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Temporal Information (temporal + information)
Selected AbstractsThe dorsal neural tube: A dynamic setting for cell fate decisionsDEVELOPMENTAL NEUROBIOLOGY, Issue 12 2010Shlomo Krispin Abstract The dorsal neural tube first generates neural crest cells that exit the neural primordium following an epithelial-to-mesenchymal conversion to become sympathetic ganglia, Schwann cells, dorsal root sensory ganglia, and melanocytes of the skin. Following the end of crest emigration, the dorsal midline of the neural tube becomes the roof plate, a signaling center for the organization of dorsal neuronal cell types. Recent lineage analysis performed before the onset of crest delamination revealed that the dorsal tube is a highly dynamic region sequentially traversed by fate-restricted crest progenitors. Furthermore, prospective roof plate cells were shown to originate ventral to presumptive crest and to progressively relocate dorsalward to occupy their definitive midline position following crest delamination. These data raise important questions regarding the mechanisms of cell emigration in relation to fate acquisition, and suggest the possibility that spatial and/or temporal information in the dorsal neural tube determines initial segregation of neural crest cells into their derivatives. In addition, they emphasize the need to address what controls the end of neural crest production and consequent roof plate formation, a fundamental issue for understanding the separation between central and peripheral lineages during development of the nervous system. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 70: 796,812, 2010. [source] Localization of KCNC1 (Kv3.1) potassium channel subunits in the avian auditory nucleus magnocellularis and nucleus laminaris during developmentDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2003Suchitra Parameshwaran-Iyer Abstract The KCNC1 (previously Kv3.1) potassium channel, a delayed rectifier with a high threshold of activation, is highly expressed in the time coding nuclei of the adult chicken and barn owl auditory brainstem. The proposed role of KCNC1 currents in auditory neurons is to reduce the width of the action potential and enable neurons to transmit high frequency temporal information with little jitter. Because developmental changes in potassium currents are critical for the maturation of the shape of the action potential, we used immunohistochemical methods to examine the developmental expression of KCNC1 subunits in the avian auditory brainstem. The KCNC1 gene gives rise to two splice variants, a longer KCNC1b and a shorter KCNC1a that differ at the carboxy termini. Two antibodies were used: an antibody to the N-terminus that does not distinguish between KCNC1a and b isoforms, denoted as panKCNC1, and another antibody that specifically recognizes the C terminus of KCNC1b. A comparison of the staining patterns observed with the panKCNC1 and the KCNC1b specific antibodies suggests that KCNC1a and KCNC1b splice variants are differentially regulated during development. Although panKCNC1 immunoreactivity is observed from the earliest time examined in the chicken (E10), a subcellular redistribution of the immunoproduct was apparent over the course of development. KCNC1b specific staining has a late onset with immunostaining first appearing in the regions that map high frequencies in nucleus magnocellularis (NM) and nucleus laminaris (NL). The expression of KCNC1b protein begins around E14 in the chicken and after E21 in the barn owl, relatively late during ontogeny and at the time that synaptic connections mature morphologically and functionally. © 2003 Wiley Periodicals, Inc. J Neurobiol 55: 165,178, 2003 [source] Auditory and speech processing and reading development in Chinese school children: behavioural and ERP evidenceDYSLEXIA, Issue 4 2005Xiangzhi Meng Abstract By measuring behavioural performance and event-related potentials (ERPs) this study investigated the extent to which Chinese school children's reading development is influenced by their skills in auditory, speech, and temporal processing. In Experiment 1, 102 normal school children's performance in pure tone temporal order judgment, tone frequency discrimination, temporal interval discrimination and composite tone pattern discrimination was measured. Results showed that children's auditory processing skills correlated significantly with their reading fluency, phonological awareness, word naming latency, and the number of Chinese characters learned. Regression analyses found that tone temporal order judgment, temporal interval discrimination and composite tone pattern discrimination could account for 32% of variance in phonological awareness. Controlling for the effect of phonological awareness, auditory processing measures still contributed significantly to variance in reading fluency and character naming. In Experiment 2, mismatch negativities (MMN) in event-related brain potentials were recorded from dyslexic children and the matched normal children, while these children listened passively to Chinese syllables and auditory stimuli composed of pure tones. The two groups of children did not differ in MMN to stimuli deviated in pure tone frequency and Chinese lexical tones. But dyslexic children showed smaller MMN to stimuli deviated in initial consonants or vowels of Chinese syllables and to stimuli deviated in temporal information of composite tone patterns. These results suggested that Chinese dyslexic children have deficits in auditory temporal processing as well as in linguistic processing and that auditory and temporal processing is possibly as important to reading development of children in a logographic writing system as in an alphabetic system. Copyright © 2005 John Wiley & Sons, Ltd. [source] Empirical Bayes estimators and non-parametric mixture models for space and time,space disease mapping