Goodwin Lab - Collaborative Projects

Grasp Stability

The seemingly simple tasks of object orientation and shape discrimination are integrated in more complex tasks such as maintaining an appropriate grasp on a cup as it is being filled.

In collaboration with Roland Johansson, Per Jenmalm and Ingvars Birznieks at Umeå University, Sweden, we have investigated how humans regulate their grip force when parameters like the shape of the object or its weight are varied.

The figure shows that the grip force is matched to the load force on the digits, regardless of the curvature of the object.

The test object equipped with two 6-axis force transducers fitted with matching curved grip surfaces.

Publications Specific to this Collaboration

Jenmalm P, Birznieks I, Goodwin AW, Johansson RS (2003) Influence of object shape on responses of human tactile afferents under conditions characteristic of manipulation. J Neurophysiol 79:1643-52.

Birznieks I, Jenmalm P, Goodwin AW, Johansson RS (2001) Encoding of direction of fingertip forces by human tactile afferents. J Neurosci 21:8222-37.

Goodwin AW, Jenmalm P, Johansson RS (1998) Control of grip force when tilting objects: effect of curvature of grasped surfaces and applied tangential torque. J Neurosci 18:10724-34.

Jenmalm P, Goodwin AW, Johansson RS (1998) Control of grasp stability when humans lift objects with different surface curvatures. J Neurophysiol 79:1643-52.

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Responses of Human Afferents

The focus of our neural experiments is to explore the neural mechanisms which underlying human tactile capacities. An underlying assumption in this pursuit is that the receptive field properties of peripheral afferent fibres in the human and monkey are similar.

This has been corroborated by studies done in collaboration with Vaughan Macefield at the Prince of Wales Medical Research Institute, Sydney in which we recorded from single units in the peripheral nerves innervating the fingerpads of human volunteers.

The protocols used were comparable to those we employed with the single fibre recordings in monkeys; the same stimuli were used but contact force was increased to account for the differences in finger size. The responses are similar to those found in the monkey as illustrated below by the curvature-response functions for 3 different contact forces.

Comparison of single afferent responses in the human and monkey to curved objects presented at different contact forces.

Publications Specific to this Collaboration

Goodwin AW, Macefield VG, Bisley JW (1997) Encoding of object curvature by tactile afferents from human fingers. J Neurophysiol 78:2881-8.