Grapheme-color synesthetes show peculiarities in their emotional brain: cortical and subcortical evidence from VBM analysis of 3D-T1 and DTI data

Abstract

Grapheme-color synesthesia is a neurological phenomenon in which viewing achromatic letters/numbers leads to automatic and involuntary color experiences. In this study, voxel-based morphometry analyses were performed on T1 images and fractional anisotropy measures to examine the whole brain in associator grapheme-color synesthetes. These analyses provide new evidence of variations in emotional areas (both at the cortical and subcortical levels), findings that help understand the emotional component as a relevant aspect of the synesthetic experience. Additionally, this study replicates previous findings in the left intraparietal sulcus and, for the first time, reports the existence of anatomical differences in subcortical gray nuclei of developmental grapheme-color synesthetes, providing a link between acquired and developmental synesthesia. This empirical evidence, which goes beyond modality-specific areas, could lead to a better understanding of grapheme-color synesthesia as well as of other modalities of the phenomenon.

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Abbreviations

GC:

Grapheme-color synesthesia

VBM:

Voxel-based morphometry

DTI:

Diffusion tensor imaging

DARTEL:

Diffeomorphic anatomical registration through exponentiated lie algebra method

FA:

Fractional anisotropy

FG:

Fusiform gyrus

IPS:

Intraparietal sulcus

TMS:

Transcranial magnetic stimulation

ORS:

Oscillatory resonance supervenience model

PHg:

Parahippocampal gyrus

TP:

Temporal pole

aIN:

Anterior insula

RSC:

Retrosplenial cortex

ACG:

Anterior cingulate gyrus

MdFG:

Middle frontal gyrus

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Acknowledgments

We thank the participants and the technical staff at the 3T scanner facility of Fundación Centro de Investigación de Enfermedades Neurológicas for their indispensable collaboration in this study. Financial support was provided by Universidad Complutense de Madrid, Fundación Centro de Investigación de Enfermedades Neurológicas and Ministerio de Ciencia e Innovación PSI2009-14415-C03-03. The authors declare that they have no competing interests. This work conforms to Standard 8 of the American Psychological Association’s Ethical Principles of Psychologist and Code of Conduct.

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Correspondence to Helena Melero.

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Melero, H., Peña-Melián, Á., Ríos-Lago, M. et al. Grapheme-color synesthetes show peculiarities in their emotional brain: cortical and subcortical evidence from VBM analysis of 3D-T1 and DTI data. Exp Brain Res 227, 343–353 (2013). https://doi.org/10.1007/s00221-013-3514-4

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Keywords

  • Grapheme-color synesthesia
  • Voxel-based morphometry
  • Cortical emotional areas
  • Subcortical gray nuclei