Different Brain Mechanisms Mediate Sensitivity to Sensory Consonance and Harmonic Context: Evidence from Auditory Event-Related Brain Potentials

Abstract

The goal of this study was to analyze the time-course of sensory (bottom-up) and cognitive (top-down) processes that govern musical harmonic expectancy. Eight-chord sequences were presented to 12 musicians and 12 nonmusicians. Expectations for the last chord were manipulated both at the sensory level (i.e., the last chord was sensory consonant or dissonant) and at the cognitive level (the harmonic function of the target was varied by manipulating the harmonic context built up by the first six chords of the sequence). Changes in the harmonic function of the target chord mainly modulate the amplitude of a positive component peaking around 300 msec (P3) after target onset, reflecting top-down influences on the perceptual stages of processing. In contrast, changes in the acoustic structure of the target chord (sensory consonance) mainly modulate the amplitude of a late positive component that develops between 300 and 800 msec after target onset. Most importantly, the effects of sensory consonance and harmonic context on the event-related brain potentials associated with the target chords were found to be independent, thus suggesting that two separate processors contribute to the building up of musical expectancy.

Electric brain responses to inappropriate harmonies during listening to expressive music

“…However, the later positivity is fairly tonic (lasting up to 1500 ms after the onset of the deviant chord), and thus also reminiscent, at least in its later time-window, to the P600 described by Patel et al (1998). This music-related late positivity has previously also been denoted as the late positive component (LPC, Besson and Faita, 1995;Regnault et al, 2001). …”

“…Instead, the amplitude of the ERAN was mainly dependent on the degree of harmonic appropriateness of Neapolitans, which varied between the different positions at which the Neapolitans were presented. Also note that effects of 'sensory dissonance' within a musical context have been reported to elicit mainly later positive potentials (Regnault et al, 2001).…”

Rhythmic context influences the auditory evoked potentials of musicians and nonmusicians

“…250 ms). This context effect has even been reported to precede a sensory effect of consonance affecting a P3b (Regnault et al, 2001). They argued that though the completion of sensory effects might be relatively slow, an earlier effect of musical expectations can build up over the presentation of the entire trial and has therefore anticipatory properties.…”

“…They found that the detection of harmonic violations were associated with a frontally orientated P3a (300-350 ms) that preceded a parietally orientated P3b (350-450 ms). Another study concerned with musical expectancies (Regnault et al, 2001) varied the harmonic function of a target chord. They also reported a large P3a, maximal over Cz, appearing around 200-300 ms. Again, this P3a was increased when expectancy was violated and smaller when harmonic expectancy was confirmed.…”

“…Behaviourally obtained ratings only provide a measure of the end product of the processes involved. Recording EPs however allows one to follow the time-course of the different processes involved in musical expectancy (Regnault et al, 2001). Additionally, EP measurements provide a very direct measure not sensitive to response-bias due to, for example group differences in skill (Gaillard, 1988).…”