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Functional Mapping (functional + mapping)
Selected AbstractsNonparametric Functional Mapping of Quantitative Trait LociBIOMETRICS, Issue 1 2009Jie Yang Summary Functional mapping is a useful tool for mapping quantitative trait loci (QTL) that control dynamic traits. It incorporates mathematical aspects of biological processes into the mixture model-based likelihood setting for QTL mapping, thus increasing the power of QTL detection and the precision of parameter estimation. However, in many situations there is no obvious functional form and, in such cases, this strategy will not be optimal. Here we propose to use nonparametric function estimation, typically implemented with B-splines, to estimate the underlying functional form of phenotypic trajectories, and then construct a nonparametric test to find evidence of existing QTL. Using the representation of a nonparametric regression as a mixed model, the final test statistic is a likelihood ratio test. We consider two types of genetic maps: dense maps and general maps, and the power of nonparametric functional mapping is investigated through simulation studies and demonstrated by examples. [source] Functional Mapping of Quantitative Trait Loci Underlying Growth Trajectories Using a Transform-Both-Sides Logistic ModelBIOMETRICS, Issue 3 2004Rongling Wu Summary The incorporation of developmental control mechanisms of growth has proven to be a powerful tool in mapping quantitative trait loci (QTL) underlying growth trajectories. A theoretical framework for implementing a QTL mapping strategy with growth laws has been established. This framework can be generalized to an arbitrary number of time points, where growth is measured, and becomes computationally more tractable, when the assumption of variance stationarity is made. In practice, however, this assumption is likely to be violated for age-specific growth traits due to a scale effect. In this article, we present a new statistical model for mapping growth QTL, which also addresses the problem of variance stationarity, by using a transform-both-sides (TBS) model advocated by Carroll and Ruppert (1984, Journal of the American Statistical Association79, 321,328). The TBS-based model for mapping growth QTL cannot only maintain the original biological properties of a growth model, but also can increase the accuracy and precision of parameter estimation and the power to detect a QTL responsible for growth differentiation. Using the TBS-based model, we successfully map a QTL governing growth trajectories to a linkage group in an example of forest trees. The statistical and biological properties of the estimates of this growth QTL position and effect are investigated using Monte Carlo simulation studies. The implications of our model for understanding the genetic architecture of growth are discussed. [source] Functional mapping of carious enamel in human teeth with Raman microspectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2008H. Kinoshita Abstract We employed Raman microspectroscopy to measure the Raman spectra of phosphate in sound and carious tooth substance. The peak intensity at 960 cm,1 of the phosphate (PO43,) symmetric stretching vibrational mode (,1) in sound enamel was stronger than that of sound dentin, which indicated that sound enamel contained more phosphate than sound dentin. Furthermore, the element analysis of phosphate in sound teeth substance, measured using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscope (EDX), gave similar results to those of the Raman measurement. In addition, the border between sound enamel and dentin was clearly demonstrated by mapping the image of the Raman spectrum of phosphate. The mapping image of phosphate in the carious enamel region revealed a heterogeneous low Raman spectrum intensity of phosphate in the area surrounding carious enamel; this finding indicates that phosphate had dissolved from the tooth substance in such areas. In contrast with the decrease in the Raman spectrum intensity of phosphate, the intensity of amide I increased mainly in the low-phosphate area. Although it remains very difficult to clinically identify the accurate border between sound and carious tooth substance, this distinction may be enabled by using the Raman spectrum of carious tooth substance. Copyright © 2008 John Wiley & Sons, Ltd. [source] Manganese-enhanced MRI of the mouse auditory pathwayMAGNETIC RESONANCE IN MEDICINE, Issue 1 2008Takashi Watanabe Abstract Functional mapping of the lateral lemniscus and the superior olivary complex as part of the auditory pathway was accomplished for the first time in mice in vivo using manganese-enhanced MRI (2.35T, 3D FLASH, 