I still remember walking down the as-usual deserted Inman Street in Cambridge, Massachusetts and suddenly pulling up short and looking around as the smell of my mother’s sambhar surrounds me! At that moment I would have given anything to get a taste of that sambhar! But I knew there were no Indian households in the area. I knew none of the sealed double-glazed windows in the vicinity could be the source of the smell. I was, in fact, having an olfactory hallucination.
Oliver Sacks, one of the most prolific neurologist-writers who through his writings let us look inside human brains through the eyes of his patients, said, while talking about his book Hallucinations, ‘We see with our eyes, but we see with our brains as well. Seeing with the brain is called imagination’. When I sit and stare into space daydreaming, I call that imagination. Michelangelo hanging upside down under the ceiling of the Sistine Chapel and visualising the hand of god reaching out to man; I call that imagination. Artists planning and cutting away around 200,000 tonnes of rock out of the side of a mountain to create the exquisite Ellora caves; I call that imagination. But what if that ‘seeing’ is involuntary, it is not in our control? If we cannot control when we start ‘seeing’ and what we ‘see’? What if we cannot tell if we are ‘seeing’ with the brain or with our eyes?
A hallucination is defined as a sensory perception that occurs in the absence of an external sensory stimulus. Hallucinations can be visual: seeing visions, ghosts or people, auditory: hearing voices, olfactory: sensing smells and tastes or tactile: feeling a touch or itching or insects crawling on the skin. Hallucinations are quite common; according to various studies 5%-70% people would experience a hallucinatory experience some time in their life. We just don’t talk about it for fear of being thought of as crazy. But seeing visions or hearing voices were not always thought of as signs of insanity; not so very long ago, they would have been considered an indication of divine powers.
But a life where you do not know the real from unreal can be hell indeed. Schizophrenia is a particularly debilitating disorder where patients see visions and hear voices that sometimes curse, berate and insult them, making them psychotic and paranoid. For instance, John Nash, the brilliant mathematician whose story was captured in the book and movie Beautiful Mind, had a friend who lived with him and had a great influence on his life, only to realise many years later that this friend was imaginary. He later developed defensive strategies to check with people around him to make sure what he was seeing was what everyone else was seeing. Imagine living with such self doubt! Elyn Saks, the law professor who has worked tirelessly for mental health patients, says it all in the title of her book chronicling her ‘journey through madness’, The Center Cannot Hold. She describes the feeling of being completely out of control when there is no boundary between reality and hallucination and the mind does not know what to believe in anymore. When the mind that you have relied on your whole life to stand by you, suddenly forsakes you.
Our brain has to deal with large amounts of sensory data throughout the day. If it attempted to decode everything with equal attention to detail, it would probably have a nervous breakdown. Instead, the brain uses many shortcuts. It learns the patterns of predictability and many times fits the sensory inputs to the ‘expected results’ thus reducing the workload on the brain. The binocular depth inversion illusion test (BDII) tests for this ability of the brain to confabulate. A convex mask rotates on its axis. As the mask flips to the concave side, the brain ‘corrects’ the image and shows us an illusion of a convex mask. Healthy, well-rested individuals see this illusion because the visual processing system shows them what the brain thinks they are seeing, not what they are actually seeing. Schizophrenia patients and sleep-deprived people are less able to see this illusion. Their brain does not ‘correct’ for the predictable.
MRI scans of people with schizophrenia who had hallucinations and those who did not, showed that people prone to hallucinations had a shorter paracingulate sulcus or PCS in their frontal lobe. They appear to be less able to distinguish between self-generated information and information received from outside sources. Other studies on schizophrenia patients prone to auditory hallucinations have also suggested that they have a weaker corollary discharge, a feedback mechanism that allows the brain to distinguish between self-generated signals and external signals; for example, they perceive no difference between self-tickling and tickling by others. Similarly, perhaps these brains cannot tell the difference between a voice generated inside their heads vs. a voice coming from outside.
Hallucinations are also common in people undergoing sensory deprivation such as people incarcerated in solitary confinement. Scientific studies depriving people of all sensory inputs have shown that individuals begin experiencing distress and hallucinating within hours. People who have lost their vision or hearing often experience visual or auditory hallucinations that are much more benign that those experienced by people with illness or distress.
Although hallucinations are frightening most of the time, indicating disease or extreme fatigue, human beings have always had a fascination with visions and voices of the mind. All cultures around the world have their favourite psychoactive plants and mushrooms that are used in religious rituals. The Western Counterculture movement of the 1960s also led to experimentation with hallucinatory chemicals such as LSD and Psilocin, tryptamines that bind to the Serotonin H2A receptors. Scientifically curious people have recorded their experiences after taking these compounds under controlled conditions and under supervision. Let me quote Weir Mitchell (as described by Oliver Sacks in Hallucinations), ‘The heavens above me, a night sky spangled with eyes of flame, dissolve into the most overpowering array of colours I have ever seen or imagined; many of the colours are entirely new–areas of the spectrum which I seem to have hitherto overlooked.’ People having epileptic seizures or those who have had near-death experiences report similar feelings of transcendence. A strange joy and oneness with the whole world. Perhaps what the ancient texts call nirvana?
Hallucinations are a symptom of certain mental illnesses and their destructive effect cannot be denied in such cases. But it also cannot be denied that sometimes our brain plays tricks on us to lead us to a better state of mind. When blind people see colourful scenes play out in front of their mind’s eye or when a bereaved spouse meets their lost love within the recesses of their mind, the brain is trying to recapture a lost experience. People who have had mushrooms and flower extracts take them on a journey of the universe unlike any they have ever imagined say that they would give anything to get that one moment back. Would you not secretly wish you too had a window of such opportunity? As brain mapping and augmented reality come of age, would we someday check into a ‘transcendence clinic’ for a few minutes of electric stimulation that would simulate a more wonderful world than the one we live in?
You can try out the binocular depth inversion illusion test (BDII) here (hyperlink below)
https://michaelbach.de/ot/fcs-hollowFace/index.html
This is the third in a series on Imagination that I am writing. The previous articles can be found here and here. (hyperlinks below)
https://science-rumblings.blogspot.com/2014/02/onlyas-far-as-we-imagine-by-chetana.html
https://science-rumblings.blogspot.com/2019/02/real-or-imagined-right-now-i-have-time.html
Cover picture Credit: Sangeetha K
Chetana Sachidanandan is a scientist-writer with a fascination for a striped fish that’s too small to eat and just too beautiful to describe.