and surveillanceENVIRONMETRICS, Issue 5 2003Dankmar Böhning Abstract The analysis of the geographic variation of disease and its representation on a map is an important topic in epidemiological research and in public health in general. Identification of spatial heterogeneity of relative risk using morbidity and mortality data is required. Frequently, interest is also in the analysis of space data with respect to time, where typically data are used which are aggregated in certain time windows like 5 or 10 years. The occurrence measure of interest is usually the standardized mortality (morbidity) ratio (SMR). It is well known that disease maps in space or in space and time should not solely be based upon the crude SMR but rather some smoothed version of it. This fact has led to a tremendous amount of theoretical developments in spatial methodology, in particular in the area of hierarchical modeling in connection with fully Bayesian estimation techniques like Markov chain Monte Carlo. It seems, however, that at the same time, where these theoretical developments took place, on the practical side only very few of these developments have found their way into daily practice of epidemiological work and surveillance routines. In this article we focus on developments that avoid the pitfalls of the crude SMR and simultaneously retain a simplicity and, at least approximately, the validity of more complex models. After an illustration of the typical pitfalls of the crude SMR the article is centered around three issues: (a) the separation of spatial random variation from spatial structural variation; (b) a simple mixture model for capturing spatial heterogeneity; (c) an extension of this model for capturing temporal information. The techniques are illustrated by numerous examples. Public domain software like Dismap is mentioned that enables easy mixture modeling in the context of disease mapping. Copyright © 2003 John Wiley & Sons, Ltd. [source] Mechanisms of time-based figure,ground segregationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2003Farid I. Kandil Abstract Figure,ground segregation can rely on purely temporal information, that is, on short temporal delays between positional changes of elements in figure and ground (Kandil, F.I. & Fahle, M. (2001) Eur. J. Neurosci., 13, 2004,2008). Here, we investigate the underlying mechanisms by measuring temporal segregation thresholds for various kinds of motion cues. Segregation can rely on monocular first-order motion (based on luminance modulation) and second-order motion cues (contrast modulation) with a high temporal resolution of ,,20 ms. The mechanism can also use isoluminant motion with a reduced temporal resolution of 60 ms. Figure,ground segregation can be achieved even at presentation frequencies too high for human subjects to inspect successive frames individually. In contrast, when stimuli are presented dichoptically, i.e. separately to both eyes, subjects are unable to perceive any segregation, irrespective of temporal frequency. We propose that segregation in these displays is detected by a mechanism consisting of at least two stages. On the first level, standard motion or flicker detectors signal local positional changes (flips). On the second level, a segregation mechanism combines the local activities of the low-level detectors with high temporal precision. Our findings suggest that the segregation mechanism can rely on monocular detectors but not on binocular mechanisms. Moreover, the results oppose the idea that segregation in these displays is achieved by motion detectors of a higher order (motion-from-motion), but favour mechanisms sensitive to short temporal delays even without activation of higher-order motion detectors. [source] The roles of the cerebellum and basal ganglia in timing and error predictionEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2002Jean-Claude Dreher Abstract Recent evidence that the cerebellum and the basal ganglia are activated during the performance of cognitive and attention tasks challenges the prevailing view of their primary function in motor control. The specific roles of the basal ganglia and the cerebellum in cognition, however, have been difficult to identify. At least three functional hypotheses regarding their roles have been proposed. The first hypothesis suggests that their main function is to switch attentional set. The second hypothesis states that they provide error signals regarding stimuli or rewards. The third hypothesis is that they operate as an internal timing system, providing a precise representation of temporal information. Using functional magnetic resonance imaging, we tested these three hypotheses using a task-switching experiment with a 2 × 2 factorial design varying timing (random relative to fixed) and task order (unpredictable relative to predictable). This design allowed us to test whether switching between tasks, timing irregularity and/or task order unpredictability activate the basal ganglia and/or the cerebellum. We show that the cerebellum is primarily activated with timing irregularity while the anterior striatum is activated with task order unpredictability, supporting their distinctive roles in two forms of readjustment. Task order unpredictability alone, independent of reward delivery, is sufficient to induce striatal activation. In addition, activation of the cerebellum and basal ganglia were not specific to switching attention because these regions were both activated during switching between tasks and during the simultaneous maintenance of two tasks without switching between them. [source] Choice of comparisons in intergroup settings: the role of temporal information and comparison motivesEUROPEAN JOURNAL OF SOCIAL PSYCHOLOGY, Issue 5 2006Rupert J. Brown Three studies investigated comparison choices in intergroup settings, a neglected but important topic for theories of intergroup relations. Two main