3,267 research outputs found
Investigation of GPGPU for use in processing of EEG in real-time
The purpose of this thesis was to investigate the use of General Purpose computing on Graphics Processing Units (GPGPU) to process electroencephalogram (EEG) signals in real-time. The main body of this work required the implementation of Independent Component Analysis were investigated: FastICA and JADE. Both were implemented three times: first using M-file syntax to serve as a benchmark, next, as native C code to measure performance of the algorithms when running natively on a CPU, and finally, as GPGPU code using the NVIDIA CUDA C language extension. In previous works, Independent Component Analysis represented the largest roadblock to achieving the real-time goal of processing 10 seconds of EEG within a 10 second window. It was found that both FastICA and JADE see speedups, with a maximum measured speedup of approximately 6x for FastICA, and approximately 2.5x for JADE, when operating on the largest datasets. In addition, speedups of between 1x and 2x were seen when working on datasets of the expected size provided by 10 seconds of 32-channel EEG sampled at 500 Hz. However, it was also found that GPGPU solutions are not necessary for real-time performance on a modern desktop computer as the FastICA algorithm is capable of a worst-case performance of between approximately 1 and 2 seconds depending on configuration parameters
Monitoring kinetic and frequency-domain properties of eyelid responses in mice with magnetic distance measurement technique
Classical eye-blink conditioning in mutant mice can be used to study the
molecular mechanisms underlying associative learning. To measure the
kinetic and frequency domain properties of conditioned (tone - periorbital
shock procedure) and unconditioned eyelid responses in freely moving mice,
we developed a method that allows adequate, absolute, and continuous
determination of their eyelid movements in time and space while using an
electrical shock as the unconditioned stimulus. The basic principle is to
generate a local magnetic field that moves with the animal and that is
picked up by either a field-sensitive chip or coil. With the use of this
magnetic distance measurement technique (MDMT), but not with the use of
electromyographic recordings, we were able to measure mean latency, peak
amplitude, velocity, and acceleration of unconditioned eyelid responses,
which equaled 7.9 +/- 0.2 ms, 1.2 +/- 0.02 mm, 28.5 +/- 1 mm/s, and 637
+/- 22 mm/s(2), respectively (means +/- SD). During conditioning, the mice
reached an average of 78% of conditioned responses over four training
sessions, while animals that were subjected to randomly paired conditioned
and unconditioned stimuli showed no significant increases. The mean
latency of the conditioned responses decreased from 222 +/- 40 ms in
session 2 to 127 +/- 6 ms in session 4, while their mean peak latency
increased from 321 +/- 45 to 416 +/- 67 ms. The mean peak amplitudes, peak
velocities, and peak acceleration of these responses increased from 0.62
+/- 0.02 to 0.77 +/- 0.02 mm, from 3.9 +/- 0.3 to 7.7 +/- 0.5 mm/s, and
from 81 +/- 7 to 139 +/- 10 mm/s(2), respectively. Power spectra of
acceleration records illustrated that both the unconditioned and
conditioned responses of mice had oscillatory properties with a dominant
peak frequency close to 25 Hz that was not dependent on training session,
interstimulus interval, or response size. These data show that MDMT can be
used to measure the kinetics and frequency domain properties of
conditioned eyelid responses in mice and that these properties follow the
dynamic characteristics of other mammals
Metabotropic Glutamate Receptor Activation in Cerebelar Purkinje Cells as Substrate for Adaptive Timing of the Classicaly Conditioned Eye Blink Response
To understand how the cerebellum adaptively times the classically conditioned nictitating membrane response (NMR), a model of the metabotropic glutamate receptor (mGluR) second messenger system in cerebellar Purkinje cells is constructed. In the model slow responses, generated postsynaptically by mGluR-mediated phosphoinositide hydrolysis, and calcium release from intracellular stores, bridge the interstimulus interval (ISI) between the onset of parallel fiber activity associated with the conditioned stimulus (CS) and climbing fiber activity associated with unconditioned stimulus (US) onset. Temporal correlation of metabotropic responses and climbing fiber signals produces persistent phosphorylation of both AMPA receptors and Ca2+-dependent K+ channels. This is responsible for long-term depression (LTD) of AMPA receptors. The phosphorylation of Ca2+-dependent K+ channels leads to a reduction in baseline membrane potential and a reduction of Purkinje cell population firing during the CS-US