Brain Topography

, Volume 3, Issue 1, pp 85–93 | Cite as

Topographical display and interpretation of event-related desynchronization during a visual-verbal task

  • G. Pfurtscheller
  • W. Klimesch


Multichannel EEG recordings were performed during a visual-verbal judgement task with a verbal response using an event-related paradigm. EEG trials of 7 sec were first digitally band pass filtered (10–12 Hz, 10–11 Hz, 11–12 Hz), and the amplitudes were then squared and averaged over all trials. This processing method results in a time course of alpha power and allows us to quantify the event-related desynchronization (ERD) in each EEG channel and to compute series of ERD maps in intervals of 125 msec. Analyzing the 10–11 Hz band, it was possible to study the time course and topographical pattern of cortical activation during visual encoding and cognition. Analysis of the 11–12 Hz band has enabled us, for the first time, to study the time course, spatial localization and extent of activation of speech, premotor and motor areas. We found that the speech centers were activated maximally 250 to 375 msec before speech onset and the SMA about 250 msec before speech onset. The results are preliminary, but demonstrate how much information can be extracted from the scalp EEG.

Key words

Brain topography Event-related desynchronization Visual encoding Verbal response 


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Copyright information

© Human Sciences Press, Inc 1990

Authors and Affiliations

  • G. Pfurtscheller
    • 1
  • W. Klimesch
    • 2
  1. 1.Department of Medical Informatics, Institute of Biomedical EngineeringGraz University of Technology, and Ludwig Boltzmann-Institute of Medical InformaticsGrazAustria
  2. 2.Department of Physiological Psychology, Institute of PsychologyUniversity of SalzburgAustria

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