  Simulation models of facial expressions propose that sensorimotor regions may
increase the clarity of facial expressions representations in extrastriate
areas. We monitored the event-related potential marker of visual working memory
(VWM) representations, namely the sustained posterior contralateral negativity
(SPCN), also termed contralateral delay activity (CDA), while participants
performed a change detection task including to-be-memorized faces with
different intensities of anger. In one condition participants could freely use
their facial mimicry during the encoding/VWM maintenance of the faces, while in
a different condition, participants had their facial mimicry blocked by a gel.
Notably, SPCN amplitude was reduced for faces in the blocked mimicry condition
when compared to the free mimicry condition. This modulation interacted with
the empathy levels of participants such that only participants with medium-high
empathy scores showed such reduction of the SPCN amplitude when their mimicry
was blocked. The SPCN amplitude was larger for full expressions when compared
to neutral and subtle expressions, while subtle expressions elicited lower SPCN
amplitudes than neutral faces. These findings provide evidence of a functional
link between mimicry and VWM for faces, and further shed light on how this
memory system may receive feedbacks from sensorimotor regions during the
processing of facial expressions.
