What is Charles Bonnet syndrome?
The human brain is a fascinating organ whose primary defining characteristic is that it requires stimulating input to function. We can see, hear, and smell without visual, auditory, or olfactory stimuli but it is only once we see grease, hear popping, and smell protein that we recognize the presence of bacon cooking.
Charles Bonnet syndrome (CBS), however, differentiates itself from normal visual functioning by producing vivid hallucinations that are utterly lacking in any stimuli. That is to say, those diagnosed with CBS see things that are very clearly not there.
What becomes immediately fascinating is that CBS manifests absent of the presence of any other sensory activation.
One diagnosed with CBS will see a person, but will be unable to hear said person speak, to smell the person, and, of course, to touch the person.
How does Charles Bonnet syndrome work?
Understanding CBS begins with understanding the way that the human brain identifies visual stimulation. In short, light from an object hits the eye, visual information is then electrically transmitted through the optic nerve to the brain, and the brain then processes the visual information. As anyone can attest, it is almost impossible to see in the dark because there is a distinct lack of light to activate our visual centres. Due to the abundance of stimuli for humans to process, our brains group stimuli together into groups. This is applicable across all of our senses. More importantly, however, is the fact that our brains group together different sensory information from the same stimulus. The sensation of eating bacon, for example, is not just reliant on our tongues and noses. Bacon is experienced through our eyes and ears as well.
This grouping together of like stimuli often results in our brains firing certain neuronal groups that encode information for unrelated stimuli. It’s why, when quickly scanning a crowd for our friends, we often tend to mistake strangers for people we know. By searching quickly, instead of slowly scanning for information, our brains sometimes send false positive signals indicating that we’ve found the person we’re looking for, when the opposite is true.
CBS, presumably, works in a similar manner. To begin with, CBS manifests in individuals with visual impairments as a result of a number of factors. Old age, diabetes, and general visual centre damage are all factors that contribute to the manifestation of CBS. The condition is thought to be a result of this visual impairment, combined with our brains’ tendencies to group stimuli together, in addition to the fact that, as we age, our brain must sift through more information before reaching a conclusion to any stimuli. As with all poorly understood phenomena, more research is required before a concrete conclusion can be drawn.
Why is Charles Bonnet syndrome important?
To begin with, CBS is not incredibly common, even in individuals who carry the perfect combinations of factors for the manifestation of the condition. In fact, studies that attempt to identify the precise prevalence of CBS conclude that diagnosis is likely in 10 to 40 per cent of adults over the age of 65 with significant vision loss. As one can assume, the exact conditions required for the manifestation of CBS are rare.
However, understanding CBS is important because it provides insight into the manner in which the human brain manifests hallucinations. Current research has a number of possible hypotheses but almost no definitive causes. As one can imagine, the manifestation of visual reactions to nonexistent stimuli is a cause of great confusion. Indeed, the manifestation of any reaction to nonexistent stimuli is a cause of great confusion.
What is the future of Charles Bonnet syndrome?
It’s important to recognize that CBS is not the only condition that produces visual hallucinations from a lack of stimuli. Phantom eye syndrome is similar to CBS, except that individuals who exhibit phantom eye syndrome do so in the absence of an eye entirely. Understanding CBS is more than just understanding visual hallucinations—it’s an opportunity to understand hallucinations as a whole.
Hallucinations are a result of observable reactions to nonexistent stimuli. As a result of the psychiatric nature of hallucinations, psychiatric medicine has taken on the issue of hallucinations. However, as with many scientific problems, CBS, visual hallucinations, and hallucinations of any nature will most likely be fully understood through the careful application of multiple points-of-view.
As always, I’m excited for the truly absurd possibilities.