Cover Image

Generalized Subspace Approach for Measurement of Latencies in Visual Evoked Potentials

Estimating a visual evoked potential (VEP) from the human brain is challenging since its signal-to-noise ratio (SNR) is generally very low. Visual evoked potentials are conventionally extracted from the spontaneous brain activity by collecting a series of time-locked electroencephalogram (EEG) epoch...

Full description

Saved in:
Bibliographic Details
Main Author: Yusoff, Mohd Zuki
Format: Thesis
Language:English
Published: 2010
Subjects:
TK Electrical engineering. Electronics Nuclear engineering
Online Access:http://utpedia.utp.edu.my/id/eprint/1064/1/mohd_zuki_yusof_1.pdf
http://utpedia.utp.edu.my/id/eprint/1064/
Tags: Add Tag
No Tags, Be the first to tag this record!
id oai:utpedia.utp.edu.my:1064
record_format eprints
spelling oai:utpedia.utp.edu.my:10642024-07-23T04:58:29Z http://utpedia.utp.edu.my/id/eprint/1064/ Generalized Subspace Approach for Measurement of Latencies in Visual Evoked Potentials Yusoff, Mohd Zuki TK Electrical engineering. Electronics Nuclear engineering Estimating a visual evoked potential (VEP) from the human brain is challenging since its signal-to-noise ratio (SNR) is generally very low. Visual evoked potentials are conventionally extracted from the spontaneous brain activity by collecting a series of time-locked electroencephalogram (EEG) epochs and performing ensemble averaging on these samples to improve the SNR. However, this multi-trial averaging contributes to loss of distinctive physiological information which may prove useful for thorough optical pathway conduction assessment, disease diagnosis, and other fields of study such as psychology and pharmaceuticals. As such, a VEP estimation scheme based on a single VEP trial which minimizes the information loss and reduces VEP recording time, is highly desirable. In this thesis, two novel variations of generalized subspace approaches (GSAs) have been proposed to estimate VEP's P100, P200 and P300 latencies from colored EEG noise. The proposed methods decompose and decorrelate the corrupted VEP space into signal and noise subspace; VEP enhancement is achieved by removing the noise subspace and estimating the clean VEPs only from the signal subspace. Since EEG is colored noise, implicit and explicit pre-whitening of the corrupted VEP waveform are performed in the proposed algorithms, to resolve diagonalization problems and achieve full VEP space decorrelation. Furthermore, the computation of a proper subspace dimension vital to the optimum extraction of VEPs has been included in GSAs. With the diagonalization and subspace dimension problems resolved, the proposed GSA techniques ultimately form a comparable VEP latency estimation system. Three single-trial approaches for VEP latency estimation proposed by various authors have also been evaluated and compared with GSAs. The results of comprehensively simulated data involving SNR from 0 to -11 dB indicate that the GSA schemes outperform the other three methods. The GSA estimators produce the lowest failure rate and average errors, and their performance is relatively independent of the given SNR in contrary to the other methods. The results of fifty real patient data further confirm that both GSAs are better estimators compared to the other studied techniques. With the favorable performance demonstrated by the outcome of the simulated and real patient data, both GSAs have the potentials to be used not only as biomedical signal estimators from the brain, but also as general purpose estimators in any other fields where SNR values are relatively low. 2010 Thesis NonPeerReviewed application/pdf en http://utpedia.utp.edu.my/id/eprint/1064/1/mohd_zuki_yusof_1.pdf Yusoff, Mohd Zuki (2010) Generalized Subspace Approach for Measurement of Latencies in Visual Evoked Potentials. Doctoral thesis, Universiti Teknologi Petronas.
institution Universiti Teknologi Petronas
building UTP Resource Centre
collection Institutional Repository
continent Asia
country Malaysia
content_provider Universiti Teknologi Petronas
content_source UTP Electronic and Digitized Intellectual Asset
url_provider http://utpedia.utp.edu.my/
language English
topic TK Electrical engineering. Electronics Nuclear engineering
spellingShingle TK Electrical engineering. Electronics Nuclear engineering
Yusoff, Mohd Zuki
Generalized Subspace Approach for Measurement of Latencies in Visual Evoked Potentials
description Estimating a visual evoked potential (VEP) from the human brain is challenging since its signal-to-noise ratio (SNR) is generally very low. Visual evoked potentials are conventionally extracted from the spontaneous brain activity by collecting a series of time-locked electroencephalogram (EEG) epochs and performing ensemble averaging on these samples to improve the SNR. However, this multi-trial averaging contributes to loss of distinctive physiological information which may prove useful for thorough optical pathway conduction assessment, disease diagnosis, and other fields of study such as psychology and pharmaceuticals. As such, a VEP estimation scheme based on a single VEP trial which minimizes the information loss and reduces VEP recording time, is highly desirable. In this thesis, two novel variations of generalized subspace approaches (GSAs) have been proposed to estimate VEP's P100, P200 and P300 latencies from colored EEG noise. The proposed methods decompose and decorrelate the corrupted VEP space into signal and noise subspace; VEP enhancement is achieved by removing the noise subspace and estimating the clean VEPs only from the signal subspace. Since EEG is colored noise, implicit and explicit pre-whitening of the corrupted VEP waveform are performed in the proposed algorithms, to resolve diagonalization problems and achieve full VEP space decorrelation. Furthermore, the computation of a proper subspace dimension vital to the optimum extraction of VEPs has been included in GSAs. With the diagonalization and subspace dimension problems resolved, the proposed GSA techniques ultimately form a comparable VEP latency estimation system. Three single-trial approaches for VEP latency estimation proposed by various authors have also been evaluated and compared with GSAs. The results of comprehensively simulated data involving SNR from 0 to -11 dB indicate that the GSA schemes outperform the other three methods. The GSA estimators produce the lowest failure rate and average errors, and their performance is relatively independent of the given SNR in contrary to the other methods. The results of fifty real patient data further confirm that both GSAs are better estimators compared to the other studied techniques. With the favorable performance demonstrated by the outcome of the simulated and real patient data, both GSAs have the potentials to be used not only as biomedical signal estimators from the brain, but also as general purpose estimators in any other fields where SNR values are relatively low.
format Thesis
author Yusoff, Mohd Zuki
author_facet Yusoff, Mohd Zuki
author_sort Yusoff, Mohd Zuki
title Generalized Subspace Approach for Measurement of Latencies in Visual Evoked Potentials
title_short Generalized Subspace Approach for Measurement of Latencies in Visual Evoked Potentials
title_full Generalized Subspace Approach for Measurement of Latencies in Visual Evoked Potentials
title_fullStr Generalized Subspace Approach for Measurement of Latencies in Visual Evoked Potentials
title_full_unstemmed Generalized Subspace Approach for Measurement of Latencies in Visual Evoked Potentials
title_sort generalized subspace approach for measurement of latencies in visual evoked potentials
publishDate 2010
url http://utpedia.utp.edu.my/id/eprint/1064/1/mohd_zuki_yusof_1.pdf
http://utpedia.utp.edu.my/id/eprint/1064/
_version_ 1805890992448995328
score 13.211869

Similar Items