Kinematic markers dissociate error correction from sensorimotor realignment during prism adaptation.
This study investigated the motor control mechanisms that enable healthy individuals to adapt their pointing movements during prism exposure to a rightward optical shift. In the prism adaptation literature, two processes are typically distinguished. Strategic motor adjustments are thought to drive the pattern of rapid endpoint error correction typically observed during the early stage of prism exposure. This is distinguished from so-called 'true sensorimotor realignment', normally measured with a different pointing task, at the end of prism exposure, which reveals a compensatory leftward 'prism after-effect'. Here, we tested whether each mode of motor compensation - strategic adjustments versus 'true sensorimotor realignment' - could be distinguished, by analyzing patterns of kinematic change during prism exposure. We hypothesized that fast feedforward versus slower feedback error corrective processes would map onto two distinct phases of the reach trajectory. Specifically, we predicted that feedforward adjustments would drive rapid compensation of the initial (acceleration) phase of the reach, resulting in the rapid reduction of endpoint errors typically observed early during prism exposure. By contrast, we expected visual-proprioceptive realignment to unfold more slowly and to reflect feedback influences during the terminal (deceleration) phase of the reach. The results confirmed these hypotheses. Rapid error reduction during the early stage of prism exposure was achieved by trial-by-trial adjustments of the motor plan, which were proportional to the endpoint error feedback from the previous trial. By contrast, compensation of the terminal reach phase unfolded slowly across the duration of prism exposure. Even after 100 trials of pointing through prisms, adaptation was incomplete, with participants continuing to exhibit a small rightward shift in both the reach endpoints and in the terminal phase of reach trajectories. Individual differences in the degree of adaptation of the terminal reach phase predicted the magnitude of prism after-effects. In summary, this study identifies distinct kinematic signatures of fast strategic versus slow sensorimotor realignment processes, which combine to adjust motor performance to compensate for a prismatic shift.
Lyon Neuroscience Research Center, ImpAct (Integrative, Multisensory, Perception, Action & Cognition) Team, INSERM U1028, CNRS UMR5292, University of Lyon 1, 69500 Bron, France; Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK. Electronic address: jacinta.oshea@ndcn.ox.ac.uk.
Jacinta
J
O'Shea
Lyon Neuroscience Research Center, ImpAct (Integrative, Multisensory, Perception, Action & Cognition) Team, INSERM U1028, CNRS UMR5292, University of Lyon 1, 69500 Bron, France.
Valérie
V
Gaveau
Lyon Neuroscience Research Center, ImpAct (Integrative, Multisensory, Perception, Action & Cognition) Team, INSERM U1028, CNRS UMR5292, University of Lyon 1, 69500 Bron, France.
Matthieu
M
Kandel
Department of Psychology, Kyoto Notre Dame University, Kyoto 606-0847, Japan.
Kazuo
K
Koga
Department of Psychology, Faculty of Applied Sociology, Kinki University, Osaka 577-8502, Japan.
Kenji
K
Susami
Lyon Neuroscience Research Center, ImpAct (Integrative, Multisensory, Perception, Action & Cognition) Team, INSERM U1028, CNRS UMR5292, University of Lyon 1, 69500 Bron, France.
Claude
C
Prablanc
Lyon Neuroscience Research Center, ImpAct (Integrative, Multisensory, Perception, Action & Cognition) Team, INSERM U1028, CNRS UMR5292, University of Lyon 1, 69500 Bron, France; Plate-forme Mouvement et Handicap, Hospices Civils de Lyon, Centre de Recherche en Neurosciences de Lyon, 69500 Bron, France. Electronic address: yves.rossetti@inserm.fr.
Yves
Y
Rossetti
D000222:Adaptation, Physiological; D000223:Adaptation, Psychological; D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D005246:Feedback; D006225:Hand / Q000502:physiology; D006801:Humans; D010775:Photic Stimulation; D011434:Proprioception; D011597:Psychomotor Performance / Q000502:physiology*; D011601:Psychophysics; D013647:Task Performance and Analysis; D013997:Time Factors; D014796:Visual Perception
Error correction; Kinematics; Motor control; Prism adaptation; Proprioception