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

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Chapter 1
and colleagues (2005) the case of synaesthete C was described. C reports
experiencing touch on her own body when observing another person being touched,
but not when observing inanimate objects being touched. These experiences have
been described as being automatic, in so far as they occur whenever she observes
another person being touched, and to have occurred throughout her lifetime. Her
experiences mirror observed touch to another person, such that observing touch to
another person’s left facial cheek leads to a sensation of touch on her own right facial
cheek (i.e. as if looking at a mirror reflection of herself). Using fMRI Blakemore and
colleagues investigated the neural systems underlying C’s synaesthetic experience by
contrasting brain activity when watching videos of humans relative to objects being
touched (the latter did not elicit synaesthesia) in the synaesthete and in 12 non-
synaesthetic control subjects. In controls a network of brain regions were activated
during the observation of touch to a human relative to an object, including primary
and secondary somatosensory cortex, premotor regions and the superior temporal
sulcus. Similar brain regions were also activated during actual touch, indicating that
observing touch to another person activates a similar neural circuit as actual tactile
experience – a “mirror touch” system. A comparison between synaesthete C and non-
synaesthetic subjects indicated that the synaesthete showed hyper activity within a
number of regions within this network (including primary somatosensory cortex) and
additional activity in the anterior insula (Figure 1.3). Thus suggesting that mirror-
touch synaesthesia is a consequence of increased neural activity in the same mirror-
touch network that is evoked in non-synaesthetic controls when observing touch to
another person (Blakemore et al., 2005).