117 ,m isotropic resolution). These and other auditory centers in the brainstem presented with pronounced signal enhancements after systemic administration of manganese chloride when animals were exposed to acoustic stimuli for 48 hr, but not when kept in a quiet environment. The results indicate an activation-dependent accumulation of manganese in the neural circuit composed of the cochlear nucleus, the superior olivary complex, the lateral lemniscus, and the inferior colliculus. The marked enhancement of the lateral lemniscus suggests that the stimulus-related accumulation of manganese reflects not only a regional uptake from extracellular fluid but also a concurrent delivery by axonal transport within the auditory system. Magn Reson Med 60:210,212, 2008. © 2008 Wiley-Liss, Inc. [source] Nonparametric Functional Mapping of Quantitative Trait LociBIOMETRICS, Issue 1 2009Jie Yang Summary Functional mapping is a useful tool for mapping quantitative trait loci (QTL) that control dynamic traits. It incorporates mathematical aspects of biological processes into the mixture model-based likelihood setting for QTL mapping, thus increasing the power of QTL detection and the precision of parameter estimation. However, in many situations there is no obvious functional form and, in such cases, this strategy will not be optimal. Here we propose to use nonparametric function estimation, typically implemented with B-splines, to estimate the underlying functional form of phenotypic trajectories, and then construct a nonparametric test to find evidence of existing QTL. Using the representation of a nonparametric regression as a mixed model, the final test statistic is a likelihood ratio test. We consider two types of genetic maps: dense maps and general maps, and the power of nonparametric functional mapping is investigated through simulation studies and demonstrated by examples. [source] Perfusion-based functional magnetic resonance imaging,CONCEPTS IN MAGNETIC RESONANCE, Issue 1 2003Afonso C. Silva Abstract The measurement of cerebral blood flow (CBF) is a very important way of assessing tissue viability, metabolism, and function. CBF can be measured noninvasively with magnetic resonance imaging (MRI) by using arterial water as a perfusion tracer. Because of the tight coupling between neural activity and CBF, functional MRI (fMRI) techniques are having a large impact in defining regions of the brain that are activated due to specific stimuli. Among the different fMRI techniques, CBF-based fMRI has the advantages of being specific to tissue signal change, a critical feature for quantitative measurements within and across subjects, and for high-resolution functional mapping. Unlike the conventional blood oxygenation level dependent (BOLD) technique, the CBF change is an excellent index of the magnitude of neural activity change. Thus, CBF-based fMRI is the tool of choice for longitudinal functional imaging studies. A review of the principles and theoretical backgrounds of both continuous and pulsed arterial spin labeling methods for measuring CBF is presented, and a general overview of their current applications in the field of functional brain mapping is provided. In particular, examples of the use of CBF-based fMRI to investigate the fundamental hemodynamic responses induced by neural activity and to determine the signal source of the most commonly used BOLD functional imaging are reviewed. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson 16A: 16,27, 2003 [source] Task-related gamma-band dynamics from an intracerebral perspective: Review and implications for surface EEG and MEGHUMAN BRAIN MAPPING, Issue 6 2009Karim Jerbi Abstract Although non-invasive techniques provide functional activation maps at ever-growing spatio-temporal precision, invasive recordings offer a unique opportunity for direct investigations of the fine-scale properties of neural mechanisms in focal neuronal populations. In this review we provide an overview of the field of intracranial Electroencephalography (iEEG) and discuss its strengths and limitations and its relationship to non-invasive brain mapping techniques. We discuss the characteristics of invasive data acquired from implanted epilepsy patients using stereotactic-electroencephalography (SEEG) and electrocorticography (ECoG) and the use of spectral analysis to reveal task-related modulations in multiple frequency components. Increasing evidence suggests that gamma-band activity (>40 Hz) might be a particularly efficient index for functional mapping. Moreover, the detection of high gamma activity may play a crucial role in bridging the gap between electrophysiology and functional imaging studies as well as in linking animal and human data. The present review also describes recent advances in real-time invasive detection of oscillatory modulations (including gamma activity) in humans. Furthermore, the implications of intracerebral findings on future non-invasive studies are discussed. