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J Neurophysiol. 2015 Oct;114(4):2295-304. doi: 10.1152/jn.00433.2015. Epub 2015 Aug 19.

Generalization of motor resonance during the observation of hand, mouth, and eye movements.

Author information

1
Robotics, Brain and Cognitive Sciences Department, Italian Institute of Technology, Genova, Italy; Dipartimento di Scienze Umane, Università Degli Studi di Udine, Udine, Italy;
2
Robotics, Brain and Cognitive Sciences Department, Italian Institute of Technology, Genova, Italy;
3
Robotics, Brain and Cognitive Sciences Department, Italian Institute of Technology, Genova, Italy; Center for Neuroprosthetics, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; and.
4
Robotics, Brain and Cognitive Sciences Department, Italian Institute of Technology, Genova, Italy; IUF, INSERM U1093 Cognition, Action et Plasticité Sensorimotrice, Université de Bourgogne, Dijon, France.
5
Robotics, Brain and Cognitive Sciences Department, Italian Institute of Technology, Genova, Italy; alessandro.dausilio@iit.it.

Abstract

Transcranial magnetic stimulation (TMS) of the motor cortex shows that hand action observation (AO) modulates corticospinal excitability (CSE). CSE modulation alternatively maps low-level kinematic characteristics or higher-level features, like object-directed action goals. However, action execution is achieved through the control of muscle synergies, consisting of coordinated patterns of muscular activity during natural movements, rather than single muscles or object-directed goals. This synergistic organization of action execution also underlies the ability to produce the same functional output (i.e., grasping an object) using different effectors. We hypothesize that motor system activation during AO may rely on similar principles. To investigate this issue, we recorded both hand CSE and TMS-evoked finger movements which provide a much more complete description of coordinated patterns of muscular activity. Subjects passively watched hand, mouth and eyelid opening or closing, which are performing non-object-directed (intransitive) actions. Hand and mouth share the same potential to grasp objects, whereas eyelid does not allow object-directed (transitive) actions. Hand CSE modulation generalized to all effectors, while TMS evoked finger movements only to mouth AO. Such dissociation suggests that the two techniques may have different sensitivities to fine motor modulations induced by AO. Differently from evoked movements, which are sensitive to the possibility to achieve object-directed action, CSE is generically modulated by "opening" vs. "closing" movements, independently of which effector was observed. We propose that motor activities during AO might exploit the same synergistic mechanisms shown for the neural control of movement and organized around a limited set of motor primitives.

KEYWORDS:

action observation network; corticospinal excitability; finger kinematics; motor generalization; transcranial magnetic stimulation

PMID:
26289463
PMCID:
PMC4609760
DOI:
10.1152/jn.00433.2015
[Indexed for MEDLINE]
Free PMC Article

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