title: Weight dependent modulation of motor resonance induced by weight estimation during observation of partially occluded lifting actions.
abstract: Seeing others performing an action induces the observers' motor cortex to "resonate" with the observed action. Transcranial magnetic stimulation (TMS) studies suggest that such motor resonance reflects the encoding of various motor features of the observed action, including the apparent motor effort. However, it is unclear whether such encoding requires direct observation or whether force requirements can be inferred when the moving body part is partially occluded. To address this issue, we presented participants with videos of a right hand lifting a box of three different weights and asked them to estimate its weight. During each trial we delivered one transcranial magnetic stimulation (TMS) pulse over the left primary motor cortex of the observer and recorded the motor evoked potentials (MEPs) from three muscles of the right hand (first dorsal interosseous, FDI, abductor digiti minimi, ADM, and brachioradialis, BR). Importantly, because the hand shown in the videos was hidden behind a screen, only the contractions in the actor's BR muscle under the bare skin were observable during the entire videos, while the contractions in the actor's FDI and ADM muscles were hidden during the grasp and actual lift. The amplitudes of the MEPs recorded from the BR (observable) and FDI (hidden) muscle increased with the weight of the box. These findings indicate that the modulation of motor excitability induced by action observation extends to the cortical representation of muscles with contractions that could not be observed. Thus, motor resonance appears to reflect force requirements of observed lifting actions even when the moving body part is occluded from view.
authors.affiliation: Neuroimaging Center, University Medical Center Groningen, A. Deusinglaan 2, 9713AW Groningen, The Netherlands; Department of Neurosciences, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands. Electronic address: nikola.valtchev@gmail.com.
authors.forename: Nikola
authors.initials: N
authors.lastname: Valchev
authors.affiliation: Neuroimaging Center, University Medical Center Groningen, A. Deusinglaan 2, 9713AW Groningen, The Netherlands; Department of Neurosciences, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Inge
authors.initials: I
authors.lastname: Zijdewind
authors.affiliation: Department of Neurosciences, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands.
authors.forename: Christian
authors.initials: C
authors.lastname: Keysers
authors.affiliation: Department of Neurosciences, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands.
authors.forename: Valeria
authors.initials: V
authors.lastname: Gazzola
authors.affiliation: IRCCS Fondazione Santa Lucia, Rome, Italy; Dipartimento di Psicologia, Università di Bologna and Centro studi e ricerche in Neuroscienze Cognitive, Campus di Cesena, Università di Bologna, Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Avenanti
authors.affiliation: Neuroimaging Center, University Medical Center Groningen, A. Deusinglaan 2, 9713AW Groningen, The Netherlands; Department of Neurology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Natasha M
authors.initials: NM
authors.lastname: Maurits
mesh_terms: D000328:Adult; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D006225:Hand / Q000502:physiology; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D017770:Lifting; D008297:Male; D009043:Motor Activity; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D014796:Visual Perception / Q000502:physiology*; D016474:Weight-Bearing; D055815:Young Adult
keywords: MEPs; Motor resonance; Weight estimation