Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

The Role of Early Recurrence in Improving Visual Representations

This dissertation proposes a computational model of early vision with recurrence, termed as early recurrence. The idea is motivated from the research of the primate vision. Specifically, the proposed model relies on the following four observations. 1) The primate visual system includes two main visual pathways: the dorsal pathway and the ventral pathway; 2) The two pathways respond to different visual features; 3) The neurons of the dorsal pathway conduct visual information faster than that of the neurons of the ventral pathway; 4) There are lower-level feedback connections from the dorsal pathway to the ventral pathway. As such, the primate visual system may implement a recurrent mechanism to improve visual representations of the ventral pathway. Our work starts from a comprehensive review of the literature, based on which a conceptualization of early recurrence is proposed. Early recurrence manifests itself as a form of surround suppression. We propose that early recurrence is capable of refining the ventral processing using results of the dorsal processing. Our work further defines a set of computational components to formalize early recurrence. Although we do not intend to model the true nature of biology, to verify that the proposed computation is biologically consistent, we have applied the model to simulate a neurophysiological experiment of a bar-and-checkerboard and a psychological experiment involving a moving contour illusion. Simulation results indicated that the proposed computation behaviourally reproduces the original observations. The ultimate goal of this work is to investigate whether the proposal is capable of improving computer vision applications. To do this, we have applied the model to a variety of applications, including visual saliency and contour detection. Based on comparisons against the state-of-the-art, we conclude that the proposed model of early recurrence sheds light on a generally applicable yet lightweight approach to boost real-life application performance

Biologically motivated keypoint detection for RGB-D data

With the emerging interest in active vision, computer vision researchers have been increasingly concerned with the mechanisms of attention. Therefore, several visual attention computational models inspired by the human visual system, have been developed, aiming at the detection of regions of interest in images. This thesis is focused on selective visual attention, which provides a mechanism for the brain to focus computational resources on an object at a time, guided by low-level image properties (Bottom-Up attention). The task of recognizing objects in different locations is achieved by focusing on different locations, one at a time. Given the computational requirements of the models proposed, the research in this area has been mainly of theoretical interest. More recently, psychologists, neurobiologists and engineers have developed cooperation's and this has resulted in considerable benefits. The first objective of this doctoral work is to bring together concepts and ideas from these different research areas, providing a study of the biological research on human visual system and a discussion of the interdisciplinary knowledge in this area, as well as the state-of-art on computational models of visual attention (bottom-up). Normally, the visual attention is referred by engineers as saliency: when people fix their look in a particular region of the image, that's because that region is salient. In this research work, saliency methods are presented based on their classification (biological plausible, computational or hybrid) and in a chronological order. A few salient structures can be used for applications like object registration, retrieval or data simplification, being possible to consider these few salient structures as keypoints when aiming at performing object recognition. Generally, object recognition algorithms use a large number of descriptors extracted in a dense set of points, which comes along with very high computational cost, preventing real-time processing. To avoid the problem of the computational complexity required, the features have to be extracted from a small set of points, usually called keypoints. The use of keypoint-based