Figure 3. Comparison of synchronization and coherence between single motor unit discharges in healthy subjects and patients with central motor pathway lesions.

A, cross-correlogram constructed between the discharges of two single motor units from first dorsal interosseus muscle (1DI) in a healthy subject. B, coherence spectra for the data used to construct the cross-correlogram in A. D, cross-correlogram constructed between the discharges of two motor units recorded from within 1DI of the affected (left) hand in a patient who had suffered an infarct of the right internal capsule 4 months previously. E, coherence spectra for the data used to construct the cross-correlogram in D. The central cross-correlogram peak is absent in the data recorded from the stroke patient; the corresponding coherence is significant only at low frequencies. Bin width in A and D, 1 ms; frequency resolution in B and E, 1 Hz. C and F, the percentage of 1DI motor unit pairs that showed significant coherence between 1 and 100 Hz. C, data from 1DI of sixteen healthy subjects (49 motor unit pairs); F, data from 1DI of eleven stroke patients (91 motor unit pairs). (Reproduced from Farmer et al. 1993a.)