Finger pressure adjustments to various object configurations during precision grip in humans and monkeys

Abstract

In this study, we recorded the pressure exerted onto an object by the index finger and the thumb of the preferred hand of 18 human subjects and either hand of two macaque monkeys during a precision grasping task. The to-be-grasped object was a custom-made device composed by two plates which could be variably oriented by a motorized system while keeping constant the size and thus grip dimension. The to-be-grasped plates were covered by an array of capacitive sensors to measure specific features of finger adaptation, namely pressure intensity and centroid location and displacement. Kinematic measurements demonstrated that for human subjects and for monkeys, different plate configurations did not affect wrist velocity and grip aperture during the reaching phase. Consistently, at the instant of fingers-plates contact, pressure centroids were clustered around the same point for all handle configurations. However, small pressure centroid displacements were specifically adopted for each configuration, indicating that both humans and monkeys can display finger adaptation during precision grip. Moreover, humans applied stronger thumb pressure intensity, performed less centroid displacement and required reduced adjustment time, as compared to monkeys. These pressure patterns remain similar when different load forces were required to pull the handle, as ascertained by additional measurements in humans. The present findings indicate that, although humans and monkeys share common features in motor control of grasping, they differ in the adjustment of fingertip pressure, probably because of skill and/or morphology divergences. Such a precision grip device may form the groundwork for future studies on prehension mechanisms.

Pinch strength is associated with the prevalence of mild cognitive impairment in patients with cardiovascular disease

“…This relationship could be explained by microvascular brain pathology that is associated with motor impairment [29]. Humans adjust finger pressure to precisely grip various visual objects, and this action involves many processes including those related to perception and cognition [28,30]. Furthermore, it was reported that manual dexterity declines in MCI patients [11] and that muscle strength is associated with the incidence of Alzheimer's disease and MCI [31].…”

Neurons of rat motor cortex become active during both grasping execution and grasping observation

“…During mECoG recording, an optical 3D motion analyzer (Qualisys Motion Capture System; Qualisys North America Inc, Charlotte, USA), in which the X-, Y-and Z-axes corresponded to the anterior, lateral and dorsal directions, respectively, was used to record the spatial position over-time a of adhesive infrared-reflective spherical markers (weight: 0.04 g, diameter: 0.30 cm) placed on the observer rat (Figures 1A and 1B), through three infrared cameras positioned around the box. This setup was previously employed to evaluate kinematics of ICMS-evoked movements in rats [19][20][21] as well as grasping in non-human primates 62,63 . To verify the absence of possible forelimb movements, one marker was positioned on the forelimb skin, i.e., the dorsal middle of the wrist.…”