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Correlates of BOLD-magnitude with finger sequence frequency in recovered patients after subcortical stroke
Imaging studies demonstrated additional cerebral activation during increasing complexity of finger movements (Gerloff et al., 1998). Patients with lesions of the pyramidal tract present increased activation comparable to those seen in healthy subjects during more complex movement performance (Gerloff et al., 2006). Motor training in contrast results in substantial decrease of cortical activity, which is centered in the primary motor cortex after training (Lotze et al., 2003). Again, a decrease of activation magnitude – especially in secondary motor areas and areas ipsilateral to movement performance (contralesional)- is described in chronic stroke patients moving their affected hand after motor recovery (Ward et al., 2004). We used fMRI (3T, TR 2s, matrix size 64*64, TE 30ms, flip angle 90 degree) to investigate 9 recovered patients (median NIH scale 1; average age 62.3 years, time since stroke 34.4 months) and 9 age matched controls (average age: 67.6 years) in a complex finger sequence task (see Figure and Lotze et al., 2006) performed in a maximal (average: 2Hz), and slower auditory paced (1Hz) frequency. Data processing with SPM5 (damaged side was always flipped to the right hemisphere) revealed increased activation for the performance of affected fingers movements in ipsilesional primary motor cortex (M1) mesial to the hand representation, ipsilesional premotor cortex (PMC), contralesional superior parietal lobe (SPL) and contralesional BA 44. Frequency performance in patients correlated with activation in ipsilesional M1 and bilateral posterior cerebellar hemispheres including the dentate nuclei. Whereas M1 has been described to code for movement frequency in healthy subjects (Kim et al., 2003) the posterior cerebellar lobe might code for temporal processes in more general terms (Mathiak et al., 2002).
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