Synesthesia: Causes and Effects of the Disorder, Research Paper Example

Abstract

The present paper is dedicated to the research of the synesthesia disorder, a unified perception of letters, colors, and sometimes digits because of the developmental peculiarities of neural connections in the gray matter of the human brain. The first part of the paper discusses the possible causes of synesthesia and explores two models of the disorder development. Further on, the research is dedicated to the issues of synesthesia being bidirectional, the exploration of the ordinal linguistic personification (OLP) phenomenon, and the implications of synesthesia and its effect on learning, memory, and perception. The conclusion is reached that the future research in synesthesia is necessary to identify the mechanisms of sensory perception in the cortical area of the human brain, and it may provide a deeper understanding of the essence of sensory impulses, as well as give the insight into how to approach teaching a synesthete in the most productive and comprehensive manner.

Introduction

There are a great number of psychological disorders, and synesthesia takes a reasonable place within their scope. The reason for the relatively current recognition of synesthesia as a mental disorder is that the strange ability to perceive one sensory stimulus in an unusual conjunction with some other sensory stimuli has long been considered a weird but normal ability, the gift for the creative, extraordinary people. Nonetheless, the scientific evidence of the neural disorder occurring in the brain and causing that conjunction of sensory stimuli has been found in the course of the 20^th century. Therefore, the causes and possible consequences of the disorder, its major ways of revelation in the human perception as well as connections existing between various types of stimuli are the major subjects of research.

There have been found several scientific articles dedicated to the issues of defining and exploring synesthesia; all of them are valuable for the present review in their own way as the reveal the subject from several angles. For example, the article of Maechler (2009) is a personal account of the author about the experience of being a synesthete, and the exploration of causes and outer symptoms of synesthesia in daily life. Maechler (2009) gives the following definition to the conventional form of synesthesia as felt by the carriers of the disorder:

“Synesthesia is a condition where the stimulation of one sense may elicit the activation of other senses. Synesthetes…perceive their surrounding differently from other people: music can be colored, letters and numbers have genders and personalities, and shapes may have a taste” (Maechler, 2009, p. 2).

Further on, the author explores the most widespread forms of synesthesia; being explored since the 1800s, the disorder is most commonly revealed in a grapheme-color-synesthesia (Maechler, 2009). The cause of the present form of the disease is seen in “an activation of the left human brain area V4 responsible for colors” (Maechler, 2009, p. 2). Since synesthesia has long been considered a product of one’s imagination and there have been no tools to check the validity of synesthetes’ experiences with images and colors, the body of knowledge on the causes of this disorder is truly scarce nowadays. However, some findings suggest that synesthetes have the increased mass of grey matter in specific parts of their brain, and more intense “neuronal connectivity between different brain regions” is observed in synesthetes in contrast to ordinary people with conventional, mono-perceptions (Maechler, 2009, p. 3).

The article is interesting in the framework of studying synesthesia because the author covers many aspects of the disorder, including the literature overview in the attempt to identify the probability of disorder occurrence in certain demographic groups, e.g. gender or race dominance (Maechler, 2009). In addition, the author is genuinely interested in the ways to identify the intensity of synesthesia and the outward reflections of its intensity, the gradation of awareness about one’s having a synesthesia disorder and the impact this awareness may pose on the social interaction of people, the synesthetic experience verbalization, attentional awareness etc. (Maechler, 2009). Finally, the findings of Maechler (2009) refer to the widely discussed impact of synesthesia on the learning ability; the researcher reviews the hypothesis about the increased memory capacity, the overall ability to learn, and the function of school in mediating the effect of the synesthetic perception.

Another article chosen for the present research reveals the nature of synesthesia, its neural causes and the connection between the perceptual reality of synesthetes and the neural basis of synesthesia (Spector & Maurer, 2009). The authors contribute much to the understanding of synesthesia causes, thus expanding the general statements given by Maecher (2009). The present research is closely focused on the theories of developmental models of synesthesia, one titled the cross-activation model, and another one – the feedback theory.

