Structural Brain Correlates of Synaesthesia

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Structural Brain Correlates of Synaesthesia

• Investigators
• Michael Banissy1, Neil Muggleton1, Ryota Kanai1,
  Vincent Walsh1
• Institute of Cognitive Neuroscience, UCL

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Background

• Synaesthesia
• Developmental condition in which one property of
  a stimulus leads to a secondary experience of
  another property not typically associated with
  the original stimulus.

• What we know
• Single DTI study on grapheme-colour synaesthesia
  (Rouw Scholte, 2007)
• Synaesthete-Control gt structural connectivity in
  inferior temporal, parietal and frontal brain
  regions.
• Greater connectivity in inferior temporal cortex
  was stronger for projectors compared with
  associators
• Presence of synaesthesia exerts a wider
  influence over veridical sensory processing
  (Barnett et al. 2008)
• VEP differences in L-C synaesthetes with simple
  visual stimuli (high spatial frequency Gabors)
  that do not evoke synaesthesia.
• The presence of synaesthesia is linked with
  enhanced sensory perception (Banissy et al. 2009)

• What we want to know
• What are the structural correlates of
  synaesthesia and how do they link with
  performance?
• Is synaesthesia linked to more widespread
  differences in sensory perception?

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Design

• DTI (2 x 2 x 2 mm)
• Gross and microstructural correlates of
  synaesthesia
• Contrast number of fibres and voxels through
  which fibers pass
• Contrast FA values in synaesthetes to control
  participants
• Contrast across subtypes of synaesthetes
• Correlate activations with behavioural
  performance (in both synaesthetes and
  non-synaesthetes)
• VBM and cortical thickness

• Synaesthetic Localiser
• Blocked design
• Strong synaesthetic inducing grapheme x Weak
  synaesthetic inducing grapheme x Non-synaesthetic
  inducing grapheme

• Retinotopy
• Comparing synaesthetes to control
• DTI based on retinotopy