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Updated: Jun 20, 2026
12:33
Corticospinal Excitability Modulation During Action Observation
Published on: December 31, 2013
Coding of visual space during motor preparation: Approaching objects rapidly modulate corticospinal excitability in
Tamar R Makin1, Nicholas P Holmes, Claudio Brozzoli
1Inserm, Unité Mixte de Recherche S "Espace et Action," Bron, France.
Summary
The human brain automatically codes visual space from a hand-centered perspective. This rapid processing helps prepare defensive behaviors, like withdrawing your hand from approaching objects.
Area of Science:
- Neuroscience
- Cognitive Science
- Motor Control
Background:
- Defensive behaviors require rapid sensorimotor transformations.
- Understanding the reference frame for visual information during motor preparation is crucial.
Purpose of the Study:
- To investigate the reference frame for coding visual information about approaching objects relative to the hand.
- To determine if visual coding is hand-centered during motor preparation.
Main Methods:
- Subjects performed a visuomanual task with a rapidly approaching distractor ball.
- Transcranial magnetic stimulation (TMS) was used to elicit motor evoked potentials (MEPs) in the hand.
- MEP amplitude was measured to assess motor cortex excitability.
Main Results:
- MEP amplitude was reduced when a ball approached near the hand, regardless of hand position (left/right).
- This suppression occurred early (70-80 ms) and was not affected by visual fixation.
- The effect was specific to approaching objects, not static distractors.
Conclusions:
- The human brain exhibits automatic hand-centered coding of visual space.
- This coding mechanism likely supports rapid defensive behaviors by anticipating potential threats relative to the body.
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