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source] Location-related differences in structure and function of the stratum corneum with special emphasis on those of the facial skinINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 6 2008H. Tagami Synopsis Between the two different kinds of the skin covering the body, the glabrous skin is found only on the palmo-plantar surface because of its rather simple function to protect the underlying living tissue with its remarkably thick stratum corneum (SC) from strong external force and friction. Thus, its barrier function is extremely poor. In contrast, the hair-bearing skin covers almost all over the body surface regardless of the presence of long hair or vellus hair. In regard to its SC, many dermatologists and skin scientists think that it is too thin to show any site-specific differences, because the SC is just present as an efficient barrier membrane to protect our body from desiccation as well as against the invasion by external injurious agents. However, there are remarkable regional differences not only in the living skin tissue but also even in such thin SC reflecting the function of each anatomical location. These differences in the SC have been mostly disclosed with the advent of non-invasive biophysical instruments, particularly the one that enables us to measure transepidermal water loss (TEWL), the parameter of the SC barrier function, and the one that evaluates the hydration state of the skin surface, the parameter of the water-holding capacity of the SC that brings about softness and smoothness to the skin surface. These in vivo instrumental measurements of the SC have disclosed the presence of remarkable differences in the functional properties of the SC particularly between the face and other portions of the body. The SC of the facial skin is thinner, being composed of smaller layers of corneocytes than that of the trunk and limbs. It shows unique functional characteristics to provide hydrated skin surface but relatively poor barrier function, which is similar to that observed in retinoid-treated skin or to that of fresh scar or keloidal scars. Moreover, there even exist unexpected, site-dependent differences in the SC of the facial skin such as the forehead, eyelid, cheek, nose and perioral regions, although each location occupies only a small area. Between these locations, the cheek shows the lowest TEWL in contrast to the perioral region that reveals the highest one. Moreover, these features are not static but change with age particularly between children and adults and maybe also between genders. Among various facial locations, the eyelid skin is distinct from others because its SC is associated with poor skin surface lipids and a thin SC cell layer composed of large corneocytes that brings about high surface hydration state but poor barrier function, whereas the vermillion borders of the lips that are covered by an exposed part of the oral mucosa exhibit remarkably poor barrier function and low hydration state. Future studies aiming at the establishment of the functional mapping in each facial region and in other body regions will shed light on more delicate site-dependent differences, which will provide us important information in planning the strategy to start so called tailor-made skin care for each location of the body. Résumé Entre les deux types différents de peau couvrant le crops, on trouve la peau glabre uniquement sur la surface palmo-plantaire du fait de sa fonction plutôt simple de protection du tissu vivant sous-jacent par un stratum corneum (SC) trés épais vis-à-vis des forces extérieures et de la friction. De ce fait, sa fonction barrière est extrêmement pauvre. Au contraire, la peau velue courve la presque totalité de la surface du crops, que ce soit par la présence de longs cheveux ou de duvet. En ce qui concerne son SC, la plupart des dermatologues et des scientifiques de la peau pensent qu'il est trop mince pour montrer une différence spécifique au site, attendu que le SC est simplement présent en tant que membrane barriére efficace pour protéger notre corps de la dessiccation ainsi que pour lutter contre l'invasion d'agents nuisibles externes. Cependant, il existe des différences importantes entre les sites, non seulement dans la peau vivante, mais également dans ce SC aussi mince, qui révèlent la fonctin de chaque site anatomique. Ces différences dans le SC ont surtout été révélées avec l'apparition d'instruments