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

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Chapter 9
cortical inhibition (and therefore increased unmasking; c.f. Cohen Kadosh and Walsh,
2006), then one may suspect that grapheme-colour synaesthetes will show more rapid
enhancements in tactile acuity following sensory deprivation compared to non-
synaesthetes.
9.5 What are the implications of heightened sensorimotor simulation in
mirror-touch synaesthesia for social cognition?
In addition to studies investigating the neurocognitive basis of synaesthesia,
there is a growing interest in using the condition to inform us about normal models of
cognitive processing (Mattingley and Ward, 2006). This approach rests on the
assumption of neuropsychology, where one is able to use a symptom affecting the
normal system to inform us about the function of the normal system. In the case of
synaesthesia the symptom is a positive one and in the case of mirror-touch
synaesthesia one is assessing the impact of facilitated sensorimotor simulation
mechanisms on cognition. Moreover, functional brain imaging has linked mirror-
touch synaesthesia to heightened neural activity in a network of brain regions which
are also activated in non-synaesthetic control subjects when observing touch to others
(the mirror-touch system; Blakemore et al., 2005). The mirror-touch system is
comprised of brain areas active during both the observation and passive experience of
touch (including primary and secondary somatosensory cortices, and premotor cortex;
Blakemore et al., 2005; Ebisch et al., 2008; Keyers et al., 2004) and has been
suggested to be a candidate neural mechanism to aid social cognition through
sensorimotor simulation (Gallese, 2006; Gallese and Goldman, 1998; Keysers and
Gazzola, 2006; Oberman and Ramachandran, 2007). Accounts of social cognition
involving sensorimotor simulation contend that, in order to understand another’s
emotions and physical states, the perceiver must map the bodily state of the observer