bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution of the Isoprene Biosynthetic Pathway in Kudzu
Authors: Sharkey Thomas D. , Yeh Sansun , Wiberley Amy E. , Falbel Tanya G. , Gong Deming , Fernandez Donna E. 
Published: January 2005

Abstract
Isoprene synthase converts dimethylallyl diphosphate, derived from the methylerythritol 4-phosphate (MEP) pathway, to isoprene. Isoprene is made by some plants in substantial amounts, which affects atmospheric chemistry, while other plants make no isoprene. As part of our long-term study of isoprene synthesis, the genetics of the isoprene biosynthetic pathway of the isoprene emitter, kudzu (Pueraria montana), was compared with similar genes in Arabidopsis (Arabidopsis thaliana), which does not make isoprene. The MEP pathway genes in kudzu were similar to the corresponding Arabidopsis genes. Isoprene synthase genes of kudzu and aspen (Populus tremuloides) were cloned to compare their divergence with the divergence seen in MEP pathway genes. Phylogenetic analysis of the terpene synthase gene family indicated that isoprene synthases are either within the monoterpene synthase clade or sister to it. In Arabidopsis, the gene most similar to isoprene synthase is a myrcene/ocimene (acyclic monoterpenes) synthase. Two phenylalanine residues found exclusively in isoprene synthases make the active site smaller than other terpene synthase enzymes, possibly conferring specificity for the five-carbon substrate rather than precursors of the larger isoprenoids. Expression of the kudzu isoprene synthase gene in Arabidopsis caused Arabidopsis to emit isoprene, indicating that whether or not a plant emits isoprene depends on whether or not it has a terpene synthase capable of using dimethylallyl diphosphate.
Functional Genomics of Eukaryotic Photosynthesis Using Insertional Mutagenesis of Chlamydomonas reinhardtii
Authors: Dent Rachel M. , Haglund Cat M. , Chin Brian L. , Kobayashi Marilyn C. , Niyogi Krishna K. 
Published: January 2005

Abstract
The unicellular green alga Chlamydomonas reinhardtii is a widely used model organism for studies of oxygenic photosynthesis in eukaryotes. Here we describe the development of a resource for functional genomics of photosynthesis using insertional mutagenesis of the Chlamydomonas nuclear genome. Chlamydomonas cells were transformed with either of two plasmids conferring zeocin resistance, and insertional mutants were selected in the dark on acetate-containing medium to recover light-sensitive and nonphotosynthetic mutants. The population of insertional mutants was subjected to a battery of primary and secondary phenotypic screens to identify photosynthesis-related mutants that were pigment deficient, light sensitive, nonphotosynthetic, or hypersensitive to reactive oxygen species. Approximately 9% of the insertional mutants exhibited 1 or more of these phenotypes. Molecular analysis showed that each mutant line contains an average of 1.4 insertions, and genetic analysis indicated that approximately 50% of the mutations are tagged by the transforming DNA. Flanking DNA was isolated from the mutants, and sequence data for the insertion sites in 50 mutants are presented and discussed.
Learning Places from Views: Variation in Scene Processing as a Function of Experience and Navigational Ability
Authors: Epstein Russell A. , Higgins J. Stephen , Thompson-Schill Sharon L. 
Published: January 2005

AbstractHumans and animals use information obtained from different viewpoints to form representations of the spatial structure of the world. We used functional magnetic resonance imaging (fMRI) adaptation to investigate the neural basis of this learning process and to show how the concomitant representations vary across individuals as a function of navigational ability. In particular, we examined the effect of repeating viewpoint and/ or place information over both short (within-trial) and long (across-scan) intervals on the neural response in scene processing regions. Short-term fMRI adaptation effects in the parahippocampal cortex were initially highly viewpoint-specific but became less so over time. Long-term fMRI repetition effects included a significant viewpoint-invariant component. When individual differences in navigational ability were considered, a significant correlation between the strength of these effects and self-reported navigational competence was observed. In particular, good navigators encoded representations that differed between new and old views and new and old places, whereas bad navigators did not. These results suggest that cortical scene representations evolve over time to become more viewpoint-invariant and that the quality of these representations directly impacts navigational ability.
Real and Imaginary Rotary Motion Processing: Functional Parcellation of the Human Parietal Lobe Revealed by fMRI
Authors: Podzebenko Katherine , Egan Gary F. , Watson John D. G. 
Published: January 2005

