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This study reports the findings of an analysis of temporal correlation between tremor of different muscles of the same and different limbs in four patients with Parkinson's disease. Spectral coherence methods were used for determining whether simultaneously occurring oscillations in the electromyograms of different muscles are statistically coupled. The incidence of significant coherence was considerably higher for muscle pairs in the same limb than for pairs in different limbs; Parkinson's disease tremor is coupled within but not between limbs. Because the characteristics of tremor are known to vary under different behavioral situations, the intralimb coupling was examined for different tasks. A mental arithmetic task resulted in an increase in the coherence between muscles of the same limb, whereas the finger-to-nose task decreased the coherence. No significant change in coherence was found for a postural task. The amplitude and regularity of tremor electromyography showed changes analogous to those in coherence. These results support the hypothesis that tremor in different limbs results from the activity of several neural circuits oscillating independently. The results also emphasize the value of these methods for rigorously characterizing tremor, in relation to disease state, behavioral conditions, and the selection of treatment strategies.

Laparoscopic techniques allow for less-invasive treatment of common surgical problems. Laparoscopic instruments are different from standard surgical instruments and generally incorporate a pistol-grip handle configuration with rings for the fingers. This handle configuration has been reported as being uncomfortable, leading to finger compression neuropathies in some cases. As an alternative, the surgeon can choose to grasp laparoscopic instruments using a more powerful palm grip during grasping motions. This study evaluates the hypothesis that the use of the palm grip requires less muscle tension than the finger-grip when grasping with laparoscopic instruments. Nine general surgeons used an Autosuture laparoscopic grasper with a ringed pistol-grip handle held in both a finger-in-ring (F) or palm (P) hand grip position to grasp and close two spring-loaded metal plates. The same task was performed with a surgical haemostat clamp (H) for comparison. Each subject performed the grasping task in a random sequence for the three instrument configurations at two grasping forces levels (0.7 and 4.2 N), and with the instrument at three angles to the subjects' sagittal plane (0 degree, 45 degrees and 90 degrees). Surface electromyographic (EMG) signals were acquired from the flexor carpi ulnaris (FCU), flexor digitorum profundus (FDP), flexor digitorum superficialis (FDS), extensor carpi ulnaris (ECU), extensor digitorum comunis (EDC) and the thenar compartment (TH). The peak root mean squared (RMS) EMG voltage was averaged for five repetitions at each instrument, force and angle condition. Statistical analysis was carried out by repeated measures ANOVA. The muscle EMG RMS amplitude while using the palm grip was decreased in the FDS, TH and EDC, was unchanged in the ECU and FCU, and was slightly higher in the FDP when compared with the finger grip. These differences were most prominent at 90 degrees to the sagittal plane where the subjects' wrists neared maximal flexion. It is concluded that the palm grip is more powerful than the finger grip when grasping with laparoscopic instruments, particularly at angles perpendicular to the surgeon's sagittal plane.

This study reports the findings of an analysis of temporal correlation between tremor of different muscles of the same and different limbs in four patients with Parkinson's disease. Spectral coherence methods were used for determining whether simultaneously occurring oscillations in the electromyograms of different muscles are statistically coupled. The incidence of significant coherence was considerably higher for muscle pairs in the same limb than for pairs in different limbs; Parkinson's disease tremor is coupled within but not between limbs. Because the characteristics of tremor are known to vary under different behavioral situations, the intralimb coupling was examined for different tasks. A mental arithmetic task resulted in an increase in the coherence between muscles of the same limb, whereas the finger-to-nose task decreased the coherence. No significant change in coherence was found for a postural task. The amplitude and regularity of tremor electromyography showed changes analogous to those in coherence. These results support the hypothesis that tremor in different limbs results from the activity of several neural circuits oscillating independently. The results also emphasize the value of these methods for rigorously characterizing tremor, in relation to disease state, behavioral conditions, and the selection of treatment strategies.