Identification of binaural processing in auditory evoked potentials

When we hear a sound, we make use of the fact that we have two ears ("channels") in order to locate its source. Since the two receivers are a little distance apart, the physical signals that reach them are slightly different. It is a fascinating accomplishment of our central nervous system to extract the location of the sound source from the tiny differences of the air pressure at the two ears. Precisely how this is achieved is not completely understood. It is clear, however, that time shifts and frequency-specific level differences play a major role in the process.

To investigate the neuronal processing of acoustical signals in humans, multichannel EEG recordings are performed on subjects hearing binaural stimuli. The data thus obtained are subjected to extensive preprocessing. This is necessary because the curves are contaminated by noise from the environment and by electrical activity of the brain that is not related to the auditory pathway (although it may sound heretical, the latter "signals" are "noise" for our purposes). The preprocessing consists of digital filtering and a number of averaging schemes. For a detailed discussion, you may wish to consult a recent conference proceeding (also available as gzipped ps-file, 91k).

The refined data we obtain in this way is used to identify equivalent electrical sources, i. e. the inverse problem of computing the charge distribution from the electrical potential it causes on a surrounding surface is solved iteratively using a parametrisation of the charge distribution.

For more details, please refer to the contributions to the Progress Report (in german) of the Graduate Program in Psychoacoustics of Helmut Riedel , Albertus Grunwald , and Michael Granzow .

If you are interested in neurocognition, check out the home page of the Sonderforschungsbereich Neurokognition (special research project neurocognition), to which this work is related.

This page is maintained by Michael Granzow who is happy about feedback via email.

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