Developmental aspects of synaesthesia across the adult lifespan

In synaesthesia, stimuli such as sounds, words or letters trigger experiences of colors, shapes or tastes and the consistency of these experiences is a hallmark of this condition. In this study we investigate for the first time whether there are age-related changes in the consistency of synaesthetic experiences. We tested a sample of more than 400 grapheme-color synaesthetes who have color experiences when they see letters and/or digits with a well-established test of consistency. Our results showed a decline in the number of consistent grapheme-color associations across the adult lifespan. We also assessed age-related changes in the breadth of the color spectrum. The results showed that the appearance of primary colors (i.e., red, blue, and green) was mainly age-invariant. However, there was a decline in the occurrence of lurid colors while brown and achromatic tones occurred more often as concurrents in older age. These shifts in the color spectrum suggest that synaesthesia does not simply fade, but rather undergoes more comprehensive changes. We propose that these changes are the result of a combination of both age-related perceptual and memory processing shifts.

Developing synaesthesia: A primer (Editorial)

Synaesthesia is a variation of human experience that involves the automatic activation of unusual concurrent experiences in response to ordinary inducing stimuli. The causes for the development of synaesthesia are not well understood yet. Synaesthesia may have a genetic basis resulting in enhanced cortical connectivity during development. However, in some cases synaesthesia has a sudden onset, for example, caused by posthypnotic suggestions, drug exposure, or brain injury. Moreover, associative learning during a critical developmental period also seems to play an important role. Synaesthesia may even be acquired by training in adulthood. In this research topic, we bring together topical hypotheses, theories and empirical studies about the development of synaesthesia.

Developing Synaesthesia

Synaesthesia is a condition in which a stimulus elicits an additional subjective experience. For example, the letter E printed in black (the inducer) may trigger an additional colour experience as a concurrent (e.g., blue). Synaesthesia tends to run in families and thus, a genetic component is likely. However, given that the stimuli that typically induce synaesthesia are cultural artefacts, a learning component must also be involved. Moreover, there is evidence that synaesthetic experiences not only activate brain areas typically involved in processing sensory input of the concurrent modality; synaesthesia seems to cause a structural reorganisation of the brain. Attempts to train non-synaesthetes with synaesthetic associations have been successful in mimicking certain behavioural aspects and posthypnotic induction of synaesthetic experiences in non-synaesthetes has even led to the according phenomenological reports. These latter findings suggest that structural brain reorganization may not be a critical precondition, but rather a consequence of the sustained coupling of inducers and concurrents. Interestingly, synaesthetes seem to be able to easily transfer synaesthetic experiences to novel stimuli. Beyond this, certain drugs (e.g., LSD) can lead to synaesthesia-like experiences and may provide additional insights into the neurobiological basis of the condition. Furthermore, brain damage can both lead to a sudden presence of synaesthetic experiences in previously non-synaesthetic individuals and a sudden absence of synaesthesia in previously synaesthetic individuals. Moreover, enduring sensory substitution has been effective in inducing a kind of acquired synaesthesia. Besides informing us about the cognitive mechanisms of synaesthesia, synaesthesia research is relevant for more general questions, for example about consciousness such as the binding problem, about crossmodal correspondences and about how individual differences in perceiving and experiencing the world develop. Hence the aim of the current Research Topic is to provide novel insights into the development of synaesthesia both in its genuine and acquired form. We welcome novel experimental work and theoretical contributions (e.g., review and opinion articles) focussing on factors such as brain maturation, learning, training, hypnosis, drugs, sensory substitution and brain damage and their relation to the development of any form of synaesthesia.