detectors allows the reduction of the processing time and the redundancy in the data. Local descriptors extracted from images have been extensively reported in the computer vision literature. Since there is a large set of keypoint detectors, this suggests the need of a comparative evaluation between them. In this way, we propose to do a description of 2D and 3D keypoint detectors, 3D descriptors and an evaluation of existing 3D keypoint detectors in a public available point cloud library with 3D real objects. The invariance of the 3D keypoint detectors was evaluated according to rotations, scale changes and translations. This evaluation reports the robustness of a particular detector for changes of point-of-view and the criteria used are the absolute and the relative repeatability rate. In our experiments, the method that achieved better repeatability rate was the ISS3D method. The analysis of the human visual system and saliency maps detectors with biological inspiration led to the idea of making an extension for a keypoint detector based on the color information in the retina. Such proposal produced a 2D keypoint detector inspired by the behavior of the early visual system. Our method is a color extension of the BIMP keypoint detector, where we include both color and intensity channels of an image: color information is included in a biological plausible way and multi-scale image features are combined into a single keypoints map. This detector is compared against state-of-art detectors and found particularly well-suited for tasks such as category and object recognition. The recognition process is performed by comparing the extracted 3D descriptors in the locations indicated by the keypoints after mapping the 2D keypoints locations to the 3D space. The evaluation allowed us to obtain the best pair keypoint detector/descriptor on a RGB-D object dataset. Using our keypoint detector and the SHOTCOLOR descriptor a good category recognition rate and object recognition rate were obtained, and it is with the PFHRGB descriptor that we obtain the best results. A 3D recognition system involves the choice of keypoint detector and descriptor. A new method for the detection of 3D keypoints on point clouds is presented and a benchmarking is performed between each pair of 3D keypoint detector and 3D descriptor to evaluate their performance on object and category recognition. These evaluations are done in a public database of real 3D objects. Our keypoint detector is inspired by the behavior and neural architecture of the primate visual system: the 3D keypoints are extracted based on a bottom-up 3D saliency map, which is a map that encodes the saliency of objects in the visual environment. The saliency map is determined by computing conspicuity maps (a combination across different modalities) of the orientation, intensity and color information, in a bottom-up and in a purely stimulusdriven manner. These three conspicuity maps are fused into a 3D saliency map and, finally, the focus of attention (or "keypoint location") is sequentially directed to the most salient points in this map. Inhibiting this location automatically allows the system to attend to the next most salient location. The main conclusions are: with a similar average number of keypoints, our 3D keypoint detector outperforms the other eight 3D keypoint detectors evaluated by achiving the best result in 32 of the evaluated metrics in the category and object recognition experiments, when the second best detector only obtained the best result in 8 of these metrics. The unique drawback is the computational time, since BIK-BUS is slower than the other detectors. Given that differences are big in terms of recognition performance, size and time requirements, the selection of the keypoint detector and descriptor has to be matched to the desired task and we give some directions to facilitate this choice. After proposing the 3D keypoint detector, the research focused on a robust detection and tracking method for 3D objects by using keypoint information in a particle filter. This method consists of three distinct steps: Segmentation, Tracking Initialization and Tracking. The segmentation is made to remove all the background information, reducing the number of points for further processing. In the initialization, we use a keypoint detector with biological inspiration. The