Kinaesthetic mirror illusion and spatial congruence

Abstract

Position sense and kinaesthesia are mainly derived from the integration of somaesthetic and visual afferents to form a single, coherent percept. However, visual information related to the body can play a dominant role in these perceptual processes in some circumstances, and notably in the mirror paradigm. The objective of the present study was to determine whether or not the kinaesthetic illusions experienced in the mirror paradigm obey one of the key rules of multisensory integration: spatial congruence. In the experiment, the participant's left arm (the image of which was reflected in a mirror) was either passively flexed/extended with a motorized manipulandum (to induce a kinaesthetic illusion in the right arm) or remained static. The right (unseen) arm remained static but was positioned parallel to the left arm's starting position or placed in extension (from 15° to 90°, in steps of 15°), relative to the left arm's flexed starting position. The results revealed that the frequency of the illusion decreased only slightly as the incongruence prior to movement onset between the reflected left arm and the hidden right arm grew and remained quite high even in the most incongruent settings. However, the greater the incongruence between the visually and somaesthetically specified positions of the right forearm (from 15° to 90°), the later the onset and the lower the perceived speed of the kinaesthetic illusion. Although vision dominates perception in a context of visuoproprioceptive conflict (as in the mirror paradigm), our results show that the relative weightings allocated to proprioceptive and visual signals vary according to the degree of spatial incongruence prior to movement onset.

The sensory origins of human position sense

“…An illusion of movement is generated in a hidden, stationary arm by watching a mirror image of the other, moving arm (Metral et al . ). The subject falsely interprets the mirror image as being their hidden arm.…”

The kinaesthetic mirror illusion: How much does the mirror matter?

“…It must also be borne in mind that masking the afferent signals from the antagonistic muscles of the arm subjected to the illusion has exactly the opposite effect; the mirror illusion occurred earlier (with reduced latency) and more intensely (with a higher perceived speed) than in the absence of proprioceptive masking (Guerraz et al 2012). Similarly, Metral et al (2015) showed that a larger degree of spatial incongruence between the mirror arm and the somaesthetically specified position of the unseen arm subjected to mirror illusion(with a shift of between 0° and 90° in the sagittal plane) was associated with a less intense kinaesthetic illusion. Finally, the illusory displacement can be either strengthened or weakened by adding proprioceptive inputs through vibration of the antagonist or agonist muscles of the hidden arm respectively (Guerraz et al 2012, Tsuge et al 2012.…”

“…The mirror paradigm was initially developed to treat phantom limb pain in unilateral amputees (Ramachandran et al 1995) but hasalso been used over the last two decadesas a rehabilitation tool for promoting recovery from hemiparesis (RamachandranandAlthschuler2009; RosenandLundborg2005; Dohle etal.2009;Guerraz 2015). More recently, experiments conducted in healthy participants showed that mirror reflection of an arm moved passively by a motorized manipulandum induces consistent, vivid kinaesthetic illusions of movement of the hidden, static arm in the direction of the mirror displacement (Guerraz et al 2012;Tsuge et al 2012;Metral et al 2015). The occurrence of this visually induced kinaesthetic illusion indicates that visual afferents might be of prime importance in sensing limb movement (i.e.…”

“…However, kinaesthesia is not exclusively derived from visual afferents; muscle spindle afferents (notably type Ia and II sensory endings; Goodwin et al 1972;Teasdale et al 1993; for a review, see Proske and Gandevia 2012) and cutaneous afferents (Collins and Prochazka 1996;Blanchard et al 2011Blanchard et al , 2013 also make significant contributions. For instance, it has been shown that the mirror illusion is less intense when the unseen arm is not in the same position as the reflected arm (Metral et al 2015). Likewise, masking the proprioceptive afferents of the unseen armincreases the illusory velocity of displacement (Guerraz et al 2012).…”

The mirror illusion’s effects on body state estimation

“…Although the mirror illusion can be induced by simply placing the limbs in the mirror context (Holmes & Spence, 2005, Holmes et al, 2006; Snijders et al 2007), other studies have required that participants perform cycles of synchronous bimanual movements prior to engaging in the main reaching task (e.g., Guerraz et al, 2012; Holmes, Crozier, & Spence, 2004; Holmes & Spence, 2005; Metral et al, 2015). One study (Holmes & Spence, 2005) showed that the magnitude of the illusion (1) was stronger when preceded by active bimanual movement than passive viewing without movement and (2) increased incrementally as the duration of bimanual movement increased (4, 8, or 12 seconds).…”