Music and the Rhythmic Brain

Music is universal and has no boundaries. But why has music evolved when there seems to be no real purpose for it like survival or reproduction? 

via pixabay

Researchers believe that music is important to human evolution in various ways: by helping babies to learn a language, aiding in the transfer of knowledge or history over generations and social bonding. Music is much more complex than just sound - it is organized, melodious and rhythmic.

Physics of Music
Music comprises fundamental elements such as pitch, tempo, timbre, key and intensity. Being a singer, I was interested in knowing the differences in the structure of distinct kinds of music and how our brains perceive them. Doing some reading, I found out that there are two major musical tunings: 'just intonation' and 'equal temperament'.

WITHOUT MUSIC, LIFE WOULD BE A MISTAKE.

- FRIEDRICH NIETZSCHE -

 
Western classical and most modern music are based on a 12-tone equal temperament system. In this musical tuning, 12 equal intervals divide the octave, with the same frequency ratio between adjacent notes. Just intonation is a musical tuning in which the octave consists of seven frequency notes which are members of harmonic series and are related by ratios of whole numbers. Indian classical music, bagpipes and barbershop quartets are based on the just intonation system [1].

Perception of Music
Have you ever wondered what is going on in your brain while you are listening to Beethoven’s 9th symphony? How are you able to disentangle the complex sounds of different instruments? And why do you feel this indescribable bliss while listening to music? How exactly do our brains process music?
Processing of music activates different prefrontal, temporal and cerebellar brain regions. Music or sound are basically the vibration of air molecules which traverses the ear drum, through the middle ear to the inner ear, where the frequency and intensity of sound waves are encoded as electrical signals by hair cells. These signals are relayed to the auditory brainstem and midbrain, where low-level processing such as interaural level and time differences occurs. This information about sound is then sent to the thalamus and to the primary auditory cortex.

UNCERTAINTY MAKES MUSIC BEAUTIFUL

Feature detection – such as pitch, rhythm and other higher-order processing – happens in the primary auditory cortex. Neurons of the auditory cortex can respond to a range of sound frequencies. These are tonotopically organized; meaning frequencies ranging from low to high are represented in the brain by neighboring regions [2]. During the perception of music, multiple sounds are processed simultaneously. The auditory system forms links between the sounds based on the fundamentals such as pitch, timing, harmony as well as the spatial location of the sound [3]. In addition, processing lyrics requires the brain's language centers.

Melody and Rhythm Processing
Studies implicate the secondary auditory cortex in melody processing, which involves comparing an anomaly or out-of-tune pitch in a melody with previous music knowledge [4]. On the other hand, the motor areas, parietal cortex, frontal cortex and cerebellum are involved in rhythm processing. A study has shown that the electrical activity in the brain occurs in phase with the beats of the rhythm [5]. An intriguing aspect of music processing is the activation of the visual cortex. Research shows that music evokes visual imagery in the listener’s mind according to the variation in the music [6].
Listening to music also activates the pleasure center in the brain (nucleus accumbens), which evokes the strong “blissful, intoxicating” feeling [7]. In Indian classical music, a ‘raga’, or series of four or more notes (in harmonic series), is known to evoke specific emotions inside the mind of the listener [8]. Our brains are also constantly predicting upcoming sequences in a song based on patterns and beats, creating a sense of anticipation. But scientists have found out that some aspect of surprise or uncertainty in music also increases its aesthetic beauty [9]!

LISTENING TO MUSIC INDUCES VISUAL IMAGERY

Music production requires complex motor control movements such as timing (as in rhythm), sequencing and spatial organization of motor movements (as in playing the notes on musical instruments). This involves various brain regions such as the primary motor cortex and the supplementary motor area, cerebellum, and basal ganglia [10].  An interesting study showed that, while playing a duet, brain waves become synchronized between the two guitarists [11]. Music indeed has an immense power on our minds that transcends our understanding!

[1] http://bit.ly/1QUrLEy
[2] Lauter et al, Hear Res, 1985
[3] Deutsch, Front Biosci, 2007
[4] Brattico et al, Brain Res, 2006
[5] Snyder and Large, Brain Res Cogn Brain Res, 2005
[6] Zatorre and Helpern, Neuron, 2005
[7] Salimpoor et al, Nat Neurosci, 2011
[8] http://bit.ly/1Q87JFf
[9] http://bit.ly/1JORqwv
[10] Zatorre et al, Nat Rev Neurosci, 2007.
[11] Sänger et al, Front Hum Neurosci, 2012

by Aarti Swaminathan, PhD Student AG Schmitz
This article originally appeared 2015 in CNS Volume 8, Issue 2, Art. And the Brain.