Please use this identifier to cite or link to this item: https://www.um.edu.mt/library/oar/handle/123456789/24143
Title: Waveform analysis of non-oscillatory independent components in single-trial auditory event-related activity in healthy subjects and Alzheimer's disease patients
Authors: Jervis, Barrie
Belal, Suliman
Cassar, Tracey A.
Besleaga, Mircea
Bigan, Cristin
Michalopoulos, Kostas
Zervakis, Michalis
Camilleri, Kenneth P.
Fabri, Simon G.
Keywords: Alzheimer's disease
Brain mapping
Evoked potentials, Auditory -- Physiology
Diagnosis, Differential
Neural conduction -- Physiology
Signal processing, Computer-assisted
Acoustic stimulation
Issue Date: 2010
Publisher: Bentham Science Publishers Ltd.
Citation: Jervis, B. W., Belal, S., Cassar, T., Besleaga, M., Bigan, C., Michalopoulos, K., Zervakis, M., Camilleri, K. P. & Fabri, S. (2010). Waveform analysis of non-oscillatory independent components in single-trial auditory event-related activity in healthy subjects and Alzheimer's disease patients. Current Alzheimer Research, 7(4), 334-347.
Abstract: The objective was to characterize the non-oscillatory independent components (ICs) of the auditory event-related potential (ERP) waveform of an oddball task for normal and newly diagnosed Alzheimer's disease (AD) subjects, and to seek biomarkers for AD. Single trial ERP waveforms were analysed using independent components analysis (ICA) and k-means clustering. Two stages of clustering depended upon the magnitudes and latencies, and the scalp topographies of the non-oscillatory back-projected ICs (BICs) at electrode Cz. The electrical current dipole sources of the BICs were located using Low Resolution Electromagnetic Tomography (LORETA). Generally 3-10 BICs, of different latencies and polarities, occurred in each trial. Each peak was associated with positive and negative BICs. The trial-to-trial variations in their relative numbers and magnitudes may explain the variations in the averaged ERP reported, and the delay in the averaged P300 for AD patients. The BIC latencies, topographies and electrical current density maximum locations varied from trial-to-trial. Voltage foci in the BIC topographies identify the BIC source locations. Since statistical differences were found between the BICs in healthy and AD subjects, the method might provide reliable biomarkers for AD, if these findings are reproduced in a larger study, independently of other factors influencing the comparison of the two populations. The method can extract artefact- and EEG-free single trial ERP waveforms, offers improved ERP averages by selecting the trials on the basis of their BICs, and is applicable to other evoked potentials, conditions and diseases.
URI: https://www.um.edu.mt/library/oar//handle/123456789/24143
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