information of the object that we want to follow is given by the extracted keypoints. The particle filter does the tracking of the keypoints, so with that we can predict where the keypoints will be in the next frame. In a recognition system, one of the problems is the computational cost of keypoint detectors with this we intend to solve this problem. The experiments with PFBIKTracking method are done indoors in an office/home environment, where personal robots are expected to operate. The Tracking Error evaluates the stability of the general tracking method. We also quantitatively evaluate this method using a "Tracking Error". Our evaluation is done by the computation of the keypoint and particle centroid. Comparing our system that the tracking method which exists in the Point Cloud Library, we archive better results, with a much smaller number of points and computational time. Our method is faster and more robust to occlusion when compared to the OpenniTracker.Com o interesse emergente na visão ativa, os investigadores de visão computacional têm estado cada vez mais preocupados com os mecanismos de atenção. Por isso, uma série de modelos computacionais de atenção visual, inspirado no sistema visual humano, têm sido desenvolvidos. Esses modelos têm como objetivo detetar regiões de interesse nas imagens. Esta tese está focada na atenção visual seletiva, que fornece um mecanismo para que o cérebro concentre os recursos computacionais num objeto de cada vez, guiado pelas propriedades de baixo nível da imagem (atenção Bottom-Up). A tarefa de reconhecimento de objetos em diferentes locais é conseguida através da concentração em diferentes locais, um de cada vez. Dados os requisitos computacionais dos modelos propostos, a investigação nesta área tem sido principalmente de interesse teórico. Mais recentemente, psicólogos, neurobiólogos e engenheiros desenvolveram cooperações e isso resultou em benefícios consideráveis. No início deste trabalho, o objetivo é reunir os conceitos e ideias a partir dessas diferentes áreas de investigação. Desta forma, é fornecido o estudo sobre a investigação da biologia do sistema visual humano e uma discussão sobre o conhecimento interdisciplinar da matéria, bem como um estado de arte dos modelos computacionais de atenção visual (bottom-up). Normalmente, a atenção visual é denominada pelos engenheiros como saliência, se as pessoas fixam o olhar numa determinada região da imagem é porque esta região é saliente. Neste trabalho de investigação, os métodos saliência são apresentados em função da sua classificação (biologicamente plausível, computacional ou híbrido) e numa ordem cronológica. Algumas estruturas salientes podem ser usadas, em vez do objeto todo, em aplicações tais como registo de objetos, recuperação ou simplificação de dados. É possível considerar estas poucas estruturas salientes como pontos-chave, com o objetivo de executar o reconhecimento de objetos. De um modo geral, os algoritmos de reconhecimento de objetos utilizam um grande número de descritores extraídos num denso conjunto de pontos. Com isso, estes têm um custo computacional muito elevado, impedindo que o processamento seja realizado em tempo real. A fim de evitar o problema da complexidade computacional requerido, as características devem ser extraídas a partir de um pequeno conjunto de pontos, geralmente chamados pontoschave. O uso de detetores de pontos-chave permite a redução do tempo de processamento e a quantidade de redundância dos dados. Os descritores locais extraídos a partir das imagens têm sido amplamente reportados na literatura de visão por computador. Uma vez que existe um grande conjunto de detetores de pontos-chave, sugere a necessidade de uma avaliação comparativa entre eles. Desta forma, propomos a fazer uma descrição dos detetores de pontos-chave 2D e 3D, dos descritores 3D e uma avaliação dos detetores de pontos-chave 3D existentes numa biblioteca de pública disponível e com objetos 3D reais. A invariância dos detetores de pontoschave 3D foi avaliada de acordo com variações nas rotações, mudanças de escala e translações. Essa avaliação retrata a robustez de um determinado detetor no que diz respeito às mudanças de ponto-de-vista e os critérios utilizados são as taxas de repetibilidade absoluta e relativa. Nas experiências realizadas, o método que apresentou melhor taxa de repetibilidade foi o