Browsing by Subject "brain"
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Item Acquisition and reconstruction of brain tissue using knife-edge scanning microscopy(Texas A&M University, 2004-09-30) Mayerich, David MatthewA fast method for gathering large-scale data sets through the serial sectioning of brain tissue is described. These data sets are retrieved using knife-edge scanning microscopy, a new technique developed in the Brain Networks Laboratory at Texas A&M University. This technique allows the imaging of tissue as it is cut by an ultramicrotome. In this thesis the development of a knife-edge scanner is discussed as well as the scanning techniques used to retrieve high-resolution data sets. Problems in knife-edge scanning microscopy, such as illumination, knife chatter, and focusing are discussed. Techniques are also shown to reduce these problems so that serial sections of tissue can be sampled at resolutions that are high enough to allow reconstruction of neurons at the cellular level.Item How does bilingualism matter? A meta-analytic tale of two hemispheres(Texas A&M University, 2004-09-30) Hull, Rachel GayleThe present investigation evaluates the effects of multiple language acquisition history on brain functional organization for language. To address a range of findings concerning the functional cerebral lateralization of the native (L1) and second languages (L2) of bilinguals, a meta-analysis was conducted on 71 studies that used behavioral paradigms to assess bilingual laterality. The predictive value of a number of theoretically identified moderators of cerebral asymmetry for language was assessed, namely, the age of second language (L2) acquisition, fluency in theL2, participant sex, experimental paradigm, linguistic task demands, relatedness of L1 and L2 structures, and context of language use. The results revealed no differences in the laterality of first and second languages within L2 acquisition age groups. Of the moderators tested, age of L2 acquisition was identified as the most reliable predictor of the direction of laterality. The conditions under which systematic similarities and differences in language lateralization among bilingual subgroups emerge are discussed in terms of implications for current models and theories concerning the functional organization of language in the bilingual brain.Item Simulation and Design of Biological and Biologically-Motivated Computing Systems(2014-04-17) Zhang, YongIn life science, there is a great need in understandings of biological systems for therapeutics, synthetic biology, and biomedical applications. However, complex behaviors and dynamics of biological systems are hard to understand and design. In the mean time, the design of traditional computer architectures faces challenges from power consumption, device reliability, and process variations. In recent years, the convergence of computer science, computer engineering and life science has enabled new applications targeting the challenges from both engineering and biological fields. On one hand, computer modeling and simulation provides quantitative analysis and predictions of functions and behaviors of biological systems, and further facilitates the design of synthetic biological systems. On the other hand, bio-inspired devices and systems are designed for real world applications by mimicking biological functions and behaviors. This dissertation develops techniques for modeling and analyzing dynamic behaviors of biologically realistic genetic circuits and brain models and design of brain-inspired computing systems. The stability of genetic memory circuits is studied to understand its functions for its potential applications in synthetic biology. Based on the electrical-equivalent models of biochemical reactions, simulation techniques widely used for electronic systems are applied to provide quantitative analysis capabilities. In particular, system-theoretical techniques are used to study the dynamic behaviors of genetic memory circuits, where the notion of stability boundary is employed to characterize the bistability of such circuits. To facilitate the simulation-based studies of physiological and pathological behaviors in brain disorders, we construct large-scale brain models with detailed cellular mechanisms. By developing dedicated numerical techniques for brain simulation, the simulation speed is greatly improved such that dynamic simulation of large thalamocortical models with more than one million multi-compartment neurons and hundreds of synapses on commodity computer servers becomes feasible. Simulation of such large model produces biologically meaningful results demonstrating the emergence of sigma and delta waves in the early and deep stages of sleep, and suggesting the underlying cellular mechanisms that may be responsible for generation of absence seizure. Brain-inspired computing paradigms may offer promising solutions to many challenges facing the main stream Von Neumann computer architecture. To this end, we develop a biologically inspired learning system amenable to VLSI implementation. The proposed solution consists of a digitized liquid state machine (LSM) and a spike-based learning rule, providing a fully biologically inspired learning paradigm. The key design parameters of this liquid state machine are optimized to maximize the learning performance while considering hardware implementation cost. When applied to speech recognition of isolated word using TI46 speech corpus, the performance of the proposed LSM rivals several existing state-of-art techniques including the Hidden Markov Model based recognizer Sphinx-4.Item Tubulin in vitro, in vivo and in silico(Texas A&M University, 2005-02-17) Mershin, AndreasTubulin, microtubules and associated proteins were studied theoretically, computationally and experimentally in vitro and in vivo in order to elucidate the possible role these play in cellular information processing and storage. Use of the electric dipole moment of tubulin as the basis for binary switches (biobits) in nanofabricated circuits was explored with surface plasmon resonance, refractometry and dielectric spectroscopy. The effects of burdening the microtubular cytoskeleton of olfactory associative memory neurons with excess microtubule associated protein TAU in Drosophila fruitflies were determined. To investigate whether tubulin may be used as the substrate for quantum computation as a bioqubit, suggestions for experimental detection of quantum coherence and entanglement among tubulin electric dipole moment states were developed.