Neural correlates of perceived consonant and dissonant dyad chords in human brain

Physiological mechanisms and musical experience work together to shape consonance and dissonance perceptions. Previous studies using evoked response potentials and magnetic resonance images have found physiological correlates for the perception of consonance and dissonance. The present study tested the following: 1. could participants attribute different degrees of consonance and pleasantness to the 12 sinusoidal dyads within an octave, when these notes were isolated from the influence of basilar membrane beats by presenting each note to a different ear (dichotic presentation), and the effects of changes in critical bandwidth were reduced by maintaining a constant average frequency as the semitone difference between the two tones increased? 2. were differences in the perception of consonance and pleasantness distinguishable in their EEG recordings? 3. did the EEG recordings show a systematic difference between participants with different cultural backgrounds. Participants did not attribute different degrees of consonance and dissonance to the 12 dyads in both conditions. ANOVA of consonance and pleasantness ratings showed no significant effect of stimulus types (1 to 12 semitones). Ethnicity (Chinese and Canadian) and conditions (dichotic and diotic) also failed to show any significant effect. Frequency spectra of the EEG responses evoked by the 12 dyads were correlated to the frequency spectra of the EEG responses evoked by the self-consonant tone (unison). Analysis of Variance comparing these correlations showed no significant difference between the two presentation conditions (diotic and dichotic), or between different dyads. Interestingly, the one significant effect found was of the locations of the recording electrode, which implied that different cortical areas had different degrees of involvement in the perception of consonance. Ratings of consonance did not significantly correlate with ratings of pleasantness. The EEG data variations in the correlation of each dyad’s EEG spectrum with the reference spectrum did not correlate with the ratings of consonance or pleasantness of the dyads. The results refuted Helmholtz and Plomp & Levelt’s theory. However, these results were not conclusive due to several major technical and methodological limitations of the present study. The present study did however lay the groundwork for further work