The Role of Beta-Frequency Neural Oscillations in Motor Control

Editor's Note: These short, critical reviews of recent papers in the Journal, written exclusively by graduate students or postdoctoral fellows, are intended to summarize the important findings of the paper and provide additional insight and commentary. For more information on the format and purpose of the Journal Club, please see Review of Feurra et al. Human sensorimotor and cognitive behavior is associated with changes in the oscillatory activity of the brain. For example , the integration of diverse aspects of a stimulus into a unitary percept is related to synchronized oscillations in the gamma range (30 –100 Hz), while power in the alpha band (8 –12 Hz) increases during relaxation. Motor activity is associated with changes in beta frequency oscillations , which has a range of 15–30 Hz and peaks at ϳ20 Hz. Voluntary movement is associated with a drop in power (desyn-chronization) in this frequency range, and the termination of movement is followed by a restoration of power (Salmelin and Hari, 1994). One hypothesis is that beta activity represents the status quo (Engel and Fries, 2010). Parkinson's disease, in which sufferers find it difficult to initiate or change movements, is notably associated with higher levels of beta synchrony (Schnitzler and Gross, 2005), suggesting that the enhanced beta activity is preventing change from the status quo. The recently developed technique of transcranial alternating current stimulation (tACS) may be a way to investigate the role of oscillatory fields in brain function. In tACS, two electrodes are placed on the head and an alternating current is passed between them. The induces an os-cillatory electrical field across the brain between the two electrodes. This is likely to induce neural synchronization at the frequency of tACS in the cortical areas underneath the electrodes, although relatively little is known of the electrophysio-logical effect of tACS on the brain (Zaghi et al., 2010). Compared with other brain stimulation techniques, such as transcra-nial magnetic stimulation (TMS) or direct transcranial current stimulation (tDCS), tACS has a number of advantages. The effect of the field is short-lived, in that no effect of tACS is evident after the current is removed, whereas the effects of tDCS outlast stimulation by several minutes. The stimulation is also usually not perceptible to the participant, whereas tDCS may prickle the skin and TMS involves an audible click. In a recent paper in The Journal of Neu-roscience, Feurra and colleagues (2011) applied tACS at four …