Elsevier

Brain Research

Volume 1212, 30 May 2008, Pages 55-62
Brain Research

Research Report
Short-term effects of processing musical syntax: An ERP study

https://doi.org/10.1016/j.brainres.2007.10.078Get rights and content

Abstract

We investigated influences of short-term experience on music-syntactic processing, using a chord-sequence paradigm in which sequences ended on a harmony that was syntactically either regular or irregular. In contrast to previous studies (in which block durations were rather short), chord sequences were presented to participants for around 2 h while they were watching a silent movie with subtitles. Results showed that the music-syntactically irregular chord functions elicited an early right anterior negativity (ERAN), and that the ERAN amplitude significantly declined over the course of the experiment. The ERAN has previously been suggested to reflect the processing of music-syntactic irregularities, and the present data show that the cognitive representations of musical regularities are influenced by the repeated presentation of unexpected, irregular harmonies. Because harmonies were task-irrelevant, the data suggest that cognitive representations of musical regularities can change implicitly, i.e., even when listeners do not attend to the harmonies, and when they are presumably oblivious of the changes of such representations. Although the ERAN amplitude was significantly reduced, it was still present towards the end of the experiment at the right anterior electrodes, indicating that cognitive representations of basic music-syntactic regularities cannot easily be erased.

Introduction

Humans familiar with major–minor (’Western’) tonal music have a sophisticated knowledge about the syntactic regularities underlying this type of music. Some syntactic regularities of tonal music are grounded on acoustic principles (such as acoustic similarity of chords belonging to the same key, Leman, 2000, Bharucha and Krumhansl, 1983) and, thus, presumably do not need extensive, if any, musical experience to be recognized. However, other syntactic regularities are culture-specific (such as harmonic progressions typical for certain musical epochs, or styles) and, hence, depend on representations of music-syntactic regularities that are shaped by listening experience. How the neural mechanisms underlying music-syntactic processing are modified by listening experience is largely unknown.

Previous studies indicated effects of long-term experience on the processing of music-syntactic information by demonstrating that musicians show stronger neural reactions, or more accurate behavioural responses to music-structural irregularities than non-musicians. For example, Bigand et al. (1999) showed that musicians respond faster, and more accurately to harmonically slightly irregular chords (a tonic-subdominant ending of a harmonic sequence, see Fig. 1 for explanation of these terms). Using ERPs, Besson and Faita (1995) showed that incongruities in melodies (whether familiar or unfamiliar) elicit a larger late positive component (LPC) in musicians than in non-musicians. Similar results were reported by a study from Regnault et al. (2001) in which musicians showed larger P300 potentials to music-syntactically slightly irregular chords (also a tonic-subdominant ending of a harmonic sequence, similar to Bigand et al., 1999). Another study using chords as stimuli (Koelsch et al., 2002a) reported that early negative brain responses to music-syntactically irregular chord functions are larger in musicians than in non-musicians, and fMRI data showed that particularly inferior frontolateral cortical areas (including Broca's area) are activated more strongly in musicians than in non-musicians in response to such chords (for an overview see Koelsch and Siebel, 2005). Similar training effects on music-syntactic processing as in the study from Koelsch et al. (2002a) have also been shown for amateur musicians (in whom training effects were less pronounced than in musicians, Koelsch et al., 2007).

These studies indicate clear effects of long-term musical experience on music-syntactic processing. In the present study we investigated effects of short-term experience on the neural correlates of music-syntactic processing. We used the early right anterior negativity (ERAN) as a neurophysiological marker of such processing. The ERAN can be elicited in chord-sequence paradigms by music-syntactically irregular chord functions, and is taken to reflect the processing of a musical (and not simply acoustical) sound expectancy violation (Koelsch et al., 2000, Loui et al., 2005, Leino et al., 2005, Patel, 2003, Brattico, 2006, Fujioka et al., 2004; the term chord function is explained in Fig. 1). In previous studies investigating the ERAN, block durations were fairly short (usually around 10 min) to avoid a possible habituation of subjects to the irregular chords. In the present study, we investigated if the neural mechanisms of music-syntactic processing (as reflected in the ERAN) are influenced by the repeated presentation of irregular chords during the course of an experimental session which lasted around 120 min. The repeated presentation of an irregular chord function might lead to an alteration of the representation of musical regularity, and thus to a decrease of sound expectancy violation. We expected that such a decrease would be reflected in an amplitude decrease of the ERAN.

Another ERP of interest was the N5, an anterior negativity with a latency of around 550 ms which usually co-occurs with the ERAN (Koelsch et al., 2000, Loui et al., 2005, Koelsch and Siebel, 2005). The N5 is taken to reflect the harmonic integration of an unexpected chord into the preceding context (reminiscent of processes of semantic integration during the perception of language, Koelsch et al., 2000, Koelsch and Siebel, 2005). We expected that the harmonic integration of music-syntactically irregular chords would become easier with repeated exposure to such chords, and that, similar to the amplitude of the ERAN, the amplitude of the N5 would decrease over the course of the experiment.

The design of the present experiment was identical to that of previous experiments (Koelsch et al., 2007) with the exception that the current experiment lasted approximately 2 h, during which the subjects were watching a silent movie with subtitles. Chord sequences ended with equal probability on either a regular, or on a music-syntactically irregular chord function (Figs. 2A and B, in previous experiments, these chords have been shown to elicit both ERAN and N5 potentials). Our data show that music-syntactically irregular chords elicit both an ERAN as well as an N5, and that the amplitude of the ERAN decreased over the course of the experimental session. The results reveal how neural mechanisms underlying the processing of highly complex auditory (music-syntactic) information are modified by short-term musical experience.

Section snippets

Results

Behaviourally, participants detected 96.12% of the deviant instruments, indicating that the task to detect these events was not difficult, and that participants responded to deviances within the physical dimension of the musical stimulus despite watching the silent movie.

The ERP data show that (task-irrelevant) STs elicited a clear ERAN compared to tonic chords (Fig. 3A). The ERAN peaked at around 180 ms, and was maximal at right anterior scalp sites (although the ERAN was also clearly present

Discussion

Music-syntactically irregular STs elicited a clear ERAN, replicating findings from a previous experiment using the same chord sequences (Koelsch et al., 2007), as well as of other studies using similar chord-sequence paradigms (Loui et al., 2005, Leino et al., 2005). Notably, final STs represent quite subtle music-syntactic irregularities: In our mentioned previous study (Koelsch et al., 2007), participants (non-musicians and amateur musicians, as in the present study) detected on average only

Conclusions

Our results show how cognitive representations of musical regularity are influenced by short-term experience: The ERAN amplitude (reflecting the processing of a music-syntactic sound expectancy violation) linearly declined during the repeated presentation of irregular chords over the course of about 2 h, but the ERAN was not abolished at the end of the experiment. This shows on the one hand that the representations of music-syntactic regularity can be altered by short-term experience, and that

Participants

20 individuals participated in the experiment (age range 20 to 30 years, mean = 24.5 years, 11 females). 11 subjects were non-musicians who never participated in extracurricular music lessons or performances, 9 subjects were amateur musicians who had learned an instrument or sung in a choir for 2–10 years (mean = 5.4 years). All subjects were right-handed (laterality quotient was > 90% according to the Edinburgh Handedness Inventory, Oldfield, 1971), and reported to have normal hearing.

Stimuli

There were

Acknowledgments

We thank D. Mietchen for calculation of roughness and pitch commonality values. Note: Examples of the stimuli are available at http://www.stefan-koelsch.de/ERAN-decline.

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