Elsevier

Neuropsychologia

Volume 47, Issue 10, August 2009, Pages 2100-2106
Neuropsychologia

Effects of brief imitative experience on EEG desynchronization during action observation

https://doi.org/10.1016/j.neuropsychologia.2009.03.022Get rights and content

Abstract

There is a good deal of evidence that observing the actions of other people is associated with activation of the observer's motor system, which may reflect involvement of the mirror neuron system (MNS) in certain aspects of action processing in humans. Furthermore, variation in the extent of this activation appears to be partly dependent on individuals’ experience with performing the observed actions. However, very little work has examined the processes through which the observation of unfamiliar actions – which are not in an observer's motor repertoire – might become associated with MNS activation. In the current study we examined differences in EEG desynchronization in alpha-range bands during action observation following very brief imitative experience with the observed actions, which were novel drawing movements. Compared to carrying out unrelated actions, brief imitative experience was specifically associated with a significantly larger desynchronization in the 11–13 Hz band at mid-frontal sites (F3 and F4) when a previously imitated action was viewed again. In addition, higher fidelity of imitation was significantly correlated with greater bilateral desynchronization of the lower mu band (8–10 Hz) at central sites (C3 and C4) during subsequent observation of the previously imitated action. Our findings point to the involvement of frontal cortical processing and the MNS in the early stages of imitative learning.

Section snippets

Methods

Twenty undergraduates (8 male and 12 female) at a large urban university in the Northeast United States participated in the study. All participants were right-handed and had given their informed consent to participate in the study. The study protocol had been approved by the Institutional Review Board at the principal investigator's university.

The novel action stimuli used in the imitation task were video sequences of a model's lower arm and hand moving a stylus on an LCD graphics tablet.

Effect of imitation on subsequent EEG desynchronization

For analysis, mean ERD scores were computed for 1-s epochs from 0 to 4 s after the onset of the model's arm movement in the first observation epoch. Repeated-measures ANOVAs were computed for each frequency band separately using the following within-subject factors: CONDITION (action imitation vs. other motor experience), TIME (0–1, 1–2, 2–3, and 3–4 s after stimulus onset), HEMISPHERE (left, right), and REGION (eight scalp regions). The regions analyzed were as follows: Frontal pole (Fp1/Fp2),

Discussion

We expected EEG desynchronization at frontal and central sites during observation of novel actions to be greater after having attempted to imitate those actions, compared with a condition in which participants had carried out a different motor action. The most salient finding in support of this hypothesis was a desynchronization at mid-frontal sites in the 11–13 Hz band during action observation following imitation, relative to action observation following execution of an unrelated motor action.

Conclusions

In summary, we assessed the effect of short-term experience with imitating novel hand movements on the desynchronization of alpha-range EEG rhythms during subsequent re-observation of the target actions. We found evidence for the involvement of fronto-central EEG rhythms in imitation, with desynchronization of alpha-range rhythms at frontal and central sites being associated with different aspects of imitative experience. Compared with carrying out an unrelated action, prior imitation of the

Acknowledgments

The authors wish to thank Ben Schimeneck, Jeremy Fesi, Kat Ruopp, and Inara O’Gorman for their assistance with data collection. This research was supported by grant BCS-0642404 from the National Science Foundation to PJM and TFS.

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