Importance of Cutaneous Feedback in Maintaining a Secure Grip During Manipulation of Hand-Held Objects

Abstract

. Importance of cutaneous feedback in maintaining a secure grip during manipulation of hand-held objects. J Neurophysiol 89: 665-671, 2003; 10.1152/jn.00249.2002. Previous research has shown that grip and load forces are modulated simultaneously during manipulation of a hand-held object. This close temporal coupling suggested that both forces are controlled by an internal model within the CNS that predicts the changes in tangential force on the fingers. The objective of the present study was to examine how the internal model would compensate for the loss of cutaneous sensation through local anesthesia of the index and thumb. Ten healthy adult subjects (5 men and 5 women aged 20 -57 yr) were asked to grasp, lift, and hold stationary, a 250 g object for 20 s. Next, the subjects were asked to perform vertical oscillatory movements over a distance of 20 cm at a rate of 1.0 Hz for 30 s. Eleven trials were performed with intact sensation, and 11 trials after a local ring-block anesthesia of the index and thumb with bupivacain (5 mg/ml). During static holding, loss of cutaneous sensation produced a significant increase in the safety margin. However, the grip force declined significantly over the 20-s static hold period. During oscillatory arm movements, grip and load forces were continuously modulated together in a predictive manner as suggested by Flanagan and Wing. Again, the grip force declined over the 30-s movement, and 7/10 subjects dropped the object at least once. With intact sensation, the object was never dropped; but with the fingers anesthetized, it was dropped on 36% of the trials, and a significant slip occurred on a further 12%. The mean correlation between the grip and load forces for all subjects deteriorated from 0.71 with intact sensation to 0.48 after digital anesthesia. However, a cross-correlation calculated between the grip and load forces indicated that the phase lag was approximately zero both with and without digital anesthesia. Taken together, the data from the present study suggest that cutaneous afferents are required for setting and maintaining the background level of the grip force in addition to their phasic slip-detection function and their role in adapting the grip force/load force ratio to the friction on initial contact with an object. Finally, at a more theoretical level, they correct and maintain an internal model of the physical properties of hand-held objects.

A new method for characterizing hand dysfunction in cervical spondylotic myelopathy: a preliminary study

“…Westling and Johansson, 14 in a study analyzing how different surface properties of the object in terms of friction affect the pinch strength in healthy subjects, demonstrated that experimental digital nerve block raised the pinch strength. Also using digital anesthesia in healthy subjects, Augurelle et al 15 and Monzée et al 16 studied the contributions of cutaneous feedback in grip force control. They demonstrated, either with the apparatus containing an accelerometer and strain gage 15 or with a linear motor equipped with load cells, 16 that cutaneous afferents have an essential role in adapting grip and lifting forces to surface friction and object weight.…”

“…Also using digital anesthesia in healthy subjects, Augurelle et al 15 and Monzée et al 16 studied the contributions of cutaneous feedback in grip force control. They demonstrated, either with the apparatus containing an accelerometer and strain gage 15 or with a linear motor equipped with load cells, 16 that cutaneous afferents have an essential role in adapting grip and lifting forces to surface friction and object weight. Furthermore, Witney et al, 17 in their review of literature, concluded that feedback from cutaneous afferents is crucial for successful feedforward control of hand-arm coordination.…”

Effect of laparoscopic grasper force transmission ratio on grasp control

“…However, the pinch force is reduced during a static hold period [21]. The cause of the slips in this study were partly due to this reduction in force during the static hold H, object grasped barehanded between the thumb and index finger; T, object grasped with tweezers; G HFTR , grasper with a high force transmission ratio; G LFTR , grasper with a low force transmission ratio period.…”

Key considerations in designing a somatosensory neuroprosthesis

“…Somatosensory signals from the hand also indicate when the object is slipping from our grasp (Johansson and Westling, 1987;Srinivasan et al, 1990). Crucially, in the case of object manipulation, vision is a poor substitute for touch and our proficiency at object manipulation and grasping declines markedly in the absence of somatosensory feedback (Augurelle et al, 2003).…”