Abstract
Functional magnetic resonance imaging was performed in 16 healthy subjects while they undertook orientation discrimination tasks of real rotating and mentally rotating alphanumeric characters. Perception of rotating and stationary abstract characters was also performed. Mental rotation and the perception of alphanumeric characters undergoing real rotation activated equivalent cortical areas, in keeping with the analogue hypothesis of mental rotation. In addition, areas along the dorsal stream, including the V5/middle temporal complex and the intraparietal sulcus (IPS), were activated during both the real and imaginary rotary conditions.
Within the parietal lobe there were areas of convergence (i.e., recruited by all three motion conditions) and areas of divergence (i.e., selectively activated by a particular condition). Tasks requiring canonical-mirror orientation discrimination revealed involvement of neural substrates localized to the ventrolateral bank of the IPS. Tasks in which this judgment was not performed and during which the subject viewed rotary motion of abstract stimuli recruited activity in the medial bank of the IPS. These results indicate subspecialization of the human posterior parietal lobe according to function.
Attention and Interhemispheric Transfer: A Behavioral and fMRI Study
Authors: Weber B. , Treyer V. , Oberholzer N. , Jaermann T. , Boesiger P. , Brugger P. , Regard M. , Buck A. , Savazzi S. , Marzi C. A. 
Published: January 2005

Abstract
When both detections and responses to visual stimuli are performed within one and the same hemisphere, manual reaction times (RTs) are faster than when the two operations are carried out in different hemispheres. A widely accepted explanation for this difference is that it reflects the time lost in callosal transmission. Interhemispheric transfer time can be estimated by subtracting RTs for uncrossed from RTs for crossed responses (crossed – uncrossed difference, or CUD). In the present study, we wanted to ascertain the role of spatial attention in affecting the CUD and to chart the brain areas whose activity is related to these attentional effects on interhemispheric transfer. To accomplish this, we varied the proportion of crossed and uncrossed trials in different blocks. With this paradigm subjects are likely to focus attention either on the hemifield contralateral to the responding hand (blocks with 80% crossed trials) or on the ipsilateral hemifield (blocks with 80% uncrossed trials). We found an inverse correlation between the proportion of crossed trials in a block and the CUD and this effect can be attributed to spatial attention. As to the imaging results, we found that in the crossed minus uncrossed subtraction, an operation that highlights the neural processes underlying interhemispheric transfer, there was an activation of the genu of the corpus callosum as well as of a series of cortical areas. In a further commonality analysis, we assessed those areas which were activated specifically during focusing of attention onto one hemifield either contra- or ipsilateral to the responding hand. We found an activation of a number of cortical and subcortical areas, notably, parietal area BA 7 and the superior colliculi. We believe that the main thrust of the present study is to have teased apart areas important in interhemispheric transmission from those involved in spatial attention.
ERP Nonword Rhyming Effects in Children and Adults
Authors: Coch Donna , Grossi Giordana , Skendzel Wendy , Neville Helen 
Published: January 2005

Abstract
In a simple prime–target auditory rhyming event-related potential (ERP) paradigm with adults and 6-, 7-, and 8-year-old children, nonword stimuli (e.g., nin–rin, ked–voo) were used to investigate neurocognitive systems involved in rhyming and their development across the early school years. Even absent semantic content, the typical CNV to primes and late rhyming effect (RE) to targets were evident in all age groups. The RE consisted of a more negative response to nonrhyming targets as compared to rhyming targets over posterior sites, with a reversal of this pattern at lateral anterior sites. The hypothesis that the CNV indexes phonological memory processes was not well supported by correlation analyses conducted with the ERP measures and scores on standardized behavioral tests. However, the onset of the rhyming effect was later in those scoring lower on phonological awareness measures.
Neural Topography and Content of Movement Representations
Authors: Lange Floris P. de , Hagoort Peter , Toni Ivan 
Published: January 2005

Abstract
We have used implicit motor imagery to investigate the neural correlates of motor planning independently from actual movements. Subjects were presented with drawings of left or right hands and asked to judge the hand laterality, regardless of the stimulus rotation from its upright orientation. We paired this task with a visual imagery control task, in which subjects were presented with typographical characters and asked to report whether they saw a canonical letter or its mirror image, regardless of its rotation. We measured neurovascular activity with fast event-related fMRI, distinguishing responses parametrically related to motor imagery from responses evoked by visual imagery and other task-related phenomena. By quantifying behavioral and neurovascular correlates of imagery on a trial-by-trial basis, we could discriminate between stimulus-related, mental rotation-related, and response-related neural activity. We found that specific portions of the posterior parietal and precentral cortex increased their activity as a function of mental rotation only during the motor imagery task. Within these regions, the parietal cortex was visually responsive, whereas the dorsal precentral cortex was not. Response- but not rotation-related activity was found around the left central sulcus (putative primary motor cortex) during both imagery tasks. Our study provides novel evidence on the topography and content of movement representations in the human brain. During intended action, the posterior parietal cortex combines somatosensory and visuomotor information, whereas the dorsal premotor cortex generates the actual motor plan, and the primary motor cortex deals with movement execution. We discuss the relevance of these results in the context of current models of action planning.
Aging and the Neural Correlates of Successful Picture Encoding: Frontal Activations Compensate for Decreased Medial-Temporal Activity
Authors: Gutchess Angela H. , Welsh Robert C. , Hedden Trey , Bangert Ashley , Minear Meredith , Liu Linda L. , Park Denise C. 
Published: January 2005

