Mirror-touch synaesthesia: the role of shared ... - UCL Discovery

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Chapter 8
CHAPTER 8: THE ROLE OF SENSORIMOTOR SIMULATION
IN FACIAL EXPRESSION RECOGNITION
The findings in chapter 7, demonstrated that the right primary somatosensory cortex
and right premotor cortex play a critical role in discriminating between the nonverbal
auditory emotions of others. Recent findings indicate that neural activity in
right primary somatosensory cortex is also necessary for the recognition of facial
expressions in healthy adults, but it remains unclear whether neural activity in
cortical regions involved in other aspects of sensorimotor simulation (e.g. simulation
of motor as opposed to somatic consequences of the perceived emotion) are also
central to the facial expression recognition abilities of healthy adults. Further, in the
face processing literature, whether neural activity in different components of the
sensorimotor simulation network are central for recognizing all expressions (i.e. an
expression-general mechanism) or for subsets of expressions remains a point of
debate (i.e. an expression-specific mechanism). Using continuous theta burst
transcranial magnetic stimulation (cTBS) in neurologically normal subjects, this
study sought to establish whether sensorimotor neural activity is critical for the facial
expression recognition abilities for some, or all, basic facial expressions. cTBS was
targeted at right primary somatosensory cortex (rSI), right inferior frontal gyrus
(rIFG) or right V5 / MT (control site) while participants completed a four-forcedchoice
expression categorization task. cTBS to rSI, but not rIFG or right V5 / MT
(control site), significantly disrupted participants abilities to correctly categorize
happy and sad facial expressions, but not disgust or neutral facial expressions. These
findings are consistent with sensorimotor simulation models of expression recognition
which suggest that in order to understand another’s facial expressions individuals
must map the perceived expression onto the same sensorimotor representations which
are active during the experience of the perceived emotion.
8.1 Introduction
As noted previously, perceiving and correctly interpreting the expressions of
others is a vital component of social interaction. The processes which facilitate this
skill have often been described through mechanisms of simulation (Adolphs, 2002;
Adolphs, 2003; Damasio, 1990; Gallese, Keysers, and Rizzolatti, G, 2004; Goldman,
and Sripada, 2005; Keysers and Gazzola, 2006). These simulation-models of
expression recognition contend that in order to understand another’s expression one
must match the perceived state onto the sensorimotor responses associated with
experiencing the expression. Supporting this contention, in the visual domain,