SUPPLEMENTARY MATERIAL EXPERIMENTAL BRAIN RESEARCH

SUPPLEMENTARY MATERIAL EXPERIMENTAL BRAIN RESEARCH Supplementary Material - Grapheme-color synesthetes show peculiarities in their emotional brain cortical and subcortical evidence from VBM analysis of 3D-T1 and DTI data. Helena Melero 1,2, Ángel Peña-Melián 3, Marcos Ríos-Lago 4,5,6 Gonzalo Pajares 6, Juan Antonio Hernández-Tamames 6,7 and Juan Álvarez-Linera 6,8 1 Departmento de Psicobiología. Facultad de Psicología. Universidad Complutense de Madrid. España. 2 Departmento de Investigación, Desarrollo y Promoción. Fundación Internacional Artecittá. España. 3 Departmento de Anatomía y Embriología Humana I. Facultad de Medicina. Universidad Complutense de Madrid. España. 4 Departmento de Psicología Básica II. U ED. Madrid. España. 5 Unidad de Daño Cerebral. Hospital Beata Mariana. Madrid. España. 6 Laboratorio de Análisis de Imagen Médica. Fundación CIE -Fundación Reina Sofía. Madrid. España. 7 Departamento de Tecnología Electrónica. Universidad Rey Juan Carlos. Madrid. España. 8 Servicio de euroradiología. Hospital Ruber Internacional. Madrid. España. Corresponding author: Helena Melero h.melero.c@gmail.com

SUPPLEMENTARY MATERIAL - INTRODUCTION Table 1. Summary of published data on the neuroanatomy of developmental grapheme-color synesthesia. In columns: reference (authors and date of publication of each study); grey matter differences regarding increased cortical volume, cortical thickness and surface area; white matter differences in regard to cortical volume and fractional anisotropy. MNI coordinates and p/t values (synesthetes > nonsynesthetes) provided in each study. P values are uncorrected for multiple comparisons except where otherwise specified (FWE) PUBLICATIO GREY MATTER DIFFERE CES M I COORD. (Hupé et al. 2011) (Rouw and Scholte 2010) (Jäncke et al. 2009) P VALUE/ Max t Increased cortical volume Increased cortical thickness Increased surface area x y z Increased volume No suprathreshold voxels L. Superior parietal (projectors+associators > controls) predicted L. Calcarine sulcus/lingual gyrus R. Lingual gyrus intracalcarine cortex (V1) R. Fusiforn gyrus L. Pericallosal sulcus R. Rectal gyrus Predicted < 0.0001 R. - Retrosplenia l cortex L. Superior temporal sulcus -11-58 61 3.5 18-46 -5 3-69 8 34-34 -25-9 -48 19 9 26-22 0.0031 0.0034 0.0005 0.0052 0.0035 WHITE MATTER DIFFERE CES Increased fractional anisotropy M I COORD x y z P VALUE/ Max t pfwe = 0.019 pfwe = 0.075 - L. Hippocampus L. Optic radiation inferior frontooccipital fasciculus L. Inferior frontooccipital fasciculus L. Splenium of corpus callosum -9-33 -14-35 -52-4 -25 20 14-12 -40 11 0.000051 0.000231 0.00041 0.000004 R. Calcarine sulcus (V2) lingual gyrus R. Intracalcarine cortex (V1) R. Fusiform gyrus (anterior V4) extending into the anterior collateral transverse sulcus R. Lateral superior occipital cortex 24-51 -2 5-65 10 29-50 -14 45-79 21 0.0002 0.0011 0.0006 0.0042 L. Orbitofrontal cortex R. Central sulcus R. Rectal gyrus R. Middle temporal gyrus R. Postcentral gyrus R. Superior circular sulcus of insula -23 12-23 48-6 41 10 25-25 68-15 -19 61-10 40 46-14 22 0.0013 0.0008 0.0023 0.0031 0.0039 0.0042 - predicted L. Fusiform gyrus R. Lingual gyrus intracalcarine cortex (V1) R. Lateral occipital cortex R. Precuneus -39-38 -35 5-76 9 30-86 7 4-59 27 0.0013 0.0018 0.0021 0.0046 (Weiss and Fink 2009) (Rouw and Scholte 2007) L. Caudal IPS R. Fusiform Gyrus (V4 as described by Rottschy et al. 2007) L. Superior Temporal Sulcus L. Cingulate gyrus (main part) L. Superior circular sulcus of insula R. Inferior circular sulcus of insula R. Orbitofrontal cortex -6 20 29-35 -14 20 40-11 -13 25 54-14 -24-64 47 34-69 -11 45-20 -8 0.0006 0.0047 0.0027 0.0049 p svc < 0.05 p svc < 0.05 0.001 - - L. Superior Frontal R. Superior Frontal L Parietal R. Temporal 20 25 55 21 21 57 17 61 55 36 40 21 3.7 4.4 4.8 4.8