método ISS3D. Com a análise do sistema visual humano e dos detetores de mapas de saliência com inspiração biológica, surgiu a ideia de se fazer uma extensão para um detetor de ponto-chave com base na informação de cor na retina. A proposta produziu um detetor de ponto-chave 2D inspirado pelo comportamento do sistema visual. O nosso método é uma extensão com base na cor do detetor de ponto-chave BIMP, onde se incluem os canais de cor e de intensidade de uma imagem. A informação de cor é incluída de forma biológica plausível e as características multi-escala da imagem são combinadas num único mapas de pontos-chave. Este detetor é comparado com os detetores de estado-da-arte e é particularmente adequado para tarefas como o reconhecimento de categorias e de objetos. O processo de reconhecimento é realizado comparando os descritores 3D extraídos nos locais indicados pelos pontos-chave. Para isso, as localizações do pontos-chave 2D têm de ser convertido para o espaço 3D. Isto foi possível porque o conjunto de dados usado contém a localização de cada ponto de no espaço 2D e 3D. A avaliação permitiu-nos obter o melhor par detetor de ponto-chave/descritor num RGB-D object dataset. Usando o nosso detetor de ponto-chave e o descritor SHOTCOLOR, obtemos uma noa taxa de reconhecimento de categorias e para o reconhecimento de objetos é com o descritor PFHRGB que obtemos os melhores resultados. Um sistema de reconhecimento 3D envolve a escolha de detetor de ponto-chave e descritor, por isso é apresentado um novo método para a deteção de pontos-chave em nuvens de pontos 3D e uma análise comparativa é realizada entre cada par de detetor de ponto-chave 3D e descritor 3D para avaliar o desempenho no reconhecimento de categorias e de objetos. Estas avaliações são feitas numa base de dados pública de objetos 3D reais. O nosso detetor de ponto-chave é inspirado no comportamento e na arquitetura neural do sistema visual dos primatas. Os pontos-chave 3D são extraídas com base num mapa de saliências 3D bottom-up, ou seja, um mapa que codifica a saliência dos objetos no ambiente visual. O mapa de saliência é determinada pelo cálculo dos mapas de conspicuidade (uma combinação entre diferentes modalidades) da orientação, intensidade e informações de cor de forma bottom-up e puramente orientada para o estímulo. Estes três mapas de conspicuidade são fundidos num mapa de saliência 3D e, finalmente, o foco de atenção (ou "localização do ponto-chave") está sequencialmente direcionado para os pontos mais salientes deste mapa. Inibir este local permite que o sistema automaticamente orientado para próximo local mais saliente. As principais conclusões são: com um número médio similar de pontos-chave, o nosso detetor de ponto-chave 3D supera os outros oito detetores de pontos-chave 3D avaliados, obtendo o melhor resultado em 32 das métricas avaliadas nas experiências do reconhecimento das categorias e dos objetos, quando o segundo melhor detetor obteve apenas o melhor resultado em 8 dessas métricas. A única desvantagem é o tempo computacional, uma vez que BIK-BUS é mais lento do que os outros detetores. Dado que existem grandes diferenças em termos de desempenho no reconhecimento, de tamanho e de tempo, a seleção do detetor de ponto-chave e descritor tem de ser interligada com a tarefa desejada e nós damos algumas orientações para facilitar esta escolha neste trabalho de investigação. Depois de propor um detetor de ponto-chave 3D, a investigação incidiu sobre um método robusto de deteção e tracking de objetos 3D usando as informações dos pontos-chave num filtro de partículas. Este método consiste em três etapas distintas: Segmentação, Inicialização do Tracking e Tracking. A segmentação é feita de modo a remover toda a informação de fundo, a fim de reduzir o número de pontos para processamento futuro. Na inicialização, usamos um detetor de ponto-chave com inspiração biológica. A informação do objeto que queremos seguir é dada pelos pontos-chave extraídos. O filtro de partículas faz o acompanhamento dos pontoschave, de modo a se poder prever onde os pontos-chave estarão no próximo frame. As experiências com método PFBIK-Tracking são feitas no interior, num ambiente de escritório/casa, onde se espera que robôs pessoais possam operar. Também avaliado quantitativamente este método utilizando um "Tracking Error". A avaliação passa pelo cálculo das centróides dos pontos-chave e das partículas. Comparando o nosso sistema com o método de tracking que existe na biblioteca usada no desenvolvimento, nós obtemos melhores resultados, com um número muito menor de pontos e custo computacional. O nosso método é mais rápido e mais robusto em termos de oclusão, quando comparado com o OpenniTracker

