Uncovering the cortical architecture of motor skill

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From playing the piano to buttoning a shirt – skilled hand movements are essential to nearly every human activity. The main objective of this research program is to understand how the human brain learns and produces complex movements. What changes in our brains as we develop expertise in a motor skill? Some current theories propose that whole movement patterns (such as a tennis serve) become engrained in the connections between neurons (or nerve cells), much like the way in which a song is stored on a record. However, the flexibility with which motor experts can combine smaller movement elements to produce a novel movement, such as a pianist improvising on a well-known melody, suggest a different architecture. Our hypothesis is that primary motor areas learn elementary movement elements, whereas secondary motor areas store a more abstract representation that then activates sequences of simpler movement primitives. To test for such neural representations, we will observe the activity in the brains of human volunteers, using a technique called functional magnetic resonance imaging (fMRI), while they perform different movement tasks. Instead of just studying which parts of the brain are activated, we investigate the fine-grained patterns of activity within of these areas. By looking at the relationship between the activity patterns for different movements, we can learn how these movements are represented, i.e., whether the brain areas reflect single movement elements, specific details about the execution, or whether they represent more abstract characteristics. The ability to uncover such representations in the human brain allows us to understand how the brains of motor skill experts, such as musicians or athletes, differ from novices; helps us to evaluate and improve training protocols; and aids in understanding the recovery of motor function after stroke, which to some degree involves similar processes as initial motor skill learning. The research program will also provide new insights into why and how a small electric current applied to the brain during motor practice (a technique called transcranial direct current stimulation) is able to improve skill learning in healthy humans.