Effects of Tactile Sensitivity on Structural Variability of Digit Forces during Stable Precision Grip

Abstract

This study investigated the effects of fingertip tactile sensitivity on the structural variability of thumb and index finger forces during stable precision grip. Thirty right-handed healthy subjects participated in the experiment. Transient perturbation of tactile afferents was achieved by wrapping up the distal pads of the thumb or index finger with transparent polyethylene films. The time-dependent structure of each digit force and the variability of interdigit force correlation were examined by detrended fluctuation analysis (DFA) and detrended cross-correlation analysis (DCCA), respectively. Results showed that the tactile sensitivity affected αDFA of the vertical shear force Fx (F 3,239 = 6.814, p < 0.001) and αDCCA of Fx (χ 2 = 16.440, p < 0.001). No significant difference was observed in αDFA or αDCCA of the normal forces produced by the thumb or index finger. These results suggested that with blurred tactile sensory inputs the central nervous system might decrease the vertical shear force flexibility and increase the interdigit shear force coupling in order to guarantee a stable grip control of an object against gravity. This study shed light on the feedback and feed-forward strategies involved in digit force control and the role of SA-II afferent fibers in regulation of vertical shear force variability for precision grip.

Dynamical Coordination of Hand Intrinsic Muscles for Precision Grip in Diabetes Mellitus

“…Considering the precision grip is a sensorimotor process, the motor systems are under both feedforward and feedback controls. The feedforward mechanism allows individuals to program appropriate motor commands prior to grasping according to previous experiences of the object properties; whereas the feedback mechanism adjusts neuromuscular activations according to real-time sensory information 27 , 34 , 43 . By examining the grip force performance in process of holding to lifting an object, Chiu et al .…”

“…By this set-up the thumb and index finger need to comply with mechanical or task constraints such as producing zero residual forces and moments; guaranteeing enough load force to counterbalance the weight of the handle; avoiding handle tilt from unbalanced forces across the digits, and accommodate to the load perturbations, etc. To fulfill all these constraints the motor system needs to produce well-coordinated digit forces 34 , 56 . The DM-related patterns observed in the dynamical muscle coordination were associated with the inter-digit force coordination during precision grip of a freely moveable apparatus.…”

“…2a–c ). The mean values and coefficient of variance of the thumb and index finger forces were calculated for the phases with and without visual feedback 33 , 34 . The root-mean-square (RMS) and median power frequency (MPF) of the EMGs recorded from the APB and FDI were also calculated for the two visual conditions (with vs. without visual feedback).…”

The Effect of Different Attentional Focus Instructions during Finger Movement Tasks in Healthy Subjects: An Exploratory Study

“…Instead, IFA operates as a self-invoking trigger that worsens the motor performance by focusing on the proprioceptive information from the finger [ 43 ]. Both these submodalities of the haptic sense are involved in motor planning and control of the effector [ 28 ], but the exteroceptive source (in our case the tactile sensation derived from the keys) seems to be the more relevant for a fine motor control of the fingers [ 44 – 46 ]. Furthermore, no differences were found between the motor performance obtained in IFA and control conditions.…”

An assimilation of TRIZ in dissecting the statistical outcomes of tactile sensitivity, pinch force and endurance among elderly people

“…This excessive force is a response to poor tactile sensitivity (Cole, 1991). For this study, the pulp pinch was selected as the type of pinch technique to be experimented on according to supports from previous studies (Cole, 1991;Li, Wei, Yue et al, 2016a, 2016b. It was also suggested that the pulp pinch is one of the more commonly used dual finger pinching techniques with regard to maximum strength applications for small objects (Nilsen et al, 2012).…”