interval. The Purkinje cell firing decrease disinhibits cerebellar nuclear cells which then produce an excitatory response corresponding to the learned movement. Purkinje cell learning times the response, while nuclear cell learning can calibrate it. The model reproduces key features of the conditioned rabbit NMR: Purkinje cell population response is properly timed, delay conditioning occurs for ISIs of up to four seconds while trace conditioning occurs only at shorter ISIs, mixed training at two different ISis produces a double-peaked response, and ISIs of 200-400ms produce maximal responding. Biochemical similarities between timed cerebellar learning and photoreceptor transduction, and circuit similarities between the timed cerebellar circuit and a timed dentate-CA3 hippocampal circuit, are noted.Office of Naval Research (N00014- 92-J-4015, N00014-92-J-1309, N00014-95-1-0409); Air Force Office of Scientific Research (F49620-92-J-0225);National Science Foundation (IRI-90-24877
Real-time human ambulation, activity, and physiological monitoring:taxonomy of issues, techniques, applications, challenges and limitations
Automated methods of real-time, unobtrusive, human ambulation, activity, and wellness monitoring and data analysis using various algorithmic techniques have been subjects of intense research. The general aim is to devise effective means of addressing the demands of assisted living, rehabilitation, and clinical observation and assessment through sensor-based monitoring. The research studies have resulted in a large amount of literature. This paper presents a holistic articulation of the research studies and offers comprehensive insights along four main axes: distribution of existing studies; monitoring device framework and sensor types; data collection, processing and analysis; and applications, limitations and challenges. The aim is to present a systematic and most complete study of literature in the area in order to identify research gaps and prioritize future research directions
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fMRI correlates of subjective reversals in ambiguous structure-from-motion
We used fMRI to examine the neural correlates of subjective reversals for bistable structure-from-motion. We compared transparent random-dot kinematograms depicting either a cylinder rotating in depth or two flat surfaces translating in opposite directions at apparently different depths. For both such stimuli, the motion of dots on the different apparent depth planes typically appears to reverse direction periodically on prolonged viewing. Yet for cylindrical but not flat stimuli, such subjective reversals also coincide with apparent reversal of 3D rotation direction. We hypothesized that the lateral occipital complex (region LOC), sensitive to 3D form, might show greater event-related activity for subjective reversals of cylindrical than flat stimuli; conversely, motion-sensitive hMT+/V5 should respond in common to subjective reversals for either type of stimuli, as both are perceived as changes in planar motion. We obtained an event-related measure of neural activity associated with subjective reversals after first factoring out block-related differences between cylindrical versus flat stimuli (and thereby the associated low-level blocked stimulus differences). In support of our hypothesis, only the cylindrical stimuli produced reversal-related activity in contralateral human LOC. In contrast, the hMT+/V5 complex was activated alike by subjective reversals for both cylindrical and flat stimuli. Intriguingly, V1 also showed (contralateral) specificity for rotational reversals, suggesting a possible feedback influence from LOC. These results reveal specific neural correlates for subjective switches of 3D rotation versus translation, as distinct from subjective reversals in general
A Flexible, Open, Multimodal System of Computer Control Based on Infrared Light
This In this paper, a system architecture that can be adapted to an individual’s motor capacity and preferences, to control a computer is presented. The system uses two different transducers based on the emission and the reflection of infrared light. These let to detect of voluntary blinks, winks, saccadic or head movements and/or sequences of them. Transducer selection and operational mode can be configured. The signal provided by the transducer is adapted, processed and sent to a computer by external hardware. The computer runs a row-column scanned switch-controlled Virtual Keyboard (VK). This sends commands to the operating system to control the computer, making possible to run any application such as a web browser, etc. The main system characteristics are flexibility and relatively low-cost hardware.Junta de AndalucĂa p08-TIC-363
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