Bimodal Beats
Poster Presentation

Georg Meyer

Sophie Wuerger

Johannes Zanker

     Abstract ID Number: 81
     Full text: Not available
     Last modified: March 20, 2005

Abstract


Bimodal Beats

Georg Meyer (1), Sophie Wuerger (1) and Johannes Zanker (2)

(1) Cognitive Neuroscience Group, School of Psychology, Liverpool, UK
(2) Department of Psychology, Royal Holloway University of London, UK


Cross-modal interactions have direct correlates in behavioural as well as neurophysiological data. If visual and auditory signals are combined non-linearly, then the electroencephalogam (EEG) should show activity not only at the visual and auditory stimulus frequencies, but also at the difference between these frequencies (beats).

We recorded steady state EEG signals in response to audio-visual stimulation from 10 healthy volunteers using an EGI 128 channel recording system. Subjects were presented with visual, auditory and audio-visual stimuli in three conditions: 5 Hz and 6 Hz, 8Hz and 12 Hz and 17Hz and 25Hz (visual / auditory). The signals were presented unimodally as well as bimodally and consisted of white noise as the auditory stimulus and an LED as the visual stimulus. Both signals were presented 60cm in front of the observer.
An analysis of the EEG signals shows no evidence for response components at the beat frequency in the spectrum, spectral coherence or phase coherence of the responses. Cross-modal responses, however, are not linear sums of the underlying unimodal responses.