questions were addressed: What is role of comparison motives in determining comparison choices in intergroup contexts? How important are temporal comparisons (of the ingroup in the past or future) in intergroup settings? In Study 1 (N,=,115), motives for Assessment or Enhancement were primed in a multi-group performance context. Compared to Controls, Assessment priming encouraged both upward and downward comparisons, while Enhancement encouraged mainly downward comparisons. In general, temporal comparisons were as prevalent as comparisons with other groups. Study 2 (N,=,199) employed a real-world setting in which members of a mid-ranking university indicated their interest in comparing with other higher or lower status universities or with their own university in the past. Temporal comparisons were once more much in evidence, and manipulating enhancement motives again encouraged downward comparisons. In Study 3 (N,=,40), set in the context of inter-nation student comparisons, Improvement motives were primed implicitly. This led to an increase in interest in an outgroup just above the ingroup but to a decrease in interest in future-oriented comparisons. Copyright © 2006 John Wiley & Sons, Ltd. [source] Dissociating the past from the present in the activity of place cellsHIPPOCAMPUS, Issue 9 2006Livia de Hoz Abstract It has been proposed that declarative memories can be dependent on both an episodic and a semantic memory system. While the semantic system deals with factual information devoid of reference to its acquisition, the episodic system, characterized by mental time travel, deals with the unique past experience in which an event took place. Episodic memory is characteristically hippocampus-dependent. Place cells are recorded from the hippocampus of rodents and their firing reflects many of the key characteristics of episodic memory. For example, they encode information about "what" happens "where," as well as temporal information. However, when these features are expressed during an animal's behavior, the neuronal activity could merely be categorizing the present situation and could therefore reflect semantic memory rather than episodic memory. We propose that mental time travel is the key feature of episodic memory and that it should take a form, in the awake animal, similar to the replay of behavioral patterns of activity that has been observed in hippocampus during sleep. Using tasks designed to evoke episodic memory, one should be able to see memory reactivation of behaviorally relevant sequences of activity in the awake animal while recording from hippocampus and other cortical structures. © 2006 Wiley-Liss, Inc. [source] Single-trial analysis of oddball event-related potentials in simultaneous EEG-fMRIHUMAN BRAIN MAPPING, Issue 7 2007Christian-G. Abstract There has recently been a growing interest in the use of simultaneous electroencephalography (EEG) and functional MRI (fMRI) for evoked activity in cognitive paradigms, thereby obtaining functional datasets with both high spatial and temporal resolution. The simultaneous recording permits obtaining event-related potentials (ERPs) and MR images in the same environment, conditions of stimulation, and subject state; it also enables tracing the joint fluctuations of EEG and fMRI signals. The goal of this study was to investigate the possibility of tracking the trial-to-trial changes in event-related EEG activity, and of using this information as a parameter in fMRI analysis. We used an auditory oddball paradigm and obtained single-trial amplitude and latency features from the EEG acquired during fMRI scanning. The single-trial P300 latency presented significant correlation with parameters external to the EEG (target-to-target interval and reaction time). Moreover, we obtained significant fMRI activations for the modulation by P300 amplitude and latency, both at the single-subject and at the group level. Our results indicate that, in line with other studies, the EEG can bring a new dimension to the field of fMRI analysis by providing fine temporal information on the fluctuations in brain activity. Hum Brain Mapp, 2007. © 2007 Wiley-Liss, Inc. [source] Recursive penalized least squares solution for dynamical inverse problems of EEG generationHUMAN BRAIN MAPPING, Issue 4 2004Okito Yamashita Abstract In the dynamical inverse problem of electroencephalogram (EEG) generation where a specific dynamics for the electrical current distribution is assumed, we can impose general spatiotemporal constraints onto the solution by casting the problem into a state space representation and assuming a specific class of parametric models for the dynamics. The Akaike Bayesian Information Criterion (ABIC), which is based on the Type II likelihood, was used to estimate the parameters and evaluate the model. In addition, dynamic low-resolution brain electromagnetic tomography (LORETA), a new approach for estimating the current distribution is introduced. A recursive penalized least squares (RPLS) step forms the main element of our implementation. To obtain improved inverse solutions, dynamic LORETA exploits both spatial and temporal information, whereas LORETA uses only spatial information. A considerable improvement in performance compared to LORETA was found when dynamic LORETA was applied to simulated EEG data, and the new method was applied also to clinical EEG data. Hum. Brain Mapp. 21:221,235, 2004. © 2004 Wiley-Liss, Inc. [source] Comparison of TCA and ICA techniques in fMRI data processingJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2004Xia Zhao MS Abstract Purpose To make a quantitative comparison of temporal cluster analysis (TCA) and independent component analysis (ICA) techniques in detecting brain activation by using simulated data and in vivo event-related functional MRI (fMRI) experiments. Materials and Methods A single-slice MRI image was replicated 150 times to simulate an fMRI time series. An