Altered Reality: Rare Brain Disorders That Change How You Perceive the World


By Adrian Sparrow
NeuLine Health


The human brain is a complex object, capable of storing more information than a computer and working significantly faster. It is the organ through which we sense and respond to the world around us. Most of the time, our brains can show us a picture that matches the physical world. Visual illusions remind us that the brain doesn’t always get it right, filling in the gaps with our past experiences and bending the perception of reality to meet our expectations. This offers room for translation errors, genetic missteps, and the opportunity for peculiar side effects in how we experience the world around us. Strange brain conditions can be caused by traumatic brain injury or genetically inherited, though many of these conditions and phenomena, far more than what is listed, have unknown origins.


Synesthesia occurs when the senses ‘overlap’. Information that’s meant to stimulate one sense instead stimulates several senses, leading to cases such as “seeing” music, “hearing” colors, and “tasting” shapes. Each of the senses stimulates a different part of the brain. Visual imagery stimulates the primary visual cortex, and in synesthesia, another part of the brain will also be stimulated, such as the parietal lobe, leading to ‘tasting’ colors. Most people with synesthesia are born with it or develop it early in childhood and might experience one or multiple overlapping senses. Researchers are unsure how common synesthesia is, but one study proposed it occurs in 2-4% of the population. While there is no treatment, many people enjoy perceiving the world differently than the general population this way. 


Aphantasia is a phenomenon where the person cannot visualize imagery or picture things in their ‘mind’s eye’. Most people can imagine an object, face, or environment, such as a bright red apple, but those with aphantasia don’t ‘see’ anything. While people with aphantasia may be able to recall facts and concepts, they wouldn’t experience any mental imagery to accompany them. This can lead to difficulty remembering faces and navigating spaces or even affect learning. People with aphantasia can experience visual imagery while dreaming, which suggests the phenomenon affects conscious, intentional thought. An estimated 1-3% of the population experiences aphantasia.


While Prosopagnosia is the inability to recognize faces, Capgras delusion is when the person believes imposters have replaced their loved ones. Those with Capgras may not recognize their relative, but they can sometimes recognize their voice. In one case, a man couldn’t recognize his parents face-to-face but recognized them over the phone with no issue. In another, a 59-year-old man began to spend time looking for his ‘real’ wife, convinced that the person in front of him was a double. Though he didn’t display aggressive behavior, he was inquisitive and doubtfully addressed her. There is no standard treatment for Capgras, but in some cases treating the underlying condition can reduce or cure symptoms.


Jerusalem Syndrome is a psychosomatic condition that occurs when visitors to Jerusalem experience religious delusions, affecting 50-100 tourists each year. Victims might feel anxiety and a compulsive urge to break away from the group on their own before donning a white sheet as a toga and wandering or visiting holy sites to preach sermons or perform rituals. Jerusalem is an important holy city for 3 of the major world religions and many come to the city on a pilgrimage, and could be more susceptible to its ‘spell’. Those with Jerusalem Syndrome may believe themselves as a figure from the old or new Testaments, like King David and the Virgin Mary. While the actual cause is still unknown, 80% of cases documented included a history of mental illness.

Other variations of this condition include Paris syndrome and Florence syndrome. The city itself is more likely a catalyst for these erratic behaviors rather than their direct cause. The best treatment is to leave the city and return to everyday life, and symptoms vanish. 


Cotard’s delusion, or Walking corpse syndrome, is a condition where the patient believes they or their body parts are dead or dying, even when evidence points to the contrary. Somebody with Cotard’s believes they are dead or rotting away, may experience paranoid delusions and hallucinations and might not eat, bathe or groom themselves because they feel they’ve already died or don’t exist. A marked symptom of Cotard’s is nihilism, or the belief that nothing has any value or meaning (or that nothing truly exists). Depression and Cotard’s are closely related: a 2011 report noted that 89% of documented cases of Cotard’s included depression. Treatment can include different kinds of medication or mental health therapy, with electroconvulsive therapy as a last resort. 




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