biophysiques non invasifs, en particulier celui qui nous permet de mesurer la perte transépidermale en eau (TEWL), le paramétre de la fonction barrière du SC et celui qui évalue l'état d'hydratation de la surface de peau, le paramètre de la capacité en rétention de l'eau du SC qui est liéà la souplesse et à la douceur à la surface de peau. Ces mesures instrumentales in vivo du SC ont révélé la présence de différences remarquables entre les propriétés fonctionnelles du SC particulièrement entre le visage et d'autres parties du corps. Le SC de la peau de la face est plus mince, car li est composé de couches plus petites de corneocytes que celui du tronc et des membres. Il montre des caractéristiques fonctionnelles uniques pour permettre l'hydratation de la surface de peau, mais une fonction barrière relativement faible, semblable à celle observée dans la peau traitée avec un rétinoïde ou à celle d'une cicatrice récente ou de cicatrices kéloidales. De plus, il existe des différences sites-dépendantes inattendues dans le SC de la peau de la face comme le front, la paupière, la joue, le nez et les régions périorales, et ce, bien que chaque emplacement occupe seulement un petit secteur. Entre ces divers emplacements, la joue montre le TEWL le plus bas par comparaison avec la région périorale qui montre le plus élevé. De plus, ces caractéristiques ne sont pas fixes, mais changent avec l'âge en particulier entre enfants et adultes et peut-être aussi entre sexes. Entre les diverses régions de la face, la peau de la paupière se distingue parce que son SC est associéà une peau pauvre en lipides de surface constituée par une mince couche de cellule composée de grand cornéocytes qui provoquent un haut état d'hydratation superficiel, mais une faible fonction barrière. A l'inverse les bordures vermillion des lévres recouvertes par une partie exposée de muqueuse orale, possèdent une fonction barrière très faible et un état d'hydratation bas. Les études futures visant àétablir la configuration fonctionnelle de chaque région de la face et d'autres régions du corps mettrons en lumière des différences sites-dépendantes plus subtiles, qui nous fourniront des informations importantes pour planifier la stratégie pour commencer le soin de la peau sur mesure si attendu pour chaque partie du corps. [source] Multiband multislice GE-EPI at 7 tesla, with 16-fold acceleration using partial parallel imaging with application to high spatial and temporal whole-brain fMRI,MAGNETIC RESONANCE IN MEDICINE, Issue 5 2010Steen Moeller Abstract Parallel imaging in the form of multiband radiofrequency excitation, together with reduced k -space coverage in the phase-encode direction, was applied to human gradient echo functional MRI at 7 T for increased volumetric coverage and concurrent high spatial and temporal resolution. Echo planar imaging with simultaneous acquisition of four coronal slices separated by 44mm and simultaneous 4-fold phase-encoding undersampling, resulting in 16-fold acceleration and up to 16-fold maximal aliasing, was investigated. Task/stimulus-induced signal changes and temporal signal behavior under basal conditions were comparable for multiband and standard single-band excitation and longer pulse repetition times. Robust, whole-brain functional mapping at 7 T, with 2 × 2 × 2mm3 (pulse repetition time 1.25 sec) and 1 × 1 × 2mm3 (pulse repetition time 1.5 sec) resolutions, covering fields of view of 256 × 256 × 176mm3 and 192 × 172 × 176mm3, respectively, was demonstrated with current gradient performance. Magn Reson Med 63:1144,1153, 2010. © 2010 Wiley-Liss, Inc. [source] Nonparametric Functional Mapping of Quantitative Trait LociBIOMETRICS, Issue 1 2009Jie Yang Summary Functional mapping is a useful tool for mapping quantitative trait loci (QTL) that control dynamic traits. It incorporates mathematical aspects of biological processes into the mixture model-based likelihood setting for QTL mapping, thus increasing the power of QTL detection and the precision of parameter estimation. However, in many situations there is no obvious functional form and, in such cases, this strategy will not be optimal. Here we propose to use nonparametric function estimation, typically implemented with B-splines, to estimate the underlying functional form of phenotypic trajectories, and then construct a nonparametric test to find evidence of existing QTL. Using the representation of a nonparametric regression as a mixed model, the final test statistic is a likelihood ratio test. We consider two types of genetic maps: dense maps and general maps, and the power of nonparametric functional mapping is investigated through simulation studies and demonstrated by examples. [source] | ||||||||||