event-related brain activation pattern with five different levels of intensity and Gaussian noise was superimposed on these images. Maximum contrast-to-noise ratio (CNR) of the signal change ranged from 1.0 to 2.0 by 0.25 increments. In vivo visual stimulation fMRI experiments were performed on a 1.9 T magnet. Six human volunteers participated in this study. All imaging data were analyzed using both TCA and ICA methods. Results Both simulated and in vivo data have shown that no statistically significant difference exists in the activation areas detected by both ICA and TCA techniques when CNR of fMRI signal is larger than 1.75. Conclusion TCA and ICA techniques are comparable in generating functional brain maps in event-related fMRI experiments. Although ICA has richer features in exploring the spatial and temporal information of the functional images, the TCA method has advantages in its computational efficiency, repeatability, and readiness to average data from group subjects. J. Magn. Reson. Imaging 2004;19:397,402. © 2004 Wiley-Liss, Inc. [source] A segmentation-based approach for temporal analysis of software version repositories,JOURNAL OF SOFTWARE MAINTENANCE AND EVOLUTION: RESEARCH AND PRACTICE, Issue 3 2008Harvey Siy Abstract Time series segmentation is a promising approach to discover temporal patterns from time-stamped numeric data. A novel approach to apply time series segmentation to discern temporal information from software version repositories is proposed. Data from such repositories, both numeric and non-numeric, are represented as item-set time series data. A dynamic programming algorithm for optimal segmentation is presented. The algorithm automatically produces a compacted item-set time series that can be analyzed to identify temporal patterns. The effectiveness of the approach is illustrated by analyzing version control repositories of several open-source projects to identify time-varying patterns of developer activity. The experimental results show that the segmentation algorithm produces segments that capture meaningful information and is superior to the information content obtained by arbitrarily segmenting software history into regular time intervals. Copyright © 2008 John Wiley & Sons, Ltd. [source] Time-resolved contrast-enhanced imaging with isotropic resolution and broad coverage using an undersampled 3D projection trajectoryMAGNETIC RESONANCE IN MEDICINE, Issue 2 2002Andrew V. Barger Abstract Time-resolved contrast-enhanced 3D MR angiography (MRA) methods have gained in popularity but are still limited by the tradeoff between spatial and temporal resolution. A method is presented that greatly reduces this tradeoff by employing undersampled 3D projection reconstruction trajectories. The variable density k -space sampling intrinsic to this sequence is combined with temporal k -space interpolation to provide time frames as short as 4 s. This time resolution reduces the need for exact contrast timing while also providing dynamic information. Spatial resolution is determined primarily by the projection readout resolution and is thus isotropic across the FOV, which is also isotropic. Although undersampling the outer regions of k -space introduces aliased energy into the image, which may compromise resolution, this is not a limiting factor in high-contrast applications such as MRA. Results from phantom and volunteer studies are presented demonstrating isotropic resolution, broad coverage with an isotropic field of view (FOV), minimal projection reconstruction artifacts, and temporal information. In one application, a single breath-hold exam covering the entire pulmonary vasculature generates high-resolution, isotropic imaging volumes depicting the bolus passage. Magn Reson Med 48:297,305, 2002. © 2002 Wiley-Liss, Inc. [source] Basic auditory dysfunction in dyslexia as demonstrated by brain activity measurementsPSYCHOPHYSIOLOGY, Issue 2 2000Teija Kujala Although the generality of dyslexia and its devastating effects on the individual's life are widely acknowledged, its precursors and associated neural mechanisms are poorly understood. One of the two major competing views maintains that dyslexia is based primarily on a deficit in linguistic processing, whereas the other view suggests a more general processing deficit, one involving the perception of temporal information. Here we present evidence in favor of the latter view by showing that the neural discrimination of temporal information within complex tone patterns fails in dyslexic adults. This failure can be traced to early cortical mechanisms that process auditory information independently of attention. [source] Space and Time in the Child's Mind: Evidence for a Cross-Dimensional AsymmetryCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 3 2010Daniel Casasanto Abstract What is the relationship between space and time in the human mind? Studies in adults show an asymmetric relationship between mental representations of these basic dimensions of experience: Representations of time depend on space more than representations of space depend on time. Here we investigated the relationship between space and time in the developing mind. Native Greek-speaking children watched movies of two animals traveling along parallel paths for different distances or durations and judged the spatial and temporal aspects of these events (e.g., Which animal went for a longer distance, or a longer time?). Results showed a reliable cross-dimensional asymmetry. For the same stimuli, spatial information influenced temporal judgments more than temporal information influenced spatial judgments. This pattern was robust to variations in the age of the participants and the type of linguistic framing used to elicit responses. This finding demonstrates a continuity between space-time representations in children and adults, and informs theories of analog magnitude representation. [source] | ||||||||||||||||