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  • 1
    Electronic Resource
    Electronic Resource
    Statistical control of artifacts in dense array EEG/MEG studies (2000)
    Oxford, UK : Blackwell Publishing
    Psychophysiology 37 (2000), S. 0 
    Details
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: With the advent of dense sensor arrays (64–256 channels) in electroencephalography and magnetoencephalography studies, the probability increases that some recording channels are contaminated by artifact. If all channels are required to be artifact free, the number of acceptable trials may be unacceptably low. Precise artifact screening is necessary for accurate spatial mapping, for current density measures, for source analysis, and for accurate temporal analysis based on single-trial methods. Precise screening presents a number of problems given the large datasets. We propose a procedure for statistical correction of artifacts in dense array studies (SCADS), which (1) detects individual channel artifacts using the recording reference, (2) detects global artifacts using the average reference, (3) replaces artifact-contaminated sensors with spherical interpolation statistically weighted on the basis of all sensors, and (4) computes the variance of the signal across trials to document the stability of the averaged waveform. Examples from 128-channel recordings and from numerical simulations illustrate the importance of careful artifact review in the avoidance of analysis errors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1469-8986.3740523
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Fleeting images: A new look at early emotion discrimination (2001)
    Oxford, UK : Blackwell Publishing
    Psychophysiology 38 (2001), S. 0 
    Details
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: The visual brain quickly sorted stimuli for emotional impact despite high-speed presentation (3 or 5 per s) in a sustained, serial torrent of 700 complex pictures. Event-related potentials, recorded with a dense electrode array, showed selective discrimination of emotionally arousing stimuli from less affective content. Primary sources of this activation were over the occipital cortices, extending to right parietal cortex, suggesting a processing focus in the posterior visual system. Emotion discrimination was independent of formal pictorial properties (color, brightness, spatial frequency, and complexity). The data support the hypothesis of a very short-term conceptual memory store (M. C. Potter, 1999)—shown here to include a fleeting but reliable assessment of affective meaning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1469-8986.3820175
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The selective processing of briefly presented affective pictures: An ERP analysis (2004)
    Oxford, UK : Blackwell Publishing
    Psychophysiology 41 (2004), S. 0 
    Details
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: Recent event-related potential (ERP) studies revealed the selective processing of affective pictures. The present study explored whether the same phenomenon can be observed when pictures are presented only briefly. Toward this end, pleasant, neutral, and unpleasant pictures from the International Affective Pictures Series were presented for 120 ms while event related potentials were measured by dense sensor arrays. As observed for longer picture presentations, brief affective pictures were selectively processed. Specifically, pleasant and unpleasant pictures were associated with an early endogenous negative shift over temporo-occipital sensors compared to neutral images. In addition, affective pictures elicited enlarged late positive potentials over centro-parietal sensor sites relative to neutral images. These data suggest that a quick glimpse of emotionally relevant stimuli appears sufficient to tune the brain for selective perceptual processing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1469-8986.2004.00174.x
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Mapping EEG-potentials on the surface of the brain: A strategy for uncovering cortical sources (1997)
    Springer
    Brain topography 9 (1997), S. 203-217 
    Details
    ISSN: 1573-6792
    Keywords: High spatial sampling EEG ; Spatial deblurring ; Current source density ; Cortical Mapping ; Spherical spline interpolation ; Inverse problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This paper describes a uniform method for calculating the interpolation of scalp EEG potential distribution, the current source density (CSD), the cortical potential distribution (cortical mapping) and the CSD of the cortical potential distribution. It will be shown that interpolation and deblurring methods such as CSD or cortical mapping are not independent of the inverse problem in potential theory. Not only the resolution but also the accuracy of these techniques, especially those of deblurring, depend greatly on the spatial sampling rate (i.e., the number of electrodes). Using examples from simulated and real (64 channels) data it can be shown that the application of more than 100 EEG channels is not only favourable but necessary to guarantee a reasonable accuracy in the calculations of CSD or cortical mapping. Likewise, it can be shown that using more than 250 electrodes does not improve the resolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01190389
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    Paper (German National Licenses)
    Fulltext
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