Abstract
Background
Motor hand skill and associated dexterity is important for meeting
the challenges of daily activity and an important resource post-stroke. In this
context, the present study investigated the finger movements of right-handed
subjects during tactile manipulation of a cuboid, a prototypical task underlying
tactile exploration. During one motor act, the thumb and fingers of one hand
surround the cuboid in a continuous and regular manner. While the object is
moved by the guiding thumb, the opposed supporting fingers are replaced once
they reach their joint limits by free fingers, a mechanism termed finger
gaiting.
Methods
For both hands of 22 subjects, we acquired the time series of
consecutive manipulations of a cuboid at a frequency of 1 Hz, using a digital
data glove consisting of 29 sensors. Using principle component analysis, we
decomposed the short action into motor patterns related to successive
manipulations of the cuboid. The components purport to represent changing grasp
configurations involving the stabilizing fingers and guiding thumb. The temporal
features of the components permits testing whether the distinct configurations
occur at the frequency of 1 Hz, i.e. within the time window of 1 s, and, thus,
taxonomic classification of the manipulation as finger gaiting.
Results
The fraction of variance described by the principal components
indicated that three components described the salient features of the single
motor acts for each hand. Striking in the finger patterns was the prominent and
varying roles of the MCP and PIP joints of the fingers, and the CMC joint of the
thumb. An important aspect of the three components was their representation of
distinct finger configurations within the same motor act. Principal component
and graph theory analysis confirmed modular, functionally synchronous action of
the involved joints. The computation of finger trajectories in one subject
illustrated the workspace of the task, which differed for the right and left
hands.
Conclusion
In this task one complex motor act of 1 s duration could be
described by three elementary and hierarchically ordered grasp configurations
occurring at the prescribed frequency of 1 Hz. Therefore, these configurations
represent finger gaiting, described until now only in artificial systems, as the
principal mechanism underlying this prototypical task.
Trial registration
clinicaltrials.gov, NCT02865642, registered 12 August 2016.
Sensing form - finger gaiting as key to
tactile object exploration - a data glove analysis of a prototypical daily
task
