Signal processing and information fusing algorithms for the synthesis of an alternative electromyogram/eye gaze tracking computer cursor control system

This research pursued the conceptualization and real-time verification of a system that allows a computer user to control the cursor of a computer interface without using his/her hands. The target user groups for this system are individuals who are unable to use their hands due to spinal dysfunction or other afflictions, and individuals who must use their hands for higher priority tasks while still requiring interaction with a computer. ^ The system receives two forms of input from the user: Electromyogram (EMG) signals from muscles in the face and point-of-gaze coordinates produced by an Eye Gaze Tracking (EGT) system. In order to produce reliable cursor control from the two forms of user input, the development of this EMG/EGT system addressed three key requirements: an algorithm was created to accurately translate EMG signals due to facial movements into cursor actions, a separate algorithm was created that recognized an eye gaze fixation and provided an estimate of the associated eye gaze position, and an information fusion protocol was devised to efficiently integrate the outputs of these algorithms. ^ Experiments were conducted to compare the performance of EMG/EGT cursor control to EGT-only control and mouse control. These experiments took the form of two different types of point-and-click trials. The data produced by these experiments were evaluated using statistical analysis, Fitts' Law analysis and target re-entry (TRE) analysis. ^ The experimental results revealed that though EMG/EGT control was slower than EGT-only and mouse control, it provided effective hands-free control of the cursor without a spatial accuracy limitation, and it also facilitated a reliable click operation. This combination of qualities is not possessed by either EGT-only or mouse control, making EMG/EGT cursor control a unique and practical alternative for a user's cursor control needs. ^

Social and environmental regulation of signal plasticity and signal reliability in the electric fish Brachyhypopomus gauderio

The balance between the costs and benefits of conspicuous signals ensures that the expression of those signals is related to the quality of the bearer. Plastic signals could enable males to maximize conspicuous traits to impress mates and competitors, but reduce the expression of those traits to minimize signaling costs, potentially compromising the information conveyed by the signals. ^ I investigated the effect of signal enhancement on the information coded by the biphasic electric signal pulse of the gymnotiform fish Brachyhypopomus gauderio. Increases in population density drive males to enhance the amplitude of their signals. I found that signal amplitude enhancement improves the information about the signaler's size. Furthermore, I found that the elongation of the signal's second phase conveys information about androgen levels in both sexes, gonad size in males and estrogen levels in females. Androgens link the duration of the signal's second phase to other androgen-mediated traits making the signal an honest indicator of reproductive state and aggressive motivation. ^ Signal amplitude enhancement facilitates the assessment of the signaler's resource holding potential, important for male-male interactions, while signal duration provides information about aggressive motivation to same-sex competitors and reproductive state to the opposite sex. Moreover, I found that female signals also change in accordance to the social environment. Females also increase the amplitude of their signal when population density increases and elongate the duration of their signal's second phase when the sex ratio becomes female-biased. Indicating that some degree of sexual selection operates in females. ^ I studied whether male B. gauderio use signal plasticity to reduce the cost of reproductive signaling when energy is limited. Surprisingly, I found that food limitation promotes the investment in reproduction manifested as signal enhancement and elevated androgen levels. The short lifespan and single breeding season of B. gauderio diminishes the advantage of energy savings and gives priority to sustaining reproduction. I conclude that the electric signal of B. gauderio provides reliable information about the signaler, the quality of this information is reinforced rather than degraded with signal enhancement.^

Expression of the Myod and T-Box Families of Transcription Factors in the Developing Purkinje Fiber

The coordinated beating of the heart depends on a group ofhighly specialized cells that constitute the cardiac conduction system. Among these cells, the Purkinje fibers are responsible for propagation of the electric impulse into the ventricles. In early stages of development, Purkinje fibers and skeletal muscle fibers originate from similar but separate populations of myocytes. The role of the MyoD family of transcription factors in the development of the myotube is well known, but the role of these factors in the development of the Purkinje fiber is not. Members of the T-Box family of transcription.The coordinated beating of the heart depends on a group ofhighly specialized cells that constitute the cardiac conduction system. Among these cells, the Purkinje fibers are responsible for propagation of the electric impulse into the ventricles. In early stages of development, Purkinje fibers and skeletal muscle fibers originate from similar but separate populations of myocytes. The role of the MyoD family of transcription factors in the development of the myotube is well known, but the role of these factors in the development of the Purkinje fiber is not. Members of the T-Box family of transcription factors are also involved in the development of various cardiac tissues, including the conduction system but little is known about their role in the development of the Purkinje fiber. We explored the expression of members of the MyoD and T-Box families in the developing cardiac conduction system in vivo and in vitro. We showed that the expression of these factors changes as the myocyte differentiates into the Purkinje fiber. We also showed that NRG-1, a secreted protein involved in the development of the Purkinje fiber, features a dose-dependent response in the differentiation of cultured ventricular myocytes.