It appears that synesthesia may be the result of abnormal brain connections, as in the case of other conditions, such as autism.
Science Magazine reported on the new research on synesthesia, the ability to directly perceive and experience multiple senses at once, where one of the five base senses are cross-wired. What does this mean in practical terms?
A person with the synesthesia will hear the colour blue and taste G sharp. It amounts to a “mingling of the senses” and sounds eerily like “colorless green ideas sleep furiously.”
It is estimated to affect only as little as 3 to 5 percent of the general population. There are different types of synesthesia, too, with grapheme-colour synesthesia, in which numbers and letters become associated with particular colors, as the most commonly studied.
University of Amsterdam researcher Romke Rouw found the results very exciting. A number of genes might predispose individuals for synesthesia. Further research may provide a window into other disorders such as autism.
It appears that synesthesia may be the result of abnormal brain connections, as in the case of other conditions, such as autism. According to Rouw’s analysis, the abnormal brain connections are tied to hyperconnectivity, where the hyperconnectivity influences the brain and so the sensation perception of the synesthete.
Psychologists and neuroscientists were unwilling to research synesthesia for decades. Some even denied its existence. It was highly difficult to study because of the subjective nature of the unusual, and involuntary, condition.
Mutations, which could be tracked in families, may serve to shed light upon the condition. Simon Fisher at the Max Planck Institute for Psycholinguistics in the Netherlands used whole-exome sequencing to find the gene variants responsible for the condition.
This type of gene-sequencing technique only targets DNA meant to encode proteins. Fisher gather genomes from four or five synesthetes, and one non-synesthete, covering three generations from each family researched.
The synesthetes had color-sound synesthesia. 37 genes predicted the family members who would and would not have the inherited synesthesia that causes cross-talk between color and sound in experience. No genetic variant appeared to be shared in the three families studied with no single synesthete gene or gene set assumed to be present based on the new research.
6 of the variants were related to genes associated with the development of connections between neurons and axons. These variants were shown to be active in the auditory and visual cortices.
In has been suggested in previous research that synesthetes have a higher number of connections between brain regions. With this research evidence, it would appear to be supported with hyperconnectivity as the principle and the regions of the brain as the marker for the type of synesthesia.
Rouw cautions, “In the end, replication is going to be key.” That is, there needs to be more research, as research scientists are commonly know to say with good reason, which means the preliminary findings here are a good means through which to further the research into synesthesia and support some hypotheses more than others to carve out the empirical truth of the matter.
Price concluded, “If the findings pan out, studying neuronal connections in synesthesia could be a boon to autism researchers. Many people with autism spectrum disorder also have an enhanced sensitivity to stimuli such as sounds or touch, and there’s mounting evidence that abnormal brain connections—more in some regions, fewer in others—might play a significant role.”
Herman, L.M. (2017, February 24). Synesthesia. Retrieved from https://www.britannica.com/science/synesthesia.
Price, M. (2016, November 15). European diseases left a genetic mark on Native Americans. Retrieved from http://www.sciencemag.org/news/2016/11/european-diseases-left-genetic-mark-native-americans.
Price, M. (2018, March 5). Synesthesia’s mysterious ‘mingling of the senses’ may result from hyperconnected neurons. Retrieved from http://www.sciencemag.org/news/2018/03/synesthesia-s-mysterious-mingling-senses-may-result-hyperconnected-neurons.
Tilot, A.K. et al. (2018, March 5). Rare variants in axonogenesis genes connect three families with sound–color synesthesia. Retrieved from http://www.pnas.org/content/early/2018/02/27/1715492115.