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  • 2000-2004  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    The intractability of scaling scalp distributions to infer neuroelectric sources (2002)
    Oxford, UK : Blackwell Publishing
    Psychophysiology 39 (2002), S. 0 
    Details
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: ERP researchers use differences in scalp distributions to infer differences in spatial configurations of neuroelectric generators. Since McCarthy and Wood (1985) demonstrated that a spatially fixed current source varying only in strength can yield a significant Condition × Electrode interaction in ANOVA, the recommended approach has been to normalize ERP amplitudes, for example, by vector length, prior to testing for interactions. The assumptions of this procedure are examined and it is shown via simulations that this application of vector scaling is both conceptually flawed and unsound in experimental practice. Because different spatial configurations of neural generators cannot reliably be inferred from different scalp topographies even after amplitude normalization, it is recommended that the procedure no longer be used for this purpose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1469-8986.3960791
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Tracking eye fixations with electroocular and electroencephalographic recordings (2002)
    Oxford, UK : Blackwell Publishing
    Psychophysiology 39 (2002), S. 0 
    Details
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: We describe a method, based on recordings of the electroencephalogram (EEG) and eye movement potentials (electrooculogram), to track where on a screen (x, y coordinates) an individual is fixating. The method makes use of an empirically derived beam-forming filter (derived from a sequence of calibrated eye movements) to isolate eye motion from other electrophysiological and ambient electrical signals. Electrophysiological researchers may find this method a simple and inexpensive means of tracking eye movements and a useful complement to scalp recordings in studies of cognitive phenomena. The resolution is comparable to that of many commercial systems; the method can be implemented with as few as four electrodes around the eyes to complement the EEG electrodes already in use. This method may also find some specialized applications such as studying eye movements during sleep and in human–machine interfaces that make use of gaze information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1469-8986.3950607
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Electrophysiological estimates of the time course of semantic and phonological encoding during implicit picture naming (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: Two different event-related potential (ERP) components were used to investigate the temporal processing of semantic and phonological encoding during implicit picture naming. Participants were shown pictures and carried out a dual choice go/nogo decision based on semantic information (i.e., whether the picture was of an object or an animal) and phonological information (i.e., whether the picture's name starts with a vowel or a consonant). In addition to the already established lateralized readiness potential (LRP; related to response preparation), we introduce the N200 (presumably related to response inhibition) as a tool for measuring online language processing. Both, the LRP and the N200 data indicated that semantic processing began earlier than phonological processing. The data are discussed in the context of language production models. Therein, the LRP and N200 results, taken together, favor a serial or cascaded processing model of language production in contrast to a parallel processing account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1469-8986.3740473
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    The impact of semantic memory organization and sentence context information on spoken language processing by younger and older adults: An ERP study (2002)
    Oxford, UK : Blackwell Publishing
    Psychophysiology 39 (2002), S. 0 
    Details
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: To examine changes in semantic memory organization and use during aging, we recorded event-related potentials as younger and older adults listened to sentences ending with the expected word, an unexpected word from the same semantic category, or an unexpected word from a different category. Half of the contexts were highly constraining. In both groups, expected words elicited less negativity 300–500 ms (N400) than unexpected ones, and unexpected words elicited smaller N400s when these were categorically related. Whereas younger adults showed the greatest N400 reduction to unexpected but related words in high constraint contexts, older adults showed the opposite tendency. Thus, unlike younger adults, older adults as a group do not seem to be using context predictively. Older adults with higher verbal fluency and larger vocabularies, however, showed the younger response pattern, suggesting resource availability may offset certain age-related changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1469-8986.3920133
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Syntactic processing with aging: An event-related potential study (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: To assess age-related changes in simple syntactic processing with normal aging, event-related brain potentials (ERPs) elicited by grammatical number violations as individuals read sentences for comprehension were analyzed. Violations were found to elicit a P600 of equal amplitude and latency regardless of an individual's age. Instead, advancing age was associated with a change in the scalp distribution of the P600 effect, being less asymmetric and more frontal (though still with a parietal maximum) in older than younger adults. Our results thus show that the brain's response to simple syntactic violations, unlike those reported for simple binary categorizations and simple semantic violations, is neither slowed nor diminished in amplitude by age. At the same time, the brain's processing of these grammatical number violations did engage at least somewhat different brain regions as a function of age, suggesting a qualitative change rather than any simple quantitative change in speed of processing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1469-8986.2004.00180.x
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    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Automatic removal of eye movement and blink artifacts from EEG data using blind component separation (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: Signals from eye movements and blinks can be orders of magnitude larger than brain-generated electrical potentials and are one of the main sources of artifacts in electroencephalographic (EEG) data. Rejecting contaminated trials causes substantial data loss, and restricting eye movements/blinks limits the experimental designs possible and may impact the cognitive processes under investigation. This article presents a method based on blind source separation (BSS) for automatic removal of electroocular artifacts from EEG data. BBS is a signal-processing methodology that includes independent component analysis (ICA). In contrast to previously explored ICA-based methods for artifact removal, this method is automated. Moreover, the BSS algorithm described herein can isolate correlated electroocular components with a high degree of accuracy. Although the focus is on eliminating ocular artifacts in EEG data, the approach can be extended to other sources of EEG contamination such as cardiac signals, environmental noise, and electrode drift, and adapted for use with magnetoencephalographic (MEG) data, a magnetic correlate of EEG.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1469-8986.2003.00141.x
    Location Call Number Limitation Availability
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    Paper (German National Licenses)
    Fulltext
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