclusion
The RNA s hape i ndex f ilter (RNAsifter) is based on the following rationale: An RNA family is characterised by structure, much more succinctly than by sequence content. Structures of individual family members, which naturally have different length and sequence composition, may exhibit structural variation in detail, but overall, they have a common shape in a more abstract sense. Given a fixed release of the Rfam data base, we can compute these abstract shapes for all families. This is called a shape index. If a query sequence belongs to a certain family, it must be able to fold into the family shape with reasonable free energy. Therefore, rather than matching the query against all families in the data base, we can first (and quickly) compute its feasible shape(s), and use the shape index to access only those families where a good match is possible due to a common shape with the query.
PITX2 gain-of-function induced defects in mouse forelimb development
Authors: Holmberg Johan , Ingner Gorel , Johansson Curt , Leander Peter , Hjalt Tord A 
Published: February 2008

Abstract

Background
Limb development and patterning originate from a complex interplay between the skeletal elements, tendons, and muscles of the limb. One of the genes involved in patterning of limb muscles is the homeobox transcription factor Pitx2 but its role in forelimb development is uncharacterized. Pitx2 is expressed in the majority of premature presumptive forelimb musculature at embryonic day 12.5 and then maintained throughout embryogenesis to adult skeletal muscle.

Results
To further study the role of Pitx2 in forelimb development we have generated transgenic mice that exhibit a pulse of PITX2 over-expression at embryonic day 13.5 and 14.5 in the developing forelimb mesenchyme. These mice exhibit a distal misplacement of the biceps brachii insertion during embryogenesis, which twists the forelimb musculature resulting in severe skeletal malformations. The skeletal malformations have some similarities to the forearm deformities present in Leri-Weill dyschondrosteosis.

Conclusion
Taken together, the tendon, muscle, and bone anomalies further support a role of Pitx2 in forelimb development and may also shed light on the interaction between the skeletal elements and muscles of the limb during embryogenesis.