Researchers at Baylor College of Medicine, Rice University, and the Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, are studying the unusual neural connections that occur in individuals who have synesthesia. Synesthesia is a condition where one type of stimulus brings about the sensation of another, such as when hearing numbers produces the visualization of a color. The researchers have looked at these connections and have found an unusual relationship between color and graphemes (numbers or letters) regions in the brain with certain stimuli helping to elucidate this phenomena.
According to Dr. Steffie N. Tomson, formerly a Ph.D. student at BCM and currently a postdoctoral fellow at the Semel Institute for Neuroscience, University of California, “People who have synesthesia experience it automatically as a normal part of their lives, so we wanted to focus on how the connections of the brain are structured differently from those who are non-synesthetes.”
The current study focused on individuals who experience “colored sequence synesthesia” which means individuals who associate colors with letter or numbers. Brain activity of synesthetes and nonsynesthetes was monitored using function MRI while listening to grapheme-rich clips from Sesame Street. Researchers observed that synesthetes and nonsynesthetes (controls) have very different neural clustering patterns during audio presentation of graphemes.
According to the first author of the study, Tomson, “Compared to nonsynesthetes, those with synesthesia had more neural connections between the regions of the brain responsible for recognizing color and letters and numbers during auditory stimuli. During a rest period where there were no stimuli, these connections were still greater in synesthetes.” Interestingly, when synesthetes were allowed to hear grapheme clips with video, their connections were similar to nonsynesthetes.
Clearly, something is happening in the visual region of synesthetes when hearing the grapheme spoken to them. Tomson points out, “There is a greater connectivity between much of the visual cortex, including color and grapheme brain regions, during this auditory exposure. These findings are helping us formulate theories, such as synesthetes may be better visualizers or perhaps the synesthetic experience depends on the way in which graphemes are presented. It gives us a new path to begin further studies.”
Check out the video below for an overview of Synesthesia: