Automatic landmark annotation and dense correspondence registration for 3D human facial images

Dense surface registration of three-dimensional (3D) human facial images holds great potential for studies of human trait diversity, disease genetics, and forensics. Non-rigid registration is particularly useful for establishing dense anatomical correspondences between faces. Here we describe a novel non-rigid registration method for fully automatic 3D facial image mapping. This method comprises two steps: first, seventeen facial landmarks are automatically annotated, mainly via PCA-based feature recognition following 3D-to-2D data transformation. Second, an efficient thin-plate spline (TPS) protocol is used to establish the dense anatomical correspondence between facial images, under the guidance of the predefined landmarks. We demonstrate that this method is robust and highly accurate, even for different ethnicities. The average face is calculated for individuals of Han Chinese and Uyghur origins. While fully automatic and computationally efficient, this method enables high-throughput analysis of human facial feature variation.Comment: 33 pages, 6 figures, 1 tabl

Linear chemically sensitive electron tomography using DualEELS and dictionary-based compressed sensing

We have investigated the use of DualEELS in elementally sensitive tilt series tomography in the scanning transmission electron microscope. A procedure is implemented using deconvolution to remove the effects of multiple scattering, followed by normalisation by the zero loss peak intensity. This is performed to produce a signal that is linearly dependent on the projected density of the element in each pixel. This method is compared with one that does not include deconvolution (although normalisation by the zero loss peak intensity is still performed). Additionaly, we compare the 3D reconstruction using a new compressed sensing algorithm, DLET, with the well-established SIRT algorithm. VC precipitates, which are extracted from a steel on a carbon replica, are used in this study. It is found that the use of this linear signal results in a very even density throughout the precipitates. However, when deconvolution is omitted, a slight density reduction is observed in the cores of the precipitates (a so-called cupping artefact). Additionally, it is clearly demonstrated that the 3D morphology is much better reproduced using the DLET algorithm, with very little elongation in the missing wedge direction. It is therefore concluded that reliable elementally sensitive tilt tomography using EELS requires the appropriate use of DualEELS together with a suitable reconstruction algorithm, such as the compressed sensing based reconstruction algorithm used here, to make the best use of the limited data volume and signal to noise inherent in core-loss EELS

Neuronale Synchronisation während perzeptueller Organisation in Schizophrenie-Patienten