Myeloarchitecture and Intrinsic Functional Connectivity of Auditory Cortex in Musicians with Absolute Pitch

Introduction This dissertation studied structures and functions of auditory cortex in musicians with a rare auditory perception called absolute pitch (AP) using an in-vivo neuroimaging technique magnetic resonance imaging (MRI). The absolute pitch is defined as an ability to recognize pitch chroma, which is musical naming in the twelve-tone equal-temperament (12-TET) system (e.g., “C#”), of any given tonal sound without external references. It has been of interest of many psychologists since the experimental methods have been introduced in psychology over a century. Early behavioral experiments reported many findings that were validated in later studies with computerized measurement of behaviors. Over the recent two decades, in-vivo neuroimaging studies have found alteration in structures and functions of the brains of musicians with AP compared to control musicians without AP. However, quantitative models on the behaviors of neural systems behind the AP have not been suggested yet. Of course, neuronal modeling is a challenging problem in cognitive neuroscience studies in general. In order to generate such models to explain auditory perceptions such as AP, detailed information on structures and functions of neural systems must be obtained. In this context, we examined microarchitecture of the auditory cortex in musicians with AP using ultra- high field MRI that currently enables the highest spatial resolution of in-vivo imaging at the moment. In addition, we examined the functional connectivity between the auditory cortex and the other regions of the whole cortex. In the dissertation, detailed introduction of the pitch chroma perception is given throughout the human auditory systems from peripheral apparatus to non-primary auditory cortex in the Chapter I. In-depth discussion on the in-vivo imaging techniques, image processing, and statistical inferences focusing on the strength and potential pitfalls of the methods and their common practice in the Chapter II. In the Chapter III and IV, I explained MRI studies of the PhD project in details with discussions on the findings. Finally in the Chapter V, I summarized the major findings and discuss possible interpretation based on the framework of ‘dual auditory pathway hypothesis’. Study of Myeloarchitecture In the first study (Chapter III), a novel MRI sequence named magnetization-prepared two rapid gradient echo (MP2RAGE) was used to investigate cortical myelination. Myeloarchitecture of cerebral cortex is the one of the important histological concepts to understand organization of cortical column as well as cytoarchitecture. Neurons in the cortex are not only linked to the other distant neurons through the white matter but also connected vertically and horizontally to adjacent neurons. These short/long-distance axonal connections form myeloarchitecture of the cortex. The MP2RAGE sequence estimates a physical quantity called longitudinal relaxation rates (R1), which is sensitive to myelin concentration of the tissue. When compared to control musicians without AP, we found greater R1 in the anterior part of the right supratemporal plane in the musicians with AP. Given the finding was specific to the middle depth of cortex, the finding is unlikely related to long-distance axonal connections but likely to local connections. The precise location of the group difference was determined as the right planum polare in the template brain as well as in all individual brains. Based on the finding, I speculated that the working principles of the AP processes might be related to the dual auditory pathway hypothesis. In the theory, spatial auditory information is processed along the dorsal pathway (from the primary auditory cortex, to planum temporale, supramarginal gyrus, parietal lobules, and dorsolateral prefrontal cortex) whereas non-spatial auditory information is processed along the ventral pathway (from the primary auditory cortex