Motor Commands of Facial Expressions: The Bereitschaftspotential of Posed Smiles

Abstract

Electroencephalographic (EEG) premotor potentials with negative polarity like the Bereitschaftspotential (BP) are known to precede self-paced voluntary movements of the limbs and other body parts. This is however the first report of such premotor potentials before posed smiles. Scalp EEG was recorded in 16 healthy participants performing self-paced unilateral and bilateral smiles and unilateral finger movements. Amplitudes over six central electrodes and voltage distributions over the entire scalp were compared across conditions at time of EMG-onset, thus focusing on the late BP. Results show the presence of a premotor potential before posed smiles with a later onset, symmetrical bilateral distribution, and smaller amplitude at time of movement-onset, compared to finger movements. Future studies should investigate the BP before various types of emotional and non-emotional facial expressions.

Should I smile or should I frown? An ERP study on the voluntary control of emotion‐related facial expressions

“…The RP has been observed preceding speech production (e.g., Wohlert, ), swallowing (Huckabee, Deecke, Cannito, Gould, & Mayr, ), and mandibular movements (e.g., Yoshida et al., ). Interestingly, Korb, Grandjean, and Scherer () observed a RP before the voluntary production of expressions of happiness, analogous in terms of amplitude and scalp topography to the RP preceding finger movements.…”

“…Our results did not reveal significant differences in the amplitude of the CNV between the two expressions studied here. Previous reports have observed a RP preceding the voluntary production of smiles (Korb et al, 2008) and other nonemotional facial movements (e.g., Huckabee et al, 2003), but none of them compared different emotional expressions. The present results do not provide evidence that the higher accuracy for validly cued expressions of happiness relative to anger relate to differential preparation or preactivation of the corresponding motor plan during the foreperiod.…”

Investigating the production of emotional facial expressions: a combined electroencephalographic (EEG) and electromyographic (EMG) approach

“…Also, the role of cortical motor areas in the production of emotional facial expressions may have been underestimated in the past. Finally, we have presented the results of a study showing the existence of a BP before posed smiles [19] This line of research is just at its beginning and, as the neuroscientific study of the production of facial expressions is a thorny endeavor and most studies in the past focused rather on the perception of facial expressions, many questions remain. For example, one can ask whether smiling and laughing result from different degrees of activation in common neural structures, or whether they rely on different mechanisms.…”

“…Although typically shown to precede voluntary movements of the limbs, the BP may also occur prior to posed smiles, as recently suggested. Korb, Grandjean, and Scherer [19] asked healthy right-handed participants to repeatedly perform five types of movements in a self-paced, voluntary manner: elevations of the right or of the left index-finger, a right or left-sided unilateral smile (consisting of pulling one mouth corner upwards and backwards), and a bilateral smile. Movements were preceded by a BP with a distinct distribution over the scalp, which at time of movement onset had a negative maximum over the contralateral hemisphere for finger movements, and a more bilateral, symmetrical, and somewhat weaker topography for bilateral smiles (see Figure 2).…”

Facial Emotion Expression, Individual Differences in

“…These differentiated analyses of movementrelated potentials have been measured for finger movements. There seems to be only one study that applied analyses of movement-related event-related brain potentials (ERPs) to voluntary facial expressions: Korb et al (2008) compared the BP before self-paced unilateral and bilateral smiles with the BP before unilateral finger movements. The BP before bilateral smiles was comparable in size to the BP for right-hand movements (in right-handers) and it showed bilateral symmetry.…”