SUPPLEMENTARY MATERIAL - METHODS Participants All synesthetes could be considered associators (Dixon et al. 2004) on the basis of their qualitative responses to Hubbard s Questionnaire and the quantitative measures provided by the Illustrated Synaesthetic Experience Questionnaire (ISEQ) (Skelton et al. 2009). In the ISEQ, only one synesthete obtained a score which classifies her as undetermined; nevertheless, her qualitative responses and the positive sign of her score suggest she is an associator synesthete. They all have a history of lifelong synesthesia. The group is heterogeneous regarding the types of synesthesia experimented besides grapheme-color. Also, they provide slightly different descriptions of the space where synesthesias appear. Some of them localize their color on a black screen inside their heads, while others see the color over a copy of the number in their mind, or just describe it as something that is inside. One of the participants reports seeing moving colors and forms while listening to music; indeed, she projects her music synesthesia, though the color of her letters belong to the mind s eye and only a few times in her life have been projected. The group is homogeneous regarding the interplay between synesthesia and emotion: they all agree that emotions, be they negative or positive, can modify the intensity and peculiarities of their synesthetic experiences; for example, emotion can be the cause of an error in the concurrent elicited by some inducers and/or intensify or suppress synesthesia (see table 2 for detailed information about the sample).

Table 2. Detailed information about the participant s synesthesia. In columns: number assigned to each synesthete in the sample, lifelong experience, other family members experience synesthesia, localization of synesthesias, bidireccionality, other types of inducers beside graphemes (phonemes, dot sets, other modalities), impact of emotion and fatigue on the synesthetic experience Synesthete Lifelong Experience synesthetes in the family Gc Localized In Space Bidireccionality Phoneme Induces syn Dot Sets Induces syn Types Beside Gc Types Localized In Space S01 Yes Yes No No Yes No Yes Sometimes Yes S02 Yes No Rarely No Sometimes No Yes Yes Yes S03 Yes Yes No No Yes No Yes No Yes S04 Yes Don t No Sometimes Yes No Yes No Yes S05 Yes Don t No Almost never Yes No Yes No Yes S06 Yes Yes No No Yes Yes Yes No Yes S07 Yes No No No No No No - Yes S08 Yes Don t No No No No Yes No Yes Modified By Emotion and/or Fatigue SUPPLEMENTARY MATERIAL - RESULTS Fig. 1 First row: Increased grey matter volume in the left IPS of synesthetes (p unc < 0.01; local maxima at x = -30; y = -72; z = 50). Second row: Crosshair position at the significant local maxima depicted in first row. Shaded areas show a representation of the bilateral anterior IPS (IP3) at different probabilities as defined by the anatomy toolbox by Eickhoff et al. (2005)

SUPPLEMENTARY MATERIAL REFERENCES Dixon MJ, Smilek D, Merikle PM (2004) Not all synaesthetes are created equal: projector versus associator synaesthetes. Cogn Affect Behav Neurosci 4 (3):335-343. doi:doi:10.3758/cabn.4.3.335 Skelton R, Ludwig C, Mohr C (2009) A novel, illustrated questionnaire to distinguish projector and associator synaesthetes. Cortex 45 (6):721-729. doi:s0010-9452(08)00137-8 [pii] 10.1016/j.cortex.2008.02.006