to planum polare, temporal pole, anterior insular, and ventrolateral prefrontal cortex) in analogous to visual system. Because pitch chroma is spatially invariant property of an auditory object, and also it is less useful for auditory scene segregation compared to separation based on general pitch range (i.e., pitch height), I suggested the observation of cortical myelin in the anterior non-primary auditory cortex might be related to the absolute recognition of pitch chroma in AP listeners. Another potential implication of the heavy myelination is the function of myelination in neural development. In a rat model, it was demonstrated that the myelination of cortex triggers protein interactions that greatly restrict neuroplasticity after the ‘critical period’ of normal development. From genetic studies, it has been found that the onset of musical training is crucial in the acquisition of AP. Since the planum polare is related to pitch chroma processing, the increase of myelination in this region might indicate the preservation of the pitch chroma representation. Study of Intrinsic Functional Connectivity In the second study (Chapter IV), to further test the hypothesis that this highly myelinated planum polare works differently in the auditory networks, analysis of intrinsic functional connectivity using functional MRI (fMRI) measurement acquired during resting was performed. Although spontaneous neural activities during resting was once regarded as Gaussian noise without particular information, extensive researches revealed that the resting-state data (fMRI and also M/EEG) bears substantial information on the subnetworks of brain that subserve various perceptual and cognitive functions. Particularly for the perception of AP, it has been known that spontaneous and unintended recognition of pitch chroma from ambient sounds such as the siren of an ambulance. Thus it is reasonable to assume that the AP-specific network would be constantly active even at rest. From the resting-state fMRI data, greater cross-correlations between the right planum polare, which was found to be highly myelinated, and several cortical areas including the right lateral superior temporal gyrus, the anterior insula, and the left inferior frontal cortex were found in musicians with better AP performance. Moreover, greater cross-coherences between the right planum polare and the medial part of superior frontal gyrus, the anterior cingulate cortex, and the left planum polare were found in musicians with greater AP performance. As speculated, the involvement of the ventral auditory pathway in the AP-specific resting state network was strongly suggested from the tightened functional coupling between anterior supratemporal planes and the left inferior frontal cortex. Interestingly, the right planum polare exhibited greater cross-coherence with the important hub regions of the default mode network, i.e., anterior cingulate cortex and medial parts of the superior frontal cortex and the orbitofrontal cortex, implicating a link between the auditory network and default-mode network in AP listeners. This might be related to constant AP processes in AP listeners, which results in spontaneous and unintentional recognition of AP. Conclusion In the dissertation, novel MRI data from musicians with AP were provided adding knowledge of the myeloarchitectonic characteristics and related intrinsic functional connectivity of the auditory cortex to the current understanding on the neural correlates of AP. The findings were in favor of the proposed involvement of the ventral auditory pathway, which is known for processing spatially invariant properties of auditory objects. Further studies on neural behaviors of the auditory cortex in relation to the myeloarchitecture are needed in developing computational models of AP in the future.Einleitung Diese Dissertation untersucht Strukturen und Funktionen des auditorischen Kortex in Musikern mit einer seltenen auditorischen Wahrnehmen, dem absoluten Gehör (aG), mit Hilfe des in-vivo Bildgebungsfahrens der Magnetresonanztomographie (MRT). Das absolute Gehör bezeichnet die Fähigkeit die Tonklasse (z.B. „C#“) innerhalb des 12-tönigen Systems gleichmäßiger Stimmung (12-TET) ohne externe Referenz benennen zu können. Das Phänomen des absoluten Gehöres ist Gegenstand psychologischer Untersuchungen seitdem die experimentellen