Disruption of synaesthesia following TMS of the right posterior parietal cortex

This study examines the role of four regions of the parietal lobe in grapheme-colour synaesthesia. TMS applied over a right parieto-occipital region disrupts performance on a synaesthetic priming task. TMS over the left parietal or a more anterior right parietal site did not have a reliable effect on synaesthesia even though one of the sites had been implicated in synaesthesia by previous fMRI studies. The same disruption is found for synaesthetes who experience colours in their "mind's eye" as well as those who project colours onto the inducing grapheme. This region may be important for binding graphemes and colours to different spatial reference frames.

[1]  N. Kanwisher,et al.  The Generality of Parietal Involvement in Visual Attention , 1999, Neuron.

[2]  J. Ward,et al.  Synaesthesia for Reading and Playing Musical Notes , 2006, Neurocase.

[3]  E. T. Bullmore,et al.  Functional magnetic resonance imaging of synesthesia: activation of V4/V8 by spoken words , 2002, Nature Neuroscience.

[4]  Arno Villringer,et al.  Visual Feature and Conjunction Searches of Equal Difficulty Engage Only Partially Overlapping Frontoparietal Networks , 2002, NeuroImage.

[5]  Anina N. Rich,et al.  The effects of stimulus competition and voluntary attention on colour-graphemic synaesthesia , 2003, Neuroreport.

[6]  Daniel Smilek,et al.  Not all synaesthetes are created equal: Projector versus associator synaesthetes , 2004, Cognitive, Affective, & Behavioral Neuroscience.

[7]  Geoffrey M. Boynton,et al.  Individual Differences among Grapheme-Color Synesthetes: Brain-Behavior Correlations , 2005, Neuron.

[8]  Jamie Ward,et al.  Synaesthesia: The Prevalence of Atypical Cross-Modal Experiences , 2006, Perception.

[9]  A. Treisman,et al.  Parietal contributions to visual feature binding: evidence from a patient with bilateral lesions , 1995, Science.

[10]  Jason B. Mattingley,et al.  Attentional Load Attenuates Synaesthetic Priming Effects in Grapheme-Colour Synaesthesia , 2006, Cortex.

[11]  Alan Cowey,et al.  Temporal aspects of visual search studied by transcranial magnetic stimulation , 1997, Neuropsychologia.

[12]  E. Bullmore,et al.  Functional magnetic resonance imaging of synesthesia : activation of V 4 / V 8 by spoken words , 2002 .

[13]  C. Kennard,et al.  The anatomy of visual neglect. , 2003, Brain : a journal of neurology.

[14]  Jamie Ward,et al.  Varieties of grapheme-colour synaesthesia: A new theory of phenomenological and behavioural differences , 2007, Consciousness and Cognition.

[15]  Jamie Ward,et al.  Is Synaesthesia an X-Linked Dominant Trait with Lethality in Males? , 2005, Perception.

[16]  C. Kennard,et al.  The anatomy of visual neglect , 2003 .

[17]  Gereon R. Fink,et al.  When visual perception causes feeling: Enhanced cross-modal processing in grapheme-color synesthesia , 2005, NeuroImage.

[18]  S. Dehaene,et al.  Interactions between number and space in parietal cortex , 2005, Nature Reviews Neuroscience.

[19]  Richard B. Ivry,et al.  Coming Unbound: Disrupting Automatic Integration of Synesthetic Color and Graphemes by Transcranial Magnetic Stimulation of the Right Parietal Lobe , 2006, Journal of Cognitive Neuroscience.