Looking at motor imagery underlying complex skill learning.

During a recent period of rehearsing for the four hands piano recital that I participated in yesterday,* I found myself observing (mentally imaging) the detailed execution of the pieces when I woke during the night or early morning. Such imaging is known to be a central part of learning skilled sequences in athletic and musical performance.  In a bit of fortuitous timing, the most recent issue of PNAS has an article by Miller et al. describing direct observation of this kind of motor imagery:

Imagery of motor movement plays an important role in learning of complex motor skills, from learning to serve in tennis to perfecting a pirouette in ballet. What and where are the neural substrates that underlie motor imagery-based learning? We measured electrocorticographic cortical surface potentials in eight human subjects during overt action and kinesthetic imagery of the same movement, focusing on power in “high frequency” (76–100 Hz) and “low frequency” (8–32 Hz) ranges. We quantitatively establish that the spatial distribution of local neuronal population activity during motor imagery mimics the spatial distribution of activity during actual motor movement. By comparing responses to electrocortical stimulation with imagery-induced cortical surface activity, we demonstrate the role of primary motor areas in movement imagery. The magnitude of imagery-induced cortical activity change was ∼25% of that associated with actual movement. However, when subjects learned to use this imagery to control a computer cursor in a simple feedback task, the imagery-induced activity change was significantly augmented, even exceeding that of overt movement.

*(I have put some rehearsal videos made before the recital here and here, but the final recordings turned out to have technical recording problems and so can't be posted.)