Methoden vor über einem Jahrhundert vorgestellt wurden. Erste behaviorale Experimente berichteten zahlreiche Ergebnisse, die später in computer-gestützten Messverfahren validiert werden konnten. In den letzten 20 Jahren konnten Studien, unter Nutzung bildgebender Verfahren, Veränderungen in der Struktur und Funktion in den Gehirnen von Musikern mit absolutem Gehör feststellen. Bisher wurden jedoch noch keine quantitativen Modelle vorgestellt, die das Verhalten neuronaler Systeme beschreiben, die dem absoluten Gehört zugrunde liegen. Die Modellierung neuronaler Systeme stellt ein anspruchsvolles Problem der gesamten kognitiven Neurowissenschaften dar. Detaillierte Informationen bezüglich der Struktur und Funktion des neuronalen Systems müssen gesammelt, um mit Hilfe von Modelle auditorische Empfindungen wie das absolute Gehör erklären zu können. In diesem Zusammenhang haben wir die Mikroarchitektur des auditorischen Kortex von Musiker mit absolutem Gehör mit Hilfe eines ultrahohem Feld-MRTs untersucht; eine Methode mit der derzeit höchsten räumlichen Auflösung aller in-vivo Bildgebungsverfahren. Außerdem wurde die funktionelle Konnektivität zwischen dem auditorischen Kortex und anderen Regionen des gesamten Kortex untersucht. In Kapitel I der Dissertation wird detailliertes Grundwissen zur Empfindung von Tonklassen, vom menschlichen auditorischen System bis zum nicht-primären auditorischen Kortex, vermittelt. Eine vertiefte Diskussion der in-vivo Bildgebungsverfahren, der Bildverarbeitung und den statistischen Rückschlüssen ist Thema von Kapitel II, mit einem Fokus auf der üblichen Verwendung, den Stärken und potentiellen Fehlern der verwendeten Methoden. In den Kapiteln III und IV habe ich die MRT-Studien der Doktorarbeit erklärt und die Ergebnisse diskutiert. Kapitel V fasst die wesentlichen Forschungsergebnisse zusammen und diskutiert eine mögliche Interpretation der Ergebnisse auf Grundlage der Dual Auditory Pathway Hypothese. Untersuchung der Myelinarchitektur In der ersten Studie (Kapitel III) wurde eine neuartige MRT Sequenz, die magnetization-prepared two rapid gradient echo (MP2RAGE) Sequenz, genutzt um die kortikale Myelinisierung zu untersuchen. Die Myelinarchitektur des zerebralen Kortex ist eine der wichtigsten histologischen Konzepte, um sowohl die Organisation einer kortikalen Kolumne als auch die Zytoarchitektur zu verstehen. Die Neuronen des Kortex sind nicht nur an entfernte Neuronen über die weiße Substanz gekoppelt, sondern auch durch vertikale und horizontale Verbindungen an unmittelbar benachbarte Neuronen. Diese kurzen und langen axonalen Verbindungen formen die Myelinarchitektur des Kortex. Die MP2RAGE Sequenz bewertet die longitudinalen Relaxations Raten (R1), welche sensitiv für die Myelinkonzentration des untersuchten Gewebes ist. Verglichen mit einer Kontrollgruppe von Musikern ohne aG konnten wir einen höheren R1- Wert im anterioren Teil der rechten supra-temporalen Ebene in Musikern mit aG feststellen. Da das Ergebnis spezifisch für eine mittlere Tiefe des Kortex war ist es wahrscheinlicher, dies auf lokale Verbindungen als auf lange axonale Verbindungen zurückzuführen. Als genauer Ort der Gruppendifferenz wurde das rechte planum polare sowohl in einem idealisierten Gehirn als auch in den individuellen Gehirnen der Probanden festgestellt. Aufgrund dieses Ergebnisses habe ich die Hypothese aufgestellt, dass die Wirkungsweise des absoluten Gehörs mit der Dual Auditory Pathway-Theorie zusammenhängt. Diese Theorie besagt, dass räumliche auditorische Information entlang einer dorsalen Bahn (vom primären auditorischen Kortex zum planum temporale, supramarginalen Gyrus, Parietallappen und dorsolateralen präfrontalen Kortex) und nicht-räumliche Informationen entlang einer ventralen Bahn (vom primären auditorischen Kortex zum planum polare, Temporalpol, anterior insular und ventrolateralen präfrontalen Kortex), ähnlich dem visuellen System, verarbeitet werden. Da die Tonklasse eine räumlich invariante Eigenschaft eines auditorischen Objektes ist und es zudem für die auditorische Szenenunterscheidung weniger bedeutsam ist als die generelle Tonhöhe, habe ich die Vermutung angestellt, dass das kortikale Myelin im anterioren nicht-primären auditorischen Kortex mit dem absoluten Gehört für die Tonklasse im Zusammenhang steht. Eine weitere Implikation der starken Myelinisierung betrifft die Funktion