The Bereitschafts-BOLD response: Event-related fMRI of voluntary movement

Cunnington, R.1, Windischberger, C.2, Deecke, L.3, and Moser, E.2
1Howard Florey Institute, University of Melbourne, Australia; 2Institute for Medical Physics, University of Vienna, Austria; 3Department of Clinical Neurology, University of Vienna and Ludwig-Boltzmann-Institute for Functional Brain Topography, Vienna, Austria

Activity within motor areas of the cortex begins to increase 1 to 2 s prior to voluntary self-initiated movement (termed the Bereitschaftspotential or readiness potential). There has been much speculation and debate over the precise source of this early premovement activity as it is important for understanding the roles of higher-order motor areas in the preparation and readiness for voluntary movement. In this study, we used high-field (3 Tesla) event-related fMRI with high temporal sampling (partial brain volumes every 250 ms) to specifically examine hemodynamic response timecourses during the preparation, readiness and execution of purely self-initiated voluntary movement. Five right-handed healthy volunteers performed a rapid sequential finger-to-thumb movement performed at self-determined times (12-15 trials). Functional images for each trial were temporally aligned and the averaged time-series for each subject was iteratively correlated with a canonical hemodynamic response function progressively shifted in time. This analysis method identified areas of activation without constraining hemodynamic response timing. All subjects showed activation within frontal mesial areas including supplementary motor area (SMA) and cingulate motor areas, as well as activation in left primary sensorimotor areas. The timecourses of hemodynamic responses showed a great deal of variability in shape and timing between subjects; however, four subjects clearly showed earlier relative hemodynamic responses within SMA/cingulate motor areas compared with left primary motor areas. These results provide further evidence that the SMA and cingulate motor areas are major contributors to early stage premovement activity and play an important role in the preparation and readiness for voluntary movement.