Changes in tremor as a function of type of augmented visual information.

The dynamics of postural finger tremor is typically investigated under conditions of natural vision of the finger. Here we investigated the effect of different types of augmented visual information feedback on finger tremor and on inter-limb tremor coordination. Four visual information conditions of postural finger tremor from either the dominant hand only or from both hands were investigated. The visual conditions were: (1) no vision, (2) natural vision, (3) augmented vision with instantaneous acceleration on a computer display, and (4) augmented vision with instantaneous and past acceleration on a computer display. Acceleration was measured with a 3D accelerometer on the distal phalanx of the index finger(s). The amount of tremor variability did not change as a function of visual information conditions. However, removing visual feedback increased tremor predictability and reduced small, random deviations of tremor acceleration output in the one finger condition. In the two-finger condition, augmented visual information increased the irregularity of the combined tremor variability. The no vision condition showed a stronger coupling between fingers than natural vision or augmented vision with past information. The findings revealed that augmented visual information increased tremor irregularity and facilitated coupling in two-hand tremor dynamics.