Crossmaps: visualization of overlapping relationships in collections of journal papers.
(57/911)
A crossmapping technique is introduced for visualizing multiple and overlapping relations among entity types in collections of journal articles. Groups of entities from two entity types are crossplotted to show correspondence of relations. For example, author collaboration groups are plotted on the x axis against groups of papers (research fronts) on the y axis. At the intersection of each pair of author group/research front pairs a circular symbol is plotted whose size is proportional to the number of times that authors in the group appear as authors in papers in the research front. Entity groups are found by agglomerative hierarchical clustering using conventional similarity measures. Crossmaps comprise a simple technique that is particularly suited to showing overlap in relations among entity groups. Particularly useful crossmaps are: research fronts against base reference clusters, research fronts against author collaboration groups, and research fronts against term co-occurrence clusters. When exploring the knowledge domain of a collection of journal papers, it is useful to have several crossmaps of different entity pairs, complemented by research front timelines and base reference cluster timelines. (+info)
Cross-modal source information and spoken word recognition.
(58/911)
In a cross-modal matching task, participants were asked to match visual and auditory displays of speech based on the identity of the speaker. The present investigation used this task with acoustically transformed speech to examine the properties of sound that can convey cross-modal information. Word recognition performance was also measured under the same transformations. The authors found that cross-modal matching was only possible under transformations that preserved the relative spectral and temporal patterns of formant frequencies. In addition, cross-modal matching was only possible under the same conditions that yielded robust word recognition performance. The results are consistent with the hypothesis that acoustic and optical displays of speech simultaneously carry articulatory information about both the underlying linguistic message and indexical properties of the talker. (+info)
Learning letters in adulthood: direct visualization of cortical plasticity for forming a new link between orthography and phonology.
(59/911)
To identify which brain regions in adults show plasticity for learning letters, Hangul letters were experimentally associated with either speech sounds (HS condition) or nonspeech sounds (HN condition) in fMRI sessions over two consecutive days. Selective activations under the HS condition were found in several regions including the left posterior inferior temporal gyrus (PITG) and the parieto-occipital cortex (PO), as compared with activations under a condition for familiar letters and speech sounds, and with those under the HN condition. The left PITG showed a selective activation increase under the HS condition over two days, the degree of which predicted individual performance improvement. Further, functional connectivity between the left PITG and the left PO was selectively enhanced under the HS condition. These results demonstrate that a new link between orthography and phonology is formed by the plasticity of a functional system involving the left PITG in association with the left PO. (+info)
Stimulus-induced brain lactate: effects of aging and prolonged wakefulness.
(60/911)
Both aging and sleep deprivation disturb the functions of the frontal lobes. Deficits in brain energy metabolism have been reported in these conditions. Neurons use not only glucose but also lactate as their energy substrate. The physiological response to elevated neuronal activity is a transient increase in lactate concentrations in the stimulated area. We have previously shown that cognitive stimulation increases brain lactate. To study the effect of prolonged wakefulness on the lactate response we designed an experiment to assess brain lactate levels during a 40-h sleep deprivation period in young (19-24 years old; n = 13) and in aged (60-68 years old; n = 12) healthy female volunteers. Brain lactate levels were assessed with proton MR-spectroscopy ((1)H MRS) during the performance of a silent word generation task. The (1)H MRS voxel location was individually selected, using functional magnetic resonance imaging, to cover the activated area in the left frontal lobe. The degree of sleepiness was verified using vigilance tests and self-rating scales. In the young alert subjects, the silent word generation test induced a 40% increase in lactate, but during the prolonged wakefulness period this response disappeared. In the aged subjects, the lactate response could not be detected even in the alert state. We propose that the absence of the lactate response may be a sign of malfunctioning of normal brain energy metabolism. The behavioral effects of prolonged wakefulness and aging may arise from this dysfunction. (+info)
Semantic memory and verbal working memory correlates of N400 to subordinate homographs.
(61/911)
N400 is an event-related brain potential that indexes operations in semantic memory conceptual space, whether elicited by language or some other representation (e.g., drawings). Language models typically propose three stages: lexical access or orthographic- and phonological-level analysis; lexical selection or word-level meaning and associate activation; and lexical integration, sentence- and discourse-level operations. The exact stage that N400 reflects is unknown, although opinion favors lexical integration over lexical selection. Surprisingly, little research has assessed relationships between neuropsychological measures of semantic memory fund of information or verbal working memory capacity and N400. Subjects performed a homograph disambiguation comprehension task with minimal working memory load. Short sentences read: The noun was adjective/verb. The nouns were either homographs or unambiguous. The adjective/verb was disambiguating for the homograph, and congruent or incongruent for the unambiguous noun. The primary noun of interest was the subordinate homograph. Comprehension of the subordinate meaning should correlate with semantic memory stores, reflecting greater knowledge. If N400 primarily reflects lexical access operations, it should also correlate with measures of semantic knowledge. If N400 reflects lexical integration, it should correlate with measures of working memory capacity. Comprehension errors were associated with semantic memory stores, but not working memory capacity. N400 was related to working memory capacity, but not semantic knowledge, suggesting that N400 primarily reflects late-stage working memory operations. N400 to subordinate disambiguating words was larger with greater working memory capacity, and thus may index the absolute capacity of working memory rather than difficulty in contextual integration. (+info)
TXTGate: profiling gene groups with text-based information.
(62/911)
We implemented a framework called TXTGate that combines literature indices of selected public biological resources in a flexible text-mining system designed towards the analysis of groups of genes. By means of tailored vocabularies, term- as well as gene-centric views are offered on selected textual fields and MEDLINE abstracts used in LocusLink and the Saccharomyces Genome Database. Subclustering and links to external resources allow for in-depth analysis of the resulting term profiles. (+info)
Word learning in a domestic dog: evidence for "fast mapping".
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During speech acquisition, children form quick and rough hypotheses about the meaning of a new word after only a single exposure-a process dubbed "fast mapping." Here we provide evidence that a border collie, Rico, is able to fast map. Rico knew the labels of over 200 different items. He inferred the names of novel items by exclusion learning and correctly retrieved those items right away as well as 4 weeks after the initial exposure. Fast mapping thus appears to be mediated by general learning and memory mechanisms also found in other animals and not by a language acquisition device that is special to humans. (+info)
A diffusion model analysis of the effects of aging in the lexical-decision task.
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The effects of aging on response time (RT) are examined in 2 lexical-decision experiments with young and older subjects (age 60-75). The results show that the older subjects were slower than the young subjects, but more accurate. R. Ratcliff s (1978) diffusion model provided a good account of RTs, their distributions, and response accuracy. The fits show an 80-100-ms slowing of the nondecision components of RT for older subjects relative to young subjects and more conservative decision criterion settings for older subjects than for young subjects. The rates of accumulation of evidence were not significantly different for older compared with young subjects (less than 2% and 5% higher for older subjects relative to young subjects in the 2 experiments). (+info)