Brain and Muscular Signatures of Local and Global Temporal Dynamics in Facial Expressions
Abstract
Natural facial expressions are inherently dynamic events governed by precise temporal coordination between facial features, yet the neurobiological mechanisms integrating kinematic timing, facial mimicry, and emotional evaluation remain poorly understood. Here, we combined event-related fMRI with simultaneous continuous facial electromyography (EMG; corrugator supercilii and zygomaticus major) and behavioral psychophysics in 27 healthy adult participants to examine how temporal global synchrony versus analytic asynchrony (8% and 18% onset lags between upper and lower facial features) across two dynamic speeds (1.5 and 3 sec.) shapes emotional processing. Naturally unfolding synchronous expressions distinctively engaged bilateral primary motor cortices, supplementary motor area (SMA), and primary somatosensory cortex. In contrast, kinematically disrupted expressions preferentially recruited the right posterior superior temporal sulcus (pSTS), fusiform gyrus, and inferior frontal gyrus (IFG). Parametric modulation analyses revealed a clear dissociation between somatic and cognitive tracking: trial-by-trial facial muscle mimicry engaged a distributed sensorimotor simulation network that severely fractured or collapsed during asynchronous kinematics. Conversely, subjective intensity evaluations of unnatural asynchronous expressions triggered an extensive recruitment of the bilateral amygdala and the entire longitudinal axis of the right STS, pointing to heightened computational demands for resolving perceptual ambiguity and social conflict. These findings demonstrate that natural temporal synchrony is a prerequisite for automatic motor-affective embodiment, whereas kinematic temporal disruptions shift processing toward lateral social-perceptual networks to analytically resolve fragmented communicative signals.
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BibTeX
@misc{skiba2026brain,
title = {{Brain and Muscular Signatures of Local and Global Temporal Dynamics in Facial Expressions}},
author = {Rafal M. Skiba and Patrik Vuilleumier},
howpublished = {PsyArXiv},
year = {2026},
month = sep,
doi = {10.31234/osf.io/79mrq_v1},
url = {https://osf.io/preprints/psyarxiv/79mrq_v1/},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Brain and Muscular Signatures of Local and Global Temporal Dynamics in Facial Expressions
AU - Rafal M. Skiba
AU - Patrik Vuilleumier
PY - 2026
DA - 2026/09/10
PB - PsyArXiv
DO - 10.31234/osf.io/79mrq_v1
UR - https://osf.io/preprints/psyarxiv/79mrq_v1/
AB - Natural facial expressions are inherently dynamic events governed by precise temporal coordination between facial features, yet the neurobiological mechanisms integrating kinematic timing, facial mimicry, and emotional evaluation remain poorly understood. Here, we combined event-related fMRI with simultaneous continuous facial electromyography (EMG; corrugator supercilii and zygomaticus major) and behavioral psychophysics in 27 healthy adult participants to examine how temporal global synchrony versus analytic asynchrony (8% and 18% onset lags between upper and lower facial features) across two dynamic speeds (1.5 and 3 sec.) shapes emotional processing. Naturally unfolding synchronous expressions distinctively engaged bilateral primary motor cortices, supplementary motor area (SMA), and primary somatosensory cortex. In contrast, kinematically disrupted expressions preferentially recruited the right posterior superior temporal sulcus (pSTS), fusiform gyrus, and inferior frontal gyrus (IFG). Parametric modulation analyses revealed a clear dissociation between somatic and cognitive tracking: trial-by-trial facial muscle mimicry engaged a distributed sensorimotor simulation network that severely fractured or collapsed during asynchronous kinematics. Conversely, subjective intensity evaluations of unnatural asynchronous expressions triggered an extensive recruitment of the bilateral amygdala and the entire longitudinal axis of the right STS, pointing to heightened computational demands for resolving perceptual ambiguity and social conflict. These findings demonstrate that natural temporal synchrony is a prerequisite for automatic motor-affective embodiment, whereas kinematic temporal disruptions shift processing toward lateral social-perceptual networks to analytically resolve fragmented communicative signals.
ER -