How Many Music Centers Are in the Brain?

Reference

Annals of the New York Academy of Sciences

Volume 930, THE BIOLOGICAL FOUNDATIONS OF MUSIC pages 273–280, June 2001

Summary

This article discussed the modularity of music functions and complexities of this topic as a result of individual neurological variables in music processing.

Traditionally it was believed there was a simple left-right hemisphere division of music and language function:  music processed on the right, language on the left. 

However, Bever and Chiarello’s [1] work in 1974 revealed the hemispheric lateralization of music processing as a result of music training.  This finding has since been supported through various studies.

The author investigated brain activation patterns of non-musicians, amateurs, and professional musicians while processing harmonic and melodic discrimination tasks.  Results of this study indicated that while non-musicians and amateurs processed these tasks bilaterally in the frontal lobes and the right temporal lobe, the musicians processed them primarily in the left frontotemporal lobe.  It is believed that musicians activate the left hemisphere due to “inner speech” when listening to and analyzing music.  For example, they may automatically name intervals or harmonic elements when listening.  The author concluded that music processing areas are more determined by “the way of listening or processing” rather than “fixed music centers”.

Various studies have brought forth evidence of music modularity, often based on isolated music functions affected by brain lesion.  Evidence suggests time components of music are primarily processed in the left temporal lobe and pitch processed more in the right.

The author noted that discussion of modularity of music processing increases in complexity when it is acknowledged that music processing can take place on various hierarchical levels.  For example, time components may be identified as meter or rhythm.  Studies following brain lesion have demonstrated isolated neural networks to process meter or rhythm.

The challenge remains for science to delineate the brain anatomy with these potential music -processing areas.  In considering this, the authored noted yet another difficulty.  In a recent study [2] of individuals who had experienced small unilateral ischemic lesions of the temporal, parietal, or frontal lobe, had a range of impairments in auditory perception.  Also, a group of individuals who had a left hemispheric stroke demonstrated a range of disassociated impairments including rhythm, meter, interval, or contour regardless of whether the lesion was anterior or posterior  to the central sulcus.   The author noted that this indicates “widespread and individually developed neural networks” involved in music processing.  As a result, the author created a study to explore these individual factors.

In order to explore this, he created a study to determine if the way someone learned music would influence neural processing when they listened to music.   If the learning style influenced the neural process of listening, this could provide further insight into the individualized processing networks.

Three groups of 13-15 years olds were created for the study.  One group learned music with traditional instruction (declarative group).  A second group was engaged in musical experiences, such as singing or playing, as they were taught (procedural group).  The third group was the control group and did not receive any musical instruction.

Instruction lasted for 5 weeks.  Following this period, EEG measurements were taken while the students listened to music.  The results revealed that the declarative group had increased activation of the left frontotemporal lobes.  The procedural group had increased activation in the right frontal and bilateral parieto-occipital lobes.  These results confirm that music training influences brain activation patterns.

The author noted "brain substrates of music processing reflect the auditory learning “biography”, the personal experiences accumulated over time".  These experiences may include listening to music, learning to play an instrument, or being a professional musician.  The various musical representations while processing music also appear to be partly interchangeable and adaptable. That is not to say that there is no hemispheric specialization, or that there are not specific areas responsive to specific musical elements.  The point is that there is individualization of processing, due in part to the “biography” of the listener.

It was also noted that increased complexity of processing requirements results in increased complexity of neural network responses.  This may explain the more extensive neural network response of musicians than of non-musicians when listening to music as they are listening for, and recognizing, more aspects of the music.

The author concluded with recognition of the scope of the challenge of learning and understanding the modularity of music including the affects of the influence of personal biographies on the individualization of some aspects of music processing, and the ongoing plastic and adaptive responses of the brain.

Reflections

The individualization of certain aspects of neural processing of music seems, in some ways, to be a double- edged sword.  It makes the concept and application of modularity of music processing more complex, but at the same time it confirms  individualized, plastic responses to a musical stimulus.  This individualized, plastic response is encouraging news for professionals using music-based interventions to address cognitive impairments following acquired brain injury.  We can attribute specific function to specific brain area, and we know that the brain is plastic and able to adapt at some level following trauma.  This is foundational in rehabilitation science.   This article’s study on the plastic changes and differences in neural response of students as a result of (simply) a teaching style highlighted again the incredible potential of the brain to change.  It reminds one of the potential for change following consistent, experience-based stimulation in rehabilitative interventions.  The extensiveness of neural networks for music processing also demonstrates music’s efficacy as a multi-site neural stimulus, especially following trauma to the brain.

In addition to the concepts discussed in the article, I appreciated the author’s description of music, stating that it is not “a mere acoustic structure in time, or a stimulus created in a laboratory to fit a well-controlled experimental design, but a phenomenon of subjective human experience”.   He continues that it is not “based on a uniform mental capacity but on a complex set of perceptive and cognitive operations…”    This to me, acknowledges not only the complexity of music itself, but also the potential range of human response to it.   These are important factors to remember when studying music and the brain, its stimulus, its impact, and its therapeutic potential.

References:

1.     Bever, T.G. & R.I. Chiarello. 1974. Cerebral dominance in musicians and non-musicians. Science. 185:537-540.

2.     Schuppert, M., T.F.Munte, B.M. Wieringa, et al. 2000. Receptive amusia: evidence for cross-hemispheric neural networks underlying music processing strategies.  Brain 123: 546-559.