Synaesthesia: Perceptual And Physiological Mechanisms

Although Synesthesia has been a well-known condition for many years, it has only become of interest to science as of recently. This revival of inquiry is due to the presumed implications Synesthesia can tell us about perception and consciousness. Synesthesia is a conscious experience in which a triggered stimulus induces other sensory attributes that are non-normative comparable to most people under the same condition. This involuntary phenomenon seems to go against common sense which is exactly why it is so interesting to study the individuals who have this condition, known as synesthetes.

This act of sensory blending seems difficult for most people to imagine as it is an unusual and abstract concept. Although the sensory experiences of synesthetes are highly specific to each individual, some perceptual mechanisms of Synaesthesia are general throughout all who have the condition. For instance, these sensory associations between the trigger stimuli (the inducer) and the non-normative perceptions (the concurrent) do not change over time which is proven by test-retest sessions given decades apart without warning. The fact that these perceptions remain stable over a lifespan indicates they are private and highly memorable experiences. Furthermore, synesthetes have noted that these perceptions are emotional and occur as projected outside the individual’s being rather than inside the mind like normal perception (Cytowic, 1995). For example, synesthetes describe their abstract sensory perceptions meticulously and are very detailed and personal with their explanations. Since these perceptions are so emotional and vivid, synesthetes are known to have excellent memory as associations between the inducer and concurrent are stronger than normal. Synaesthesia perception is unlike anything non-synesthetes experience which leads us to question what differs in the neurology of those with the condition and those without. Furthermore, research into the physiological properties of Synesthesia has been limited however, some important discoveries have been made. Experimental evidence shows that for most synesthetes, the condition is unidirectional meaning that each specific concurrent is typically triggered by only one inducer and highly specific in its perception. These facts allow for an understanding that there is variation in how the concurrents are spatially perceived which could directly map onto neural representations (Grossenbacher & Lovelace, 2001). For instance, Synesthesia is said to activate higher-order visual cortical networks rather than simply arising at the earliest levels of cortical visual processing like that of normative physiology. Perceptually, when synesthetes experience an out-of-body action when the non-normative concurrent occurs, neural representations specific to that individual are activated, making the concurrent involuntary, personal, highly memorable and unable to be dismissed.

Billy Joel is a household name, a fantastic musician and also a synesthete. Joel explains his synaesthesia as emotional in the sense that he has associated very vivid colours to the vowel endings of words since he was a child, otherwise known as developmental synaesthesia. For Billy Joel, these vowel sounds play an important role in his musical abilities as they act as a device which creates strong associations and thereby strong memories. Joel realized his experiences were unique as a child through abstract, non-physical dreams of melodies and ballads, something which he still experiences today when thinking of songs. Although synaesthesia is uncommon amongst the world population, it does not mean it hinders an individual as seen here through the success of Billy Joel.

In conclusion, Synaesthesia is an incredibly dynamic condition that although not well understood, has an interesting effect on perception and thereby physiological mechanisms. From out-of-body projections of perception to activation of varying neural pathways, Synaesthesia is highly specific to the individual but in general notably different to that of normative sensory perception. Apart from this distinction, Synaesthesia has no real consequences, seen in the example of Billy Joel, and is rather a condition that can be appreciated mostly for its uniqueness.

References

• Cytowic, Richard. (1995). Synesthesia: Phenomenology And Neuropsychology A Review of Current Knowledge. Psyche. 2.
• Grossenbacher, P. G., & Lovelace, C. T. (2001). Mechanisms of synesthesia: Cognitive and physiological constraints. Trends in Cognitive Sciences, 5(1), 36-41. doi:10.1016/s1364-6613(00)01571-0
• Seaberg, M. (2012). He's Got A Way About Him. Psychology Today.
• Ward, J. (2013). Synesthesia. Annual Review of Psychology. 64(1), 49-75. https://doi.org/10.1146/annurev-psych-113011-143840