Enhanced associative memory for colour (but not shape or location) in synaesthesia

People with grapheme-colour synaesthesia have been shown to have enhanced memory on a range of tasks using both stimuli that induce synaesthesia (e.g. words) and, more surprisingly, stimuli that do not (e.g. certain abstract visual stimuli). This study examines the latter by using multi-featured stimuli consisting of shape, colour and location conjunctions (e.g. shape A + colour A + location A; shape B + colour B + location B) presented in a recognition memory paradigm. This enables distractor items to be created in which one of these features is ‘unbound’ with respect to the others (e.g. shape A + colour B + location A; shape A + colour A + location C). Synaesthetes had higher recognition rates suggesting an enhanced ability to bind certain visual features together into memory. Importantly, synaesthetes’ false alarm rates were lower only when colour was the unbound feature, not shape or location. We suggest that synaesthetes are “colour experts” and that enhanced perception can lead to enhanced memory in very specific ways; but, not for instance, an enhanced ability to form associations per se. The results support contemporary models that propose a continuum between perception and memory.

Diagnosing synaesthesia with online colour pickers: Maximising sensitivity and specificity

The most commonly used method for formally assessing grapheme-colour synaesthesia (i.e., experiencing colours in response to letter and/or number stimuli) involves selecting colours from a large colour palette on several occasions and measuring consistency of the colours selected. However, the ability to diagnose synaesthesia using this method depends on several factors that have not been directly contrasted. These include the type of colour space used (e.g., RGB, HSV, CIELUV, CIELAB) and different measures of consistency (e.g., city block and Euclidean distance in colour space). This study aims to find the most reliable way of diagnosing grapheme-colour synaesthesia based on maximising sensitivity (i.e., ability of a test to identify true synaesthetes) and specificity (i.e., ability of a test to identify true non-synaesthetes). We show, applying ROC (Receiver Operating Characteristics) to binary classification of a large sample of self-declared synaesthetes and non-synaesthetes, that the consistency criterion (i.e., cut-off value) for diagnosing synaesthesia is considerably higher than the current standard in the field. We also show that methods based on perceptual CIELUV and CIELAB colour models (rather than RGB and HSV colour representations) and Euclidean distances offer an even greater sensitivity and specificity than most currently used measures. Together, these findings offer improved heuristics for the behavioural assessment of grapheme-colour synaesthesia.

Correcting misconceptions about synaesthesia

In the annals of cognitive neuroscience there are examples of fantastic memory abilities (e.g., Luria, 1968) that befuddle the vast majority of us with normal mnemonic skills. Although such feats have yet to be demonstrated in other species, extraordinary memory may not be unique to humans. One possible example comes from a study by Inoue and Matsuzawa (2007), which showed that following extensive training, a chimpanzee, Ayumu, displayed superior working memory than human volunteers. Recently, Humphrey (2012) hypothesized that Ayumu outperformed the human participants because he had synaesthesia, a condition in which a stimulus (an inducer) will involuntarily elicit an atypical ancillary experience (a concurrent) (e.g., graphemes eliciting color photisms) (Ward, 2013). Specifically, Humphrey posits that Ayumu spontaneously developed grapheme-colour synaesthesia through “cross-cortical leakage” (p. 354) between the parietal cortex, which may support the storage of overlearned sequences, and adjacent colour-coding regions, during working memory training. Humphrey speculates that the synaesthetic associations elicited colour after-images during training with numerals, and, in turn, facilitated superior performance. Here we challenge this hypothesis and argue that it makes a number of assumptions that are not supported by current research.