Abstract
We investigated the hypothesis that increased prefrontal activations in older adults are compensatory for decreases in medial-temporal activations that occur with age. Because scene encoding engages both hippocampal and prefrontal sites, we examined incidental encoding of scenes by 14 young and 13 older adults in a subsequent memory paradigm using functional magnetic resonance imaging (fMRI). Behavioral results indicated that there were equivalent numbers of remembered and forgotten items, which did not vary as a function of age. In an fMRI analysis subtracting forgotten items from remembered items, younger and older adults both activated inferior frontal and lateral occipital regions bilaterally; however, older adults showed less activation than young adults in the left and right parahippocampus and more activation than young adults in the middle frontal cortex. Moreover, correlations between inferior frontal and parahippocampal activity were significantly negative for old but not young, suggesting that those older adults who showed the least engagement of the parahippocampus activated inferior frontal areas the most. Because the analyses included only the unique activations associated with remembered items, these data suggest that prefrontal regions could serve a compensatory role for declines in medial-temporal activations with age.
Brain Responses to Segmentally and Tonally Induced Semantic Violations in Cantonese
Authors: Schirmer Annett , Tang Siu-Lam , Penney Trevor B. , Gunter Thomas C. , Chen Hsuan-Chih 
Published: January 2005

Abstract
The present event-related potential (ERP) study examined the role of tone and segmental information in Cantonese word processing. To this end, participants listened to sentences that were either semantically correct or contained a semantically incorrect word. Semantically incorrect words differed from the most expected sentence completion at the tone level, at the segmental level, or at both levels. All semantically incorrect words elicited an increased frontal negativity that was maximal 300 msec following word onset and an increased centroparietal positivity that was maximal 650 msec following word onset. There were differences between completely incongruous words and the other two violation conditions with respect to the latency and amplitude of the ERP effects. These differences may be due to differences in the onset of acoustic deviation of the presented from the expected word and different mechanisms involved in the processing of complete as compared to partial acoustic deviations. Most importantly, however, tonally and segmentally induced semantic violations were comparable. This suggests that listeners access tone and segmental information at a similar point in time and that both types of information play comparable roles during word processing in Cantonese.
Parietal rTMS Disrupts the Initiation but not the Execution of On-line Adjustments to a Perturbation of Object Size
Authors: Glover Scott , Miall R. Chris , Rushworth Matthew F. S. 
Published: January 2005

Abstract
Previous studies have implicated the human parietal lobes in the on-line guidance of action. However, no study to date has examined at what stage in the on-line adjustment process do the parietal lobes play their most critical role. Repetitive transcranial magnetic stimulation (rTMS) was applied over the left intraparietal sulcus as participants reached to grasp a small or large illuminated cylinder. On some trials, the illumination could suddenly switch from the small to large cylinder, or vice-versa. Small–Large switches were associated with relatively early grip aperture adjustments, whereas Large–Small switches were associated with relatively late grip aperture adjustments.
When rTMS was applied early in the movement, it disrupted on-line adjustments to Small–Large target switches, but not to Large–Small switches. Conversely, when rTMS was applied late in the movement, it disrupted adjustments to Large–Small target switches but not to Small–Large switches. The timing of the disruption by rTMS appeared linked to the initiation of the adjustment. It was concluded that the left parietal lobe plays a critical role in initiating an on-line adjustment to a change in target size, but not in executing that adjustment. The implications of these results for current views of on-line control are discussed.
Influence of Prosodic Information on the Processing of Split Particles: ERP Evidence from Spoken German
Authors: Isel Frédéric , Alter Kai , Friederici Angela D. 
Published: January 2005

AbstractSpoken language comprehension involves the use of different sources of linguistic information such as prosodic, syntactic, lexical, and semantic information. The question, however, of “when” and “how” these sources of information are exploited by the language processing system still remains unanswered. In the present study, we used event-related brain potentials (ERPs) to investigate the interaction between prosodic, syntactic, and lexical information during the processing of spoken German sentences. The sentence structure was manipulated by positioning a split particle at the end of the sentences after the occurrence of inflected verb whose lexical entry does not contain a split particle (e.g., *Sie alarmierte den Detektiv an [*She alerted at the detective]) [According to linguistic convention, incorrect sentences are marked by an asterisk.]. The prosodic contour of the verb stems was manipulated such that it marked either the presence of a split particle at a later position in the sentence or not. Participants performed an off-line probe-detection task. ERP data indicate that prosodic information of German-inflected verb stems is consulted on-line by the language processing system (“parser”) in order to “predict” the presence of a split particle at a later position in the sentence. An N400 effect was observed for the processing of split particles following verb stems which do not take a particle. However, this effect was only observed when the prosody of the verb stem did signal the presence of a split particle. We argue that the N400 component reflects the high costs associated with the lexical search that the language processing system has to perform when confronted with nonexisting words such as these resulting from the combination of the split particle and the verb stem in the present study. Furthermore, as a general reflection of prosodic processes, a Closure Positive Shift (CPS) was found at intonational phrase boundaries. In sum, the present findings provide strong evidence that prosodic information is a good “predictor” of upcoming information during the auditory processing of German sentences.
Effects of Aging on Arithmetic Problem-Solving: An Event-related Brain Potential Study
Authors: Yagoubi Radouane El , Lemaire Patrick , Besson Mireille 
Published: January 2005

