University of Maryland, College Park

A neuroscientist marvels at our ability to learn unnatural tasks.

I find driving mind-boggling. As a neuroscientist studying motor control, I am amazed that nervous systems can adapt to the unnatural demands of operating a car. After all, humans did not evolve in habitats with steering wheels or accelerator pedals. What makes our ability to drive so curious is that it requires the modification of reflexes — twisting the steering wheel, for instance, rather than jumping aside, when an obstacle approaches.

Mark Wagner and Maurice Smith have shed some light on this curiosity. They show that the brain generalizes unnatural physical regimes, such as driving, to produce an appropriate corrective response to an unexpected change, even when that change has not been met before (M. J. Wagner and M. A. Smith J. Neurosci. 28, 10663–10673; 2008).

The duo trained undergraduates to reach quickly for a target with one hand while holding on to a motorized arm with the other. The faster the students reached, the stronger the motorized arm pushed them off course.

Initially, the students made large errors, but they soon compensated for the lateral forces. Were their brains learning the dynamics of the new force, though, or were they reassigning the activation of muscles in the spinal cord from those for reaching towards those that normally help to generate sideways pushes?

Surprising the students with a sudden pulse of force in the reaching direction provided an answer. They compensated with almost ideal corrective forces, which spinal reflexes alone could not have achieved. The slight delay in the students' responses also indicates that their brains were working from an internal model of the new force regime. How the brain develops such a model is unknown, but this paper should drive that research.