Abstract
The passive observation of hand actions is associated with increased motor cortex excitability, presumably reflecting activity within the human mirror neuron system (MNS). Recent data show that in-group ethnic membership increases motor cortex excitability during observation of culturally relevant hand gestures, suggesting that physical similarity with an observed body part may modulate MNS responses. Here, we ask whether the MNS is preferentially activated by passive observation of hand actions that are similar or dissimilar to self in terms of sex and skin color. Transcranial magnetic stimulation-induced motor evoked potentials were recorded from the first dorsal interosseus muscle while participants viewed videos depicting index finger movements made by female or male participants with black or white skin color. Forty-eight participants equally distributed in terms of sex and skin color participated in the study. Results show an interaction between self-attributes and physical attributes of the observed hand in the right motor cortex of female participants, where corticospinal excitability is increased during observation of hand actions in a different skin color than that of the observer. Our data show that specific physical properties of an observed action modulate motor cortex excitability and we hypothesize that in-group/out-group membership and self-related processes underlie these effects.
Highlights
The contribution of the frontoparietal mirror neuron system (MNS) to action understanding has been well documented in the human brain
There was a significant interaction between Skin color and Hand color (F = 14.07, P = 0.004), which was explained by the fact that in both white and black female participants, observation of a finger movement executed by a hand in a different skin color produced greater corticospinal faciliation than observation of a hand in a similar color (Figure 3)
Women scored significantly higher than men on an empathy scale, the absence of correlation with corticospinal excitability does not support the hypothesis that MNS sex differences are related to empathy
Summary
The contribution of the frontoparietal mirror neuron system (MNS) to action understanding has been well documented in the human brain (see [1]). At the motor cortex level, passive observation of hand actions increases M1 excitability, presumably reflecting mirror neuron activity originating from premotor areas [2]. Using transcranial magnetic stimulation (TMS), Fadiga and collaborators [3] have shown that observation of hand grasping movements significantly increases the amplitude of TMS-induced motor evoked potentials (MEPs). Corticospinal facilitation has been found to be specific to the muscles involved in the observed action [3,4,5] and to follow the temporal structure of the observed movement [6]. Paired-pulse TMS evidence suggests cortical involvement in the modulation of M1 excitability during action observation [4]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