Abstract
Younger and older participants were asked to indicate if 240 complex two-digit addition problems were smaller than 100 or not. Half of the problems were small-split problems (i.e., the proposed sums were 2% or 5% away from 100; e.g., 53 + 49) and half were large-split problems (i.e., proposed sums were 10% or 15% away from 100; 46 + 39). Behavioral and event-related potential (ERP) data revealed that (a) both groups showed a split effect on both reaction times and percent errors, (b) split effects were smaller for older than for younger adults in ERPs, and (c) the hemispheric asymmetry (left hemisphere advantage) reported for younger adults was reduced in older adults (age-related hemispheric asymmetry reduction). These results suggest that older adults tend to use only one strategy to solve all problems, whereas younger adults flexibly and adaptively use different strategies for small- and large-split problems. Implications of these findings for our understanding of age-related similarities and differences in arithmetic problem-solving are discussed.
Dynamic Dopamine Modulation in the Basal Ganglia: A Neurocomputational Account of Cognitive Deficits in Medicated and Nonmedicated Parkinsonism
Authors: Frank Michael J. 
Published: January 2005

AbstractDopamine (DA) depletion in the basal ganglia (BG) of Parkinson's patients gives rise to both frontal-like and implicit learning impairments. Dopaminergic medication alleviates some cognitive deficits but impairs those that depend on intact areas of the BG, apparently due to DA “overdose.” These findings are difficult to accommodate with verbal theories of BG/DA function, owing to complexity of system dynamics: DA dynamically modulates function in the BG, which is itself a modulatory system. This article presents a neural network model that instantiates key biological properties and provides insight into the underlying role of DA in the BG during learning and execution of cognitive tasks. Specifically, the BG modulates the execution of “actions” (e.g., motor responses and working memory updating) being considered in different parts of the frontal cortex. Phasic changes in DA, which occur during error feedback, dynamically modulate the BG threshold for facilitating/suppressing a cortical command in response to particular stimuli. Reduced dynamic range of DA explains Parkinson and DA overdose deficits with a single underlying dysfunction, despite overall differences in raw DA levels. Simulated Parkinsonism and medication effects provide a theoretical basis for behavioral data in probabilistic classification and reversal tasks. The model also provides novel testable predictions for neuropsychological and pharmacological studies, and motivates further investigation of BG/DA interactions with the prefrontal cortex in working memory.
Grammatical Gender and Number Agreement in Spanish: An ERP Comparison
Authors: Barber Horacio , Carreiras Manuel 
Published: January 2005

Abstract
The role of grammatical gender and number representations in syntactic processes during reading in Spanish was studied using the event-related potentials (ERPs) technique. The electroencephalogram was recorded with a dense array of 128 electrodes while Spanish speakers read word pairs (Experiment 1) or sentences (Experiment 2) in which gender or number agreement relationships were manipulated. Disagreement in word pairs formed by a noun and an adjective (e.g., faro–alto [lighthouse–high]) produced an N400-type effect, while word pairs formed by an article and a noun (e.g., el–piano [the-piano]) showed an additional left anterior negativity effect (LAN). Agreement violations with the same words inserted in sentences (e.g., El piano estaba viejo y desafinado [the m-s piano m-s was old m-s and off-key]) resulted in a pattern of LAN–P600. This effect was found both when the violation occurred in the middle of the sentence (at the adjective), as well as when this happened at the beginning of the sentence (at the noun), but the last segment of the P600 effect was greater for the middle sentence position, which could indicate differences in the complexity of reanalysis processes. Differences between grammatical gender and number disagreement were found in late measures. In the word pairs experiment, P3 peak latency varied across conditions, being later for gender than for number disagreement. Similarly, in the sentence experiment, the last segment of the P600 effect was greater for gender than for number violations. These event-related potentials (ERPs) effects lend support to the idea that reanalysis or repair processes after grammatical disagreement detection could involve more steps in the case of gender disagreement, as grammatical gender is a feature of the lexical representation in contrast to number, which is considered a morphological feature that combines with the stem of the word.