Abstract spatial, but not body-related, visual information guides bimanual coordination

Abstract

Visual spatial information is paramount in guiding bimanual coordination, but anatomical factors, too, modulate performance in bimanual tasks. Vision conveys not only abstract spatial information, but also informs about body-related aspects such as posture. Here, we asked whether, accordingly, visual information induces body-related, or merely abstract, perceptual-spatial constraints in bimanual movement guidance. Human participants made rhythmic, symmetrical and parallel, bimanual index finger movements with the hands held in the same or different orientations. Performance was more accurate for symmetrical than parallel movements in all postures, but additionally when homologous muscles were concurrently active, such as when parallel movements were performed with differently rather than identically oriented hands. Thus, both perceptual and anatomical constraints were evident. We manipulated visual feedback with a mirror between the hands, replacing the image of the right with that of the left hand and creating the visual impression of bimanual symmetry independent of the right hand's true movement. Symmetrical mirror feedback impaired parallel, but improved symmetrical bimanual performance compared with regular hand view. Critically, these modulations were independent of hand posture and muscle homology. Thus, visual feedback appears to contribute exclusively to spatial, but not to body-related, anatomical movement coding in the guidance of bimanual coordination.Whether we type on a keyboard, applaud, or ride a bike -bimanual coordination is crucial in many of our everyday activities. Therefore, the principles that guide bimanual coordination have received much interest, not least to inform treatment to restore regular bimanual function in clinical settings. Beyond therapeutic considerations, coordinative action can be viewed as an ecologically valid model to understand the principles of movement planning 1 . Accordingly, experiments have studied the factors that constrain bimanual movement execution. A prominent and consistent finding has been that humans can perform symmetrical movements -with symmetry usually defined relative to the sagittal body midline -with higher precision and at higher speeds than parallel movements [2][3][4] . During symmetrical movements, the two effectors move towards opposite sides of space; for instance, one hand moves to the right while the other concurrently moves to the left. Conversely, parallel movements implicate movements towards the same direction of space; for instance, both hands synchronously move to the left or to the right.The symmetry bias has been demonstrated across a variety of effectors and movement types, such as finger flexion and extension 5,6

Protracted development of visuo-proprioceptive integration for uni-and bimanual motor coordination

“…Bingham et al, 2018). Qualitatively, this measure renders similar results as the phase difference (Brandes et al, 2017), but we report it in the Supplementary Information to aid comparison with earlier work.…”

“…However, later studies also demonstrated a role of perceptual factors (Brandes, Rezvani, & Heed, 2016;Heed & Röder, 2014;Oliveira & Ivry, 2008;Swinnen et al, 1998;Temprado, Swinnen, Carson, Tourment, & Laurent, 2003; for review, see Shea, Buchanan, & Kennedy, 2016). For instance, when the index fingers are wiggled with one hand turned up, and the other down, symmetrical movements are still performed more successfully than parallel ones, although they now require concurrent activation of non-homologous muscles (Brandes et al, 2017;Heed & Röder, 2014;Mechsner et al, 2001).…”

“…Yet, even if callosal maturation reduces automatic bilateral movement, adults preferentially synchronize bimanual movements symmetrically, especially when movement speed is high (e.g. Brandes, Rezvani, & Heed, 2017; Kelso, Scholz, & Schöner, 1986; Spencer, Ivry, Cattaert, & Semjen, 2005; for review, see Gooijers & Swinnen, 2014). Moreover, older children and adults integrate visual information to aid (bimanual) motor coordination, whereas younger children appear not to do so.…”

“…However, other studies have demonstrated a pivotal role of perceptual signals (for review, see Shea et al, 2016), even culminating in the suggestion that symmetry in movement coordination relies entirely on perceptual rather than motor processing (Bingham, 2004). For instance, when the index fingers are wiggled with one hand turned up and the other down, movements are performed best when they are symmetrical in space, although such coordination requires concurrent activation of non-homologous muscles and, thus, cannot not rely on one single, common motor command (Brandes et al, 2017; Heed & Röder, 2014; Mechsner et al, 2001). Moreover, it is impossible for most adults to circle the two hands at different speeds (e.g., four turns with the left for every three turns with the right).…”

The effects of feedback format, and egocentric & allocentric relative phase on coordination stability

“…Amazeen, DaSilva, & Amazeen, 2008;Meesen, Wenderoth, Temprado, Summers, & Swinnen, 2006;Salesse, Temprado, & Swinnen, 2005;Wilson, Collins, & Bingham, 2005a, 2005b, homology tends to show larger effect sizes and can often dominate (e.g. Kagerer, Summers, & Semjen, 2003;Li, Levin, Forner-Cordero, Ronsse & Swinnen, 2008;Peper, de Boer, de Poel, & Beek, 2008;Temprado, Swinnen, Carson, Tourment & Laurent, 2003;although see Meschner, Kerzel, Knoblich &Prinz, 2001, andBrandes, Rezvani, &Heed, 2017, for examples of allocentric dominance).…”