Sensing form - finger gaiting as key totactile object exploration - a data glove analysis of a prototypical dailytask

Werner Krammer,Manuela Pastore-Wapp,Roland Wiest,John H Missimer,Simon Habegger,Bruno J Weder

doi:10.1186/s12984-020-00755-6

Werner Krammer, Manuela Pastore-Wapp + Show 4 more

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https://doi.org/10.1186/s12984-020-00755-6

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Abstract

BackgroundMotor hand skill and associated dexterity is important for meetingthe challenges of daily activity and an important resource post-stroke. In thiscontext, the present study investigated the finger movements of right-handedsubjects during tactile manipulation of a cuboid, a prototypical task underlyingtactile exploration. During one motor act, the thumb and fingers of one handsurround the cuboid in a continuous and regular manner. While the object ismoved by the guiding thumb, the opposed supporting fingers are replaced oncethey reach their joint limits by free fingers, a mechanism termed fingergaiting.MethodsFor both hands of 22 subjects, we acquired the time series ofconsecutive manipulations of a cuboid at a frequency of 1 Hz, using a digitaldata glove consisting of 29 sensors. Using principle component analysis, wedecomposed the short action into motor patterns related to successivemanipulations of the cuboid. The components purport to represent changing graspconfigurations involving the stabilizing fingers and guiding thumb. The temporalfeatures of the components permits testing whether the distinct configurationsoccur 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.ResultsThe fraction of variance described by the principal componentsindicated that three components described the salient features of the singlemotor acts for each hand. Striking in the finger patterns was the prominent andvarying roles of the MCP and PIP joints of the fingers, and the CMC joint of thethumb. An important aspect of the three components was their representation ofdistinct finger configurations within the same motor act. Principal componentand graph theory analysis confirmed modular, functionally synchronous action ofthe involved joints. The computation of finger trajectories in one subjectillustrated the workspace of the task, which differed for the right and lefthands.ConclusionIn this task one complex motor act of 1 s duration could bedescribed by three elementary and hierarchically ordered grasp configurationsoccurring at the prescribed frequency of 1 Hz. Therefore, these configurationsrepresent finger gaiting, described until now only in artificial systems, as theprincipal mechanism underlying this prototypical task.Trial registrationclinicaltrials.gov, NCT02865642, registered 12 August 2016.

Highlights

Motor hand skill and associated dexterity is important for meeting the challenges of daily activity and an important resource post-stroke
We propose that the short motor actions performed during the task can be decomposed into single motor acts of opposing thumb and finger configurations represented by the principal components
Sensori-motor assessment As indicated in Table S1 in Supporting Information, the results of the sensori-motor assessments were consistent with published data regarding age- and gender-matched healthy controls for power and precision grip [19], Picking Small Objects” (PSO) [20], two point discrimination and tactile object recognition (TOR) [22]

Summary

Introduction

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 righthanded subjects during tactile manipulation of a cuboid, a prototypical task underlying tactile exploration. Roland and Mortensen [6] developed a theoretical model of human somatosensory exploration of kinesthesia, macrogeometry, size and shape which describes the input-output relationships of tactile exploration Using their fully quantified macrogeometrical stimuli, i.e. a set of parallelepipeds and spheres of identical volume representing non-real objects, we and others have verified in functional magnetic resonance imaging (fMRI) studies three modes of exploration in extended actions of digital object exploration [7, 8]. These modes of exploration disappeared in over-learned pure motor sequences at high frequency [10]

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