Music and Language syntax

“Musical syntax is processed in Broca’s area” (Maess et al., 2001)

A new article in press in Cortex investigates the role of traditionally associated language syntax processing areas of the brain, namely Broca’s area (inferior Brodman area 44), in the processing of musical sounds. The EEG study was conducted by Sammler, Koelsch and Friederici (2010) and aimed to investigate brain activity associated with the presentation of musical sequences in patients with lesions in left inferior frontal gyrus (Broca’s area)

* (the authors also looked at activation in patients with lesions in anterior superior temporal gyrus (aSTG) but I’m not going to go into detail about that area here for the sake of brevity!)

The background: Over the years a number of strands of neuroimaging evidence have implicated language syntax processing areas of the brain with activation during the presentation of musical sequences. Previous studies had suggested that Broca’s area in particular was associated with syntactical and hierarchical processing in language. However the quote at the start of my blog, which is included in the present study by Sammler et al (2010), suggests that some researchers now believe that Broca’s area might “process syntactic information that is less language-specific than previously believed”. And music has been a key focus. One reason is that, like language, music is composed of a series of discrete elements (notes) which are compiled using structural rules (syntax; harmony) in order to form meaningful phrases.

So in principle it seems logical to suggest that the demands of integrating sound streams such as language and music into meaningful phrases might share cognitive resources in the brain (see Patel, 2008). One of the strongest sources of evidence that Broca’s might be involved in music processing is that the Early Right Anterior Negativity (ERAN), an event- related potential (ERP) component that can be reliably elicited by harmonically unexpected chords and which is taken as an index for early music-syntactic processing (Koelsch et al., 2000; Koelsch, 2009) can be source located to Broca’s area.

The hypothesis: If Broca’s area is involved in the processing of musical syntactic irregularities then patients with lesions Broca’s area would be expected to display deficits or irregularities in the ERAN component, localised in Broca’s area, in response to musical irregularities.

The task: Participants were presented with chord sequences followed a progression of dominant [V] – tonic [I] – subdominant [IV] – supertonic [II] – dominant [V]. In regular sequences (no syntactic irregularities) this sequence finished on the tonic [I] and in irregular sequences the sequence finished on the double dominant [II3+]. In total participants listened to 192 regular and 192 irregular sequences and 48 control sequences where a deviant instrument was introduced. EEG signals were recorded.

The findings: Patient’s with lesions in Broca’s area (which were older than 4 years) showed an abnormal ERAN scalp distribution and subtle behavioural deficits in detecting music syntactic irregularities. In one patient, the ERAN is reported to be ‘extinguished’ and behavioural performance correspondingly lay at chance levels.

Conclusions: The authors conclude that their study complements a growing literature supporting the role of the left IFG, and Broca’s area in particular, in the generation of the ERAN component. Therefore, the results support findings that suggest Broca’s role in processing of syntactic structure is more likely to be general (in this case applying to music) rather than language-specific.

References:

Maess, B., S. Koelsch, T. C. Gunter and A. D. Friederici (2001). Musical syntax is processed in Broca’s area: an MEG study. Nature Neuroscience 4: 540-545.

Sammler D et al., Are left fronto-temporal brain areas a prerequisite for normal music-syntactic processing?, Cortex (2010), doi: 10.1016/j.cortex.2010.04.007

Koelsch (2009) Music-syntactic Processing and Auditory Memory – Similarities and Differences between ERAN and MMN, Psychophysiology

Koelsch et al. (2000) Brain indices of music processing – nonmusicians are musical Journal of Cognitive Neuroscience, 12

Patel (2008) Music, Language, and the Brain (OUP)