The cross-activation theory is based on the assumption that all sensory cortical areas of the human brain are traditionally in charge of one sensory modality, with the sensual perceptions being transmitted to the corresponding cortical zone by means of neural connections in the brain (Spector & Maurer, 2009). However, the brain of a synesthete usually has the cortical areas cross-activated by means of synapses pruning not complete between particular contiguous areas in the developmental process (Spector & Maurer, 2009). Therefore, the activation of one sensory area may activate an accompanying impulse to another sensory area that is not conventionally activated in the sensory process of that kind. The sensory areas of synesthetes appear not as specialized as the ones of people without a disorder, being responsible for several sensory impulses at once (Spector & Maurer, 2009).

Another theory explored by Spector and Maurer (2009) is the feedback theory that states synesthesia emerges in case re-entrant feedback developing from higher cortical areas to the lower ones is not strong enough to inhibit the effects from connections between primary sensory cortical areas, which causes the additional connections emerging in the unpredicted manner (Spector & Maurer, 2009). As compared to people without the synesthesia disorder, the human brain is expected to fire the neurons consistent with the expected stimulus, and inhibit the inconsistent neurons. In case this process does not occur, the disinhibited feedback may penetrate to other sensory cortical areas and cause the synesthetic effect. However, one should note that both theories described as the aspects of the normal developmental processes of the human brain (Spector & Maurer, 2009).

The researchers investigate the notion of adult synesthesia with regard to the ability of infants to associate sounds with images, colors and scents, and argue that the synesthesia research may be useful and fruitful not only for the field of neuropsychology but for philology, developmental science and many other fields:

“adult synesthesia can inform the study of the development of perception and even of language, because it appears to represent one way in which normal developmental mechanisms can play out. In a sense, it magnifies connections present in early life that are pruned and/or inhibited during development and that persist in muted form in all adults” (Spector & Maurer, 2009, p. 175).

The present quotation suggests a vast field of research and discovery in synesthesia that will enhance many other sciences. The researchers continue to research the neural basis of synesthesia and support the findings of Maechler (2009) about the activation of certain brain areas and increase in the mass of gray matter for synesthetes. They also add some more detailed brain change information deriving from recent in-depth mechanisms –

“in some studies, there was activation of the primary visual cortex, of a number of higher visual association areas, and of areas in the parietal cortex in the angular gyrus that bind color to shape” (Spector & Maurer, 2009, p. 176).

Deriving the judgment on the essence and cause of synesthesia from the review of Maechler (2009) and Spector and Maurer (2009), one can proceed to the discussion of consequences of various types of synesthesia and the experiments conducted recently to estimate the synesthesia effect on learning, perception, and cognitive interrelation of various stimuli presented to synesthetes. The current research is mostly focused on several issues about synesthesia: first of all, it is the ability of synesthesia to influence overt visual perception (discussed in the work of Carriere, Eaton, Reynolds, Dixon, and Smilek (2008)), the connection of ordinal linguistic personification (OLP) with the synesthetic perception of linguistic units (reviewed in the work of Simner and Holenstein (2007)), and the study of the unidirectional vs. bidirectional nature of the letter-color or digit-color synesthesia researched by Weiss, Kalckert, and Fink (2008). Each of the works covers a substantial amount of material directly pertaining to the issues at the foreground of synesthesia research: whether the disorder is revealed at the occurrence of any of the stimuli, both the stimuli and the concurrent, and in which way the sensory interconnections are revealed in the synesthetes’ practice.

The study of Simner and Holenstein (2007) is highly topical for the present paper as it explores not only the image-color connected perception of synesthetes, but the ordinal linguistic personification that refers to an additional connection between colors, letters, and attribution of animate-like qualities to them, such as gender and personality. The researchers also have their neuro-physiological grounding or the phenomenon:

“The condition is thought to arise from a neurodevelopmental tendency to preserve or develop atypical interactions between brain regions that normally do not communicate” (Simner & Holenstein, 2007, p. 694).