von Myelin in der neuronalen Entwicklung. Im Tiermodell einer Ratte konnte gezeigt werden, dass die Myelinisierung des Kortex Proteininteraktionen auslöst, die die Neuroplastizität nach einer ‚kritischen Periode‘ der normalen Entwicklung erheblich einschränkt. Genetische Studien haben gezeigt, dass der Beginn der musikalischen Ausbildung für die Entwicklung des absoluten Gehöres entscheidend ist. Da das planum polare mit der Verarbeitung von Tonklassen in Verbindung gebracht wird, könnte ein Anstieg der Myelinisierung in diesem Bereich einen Erhalt der Tonklassenrepräsentation bedeuten. Untersuchung der intrinsischen funktionellen Konnektivität In der zweiten Studie (Kapitel IV) wurde die Hypothese, dass das stark myelinisierte planum polare in den auditorischen Netzwerken verschieden wirkt, mittels funktioneller MRT (fMRT) im entspannten Wachzustand weiter untersucht. Spontane Hirnaktivität wurde lange Zeit als Gaußsches Rauschen ohne spezielle Informationen angesehen. Umfangreiche Studien konnten jedoch zeigen, dass Messungen des Ruhezustandes, sowohl fMRT als auch M/EEG, Information bezüglich der Sub-Netzwerke tragen, die Hirnfunktionen der Wahrnehmung und Kognition unterstützen. Besonders in Bezug auf die Wahrnehmung mit absolutem Gehör konnte festgestellt werden, dass Umgebungstöne wie die Sirene eines Krankenwagens unbewusst hinsichtlich der Tonklasse erkannt werden. Diese Erkenntnis stützt die Annahme, dass das aG-Netzwerk auch im Ruhezustand aktiv ist. Mit Hilfe der fMRT-Daten wurde festgestellt, dass die Kreuzkorrelation zwischen dem stark myelinisierten rechten planum polare und weiteren kortikalen Arealen wie dem rechten lateral- superioren temporalen Gyrus, der anterioren insula und dem linken inferior-frontalen Kortex in Musikern mit besserer aG-Performanz erhöht ist. Weiterhin wurde eine erhöhte Kreuzkorrelation zwischen dem rechten planum polare und dem medialen Teil des superior-frontalen Gyrus, dem anterioren cingulate Kortex und dem linken planum polare in Musikern mit noch besser aG- Performanz festgestellt. Die erhöhte funktionelle Kopplung der anterioren supra-temporalen Ebene mit dem linken inferior-frontalen Kortex bekräftigt die Hypothese, dass der ventrale auditorische Pfad in dem aG- spezifischen Netzwerk des Ruhezustands beteiligt ist. Bemerkenswerterweise zeigte das rechte planum polare eine erhöhte Kreuzkorrelation mit wichtigen Hub-regionen des Default-Mode Netzwerkes, also dem anterioren cingulate Kortex und medialen Teilen des superior-frontalen Kortex, sowie dem orbito-frontalen Kortex. Dies bedeutet eine Verknüpfung des auditorischen Netzwerkes und des Default-Mode Netzwerkes in Menschen mit absolutem Gehör und könnte mit aG-Prozessen zusammenhängen, die die spontane und unbewusste Erkennung des absoluten Gehörs erlauben. Schlussfolgerung In dieser Dissertation wurden MRT-Daten von Musikern mit absolutem Gehör untersucht und damit zur Erweiterung des Wissensstandes bezüglich der Myelinarchitektur und der damit zusammenhängenden funktionellen Konnektivität des auditorischen Kortex beigetragen. Die Ergebnisse sprechen zugunsten der Einbindung des ventralen auditorischen Pfades, bekannt für die Verarbeitung räumlich-invarianter Eigenschaften auditorischer Objekte. Weitere Untersuchungen bezüglich des neuronalen Verhaltens des auditorischen Kortex in Verbindung mit der Myelinarchitektur sind notwendig, um quantitative Modelle des absoluten Gehörs entwickeln zu können

Aerospace Medicine and Biology: A continuing bibliography with indexes (supplement 156)

This bibliography lists 170 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 1976

Biometric Systems

Because of the accelerating progress in biometrics research and the latest nation-state threats to security, this book's publication is not only timely but also much needed. This volume contains seventeen peer-reviewed chapters reporting the state of the art in biometrics research: security issues, signature verification, fingerprint identification, wrist vascular biometrics, ear detection, face detection and identification (including a new survey of face recognition), person re-identification, electrocardiogram (ECT) recognition, and several multi-modal systems. This book will be a valuable resource for graduate students, engineers, and researchers interested in understanding and investigating this important field of study