Feeling detached from reality? The claustrum could be why

Doctor, I have a strange problem,” he paused. “Sometimes I feel as though I am watching myself.” He was 48, a professor of philosophy, which immediately made me suspicious. Philosophers are uniquely capable of turning perfectly ordinary neurological symptoms into existential crises.

For several months, he had been experiencing brief episodes in which the world seemed to change texture. He would be sitting in his study, reading, and suddenly everything around him felt distant. Familiar objects looked strangely unfamiliar. His own hands seemed somehow detached from him. Once, during a lecture, he stopped halfway through a sentence because he had the peculiar sensation that he was watching himself from somewhere outside his body. The episodes lasted less than a minute, after which he was completely normal. There were no dramatic convulsions. No loss of consciousness. Just a fleeting disturbance in the most fundamental assumption we make every morning: I am me, and this is the world.

His MRI revealed a small tumour deep within the brain, involving an obscure structure called the claustrum. The name itself comes from the Latin claustrum, meaning an enclosed place or a hidden room. It is a wafer-thin sheet of grey matter, tucked between the insula and the deeper structures of the brain. Almost nobody has heard of it. Yet, one of the most celebrated molecular biologists of the 20th century, Francis Crick, became fascinated by it and proposed that the claustrum might play a role in binding together the disparate pieces of information that produce our unified conscious experience. It was an extraordinary idea: that this tiny, hidden sheet might somehow help the brain turn sights, sounds, memories, emotions and sensations into the singular experience we call being alive.

The mystery becomes even more intriguing when you look at the anatomy. The claustrum is not responsible for one obvious function like vision, movement or speech. Instead, it has extensive connections with many different regions of the cortex. Think of the brain as a vast city. The frontal lobe has its offices. The temporal lobe has its archives. The visual cortex has its cinema. The limbic system has, depending on the day, either a counselling centre or a theatre of unnecessary emotional drama. And somewhere between these neighbourhoods sits the claustrum, communicating with almost everyone.

Neuroscience has discovered an astonishing amount about the brain, but consciousness remains stubbornly resistant to explanation. We can describe electrical activity. We can map networks. We can watch different regions illuminate on functional MRI. But none of this completely answers the strangest question of all: how does matter produce experience?

The tumour was small, but its position made surgery challenging. The claustrum lies deep beneath the insular cortex, surrounded by important white-matter pathways and major blood vessels. Reaching it meant navigating through some of the brain’s most eloquent territory without damaging the networks that gave our patient his language, movement and personality. Under the microscope, the claustrum appeared almost disappointingly ordinary—a thin, grey sliver of tissue hidden among structures of far greater size. Yet, here was the paradox of neurosurgery: some of the smallest things can carry the largest questions.

We approached the tumour carefully, using image guidance and functional mapping to define the safest corridor. The tumour separated reasonably well from the surrounding brain, and millimetre by millimetre it was removed. There was no dramatic moment when consciousness suddenly emerged from the microscope. As the tumour disappeared, I found myself thinking about how strange our profession really is. We spend our careers cutting into the physical machinery of thought while knowing that the thing we are ultimately trying to preserve—consciousness, personality, identity—cannot be held in our hands.

His episodes disappeared after surgery. At his follow-up several months later, he told me that the strangest thing was how ordinary everything felt again. “The room is just a room,” he said. “My hands feel like my hands. And when I lecture, I don’t feel like I’m sitting somewhere above myself watching. I suppose that’s what normal feels like.” Perhaps, that is the greatest trick consciousness plays on us. It makes the extraordinary feel completely ordinary. We wake up and assume we are ourselves. We look at our hands and never wonder how the brain knows they belong to us. We see a face and instantly recognise someone we love. We rarely stop to appreciate that every one of these experiences is the product of billions of neurons communicating in a system so complex that we are still struggling to understand its most basic mystery.

At his final visit, he looked at me thoughtfully and said, “So, doctor, after all that, do we actually know what the claustrum does?” I smiled, “We know considerably more than we did before.” “That wasn’t quite my question,” he said. “No,” I said, “it wasn’t.” He laughed. Then he stood up, put on his jacket and walked towards the door. He stopped. “Maybe consciousness,” he said, “is the brain’s way of asking itself what it is.” I thought that was rather good.

“Professor,” I replied, “if you publish that, I shall claim I taught you everything you know.”

He smiled. “Don’t worry, doctor. I don’t remember saying it.”

Somewhere deep inside the brain, I suspect the claustrum approved.

The author is consultant neurosurgeon at Wockhardt Hospital, Mumbai.

mazdaturel@gmail.com @mazdaturel