Current theories of schizophrenia suggest that the pathophysiology of the disorder may be the result of a deficit in the coordination of neural activity within and between areas of the brain, which may lead to impairments in basic cognitive functions such as contextual disambiguation and dynamic grouping (Phillips and Silverstein, 2003). This notion has been supported by recent studies showing that patients with schizophrenia are characterized by reduced synchronous, oscillatory activity in the gamma-frequency band during sensory processing (Spencer et al. 2003, Green et al. 2003, Wynn et al. 2005). However, it is currently unclear to what extent high-frequency gamma-band oscillations (> 60 Hz) contribute to impaired neural synchronization as research has so far focussed on gamma-band oscillations between 30 and 60 Hz. In addition, it is not known whether deficits in high-frequency oscillations are already present at the onset of the disorder and to what extent reductions may be related to the confounding influence of antipsychotic medication. Finally, the neural generators underlying impairments in synchronous oscillatory activity in schizophrenia have not been investigated yet. To address these questions, we recorded MEG activity during a visual closure task (Mooney faces task) in medicated chronic schizophrenia patients, drug-naive first-episode schizophrenia patients and healthy controls. MEG data were analysed for spectral power between 25 and 150 Hz, and beamforming techniques were used to localize the sources of oscillatory gamma-band activity. In healthy controls, we observed that the processing of Mooney faces was associated with sustained high-frequency gamma-band activity (> 60 Hz). A time-resolved analysis of the neural generators underlying perceptual closure revealed a network of distributed sources in occipito-temporal, parietal and frontal regions, which were differentially activated during specific time intervals. In chronic schizophrenia patients, we found a pronounced reduction of high-frequency gamma-band oscillatory activity that was accompanied by an impairment in perceptual organization and involved reduced source power in various brain regions associated with perceptual closure. First-episode patients were also characterized by a deficit in high-frequency gamma-band activity and reductions of source power in multiple areas; these impairments, however, were less pronounced than in chronic patients. Regarding behavioral performance, first-episode patients were not impaired in their ability to detect Mooney faces, but exhibited a loss in specificity of face detection. In conclusion, our results suggest that schizophrenia is associated with a widespread reduction in high-frequency oscillations that indicate local network abnormalities. These dysfunctions are independent of medication status and already present at illness onset, suggesting a possible progressive deficit during the course of the disorder.Aktuelle Theorien gehen davon aus, dass die Pathophysiologie der Schizophrenie auf eine Störung in der Koordination neuronaler Prozesse zurückzuführen ist, welche zu einer Beeinträchtigung in der Integration von Informationen führt und sich in Defiziten bei frühen Wahrnehmungsprozessen und höheren kognitiven Funktionen widerspiegelt. Diese Hypothese wird durch eine Reihe von Studien gestützt, die eine Reduktion oszillatorischer Aktivität im Beta- und Gamma-Frequenzband im Elektroenzephalogramm während visueller Wahrnehmungsprozesse bei Patienten mit Schizophrenie nachweisen konnten. Die Bedeutung von hochfrequenten Gamma-Band Oszillationen (> 60 Hz) für das Verständnis von perzeptuellen Dysfunktionen bei Patienten mit Schizophrenie ist jedoch bislang wenig erforscht. Zudem ist unklar, ob und in welchem Umfang eine Veränderung oszillatorischer Aktivität bereits zu Beginn der Erkrankung und ohne den Einfluss von antipsychotischen Medikamenten vorhanden ist. Des Weiteren gibt es bislang keine Befunde zu den neuronalen Quellen, die den Defiziten oszillatorischer Aktivität bei Schizophrenie-Patienten zugrunde liegen. Um diese Fragen zu untersuchen, wurden im Rahmen der vorliegenden Dissertation drei Studien durchgeführt, in denen die Hirnaktivität während einer visuellen Gestaltaufgabe (Mooney faces-Aufgabe) bei chronischen medizierten Schizophrenie-Patienten, ersterkrankten nicht-medizierten Schizophrenie-Patienten sowie bei gesunden Kontrollprobanden mittels Magnetoenzephalographie (MEG) gemessen wurde. Die Auswertung der MEG-Daten beinhaltete auf der Sensoren-Ebene eine Auswertung der spektralen Power zwischen 25 und 150 Hz und auf der Quellen-Ebene eine Rekonstruktion der Generatoren oszillatorischer Aktivität mit Hilfe von Beamforming-Techniken. Die Hauptbefunde lassen sich wie folgt zusammenfassen: Das neuronale Netzwerk perzeptueller Organisation bei Mooney faces zeigte eine ausgeprägte oszillatorische Aktivität im hochfrequenten Gamma-Band (> 60 Hz) in gesunden Kontrollprobanden und umfasste okzipito-temporale, parietale und frontale Areale, die zu verschiedenen Zeitpunkten der Informationsverarbeitung aktiviert wurden. Unsere Ergebnisse lassen vermuten, dass perzeptuelle Organisationsprozesse bei Mooney faces auf einer frühen Interaktion zwischen Arealen beruhen, die mit der Verarbeitung von Schattierungsreizen zusammenhängen, gesichtsspezifischen Arealen, und Arealen, die mit dem Abruf von Informationen aus dem Langzeitgedächtnis in Verbindung stehen. Im Vergleich zu den Kontrollprobanden zeigten chronische Schizophrenie-Patienten ein deutliches Defizit in der hochfrequenten (60 – 120 Hz) Gamma-Band Power, welches mit reduzierten Detektionsraten bei der Mooney faces-Aufgabe und mit verringerten Aktivierungen in den für perzeptuelle Organisationsprozesse relevanten Arealen einherging. Ersterkrankte nicht-medizierte Schizophrenie-Patienten zeigten ebenfalls eine Reduktion hochfrequenter Gamma-Band Power in verschiedenen Hirnarealen. Dieses Defizit war jedoch weniger stark ausgeprägt als in den chronischen Schizophrenie-Patienten. Im Gegensatz zu den chronischen Patienten zeigten die ersterkrankten Patienten keine Beeinträchtigung bei der Detektion von Gesichtern in aufrecht präsentierten Mooney face Stimuli; jedoch wiesen sie ein Defizit in der Diskrimination zwischen Gesichtern und Nicht-Gesichtern auf. Unsere Befunde deuten darauf hin, dass bei Patienten mit Schizophrenie ausgeprägte Defizite in lokalen Synchronisationsprozessen vorliegen, welche mit perzeptuellen Dysfunktionen einhergehen. Die beeinträchtigte Koordination neuronaler Aktivität könnte auf Veränderungen in GABAergen und glutamatergen Neurotransmittersystemen bei Schizophrenie-Patienten zurückzuführen sein. Unsere Ergebnisse zeigen weiterhin, dass Beeinträchtigungen neuronaler Synchronisation bereits zu Beginn der Erkrankung und ohne den Einfluss von antipsychotischer Medikation vorhanden sind. Die stärkere Beeinträchtigung in den chronischen im Vergleich zu den ersterkrankten Patienten deutet auf einen progressiven Verlauf der Beeinträchtigung oszillatorischer Aktivität bei Schizophrenie-Patienten hin

