This+is+Your+Brain+on+Drums+(The+Neuroanatomy+of+Rhythm+Perception)

=This is Your Brain on Drums: The Neuroanatomy of Rhythm Perception=

Part One: Motor Areas
We all do it. A song enters our sonic space and our natural response is to move. Some respond with a subtle toe tap or leg twitch. Others opt for an overstated head bob, enthusiastically broadcasting their approval. All are responding to the same stimulus: the beat. The question is, is there a physical basis for this apparent link between rhythm perception and motion?

Many studies have utilized fMRi to reveal that there is indeed activation in motor areas of the brain during rhythm perception. These areas include the pre-SMA/SMA (supplementary motor area), PMd, (dorsal premotor area), basal ganglia, and cerebellum (Grahn & Brett, 2007).

//Background://
//**Supplementary Motor Area:** The SMA is generally involved in the planning of motor actions. http://en.wikipedia.org/wiki/Supplementary_motor_area

http://jn.physiology.org/cgi/content/full/79/2/1092
 * Dorsal Premotor Area:** The PMd has been shown to be involved in mental rehearsal and selecting stimulus guided movements.

http://en.wikipedia.org/wiki/Basal_ganglia
 * Basal Ganglia:** The basal ganglia are involved in motor control, cognition, emotion, and learning.

http://en.wikipedia.org/wiki/Cerebellum//
 * Cerebellum:** The cerebellum is involved with coordination of movement, fine motor control, as well as timing.

In these studies, participants were instructed not to move and monitored closely to ensure that the instructions were heeded. In addition, had participants managed to surreptitiously move a body part, this would have been flagged by activation in the primary motor cortex, which was not seen. Thus, the motor areas exhibiting activation are doing so in response simply to the perception of rhythm!

//Movement and Rhythm in Infants//
One interesting study conducted in 2005 by Phillips-Silver and Trainor examined the connection between movement and rhythm in infants. 7-month-old infants were played ambiguous rhythms, meaning that the rhythms did not have a recognizable meter. Half of the infants were bounced on the 2nd beat, half on the 3rd. Afterward; the same infants were presented with rhythms in duple and triple meter. The infants showed a preference for rhythms that mimicked the emphasis to which they had previously been exposed: those bounced on the 2nd beat preferred rhythms in duple meter, whereas those bounced on the 3rd preferred rhythms in triple form. Thus, it would appear that some amount of learning had taken place, based upon the proprioceptive input that the baby received in correlation with the auditory input of the rhythm, eluding to "a strong multisensory connection between body movement and auditory rhythm processing" (Phillips-Silver & Trainor, 2005).

The experiment was also repeated in similar, but slightly altered fashion. This time the infants themselves were not moved, but instead watched an experimenter bounce on either the 2nd or 3rd beats. In this case, the infants showed no preference when presented with duple and triple meter rhythms, indicating that personal movement is necessary.

//Are musicians speaking the language of rhythm?//
Although activation in motor areas has been observed in both non-musicians and musicians alike, there are some notable differences that seem to occur in response to varying levels of musicianship. For starters, musicians display significantly more activation in the motor areas previously mentioned (Grahn & Brett, 2007).

Even more interesting, however, is the observation that musicians utilize more of the left hemisphere when listening to rhythms, the hemisphere containing mechanisms associated with analytic processing (Limb et al., 2006). Specifically, left hemisphere activation observed in musicians mirrors that seen in studies of language comprehension of sentences and narrative (Limb et al., 2000; Papathanassiou et al., 2000; Xu et al., 2005). It would appear that musicians comprehend rhythm in much the same way individuals comprehend language!

Sources:
Grahn JA, Brett M. 2007. Rhythm and Beat Perception in Motor Areas of the Brain. http://www.mitpressjournals.org/doi/abs/10.1162/jocn.2007.19.5.893

Phillips-Silver J, Trainor LJ. 2005. Feeling the Beat: Movement Influences Infant Rhythm Perception. http://www.sciencemag.org/cgi/content/full/308/5727/1430

Limb CJ, Kemeny S, Ortigoza EB, Rouhani S, Braun AR. Left Hemispheric Lateralization of Brain Activity During Passive Perception in Musicians. http://www3.interscience.wiley.com/journal/112510880/abstract?CRETRY=1&SRETRY=0

Papathanassiou D, Etard O, Mellet E, Zago L, Mayzoyer B, Tzourio-Mazoyer N. 2000. A Common Language Network for Comprehension and Production: A Contribution to the Definition of Language Epicenters with PET. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WNP-45C0TS3-3N&_user=4429&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000059602&_version=1&_urlVersion=0&_userid=4429&md5=83bfa6d3b6f9f89a8507ecc3c5de633f

Xu J, Kemeny S, Park G, Frattali C, Braun A. 2004. Language in context: emergent features of word, sentence, and narrative comprehension. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WNP-4FG2X4C-3&_user=4429&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000059602&_version=1&_urlVersion=0&_userid=4429&md5=d5179874ab294bca2896f86858bc78b8