Brain Implants and Artificial Eyes

A recent post by Ocularists Paul and Jenny Geelan relates their experiences with patients who have been fitted with artificial eyes after eye loss. They report that:

    “Weve had some very interesting feedback from a small number of our clients about being affected by bright light. In particular, glare from the sun is a problem for them. You might be amazed to learn that two of these people have bilateral eye loss and so have a pair of artificial eyes. Another person has one artificial eye and finds that she has to close that eye when looking upwards because of the dazzling glare. This phenomenon isnt just an effect of the sun as the glare is also detected in a bright room.”

There appears to be no logical explanation yet, but it does happen. This made me think of passage in Richard Dawkin’s book, The God Delusion, which I recently read, in which he theorizes that bats can “see” colors and objects by their sonar. His premise was that our human brains can be thought of as sophisticated modelling software allowing us to navigate through and interact with our sensory input.

As the book was involved with a discussion of evolutionary theory, he went on to posit that the “modelling software” in other species would be adapted to their sensory input so as to enable them to build a navigable model of the world in their brains.

All of which is to say, I also recently stumbled upon a website, seeingwithsound.com, about synthetic vision technology for the blind which fascinated me. From their site:

    “The vOICe vision technology for the totally blind offers the experience of live camera views through sophisticated image-to-sound renderings. In theory this could lead to synthetic vision with truly visual sensations (“qualia”) through crossmodal sensory integration, by exploiting the existing multisensory processing and neural plasticity of the human brain through training and education. The vOICe implements a form of sensory substitution where the goal is to bind visual input to visual qualia with a minimum of training time and effort.”

So, could these patients with artificial eyes be somehow experiencing a form of synesthesia* as well?

      *Synesthesia is a neurological condition in which two or more bodily senses are coupled. In one common form of synesthesia, known as grapheme, color synesthesia, letters or numbers are perceived as inherently colored, while in ordinal linguistic personification, numbers, days of the week and months of the year evoke personalities. In spatial-sequence, or number form synesthesia, numbers, months of the year, and/or days of the week elicit precise locations in space (for example, 1980 may be “farther away” than 1990), or may have a three-dimensional view of a year as a map (clockwise or counterclockwise).

While cross-sensory metaphors (e.g., “loud shirt”, “bitter wind” or “prickly laugh”) are sometimes described as “synesthetic”, true neurological synesthesia is involuntary. It is estimated that synesthesia may be as prevalant as 1 in 23 persons across its range of variants (Simner et al. 2006). It runs strongly in families, possibly inherited as an X-linked dominant trait. Synesthesia is also sometimes reported by individuals under the influence of psychedelic drugs, after a stroke, or as a consequence of blindness or deafness.

Synesthesia that arises from such non-genetic events is referred to as adventitious synesthesia to distinguish it from the more common congenital forms of synesthesia. Adventitious synesthesia involving drugs or stroke (but not blindness or deafness) apparently only involves sensory linkings such as sound, vision or touch, hearing; there are few if any reported cases involving culture-based, learned sets such as graphemes, lexemes, days of the week, or months of the year.