Brain Activity Linked While Anticipating Musical Structures
Neuroscientists at Georgetown University Medical Center have, for the first time, shown what brain activity looks like when someone anticipates an action or sensory input which soon follows.
In the February 25 issue of the Journal of Neuroscience, they say this neural clairvoyance involves strong activity in areas of the brain responsible for preparing the body to move.
The findings were made by using functional magnetic resonance imaging (fMRI) in a group of student volunteers who brought with them favorite music CDs. The scientists examined brain images during the silence between songs, and found it brimming with activity. Other students who listened to music they had never heard in sequence before did not have that same neural bustle.
“This now explains how it is that, even before an anticipated song is actually heard, a person can start to tap fingers, dance, or sing to the music they imagine is coming next,” says Josef Rauschecker, PhD, director of the Program in Cognitive and Computational Sciences (PICCS), at Georgetown University Medical Center.
While it makes sense that song sequences can be memorized and thus anticipated by a listener, no one before has ever documented the brain activity that is underway in the silence between songs, he says.
“The brain is all about anticipation and prediction, yet no one has shown what that looks like in terms of neural action,” says Rauschecker.
He adds that this same process, known as cued associative learning, likely occurs whenever a human is expecting any particular action to happen, be it in sports, music, or language.
“It is how a skier is mentally prepared to go down a familiar course during the Olympics, or how a piano player knows to move fingers along the keyboard to hit the next correct key,” Rauschecker says.
This sounds simple, but it isn’t, he says. “It is not trivial to store a temporal sequence in the brain, because the brain doesn’t have any moving parts like a tape recorder or CD player. The whole brain needs to be involved because it has to be ready to execute that sequence. “
In the students who knew the order of songs on their CD, the researchers found that during the anticipatory silence between the songs excitatory signals passed from the prefrontal cortex to the nearby premotor cortex. The prefrontal cortex is the brain’s “executive” center, which plans and orchestrates complex cognitive behaviors. The premotor cortex and its associated systems, which include the basal ganglia and the cerebellum, is involved in preparing the body to act – perhaps to move or to sing.
“These structures are involved in both thinking and acting, and it appears that music patterns are being stored and learned here,” Rauschecker says.
“We hadn’t anticipated that,” he adds with a laugh. “We didn’t know the premotor areas would be involved.”
All animals have some ability to cognitively predict motor activity, he says. “That’s why a bird can sing. But humans are the most associative of animals, which is why we have such a large prefrontal cortex. We have a lot of sequences that we need to store in order to predict what we should do.”
The Journal of Neuroscience, February 25, 2009, 29(8):2477-2485; doi:10.1523/JNEUROSCI.4921-08.2009
Brain Activation during Anticipation of Sound Sequences.
Amber M. Leaver, Jennifer Van Lare, Brandon Zielinski, Andrea R. Halpern, and Josef P. Rauschecker.
Music consists of sound sequences that require integration over time. As we become familiar with music, associations between notes, melodies, and entire symphonic movements become stronger and more complex. These associations can become so tight that, for example, hearing the end of one album track can elicit a robust image of the upcoming track while anticipating it in total silence. Here, we study this predictive “anticipatory imagery” at various stages throughout learning and investigate activity changes in corresponding neural structures using functional magnetic resonance imaging. Anticipatory imagery (in silence) for highly familiar naturalistic music was accompanied by pronounced activity in rostral prefrontal cortex (PFC) and premotor areas. Examining changes in the neural bases of anticipatory imagery during two stages of learning conditional associations between simple melodies, however, demonstrates the importance of fronto-striatal connections, consistent with a role of the basal ganglia in “training” frontal cortex (Pasupathy and Miller, 2005). Another striking change in neural resources during learning was a shift between caudal PFC earlier to rostral PFC later in learning. Our findings regarding musical anticipation and sound sequence learning are highly compatible with studies of motor sequence learning, suggesting common predictive mechanisms in both domains.
Key words: prefrontal cortex; basal ganglia; auditory; fMRI; learning and memory; motor learning