Summary
In manipulating ‘passive’ objects, for which the physical properties are stable and therefore predictable, information essential for the adaptation of the motor output to the properties of the current object is principally based on ‘anticipatory parameter control’ using sensorimotor memories, i.e., an internal representation of the object's properties based on previous manipulative experiences. Somatosensory afferent signals only intervene intermittently according to an ‘event driven’ control policy. The present study is the first in a series concerning the control of precision grip when manipulating ‘active’ objects that exert unpredictable forces which cannot be adequately represented in a sensorimotor memory. Consequently, the manipulation may be more reliant on a moment-to-moment sensory control. Subjects who were prevented from seeing the hand used the precision grip to restrain a manipulandum with two parallel grip surfaces attached to a force motor which produced distally directed (pulling) loads tangential to the finger tips. The trapezoidal load profiles consisted of a loading phase (4 N/s), plateau phase and an unloading phase (4 N/s) returning the load force to zero. Three force amplitudes were delivered in an unpredictable sequence; 1 N, 2 N and 4 N. In addition, trials with higher load rate (32 N/s) at a low amplitude (0.7 N), were superimposed on various background loads. The movement of the manipulandum, the load forces and grip forces (normal to the grip surfaces) were recorded at each finger. The grip force automatically changed with the load force during the loading and unloading phases. However, the grip responses were initiated after a brief delay. The response to the loading phase was characterized by an initial fast force increase termed the ‘catch-up’ response, which apparently compensated for the response delay — the grip force adequately matched the current load demands by the end of the catch-up response. In ramps with longer lasting loading phases (amplitude ≥ 2 N) the catch-up response was followed by a ‘tracking’ response, during which the grip force increased in parallel with load force and maintained an approximately constant force ratio that prevented frictional slips. The grip force during the hold phase was linearly related to the load force, with an intercept close to the grip force used prior to the loading. Likewise, the grip force responses evoked by the fast loadings superimposed on existing loads followed the same linear relationship. The grip force response to the unloading phase showed a rather smooth, nearly bell shaped, rate profile that suggested it was programmed for the inter-trial grip force. The stiffness in the loading direction increased with the load force in a manner suggesting that the two forces were subjected to similar coordinative constraints as in the manipulation of ‘passive’ objects.
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References
Abend W, Bizzi E, Morasso P (1982) Human arm trajectory formation. Brain 105:331–348
Brooks VB (1979) Some examples of programmed limb movements. Brain Res 71:299–308
Brooks VB (1984) How are “move” and “hold” programs matched. In: Bloedel et al. (eds) Cerebellar functions. Springer, Berlin, pp 1–23
Cole KJ, Abbs JH (1988) Grip force adjustments evoked by load force perturbations of grasped object. J Neurophysiol 60:1513–1522
Cordo PF (1987) Mechanisms controlling accurate changes in elbow torque in humans. J Neurosci 7:432–442
Diener HC, Horak FB, Nashner LM (1988) Influence of stimulus parameters on human postural responses. J Neurophysiol 50:1888–1905
Evarts EV, Shinoda Y, Wise SP (1984) Neurophysiological approaches to higher brain functions. Wiley, New York
Forssberg H, Eliasson AC, Kinoshita H, Johansson RS, Westling G (1991a) Development of precision grip. I. Basic coordination of force. Exp Brain Res 85:451–457
Forssberg H, Kinoshita H, Eliasson AC, Johansson RS, Westling G, Gordon AM (1991b) Development of human precision grip II. Anticipatory control of isometric forces targeted for object's weight. Exp Brain Res (in press)
Fuchs AF (1967) Saccadic and smooth pursuit eye movements in the monkey. J Physiol (London) 191:609–631
Gordon AM, Forssberg H, Johansson RS, Westling G (1991a) Visual size cues in the programming of manipulative forces during precision grip. Exp Brain Res 83:477–482
Gordon AM, Forssberg H, Johansson RS, Westling G (1991b) The integration of haptically acquired size information in the programming of the precision grip. Exp Brain Res 83:483–488
Gordon AM, Forssberg H, Johansson RS, Westling G (1991c) Integration of sensory information during the programming of precision grip: comments on the contributions of size cues. Exp Brain Res 85:226–229
Johansson RS, Westling G (1984) Roles of glabrous skin receptors and sensorimotor memory in automatic control of precision grip when lifting rougher or more slippery objects. Exp Brain Res 56:550–564
Johansson RS, Westling G (1987) Signals in tactile afferents from the fingers eliciting adaptive motor responses during precision grip. Exp Brain Res 66:141–154
Johansson RS, Westling G (1988a) Coordinated isometric muscle commands adequately and erroneously programmed for the weight during lifting task with precision grip. Exp Brain Res 71:59–71
Johansson RS, Westling G (1988b) Programmed and triggered actions to rapid load changes during precision grip. Exp Brain Res 71:72–86
Johansson RS, Westling G (1990) Tactile afferent signals in the control of precision grip. In: Jeannerod M (eds) Attention and performance, Vol XIII. Erlbaum, Hillsdale NJ, pp 677–713
Johansson RS (1991) How is grasping modified by somatosensory input? In: Humphrey DR, Freund HJ (eds) Motor control: concepts and issues. Dahlem Konferenzen. John Wiley & Sons Ltd, Chichester, pp 331–355
Johansson RS, Häger C, Riso R (1992a) Somatosensory control of precision grip during unpredictable pulling loads. II. Changes in load force rate. Exp Brain Res 89:192–203
Johansson RS, Häger C, Bäckström L (1992b) Somatosensory control of precision grip during unpredictable pulling loads: III. Impairments during digital anesthesia. Exp Brain Res 89:204–213
Muir RB (1985) Small hand muscles in precision grip: a corticospinal prerogative. In: Goodwin AW and Darian-Smith I (eds) Hand function and the neocortex. Springer, Berlin, pp 155–174
Poulton EC (1981) Human manual control. In: Brooks VB (eds) Handbook of physiology, Sect 1. The nervous system, Vol 2. Motor control. American Physiological Society, Bethesda, pp 1337–1389
Siegel S (1956) Nonparametric statistics for the behavioral sciences. McGraw-Hill, Tokyo
Smith AM (1981) The coactivation of antagonist muscles. Can J Physiol Pharmacol 59:733–747
Westling G, Johansson RS (1984) Factors influencing the force control during precision grip. Exp Brain Res 53:277–284
Westling G, Johansson RS (1987) Responses in glabrous skin mechanoreceptors during precision grip in humans. Exp Brain Res 66:128–140
Vicario DS, Ghez C (1984) The control of rapid limb movement in the cat. IV. Updating of ongoing isometric responses. Exp Brain Res 55:134–144
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Johansson, R.S., Riso, R., Häger, C. et al. Somatosensory control of precision grip during unpredictable pulling loads. Exp Brain Res 89, 181–191 (1992). https://doi.org/10.1007/BF00229015
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DOI: https://doi.org/10.1007/BF00229015