PMC4927838_01
Accelerometry recordings of the 'pointing test' performed with the left hand. (a) A truly fast grasping movement of the left hand results in a transient arrest of right-sided hand tremor. However, during a slower grasping movement, as depicted in (b), the right hand tremor continues with lower amplitude. R = right hand, L = left hand, vertical arrow indicates onset of grasping movement. Vertical solid lines indicate 1 second; recording parameters: 20 mm/sec and 30 mV/cm.
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This abnormal clinical pointing test was substantiated by accelerometry recording (Fig. 1A and B; sensors attached to the dorsum of the hands). It typically started around 0.2 seconds after movement onset and lasted for 0.8 to 1.6 seconds (Fig. 1A). A slower ballistic movement of the left arm did not produce this effect, with only an amplitude reduction but not tremor cessation (Fig. 1B).