The Musical Brain: Novel Study of Jazz Players Shows Common Brain Circuitry Processes Both Music and Language

The brains of jazz musicians engrossed in spontaneous, improvisational musical conversation showed robust activation of brain areas traditionally associated with spoken language and syntax, which are used to interpret the structure of phrases and sentences. But this musical conversation shut down brain areas linked to semantics - those that process the meaning of spoken language, according to results of a study by Johns Hopkins researchers.

The study used functional magnetic resonance imaging (fMRI) to track the brain activity of jazz musicians in the act of “trading fours,” a process in which musicians participate in spontaneous back and forth instrumental exchanges, usually four bars in duration. The musicians introduce new melodies in response to each other’s musical ideas, elaborating and modifying them over the course of a performance.

The results of the study suggest that the brain regions that process syntax aren’t limited to spoken language, according to Charles Limb, M.D., an associate professor in the Department of Otolaryngology-Head and Neck Surgery at the Johns Hopkins University School of Medicine. Rather, he says, the brain uses the syntactic areas to process communication in general, whether through language or through music.

Limb, who is himself a musician and holds a faculty appointment at the Peabody Conservatory, says the work sheds important new light on the complex relationship between music and language.

"Until now, studies of how the brain processes auditory communication between two individuals have been done only in the context of spoken language," says Limb, the senior author of a report on the work that appears online Feb. 19 in the journal PLOS ONE. “But looking at jazz lets us investigate the neurological basis of interactive, musical communication as it occurs outside of spoken language.

"We’ve shown in this study that there is a fundamental difference between how meaning is processed by the brain for music and language. Specifically, it’s syntactic and not semantic processing that is key to this type of musical communication. Meanwhile, conventional notions of semantics may not apply to musical processing by the brain."

To study the response of the brain to improvisational musical conversation between musicians, the Johns Hopkins researchers recruited 11 men aged 25 to 56 who were highly proficient in jazz piano performance. During each 10-minute session of trading fours, one musician lay on his back inside the MRI machine with a plastic piano keyboard resting on his lap while his legs were elevated with a cushion. A pair of mirrors was placed so the musician could look directly up while in the MRI machine and see the placement of his fingers on the keyboard. The keyboard was specially constructed so it did not have metal parts that would be attracted to the large magnet in the fMRI.

The improvisation between the musicians activated areas of the brain linked to syntactic processing for language, called the inferior frontal gyrus and posterior superior temporal gyrus. In contrast, the musical exchange deactivated brain structures involved in semantic processing, called the angular gyrus and supramarginal gyrus.

"When two jazz musicians seem lost in thought while trading fours, they aren’t simply waiting for their turn to play," Limb says. "Instead, they are using the syntactic areas of their brain to process what they are hearing so they can respond by playing a new series of notes that hasn’t previously been composed or practiced."

Brain structure shows affinity with numbers

The structure of the brain shows the way in which we process numbers. People either do this spatially or non-spatially. A study by Florian Krause from the Donders Institute in Nijmegen shows for the first time that these individual differences have a structural basis in the brain. The Journal of Cognitive Neuroscience published the results in an early access version of the article.

People who process numbers spatially do this using an imaginary horizontal line along which the numbers are arranged from low to high, left to right. A non-spatial representation is also possible, by comparing numbers to other magnitudes such as force or luminosity.

Different grey matter volumes

Florian Krause identified this predisposition to spatial or non-spatial number processing in MRI scans of test subjects. He discovered differences in grey matter volume, which contains the cell bodies of nerve cells, in two specific locations. Spatially oriented brains have an above-average grey matter volume in the right precuneus, a small area of the brain associated with processing visual-spatial information. Non-spatially oriented brains have more grey matter in the left angular gyrus, an area associated with semantic and conceptual processing.

Spatial numbers

For a long time, scientists thought that everyone processed numbers predominantly in a spatial way. Krause demonstrates that this is not the case. In his own words: ‘Our current study stresses the importance of non-spatial number representations. This is important since researchers in the field tend to focus mainly on spatial representations. Personally, I think that numbers are understood in terms of our body experiences. We use information about size in real life to understand number size in our heads.’

Classifying numbers

The thirty people taking part in the study were put into an MRI scanner and were shown numbers between 1 and 9 (except 5). In two consecutive judgement tasks, they had to classify the presented digits as odd or even. Both tasks differed only in the required response: in the spatial task subjects had to click with their index finger or middle finger to classify the digits, and in the non-spatial task they applied either a small or a large force on a pressure sensor with their thumb. Both tests were carried out using the right hand. Importantly, participants coupled the spatial response as well as the force response to the size of the presented number, as they responded faster with a left or soft press for small numbers and with a right or hard press for large numbers. Krause worked out those couplings for each subject, and compared the scores with the information from their brain scan.

Potential benefits for teaching maths

At present, maths is largely taught on the basis of a spatial number processing. ‘People with a non-spatial representation of numbers would probably benefit from a different approach to maths teaching’, says Krause. ‘It is possible to let pupils experience the size of numbers in a non-spatial way. This could involve expressing numbers with your body while doing simple arithmetics, for example.’ Krause is planning several new studies to explore the scientific basis of methods like these in more detail.