A PCA approach to the object constancy for faces using view-based models of the face

The analysis of object and face recognition by humans attracts a great deal of interest, mainly because of its many applications in various fields, including psychology, security, computer technology, medicine and computer graphics. The aim of this work is to investigate whether a PCA-based mapping approach can offer a new perspective on models of object constancy for faces in human vision. An existing system for facial motion capture and animation developed for performance-driven animation of avatars is adapted, improved and repurposed to study face representation in the context of viewpoint and lighting invariance. The main goal of the thesis is to develop and evaluate a new approach to viewpoint invariance that is view-based and allows mapping of facial variation between different views to construct a multi-view representation of the face. The thesis describes a computer implementation of a model that uses PCA to generate example- based models of the face. The work explores the joint encoding of expression and viewpoint using PCA and the mapping between viewspecific PCA spaces. The simultaneous, synchronised video recording of 6 views of the face was used to construct multi-view representations, which helped to investigate how well multiple views could be recovered from a single view via the content addressable memory property of PCA. A similar approach was taken to lighting invariance. Finally, the possibility of constructing a multi-view representation from asynchronous view-based data was explored. The results of this thesis have implications for a continuing research problem in computer vision – the problem of recognising faces and objects from different perspectives and in different lighting. It also provides a new approach to understanding viewpoint invariance and lighting invariance in human observers

Alive Caricature from 2D to 3D

Caricature is an art form that expresses subjects in abstract, simple and exaggerated view. While many caricatures are 2D images, this paper presents an algorithm for creating expressive 3D caricatures from 2D caricature images with a minimum of user interaction. The key idea of our approach is to introduce an intrinsic deformation representation that has a capacity of extrapolation enabling us to create a deformation space from standard face dataset, which maintains face constraints and meanwhile is sufficiently large for producing exaggerated face models. Built upon the proposed deformation representation, an optimization model is formulated to find the 3D caricature that captures the style of the 2D caricature image automatically. The experiments show that our approach has better capability in expressing caricatures than those fitting approaches directly using classical parametric face models such as 3DMM and FaceWareHouse. Moreover, our approach is based on standard face datasets and avoids constructing complicated 3D caricature training set, which provides great flexibility in real applications.Comment: Accepted to CVPR 201

A full Eulerian finite difference approach for solving fluid-structure coupling problems

A new simulation method for solving fluid-structure coupling problems has been developed. All the basic equations are numerically solved on a fixed Cartesian grid using a finite difference scheme. A volume-of-fluid formulation (Hirt and Nichols (1981, J. Comput. Phys., 39, 201)), which has been widely used for multiphase flow simulations, is applied to describing the multi-component geometry. The temporal change in the solid deformation is described in the Eulerian frame by updating a left Cauchy-Green deformation tensor, which is used to express constitutive equations for nonlinear Mooney-Rivlin materials. In this paper, various verifications and validations of the present full Eulerian method, which solves the fluid and solid motions on a fixed grid, are demonstrated, and the numerical accuracy involved in the fluid-structure coupling problems is examined.Comment: 38 pages, 27 figures, accepted for publication in J. Comput. Phy