Attention to changes in chord complexity by non-musicians: An event-related potential study

Music therapists make regular decisions about the harmony they use in composing, improvising and accompanying for their clients. Research into the brain's responses to harmonic changes can provide information for that decision-making process. Among the ways to assess neurological activity is the measurement of Event-Response Potentials (ERPs) which are indicators of electrical activity in the cortex and are recorded as waveforms. Certain ERPs occur in the auditory cortex when a repeated aural stimulus is randomly and infrequently interrupted by a second, distinctively different aural stimulus (an "oddball"). Previous extensive research has demonstrated that when listeners are paying attention to something else when the auditory change occurs, an ERP "mismatched negativity" (MMN) negative-going peak occurs approximately 200 milliseconds after the change. When listeners focus on and anticipate the change, a positive-going ERP peak occurs approximately 300 milliseconds afterwards (a "P300").;This research was designed to examine neurological responses to two chord changes that music therapists use frequently. Twelve non-musicians heard repeated C major chords interrupted first by a C major 7th "oddball" and then by a C major chord with a 4-3 suspension. As they listened, three electrodes placed on the scalp recorded electrical activity in the right auditory cortex; subsequently, the waveforms were examined for evidence of the MMN and P300 responses. The results of this experiment showed that the participants perceived the differences in both pairs of chords as evidenced by the presence of clear MMN responses and that the change from C major to C major 7th may have been easier to detect than the change from C major to a C chord with a 4-3 suspension. The recordings of activity in the P300 range did not reveal any obvious responses; the possible reasons for this result are discussed, as are the implications of the results of the MMN recordings.