Digital signage application : developing a public venue multimedia touch-screen

La señalización digital o digital signage es una tecnología de comunicaciones digital que se está usando en los últimos años para reemplazar a la antigua publicidad impresa. Esta tecnología mejora la presentación y promoción de los productos anunciados, así como facilita el intercambio de información gracias a su colocación en lugares públicos o al aire libre. Las aplicaciones con las que cuenta este nuevo método de publicidad son muy variadas, ya que pueden variar desde ambientes privados en empresas, hasta lugares públicos como centros comerciales. Aunque la primera y principal utilidad de la señalización digital es la publicidad para que el usuario sienta una necesidad de adquirir productos, también la posibilidad de ofrecer más información sobre determinados artículos a través de las nuevas tecnologías es muy importante en este campo. La aplicación realizada en este proyecto es el desarrollo de un programa en Adobe Flash a través de lenguaje de programación XML. A través de una pantalla táctil, el usuario de un museo puede interactivamente acceder a un menú en el que aparecen los diferentes estilos de arte en un determinado tiempo de la historia. A través de una línea de tiempo se puede acceder a información sobre cada objeto que esté expuesto en la exhibición. Además se pueden observar imágenes de los detalles más importantes del objeto que no pueden ser vistos a simple vista, ya que no está permitido manipularlos. El empleo de la pantalla interactiva sirve para el usuario de la exhibición como una herramienta extra para recabar información sobre lo que está viendo, a través de una tecnología nueva y fácil de usar para todo el mundo, ya que solo se necesita usar las propias manos. La facilidad de manejo en aplicaciones como estas es muy importante, ya que el usuario final puede no tener conocimientos tecnológicos por lo que la información debe darse claramente. Como conclusión, se puede decir que digital signage es un mercado que está en expansión y que las empresas deben invertir en el desarrollo de contenidos, ya que las tecnologías avanzan aunque el digital signage no lo haga, y este sector podría ser muy útil en un futuro no muy lejano, ya que la información que es capaz de transmitir al espectador en todos los lugares es mucho más válida y útil que la proporcionada por un simple póster impreso en una valla publicitaria. Abstract The Digital signage is a digital communications technology being used in recent years to replace the old advertising printed. This technology improves the presentation and promotion of the advertised products, and makes easy the exchange of information with its placement in public places or outdoors. The applications that account this new method of advertising are several; they can range from private rooms in companies, to public places like malls. Although the first major utility of Digital signage is the advertising that makes the user feel and need of purchasing products. In addition, the chance of providing more information about certain items through new technologies is very important in this field. The application made in this project is the development of a program in Adobe Flash via XML programming language. Through a touch-screen, a museum user can interactively access a menu in which different styles of art in a particular time in history appears. Through a timeline you can access to information about each object that is exposed on display. Also you can see pictures of the most important details of the object that can not be seen with the naked eye, since it is not allowed to manipulate it. The use of the interactive screen serves to the user exhibition as an extra tool to gather information about what is seeing through a new technology and easy to use for everyone, since only need to use one’s own hands. The ease of handling in applications such as this is very important as the end user may not have expertise technology so the information should be clearly. As conclusion, one can say digital signage is an expansion market and companies must invest in content development, as although digital technologies advance digital signage does not, and this sector could be very useful in a near future, because information that is able of transmitting the everywhere viewer is much more valid and useful than that provided by a simple printed poster on a billboard.

P2Y1 purinergic receptors in sensory neurons: contribution to touch-induced impulse generation.

Somatic sensation requires the conversion of physical stimuli into the depolarization of distal nerve endings. A single cRNA derived from sensory neurons renders Xenopus laevis oocytes mechanosensitive and is found to encode a P2Y1 purinergic receptor. P2Y1 mRNA is concentrated in large-fiber dorsal root ganglion neurons. In contrast, P2X3 mRNA is localized to small-fiber sensory neurons and produces less mechanosensitivity in oocytes. The frequency of touch-induced action potentials from frog sensory nerve fibers is increased by the presence of P2 receptor agonists at the peripheral nerve ending and is decreased by the presence of P2 antagonists. P2X-selective agents do not have these effects. The release of ATP into the extracellular space and the activation of peripheral P2Y1 receptors appear to participate in the generation of sensory action potentials by light touch.

Genetic interactions affecting touch sensitivity in Caenorhabditis elegans.

At least 13 genes (mec-1, mec-2, mec-4-10, mec-12, mec-14, mec-15, and mec-18) are needed for the response to gentle touch by 6 touch receptor neurons in the nematode Caenorhabditis elegans. Several, otherwise recessive alleles of some of these genes act as dominant enhancer mutations of temperature-sensitive alleles of mec-4, mec-5, mec-6, mec-12, and mec-15. Screens for additional dominant enhancers of mec-4 and mec-5 yielded mutations in previously known genes. In addition, some mec-7 alleles showed allele-specific, dominant suppression of the mec-15 touch-insensitive (Mec) phenotype. The dominant enhancement and suppression exhibited by these mutations suggest that the products of several touch genes interact. These results are consistent with a model, supported by the known sequences of these genes, that almost all of the touch function genes contribute to the mechanosensory apparatus.