Color-grapheme synesthesia: A study of population prevalence

Given the current state of the literature and weaknesses of many previous prevalence studies, the primary purpose of this research study was to gather base-rate data of color-grapheme synesthesia in a general population sample. Over a period of seven months, 502 participants enrolled in the study on Mechanical Turk and completed the online Synesthesia Battery. The primary data collected was the participant’s score on the synesthesia test, whereby a score of a one or below is deemed by the battery to be indicative of someone with a color-grapheme synesthetic ability. Of the 502 participants, eight percent (0.082) of the population sampled had scores below one, the cutoff suggestive of synesthesia on the Synesthesia Battery. This is a much higher percentage of the population than previously reported by previous studies. Exploratory analyses of demographic variables revealed some significant findings for handedness and education, such that left-handed people may have a greater representation among synesthetes than right-handed people and participants meeting the one score cutoff suggestive of synesthesia were more likely to have a graduate education

Synestetické asociace a psychopatologické symptomy.

1 Synestetické asociace a psychopatologické symptomy Marcel Necká Abstrakt Synestézie v obecném smyslu p edstavuje jev intersenzorického a intrasenzorického propojení, které m že být pozorováno za r zných fyziologických a patologických okolností, nap íklad jako kreativita v um ní nebo v ípad n kterých mozkových dysfunkcí. Synestézie jako jev je p edevším formována prost ednictvím transmodálních asociativních spojení, které mohou tvo it kontinuum od tzv. "silných" synestetických jev až k jejím mírným formám, které pravd podobn umož ují tvorbu synestetických metaphor a imaginace. Tato studie je zam ena na projektivní analýzu slovn barevných asociací a jejich vztahu k psychoaptologickým m ením reflektujícím stres, depresi, disociaci a dalších psychometrických m ení u 154 ú astník vybraných z obecné populace. Výsledky této studie jsou v souladu s dosavadními publikovanými poznatky, které dokládají, že sv tlejší barvy jsou mnohem ast ji asociovány s pozitivními emocionálními významy ve srovnání s tmavšími barvami. Navíc výsledky této studie ukazují vztahy t chto barevn -slovních asociací k psychopatologickým symptom m a to prost ednictvím vztahu n kterých specifických slov k symptom m deprese, úzkosti, alexithymie a n kterým symptom m traumatického stresu. Tyto výsledky jsou v souladu s existujícími poznatky...1 Synesthetic associations and psychopathological symptoms Marcel Necká Abstract Synesthesia in general is a phenomenon of intersensory and intrasensory linkage that may be observed in various conditions including artistic creativity and also manifests in conditions of various brain dysfunctions and injuries. Synesthesia is a phenomenon represented by transmodal associative connections that may represent a continuum from strong synesthetic phenomena to its mild forms that may enable creation of "synesthetic" metaphors. This study is focused on projective assessments of word-color association and their relationship to psychopathological measures reflecting stress, depression, dissociation and other psychometric measures in 154 participants selected from general population. The results are in agreement with previous reported studies suggesting that lighter colors are more frequently associated with positive emotional meanings. In addition the results indicate significant relationships of color- word associations to some specific words with depression, anxiety, alexithymia and symptoms of traumatic stress. These results are in ac-cordance with existing findings in context of the so-called metaphorical synesthesia where significant role might be attributed to color intensity. In this context, results of this...Psychiatrická klinika 1. LF a VFN v PrazeDepartment of Psychiatry First Faculty of Medicine and General University Hospital in PragueFirst Faculty of Medicine1. lékařská fakult

Short- and Long-range Neural Synchrony in Grapheme–Color Synesthesia

Grapheme–color synesthesia is a perceptual phenomenon where single graphemes (e.g., the letter “E”) induce simultaneous sensations of colors (e.g., the color green) that were not objectively shown. Current models disagree as to whether the color sensations arise from increased short-range connectivity between anatomically adjacent grapheme- and color-processing brain structures or from decreased effectiveness of inhibitory long-range connections feeding back into visual cortex. We addressed this issue by examining neural synchrony obtained from EEG activity, in a sample of grapheme–color synesthetes that were presented with color-inducing versus non-color-inducing graphemes. For color-inducing graphemes, the results showed a decrease in the number of long-range couplings in the theta frequency band (4–7 Hz, 280–540 msec) and a concurrent increase of short-range phase-locking within lower beta band (13–20 Hz, 380–420 msec at occipital electrodes). Because the effects were both found in long-range synchrony and later within the visual processing stream, the results support the idea that reduced inhibition is an important factor for the emergence of synesthetic colors

Automatic letter-colour associations in non-synaesthetes and their relation to grapheme-colour synaesthesia

Although grapheme-colour synaesthesia is a well-characterized phenomenon in which achromatic letters and/or digits involuntarily trigger specific colour sensations, its underlying mechanisms remain unresolved. Models diverge on a central question: whether triggered sensations reflect (i) an overdeveloped capacity in normal cross-modal processing (i.e., sharing characteristics with the general population), or rather (ii) qualitatively deviant processing (i.e., unique to a few individuals). We here address this question on several fronts: first, with adult synaesthesia-trainees and second with congenital grapheme-colour synaesthetes. In Chapter 3, we investigate whether synaesthesia-like (automatic) letter-colour associations may be learned by non- synaesthetes into adulthood. To this end, we developed a learning paradigm that aimed to implicitly train such associations while keeping participants naïve as to the end-goal of the experiments (i.e., the formation of letter-colour associations), thus mimicking the learning conditions of acquired grapheme- colour synaesthesia (Hancock, 2006; Witthoft & Winawer, 2006). In two experiments, we found evidence for significant binding of colours to letters by non-synaesthetes. These learned associations showed synaesthesia-like characteristics despite an absence of conscious, colour concurrents, correlating with individual performance on synaesthetic Stroop-tasks (experiment 1), and modulated by the colour-opponency effect (experiment 2) (Nikolic, Lichti, & Singer, 2007), suggesting formation on a perceptual (rather than conceptual) level. In Chapter 4, we probed the nature of these learned, synaesthesia-like associations by investigating the brain areas involved in their formation. Using transcranial Direct Current Stimulation to interfere with two distinct brain regions, we found an enhancement of letter-colour learning in adult trainees following dlPFC-stimulation, suggesting a role for the prefrontal cortex in the release of binding processes. In Chapter 5, we attempt to integrate our results from synaesthesia-learners with the neural mechanisms of grapheme-colour synaesthesia, as assessed in six congenital synaesthetes using novel techniques in magnetoencephalography. While our results may not support the existence of a “synaesthesia continuum,” we propose that they still relate to synaesthesia in a meaningful way