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  • 1
    Electronic Resource
    Electronic Resource
    Is the target-to-target interval a critical determinant of P3 amplitude? (1999)
    Oxford, UK : Blackwell Publishing
    Psychophysiology 36 (1999), S. 0 
    Details
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: The P3 amplitude is augmented by decrements in target-probability, increments in the number of nontargets preceding the target, and extensions of the interstimulus interval (ISI). Each of these changes prolongs the target-to-target interval (TTI) and, consequently, results attributed to these factors might, at least partially, be accounted for by the TTI. Recent research also indicates that the P3s elicited by targets in one-, two-, and three-stimuli tasks (in which the TTI remains invariant) are similar. However, the TTI has not been examined systematically in previous research. The present study had subjects listen to a randomized ISI (0.5, 1, 2, or 4 s) version of the auditory oddball task in which targets occurred after one, two, three, four, or five nontargets. Event-related potentials were analyzed based on ISI, sequential structure, and TTI. The study examined sequence and ISI effects independent of TTI effects and demonstrated that extensions of ISI affected N1 but not P3 amplitude, extensions of TTI enhanced P3 amplitude independent of sequential structure, and sequential structure failed to influence P3 amplitude when TTI was controlled.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1469-8986.3650643
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Prestimulus EEG alpha phase synchronicity influences N100 amplitude and reaction time (1998)
    Oxford, UK : Blackwell Publishing
    Psychophysiology 35 (1998), S. 0 
    Details
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: The influence of the level of prestimulus alpha phase synchronicity on the N100 component and reaction time (RT) was examined, in target auditory oddball data from 25 normal subjects. Alpha phase synchronicity is a new measure consisting (for a given stimulus presentation) of the angular or circular variance of the alpha phase at stimulus onset across the parieto-occipital sites. The lower the angular variance, the higher the phase synchronicity (the more closely in phase the alpha activity across these sites) and vice versa. Subaveraged event-related potentials (ERPs) were formed for high and low prestimulus alpha phase synchronicity stimulus presentations. N100 amplitude was significantly greater in the high than the low phase synchronicity subaverages. In addition, RT was significantly reduced in the high prestimulus alpha phase synchronicity cases. Alpha phase synchronicity reflects an aspect of brain state that influences subsequent stimulus processing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1017/S0048577298970512
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Numerical Fourier transform spectroscopy of EMG half-waves: fragmentary-decomposition-based approach to nonstationary signal analysis (1999)
    Springer
    Biological cybernetics 81 (1999), S. 457-467 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract.  A nonstationary signal analysis technique is introduced, which regards an oscillatory physiological signal as a sum of its fragments, presented in the form of a fragmentary decomposition (FD). The virtue of FD is that it is free of the necessity to choose a priori the basis functions intended for signal analysis or synthesis. FD uses an unchanged signal fragment between adjacent zero-crossings, as a natural basis function called the half-wave function (HWF). To show that such a function is a physically meaningful object, Fourier transform methods were employed, supported by the similar basis function (SBF) algorithm, which provides the means for numerical Fourier transform spectroscopy of separate half-waves and their frequency domain description in terms of both amplitude and phase. The application of this method to parameter identification of 751 EMG half-waves from the eye blink EMG records of ten normal subjects showed that HWF's frequency domain image represents a Gaussian distribution, which applies over a defined range of relative frequencies. This empirical evidence shows that HWFs are produced by a specific system of first-order nonlinear differential equations, whose dependency on a number of random factors is characteristic of deterministic chaos. The particular form of solutions indicates that statistical regularities relevant to the central limit theorem are likely to underlie the genesis of the mass potentials studied. FD shows potential utility in a range of nonstationary physiological signals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004220050575
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Projection onto Centroids Difference Vectors: A new approach to determine between group topographical differences, applied to P3 amplitude in Schizophrenia (1995)
    Springer
    Brain topography 8 (1995), S. 67-73 
    Details
    ISSN: 1573-6792
    Keywords: ERP ; Statistical analysis ; SPM ; PCA ; P3 ; Schizophrenia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A common problem in electrophysiological research concerns between group analysis of EEG and ERP topography. This paper proposes a new technique for determining whether or not a significant difference exists between multiple scalp site measurements from two groups. The method requires noa priori assumptions about the data and is thus ideal for exploratory data analysis, and it also requires that only one statistical test need be performed (significantly reducing the possibility of type I errors). The Projection onto Centroids Difference Vectors (PCDV) method involves deriving a measure from each individual of whether their measurements across sites are closer overall to the mean measurements of the rest of their experimental group, or to the other group. These measures from each individual are then compared between groups using a Student'st test, which indicates whether one group's data is significantly spatially different from the other. In this study we describe the method in detail and apply it to both simulated data and to real auditory P3 data in unmedicated, medicated schizophrenics and matched normal controls. The PCDV method was also compared with statistical probability mapping (SPM). The PCDV method revealed the differences between the normal and patient groups more unambiguously than SPM, and the simulated data revealed that it was not liable to type I errors. PCDV provides an appropriate method for testing any between group EEG and ERP topographical differences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01187671
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    Paper (German National Licenses)
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