S.F. and J.M.T. contributed equally to this work.
Modulation of cortical motor outputs by the symbolic meaning of visual stimuli
Article first published online: 18 JUN 2010
© The Authors (2010). Journal Compilation © Federation of European Neuroscience Societies and Blackwell Publishing Ltd
European Journal of Neuroscience
Volume 32, Issue 1, pages 172–177, July 2010
How to Cite
Fecteau, S., Tormos, J. M., Gangitano, M., Théoret, H. and Pascual-Leone, A. (2010), Modulation of cortical motor outputs by the symbolic meaning of visual stimuli. European Journal of Neuroscience, 32: 172–177. doi: 10.1111/j.1460-9568.2010.07285.x
- Issue published online: 6 JUL 2010
- Article first published online: 18 JUN 2010
- Received 16 January 2010, revised 19 April 2010, accepted 19 April 2010
- mirror neuron system;
- primary motor cortex;
- transcranial magnetic stimulation
The observation of an action modulates motor cortical outputs in specific ways, in part through mediation of the mirror neuron system. Sometimes we infer a meaning to an observed action based on integration of the actual percept with memories. Here, we conducted a series of experiments in healthy adults to investigate whether such inferred meanings can also modulate motor cortical outputs in specific ways. We show that brief observation of a neutral stimulus mimicking a hand does not significantly modulate motor cortical excitability (Study 1) although, after prolonged exposure, it can lead to a relatively nonspecific modulation (Study 2). However, when such a neutral stimulus is preceded by exposure to a hand stimulus, the latter appears to serve as a prime, perhaps enabling meaning to the neutral stimulus, which then modulates motor cortical excitability in accordance with mirror neuron-driving properties (Studies 2 and 3). Overall results suggest that a symbolic value ascribed to an otherwise neutral stimulus can modulate motor cortical outputs, revealing the influence of top-down inputs on the mirror neuron system. These findings indicate a novel aspect of the human mirror neuron system: an otherwise neutral stimulus can acquire specific mirror neuron-driving properties in the absence of a direct association between motor practice and perception. This significant malleability in the way that the mirror neuron system can code otherwise meaningless (i.e. arbitrarily associated) stimuli may contribute to coding communicative signals such as language. This may represent a mirror neuron system feature that is unique to humans.