Abstract
Human tactile afferents provide essential feedback for grasp stability during dexterous object manipulation. Interacting forces between an object and the fingers induce slip events that are thought to provide information about grasp stability. To gain insight into this phenomenon, we made a transparent surface slip against a fixed fingerpad while monitoring skin deformation at the contact. Using microneurography, we simultaneously recorded the activity of single tactile afferents innervating the fingertips. This unique combination allowed us to describe how afferents respond to slip events and to relate their responses to surface deformations taking place inside their receptive fields. We found that all afferents were sensitive to slip events, but fast-adapting type I (FA-I) afferents in particular faithfully encoded compressive strain rates resulting from those slips. Given the high density of FA-I afferents in fingerpads, they are well suited to detect incipient slips and to provide essential information for the control of grip force during manipulation.
Highlights
The most fundamental requirement for dexterous manipulation is the ability to handle objects without slippage and dropping of the object
We found that all tactile afferents in the fingertip responded to slip events, but that fast-adapting type I (FA-I) afferents in particular faithfully signaled local skin compressions related to the progression of slips
We focused on FA-I and SA-I afferents, which respond to local deformation events and have small, well-defined receptive fields (Johansson and Vallbo, 1983)
Summary
The most fundamental requirement for dexterous manipulation is the ability to handle objects without slippage and dropping of the object. Exerting an excessive grip is inefficient and can result in crushing the object. A minimal amount of force is required to avoid slip and is dictated by friction: a stronger grip is required for slippery surfaces and a looser grip is sufficient for sticky surfaces. A good strategy is to adjust the grip to friction with an amount of force slightly above the minimum. Tactile feedback is necessary for grip adjustments to take place as disruption of this feedback abolishes the normal, fine-tuned grasp control and results in frequent object dropping despite excessive compensatory grip forces (Westling and Johansson, 1987; Augurelle et al, 2003; Witney et al, 2004). How information about friction is encoded by tactile afferents is largely unknown
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
