Motor illusions: What do they reveal about proprioception?

Abstract

Five illusions involving distortions in the perception of limb position, movement, and weight are described in the context of their contribution to understanding the sensory processes involved in proprioception. In particular, these illusions demonstrate that the position sense representation of the body and the awareness of limb movement result from the cross-calibration of visual and proprioceptive signals. Studies of the vibration illusion and phantom-limb phenomenon indicate that the perception of limb movement and position are encoded independently and can be dissociated. Postural aftereffects and the illusions of movement induced by vibration highlight the remarkable lability of this sense of limb position, which is a necessary feature for congruence between the spatial senses. Finally, I discuss the role of corollary discharges in the central processing of afferent information with respect to the size-weight and vibration illusions.The study of visual illusions has provided many valuable clues about the operation of the visual system (Coren & Girgus, 1978), to the extent that visual aftereffects have been described as the psychologist's microelectrode (Frisby, 1979). With the notable exception of the size-weight illusion, which was first described in the late nineteenth century (Charpentier, 1891), illusions involving the motor system have received much less attention. However, recent reports of illusory movements induced by mechanical vibration of the muscle tendon (Goodwin, McCloskey, & Matthews, 1972;Roll & Vedel, 1982;Vedel & Roll, 1983) have led to a revival of interest in kinesthetic illusions (Feldman & Latash, 1982a;Goodwin, 1976;Granit, 1972;Matthews, 1982). As with the classical visual illusions, these phenomena offer valuable insights into the perceptual mechanisms involved in proprioception and must be explained in terms of normal physiological mechanisms. I discuss disturbances in the perception of limb position and movement and of force and weight in this review in the context of their contribution to understanding perceptual processing in the sensorimotor system. Vibration-Induced Illusions Illusions of MovementIn 1972, two publications describing the effects of vibration on the perception of limb position and movement independently showed that vibration of a muscle tendon at 100 Hz induces illusory movements of the limb about which the vibrated Preparation of this article was supported by the Medical Research Council of Canada.Correspondence concerning this article should be addressed to Lynette A. Jones, School of Physical and Occupational Therapy, McGill University, 3654 Drummond Street, Montreal, Quebec H3G 1Y5, Canada. muscle acts (Eklund, 1972;Goodwin et al., 1972). Using blindfolded subjects who were required to track the position of their vibrated arm with the unperturbed arm, Goodwin et al. investigated the effects of percutaneous muscle-tendon vibration on position sense at the elbow. They found that vibration of the biceps tendon in an immobilized arm consistently produced the il...

Spatial and physical frames of reference in positioning a limb

“…With respect to other illusions reviewed by Jones (1988), aspects of the present results conform to the so-called phenomenon of postural persistence investigated by Hoff and Schilder (1925), Selling (1930), andJackson (1954). Specifically, in Experiments I and 2 the forearm with Splints Sand S· was judged horizontal when it was above the horizon.…”

“…The effect of rotating {ed relative to {(Jd parallels a number of so-called illusory effects oflimb position that occur as a result of tendon vibration of a secured arm and as a result of a briefly sustained prior limb position (see Jones, 1988, for a review). A vibrated limb is felt to be at a position other than its actual spatial position.…”

Representational momentum and related displacements in spatial memory: A review of the findings

“…If displacement in a direction not aligned with implied gravitational attraction is measured, target size does not influence displacement, whereas if displacement in the direction aligned with implied gravitational attraction is measured, larger targets exhibit larger downward displacement, regardless of the direction of target motion (for ascending targets, a smaller forward displacement is exhibited in memory for larger targets, and this is consistent with the general notion that larger targets are remembered as being lower in the display). Given that visually larger objects are usually perceived to be heavier (i.e., the size-weight illusion; Koseleff, 1957; for a review, see Jones, 1988), this pattern suggested that displacement was influenced by the implied weight of the target, rather than by the implied mass of the target. Weight is experienced along the axis aligned with gravitational attraction (weight ϭ mass ϫ acceleration due to gravity) and reflects the subjective experience of mass for observers whose lifetimes have been spent within a gravitational field of constant strength (as found on the surface of the Earth).…”

The role of sensory signals in perception of the body

“…The influence of peripheral afferent signals from muscles on perception of the body is investigated by directly changing proprioceptive signals, using muscle vibration. When the tendon of a limb is vibrated at 80 Hz [5][6][7] , the illusion of movement is created, even though the limb is not actually moving [8][9][10][11] . The illusion is elicited, because the vibration of the tendon activates the muscle spindles in a similar manner, as when the muscle is actually stretched 6,7,12) .…”