THE EFFECT OF ALPHA UPON THE P300.
Item
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Title
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THE EFFECT OF ALPHA UPON THE P300.
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Identifier
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AAI8713766
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identifier
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8713766
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Creator
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JASIUKAITIS, PAUL ALEXANDER.
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Contributor
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Gad Hakerem
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Date
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1987
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Language
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English
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Publisher
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City University of New York.
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Subject
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Psychology, Psychobiology
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Abstract
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The overlap between alpha-blocking and P300-eliciting stimulus sets is considerable. Both phenomena require novel, target or salient stimulation and are not found upon stimuli which fail to engage the subject's attention. We had noticed that the blocking of EEG alpha spindles by auditory stimulation was often accompanied by a sharp positive shift in the EEG baseline. We hypothesized that this positive shift is a facet of alpha-blocking and that it might be sufficiently time-locked after stimulus presentation to contribute to, or even be responsible for, the formation of the P300.;The experiments described below are what we call alpha sorts. Trials on which highly discrepant 'oddball' stimuli were presented, were sorted into two bins on the basis of pre-stimulus alpha band RMS magnitude. The trial bins were then separately averaged to produce a 'high alpha' evoked potential and a 'low alpha' evoked potential for each subject. The rare stimulus trials were embedded within a near-threshold auditory intensity discrimination task. The purpose of this was to constrain the subject's EEG to frequencies above delta/theta and to prevent fluctuations in wakefulness from contributing to effects upon the evoked potential.;Study 1 found that larger amplitude P300s were produced by selectively averaging for high pre-stimulus alpha. No effect of alpha was found upon the N100. These findings established specificity of the alpha effect for the P300 component. Study 2 employed the extra factors of direction of stimulus intensity change (increases and decreases) and separate trial sorting based on alpha RMS both pre-stimulus and post-stimulus. The purpose of the post-stimulus sort was to determine whether it was pre-stimulus alpha alone which enhanced the P300 or pre-stimulus alpha in conjunction with low alpha post-stimulus, i.e. alpha-blocking. It was found that P300 enhancement by pre-stimulus alpha did not interact with stimulus intensity and appeared to be independent of alpha post-stimulus. The data are discussed in terms of cascaded inhibition from the mesencephalic reticular formation to nucleus reticularis of the thalamus to a thalamo-cortical system responsible for both alpha and the P300.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Psychology
