A Cortical Substrate For Hand Skill: An MEG Evaluation

Abstract

It is well established that, independent of culture, approximately 90% of the human population demonstrates a right hand preference on most tasks. This population asymmetry is especially noteworthy because of its magnitude and because it is uniquely human. The current study is an attempt to relate differential hand skill directly to a measure of cortical functional anatomy. Specifically, it was hypothesized that more sensorimotor cortex would be dedicated to the dominant versus non-dominant hand. To assess this, we utilized magnetic source imaging, a method that combines magnetoencephalographic (MEG) data on brain function with magnetic resonance (MR) data on brain structure. Current flow associated with neuronal activity produces a magnetic field, just as does the current flow in a wire. The magnetic field that can be measured outside the head selectively reflects current flow within the dendrites of pyramidal cells oriented parallel to the skull surface. Using signal averaging techniques it is possible to identify the magnetic signals time-locked to particular motor or sensory events.