UA PSY 501A - Advanced Signal Processing I & II (58 pages)

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Advanced Signal Processing I & II



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Advanced Signal Processing I & II

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Lecture Notes


Pages:
58
School:
University of Arizona
Course:
Psy 501a - Principles of Psychophysiology

Unformatted text preview:

Advanced Signal Processing I II aka Acronym Day Ocular Artifact Correction acronym free Digital Filters FIR Latency Jitter and Woody Filters acronym free PCA Inference Problems with Scalp Topography acronym free BESA IFA Simultaneous ERP with ICA and fMRI The Problem of Latency Jitter The averaging assumption of invariance in signal is not always warranted Especially for the later endogenous components To the extent that the signal varies from trial to trial the average will produce potentially misleading results Two common possibilities Smearing of components will underestimate amplitude of component especially a problem if comparing groups one group with more latency jitter Bimodal or multi bumped components The Solution The Woody Adaptive Filter Woody 1967 Based on Cross correlation Assumptions less restrictive than averaging methods Waveform morphology must be constant across trials Latency need not be constant Details Cross correlational series For two waveforms the correlation between each of them is computed first with no lag in time a1 a2 an with b1 b2 bn then with one lagged with respect to the other a1 a2 an with b2 b3 bn 1 A series of correlation values is obtained by progressively increasing the size of the lag Extreme and fictitious example More Details Can be used as a template matching procedure Compare running average with raw EEG epochs This is a method of single trial signal detection First create a template either predetermined e g sine wave or empirically determined e g average Then calculate cross correlational series between each raw EEG epoch and the template If some maximum correlation achieved conclude signal is present If correlation not achieved conclude absent This can also be used as a method of determining the latency of a component by examining the trial by trial shifts or of determining the variability in response for a given individual again by examining the trial by trail shifts Woody s Instantiation The Woody Adaptive Filter



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