title: Stimulation of PPC Affects the Mapping between Motion and Force Signals for Stiffness Perception But Not Motion Control.
abstract: How motion and sensory inputs are combined to assess an object's stiffness is still unknown. Here, we provide evidence for the existence of a stiffness estimator in the human posterior parietal cortex (PPC). We showed previously that delaying force feedback with respect to motion when interacting with an object caused participants to underestimate its stiffness. We found that applying theta-burst transcranial magnetic stimulation (TMS) over the PPC, but not the dorsal premotor cortex, enhances this effect without affecting movement control. We explain this enhancement as an additional lag in force signals. This is the first causal evidence that the PPC is not only involved in motion control, but also has an important role in perception that is disassociated from action. We provide a computational model suggesting that the PPC integrates position and force signals for perception of stiffness and that TMS alters the synchronization between the two signals causing lasting consequences on perceptual behavior.
  
  
  
  When selecting an object such as a ripe fruit or sofa, we need to assess the object's stiffness. Because we lack dedicated stiffness sensors, we rely on an as yet unknown mechanism that generates stiffness percepts by combining position and force signals. Here, we found that the posterior parietal cortex (PPC) contributes to combining position and force signals for stiffness estimation. This finding challenges the classical view about the role of the PPC in regulating position signals only for motion control because we highlight a key role of the PPC in perception that is disassociated from action. Altogether this sheds light on brain mechanisms underlying the interaction between action and perception and may help in the development of better teleoperation systems and rehabilitation of patients with sensory impairments.
authors.affiliation: Department of Biomedical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel, Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London WC1N3BG, United Kingdom, and leibra@post.bgu.ac.il.
authors.forename: Raz
authors.identifier: 0000-0002-3940-2651
authors.initials: R
authors.lastname: Leib
authors.affiliation: Department of Physical Medicine and Rehabilitation, Johns Hopkins School of Medicine, Baltimore, Maryland 21205.
authors.forename: Firas
authors.initials: F
authors.lastname: Mawase
authors.affiliation: Department of Biomedical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
authors.forename: Amir
authors.initials: A
authors.lastname: Karniel
authors.affiliation: Department of Biomedical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
authors.forename: Opher
authors.identifier: 0000-0003-0963-4467
authors.initials: O
authors.lastname: Donchin
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London WC1N3BG, United Kingdom, and.
authors.forename: John
authors.identifier: 0000-0003-1367-6467
authors.initials: J
authors.lastname: Rothwell
authors.affiliation: Department of Biomedical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
authors.forename: Ilana
authors.identifier: 0000-0003-4128-9771
authors.initials: I
authors.lastname: Nisky
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London WC1N3BG, United Kingdom, and Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Biomedical Sciences Group, Department of Kinesiology, Katholieke Universiteit Leuven, 3001 Leuven, Belgium.
authors.forename: Marco
authors.identifier: 0000-0002-4670-0251
authors.initials: M
authors.lastname: Davare
mesh_terms: D000328:Adult; D001676:Biofeedback, Psychology; D001931:Brain Mapping; D004192:Discrimination, Psychological / Q000502:physiology; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008959:Models, Neurological; D009038:Motion; D010296:Parietal Lobe / Q000502:physiology*; D010465:Perception / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D013826:Theta Rhythm / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: PPC; cTBS; delay; perception; position control; stiffness