In their study, the influence of distraction was limited to the primary sensorimotor cortex of the contralateral hemisphere, whereas in our study the effect was seen in the primary sensorimotor cortex of both hemispheres. The main difference between the studies is ROI definition. Johansen-Berg and Matthews (2002) chose a solely anatomical definition, Inhibitors,research,lifescience,medical whereas we defined the ROIs combining anatomical and functional information for each subject separately. However, with their whole-brain group analysis, Johansen-Berg and Matthews (2002) could identify a spot in the ipsilateral learn more hemisphere in the sulcus centralis, which also showed a decrease of activity but which was not included in their anatomically defined

ROI. Hence, there is evidence for a bihemispheric effect in their study as well. Findings

regarding primary sensorimotor cortex activity in the ipsilateral hemisphere per se are relatively heterogeneous. For example, some (Wassermann et al. 1991, 1994; Inhibitors,research,lifescience,medical Cramer et al. 1999) but not all (Jäncke et al. 1998; Nirkko et al. 2001) studies showed an ipsilateral coactivation during motor tasks. There Inhibitors,research,lifescience,medical are also hints that ipsilateral active regions lie more lateral in comparison with contralateral activity (Wassermann et al. 1994), and that active regions can change with motor learning (Sanes et al. 1992). In our study, we observed a slight coactivation in the ipsilateral finger area in the primary sensorimotor cortex, which was also affected by the distraction condition. Rodríguez et al. (2004) reported a decrease of activity within contralateral primary motor cortex under distraction while subjects performed Inhibitors,research,lifescience,medical a phasic movement (increasing the metacarpusphalange

joint angle from 0° to 45° while stretching an elastic band and passively returning to the initial position) with the dominant hand. Using a voxel-based fine-mapping approach and a time course analysis, they showed a significant decrease of active area size and signal Inhibitors,research,lifescience,medical intensity within the contralateral primary motor cortex. Furthermore, they could show a reconfiguration of the active field in the contralateral primary motor cortex whereby some voxels were active solely under the basal condition while others were active under distraction. It is important to note that before starting fMRI, Rodríguez et al. (2004) made sure Cell press to include only subjects who were able to perform the task correctly. However, they did not check for behavioral differences in the fMRI experiment itself. Thus, confound from behavioral differences cannot be excluded in their study. Under the premise that there were no such behavioral differences in the fMRI task, the results of Rodríguez et al. (2004) demonstrate that with a more complex motor task together with a fine-mapping analysis approach influences of attention on the primary motor cortex can be observed while the dominant hand is used as well.