Seminar Abstract

20 Sep 2006:
Speaker: Natalia Passynkova
                  Leibniz-Institute of Neurobiology, Magdeburg, Germany
                  University of Plymouth
Venue:     Devonport Lecture Theatre, Portland Square
Time:       12:00

Functional Neuroanatomy of Harmony Perception, fMRI and EEG study

Music processing is a complex perceptual and cognitive task that is based on several ways of categorizing auditory stimuli. This categorization requires distinct neuronal network processing corresponding to the basic structural components of music. Harmony, or vertical structure, i.e. chords or intervals, is not only one of the fundamental principles of music but also the information bearing element in complex acoustic signals of animate and inanimate environments. Harmony is characterized by a sensation of consonance or dissonance. The neuronal basis underlying consonance/dissonance processing is the focus of our scientific interest. Harmony perception, like other higher cognitive processes, is based upon two complimentary principal of brain organization: functional specialization and functional integration. Our study was designed to tackle both of these aspects using a combination of fMRI and EEG coherence methods.

The results indicate that a network sensitive to the distinction between consonance and dissonance is localized in the left nonprimary posterior auditory territory where we observed a higher activation for consonant chords. Interestingly, this area includes Wernicke’ center, which is also known to be crucially involved in verbal processing.

We also identified two lines of inter-hemispheric connectivity; one localized anterior being sensitive to consonance and one localized posterior sensitive to dissonance. Stronger right intra-hemispheric connectivity for consonance than dissonance was associated with higher pleasantness ratings. The relationship between sensory aspects of perceived consonance and left intra-hemispheric connectivity was interpreted as processing of vertical harmony without emotional involvement. The stronger connectivity along the axis “left anterior-right posterior” for dissonance than consonance is discussed as a correlate of novelty processing. The evidence obtained in this study lead us to reformulate the existing concept of hemispherical specialization for music processing. We challenge the view that the left auditory cortex specifically serves the function of speech perception, and that musical processing occurs predominantly in the right hemisphere. By introducing a “multi object hypothesis” we suggest to extend the present concept of harmony perception. We believe that “auditory object dissociation” is a component of “sensory dissonance”.