The genetics of colored sequence synesthesia: Suggestive evidence of linkage to 16q and genetic heterogeneity for the condition
Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA. Behavioural brain research
(Impact Factor: 3.03).
09/2011; 223(1):48-52. DOI: 10.1016/j.bbr.2011.03.071
Synesthesia is a perceptual condition in which sensory stimulation triggers anomalous sensory experiences. In colored sequence synesthesia (CSS), color experiences are triggered by sequences such as letters or numbers. We performed a family based linkage analysis to identify genetic loci responsible for the increased neural crosstalk underlying CSS. Our results implicate a 23 MB region at 16q12.2-23.1, providing the first step in understanding the molecular basis of CSS.
Available from: Duncan A Carmichael
- "In combination with previous studies from our own lab and elsewhere, we conclude there no very strong female bias (Simner et al., 2009, 2006), that families containing synaesthetes are equally likely to produce female or male offspring (Barnett et al., 2008; Ward & Simner, 2005), that there are confirmed cases of male-to-male transmission (Asher et al., 2009), and one case of monozygotic male twins who are discordant for synaesthesia (Smilek, Dixon & Merikle, 2005). Finally, neither Asher et al. (2009) nor Tomson et al. (2011) "
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ABSTRACT: Synaesthesia is a familial condition that gives rise to unusual secondary percepts. We present a large-scale prevalence study which informs our ideas on whether the condition is more prevalent in men or women. A number of studies over the last 20 years have suggested the condition is found more commonly in women, with up to six times more female synaesthetes than male. Other studies attributed this female bias to merely a recruitment confound: women synaesthetes may be more likely to self-refer for study. We offer two pieces of evidence that there is no extreme female bias in synaesthesia: first we re-analyse previous reports of very large female biases to show again that they likely arose from self-referral or other methodological issues. Second, we present the largest published prevalence study to date on grapheme→colour synaesthesia in which our prevalence (1.39% of the population) replicates our earlier estimates (e.g., Simner et al., 2006) and in which we demonstrate no strong female bias even with sufficient power to detect such a difference.
Available from: Hannah Bosley
- "In line with previous studies    , we find suggestive evidence of a heritable element of synesthesia. However, consonant with the findings of Smilek et al.   our large sample size verifies that synesthesia is not completely conferred by genetics (otherwise monozygotic twins would have had 100% concordance). "
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ABSTRACT: Colored-sequence synesthesia (CSS) is a neurological condition in which sequential stimuli such as letters, numbers, or days of the week trigger simultaneous, involuntary color perception. Although the condition appears to run in families and several studies have sought a genetic link, the genetic contribution to synesthesia remains unclear. We conducted the first comparative twin study of CSS and found that CSS has a pairwise concordance of 73.9% in monozygotic twins, and a pairwise concordance of 36.4% in dizygotic twins. In line with previous studies, our results suggest a heritable element of synesthesia. However, consonant with the findings of previous single-pair case studies, our large sample size verifies that synesthesia is not completely conferred by genetics; if it were, monozygotic twins should have 100% concordance. These findings implicate a genetic mechanism of CSS that may work differently than previously thought: collectively, our data suggest that synesthesia is a heritable condition with incomplete penetrance that is substantially influenced by epigenetic and environmental factors.
Copyright © 2015. Published by Elsevier B.V.
Available from: Romke Rouw
- "This is most commonly interpreted as reflecting the “hyper binding” present in synesthetes (although the parietal cortex has also other roles (Hubbard et al., 2005b; Cohen Kadosh et al., 2008). Importantly, next to these behavioral and brain differences between synesthetes and non-synesthetes, there is evidence for a genetic predisposition for synesthesia (Asher et al., 2009; Brang and Ramachandran, 2011; Mitchell, 2011; Tomson et al., 2011) and synesthesia has been found “running in the family” (Barnett et al., 2008a). The studies on the patterns of color preferences show how the nature of the color experiences are different: the (putative) synesthetes show more diverse, more specific, more consistent color associations than the non-synesthetes (Palmeri et al., 2002; Hubbard and Ramachandran, 2005; Eagleman et al., 2007). "
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ABSTRACT: While colors are commonplace in everyday metaphors, relatively little is known about implicit color associations to linguistic or semantic concepts in a general population. In this study, we test color associations for ordered linguistic concepts (letters and days). The culture and language specificity of these effects was examined in a large group (457) of Dutch-speaking participants, 92 English-speaking participants, and 49 Hindi-speaking participants. Non-random distributions of color choices were revealed; consistencies were found across the three language groups in color preferences for both days and letters. Interestingly, while the Hindi-speaking participants were presented with letter stimuli matched on phonology, their pattern of letter-to-color preferences still showed similarities with Dutch- and English-speaking participants. Furthermore, we found that that the color preferences corresponded between participants indicating to have conscious color experiences with letters or days (putative synesthetes) and participants who do not (non-synesthetes). We also explored possible mechanisms underlying the color preferences. There were a few specific associations, including red for "A," red for "Monday," and white for "Sunday." We also explored more general mechanisms, such as overall color preferences as shown by Simner et al. (2005). While certainly not all variation can be explained or predicted, the results show that regularities are present in color-to-letter or color-to-day preferences in both putative synesthetes and non-synesthetes across languages. Both letter-to-color and day-to-color preferences were influenced by multiple factors. The findings support a notion of abstract concepts (such as days and letters) that are not represented in isolation, but are connected to perceptual representational systems. Interestingly, at least some of these connections to color representations are shared across different language/cultural groups.
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