The findings Simner and Holenstein (2007) reach in their research are that OLP co-occurs with other variants of synesthesia, and that OLP associations are highly consistent over time, in contrast to people who have not the disorder but the temporary synesthesia occurring during drug impact and other external influences. In addition, the researchers assume that OLP has a letter-to-word transference, which means that animate-like features may be distributed not only to separate letters but to coherent words as well. The inferences they make are connected to both the “projector” and the “associator” synesthesia types (Simner & Holenstein, 2007).

Another article, the one of Weiss et al. (2008), is dedicated to finding the bidirectional nature of synesthesia. The present research aims at identifying whether only letters induce the synesthetes to associate them with colors or other sensory perceptions, or the certain colors or color combinations, shapes etc. may have the potential for the reverse effect, i.e. instigating the letter association. The authors conclude that

“an implicit activation of the letter representation can be elicited by the color which corresponds to the colored synesthetic photism associated with that letter” (Weiss et al., 2008).

Making this inference, the authors actually prove the bidirectional nature of the synesthesia disorder and open new possibilities for the research from various angles, by tying the associations to both letters and colors being the initial stimuli.

Finally, the article of Carriere et al. (2008) contributes to the present research greatly as it examines the ability of synesthesia to influence overt visual perception. The authors state that synesthetes have a color congruity bias, and they manage to fixate the congruently colored letters much better, quicker, and for a much more sustainable period of time than they do with incongruently colored letters (Carriere et al., 2008). The research pertains directly to the investigation of the visual attention patterns of synesthetes, which may have a tremendous impact on the design of learning curricula for them that would suit their specific learning needs. The authors conclude that “both a congruity bias and deficits in identifying incongruently colored letters influence the eye movements of grapheme–color synesthetes” (Carriere et al., 2008, p. 257). These findings make a serious input into the study of the cognitive and perceptional patterns enacted in the synesthetes’ perception and attribution of meaning to the letters or colors seen. Further on, the results suggest more attention to both high-level and low-level sensory processes that take place in the human brain.

Drawing a conclusion from the present account of the synesthesia disorder, one may refer to the finding of Spector and Maurer (2009) that synesthesia is both an intersensory and intrasensory phenomenon that derives from the balance of synaptic pruning and mixture of responsibilities of the sensory cortical areas or the improper inhibition of inconsistent neural signals coming to the human brain. The disorder is not fully researched yet, and there any many aspects needing urgent attention and examination for the sake of making valid conclusions on the range of possible impacts synesthesia may have on the human life, social interaction, and learning. The modern state of research and the body of knowledge derived from the experiments with synesthetes is rather contradictory, and the role of school in mitigating the effect of synesthesia for the sake of increased learning skills still is to be decided. Therefore, the implications for further research pertain to the field of further exploration of sensory mechanisms of the human brain, the interconnections between stimuli and concurrent, and the possible combinations of synesthetic experiences that may lead the individuals to better understanding of their own disorder and awareness of the way it may be handled.

References

Carriere, J.S.A., Eaton, D., Reynolds, M.G., Dixon, M.J., & Smilek, D. (2008). Grapheme–Color Synesthesia Influences Overt Visual Attention. Journal of Cognitive Neuroscience, 21(2), pp. 246–258.

Maechler, M-J. Synaesthesia and Learning: A Differentiated View of Synesthetic Perceptional Awareness. Swiss Federal Institute of Technology Zurich. Retrieved December 1, 2010, from http://www.synaesthesia.com/media/ uploads/Synaesthesia_Learning.pdf

Simner, J., & Holenstein, E. (2007). Ordinal Linguistic Personification as a Variant of Synesthesia. Journal of Cognitive Neuroscience, 19(4), pp. 694–703.

Spector, F., & Maurer, D. (2009). Synesthesia: A New Approach to Understanding the Development of Perception. Developmental Psychology, Vol. 45, No. 1, 175–189.

Weiss, P.H., Kalckert, A., & Fink, G.R. (2008). Priming Letters by Colors: Evidence for the Bidirectionality of Grapheme–Color Synesthesia. Journal of Cognitive Neuroscience, 21(10), pp. 2019–2026.