The science non-fiction of a bodiless brain

Brain in jarThe brain. Nestled cozily inside its skull and properly integrated with its body’s peripheral nervous and circulatory systems, the organ is revered as a sacred abode for our thoughts, emotions, and identity. But extracted from this natural habitat, its slimy cortex and gyrating gyri can make one squeamish. Don’t worry, we neuroscientists aren’t offended. It’s understandable that the brain would be more unnerving than say, a lung, given its elevated status above other internal organs. Its integrity determines your position across the boundary of existence and non-existence, you and no-you (I’ll spare you that DrEADful four letter word). Without your brain, “you” are no longer. But what is a brain without the body? Could it maintain the basic biological functions necessary for life, sustain consciousness or give rise to a veritable human existence? Could it distinguish between the reality of its isolated existence and a world engendered by virtual sensations and interactions?

Feed those hungry neurons

We’ll play philosopher-of-mind soon enough, but for the moment, let’s ponder the glob of organic tissue that constitutes the material brain. Every living cell, including those in the brain, has a few essential requirements for life. Neurons communicate by triggering action potentials and synaptic transmission, processes reliant on the movement of ions (sodium, potassium, calcium and chloride are the big players) across cell membranes. The brain also needs fuel (mmm … sugar!) to power activities such as maintaining ion gradients, recycling neurotransmitters, and metabolic housekeeping in neurons and glia 1. To tap into that energy source, the brain needs a continuous supply of oxygen. These necessities could be supplied by perfusing the brain with some oxygenated cerebral spinal fluid, or bathing it in your favorite concoction of glucose-rich oxygenated electrolyte solution. For a bit more fun, we could alternatively attach the brain to a machine to feed the brain these nutrients, or even better, transplant it to the circulatory system of another organism.

Alive but alone

Implementing a brain-on-life-support or Frankenbrain might thus be perfectly feasible, but what would be the subjective experience of such an entity? In its natural habitat, a brain is in constant communication with its environment. It processes input from its various sensory systems, and responds to visual, auditory, olfactory and somatosensory stimuli with automatic reflexes as well as voluntary speech and movement, permitting a dynamic interactive flow between the brain, body and surroundings. But without a bodily interface, the doorways to both the external world and one’s internal environment are shut. Does solitary confinement sound torturous? Imagine the same isolation, only as a blind, deaf and limbless mute. Unless simulated by a perfect storm of spontaneous neural activity, the experience of laughing at a good joke, warming by a fire, or the taste of a gourmet meal, would be impossible.

Cyborgs and brain-bots

But this is the 21st century. Simple “mind control” and bionics are no longer science fiction, but real and practical (though perhaps disappointingly, not so ominous) applications of advanced neuroscience technology. As such, why isolate a brain in a jar when it could be integrated with its environment? Neural communication is but the transmission of electrical and chemical signals. Provide input to the optic nerve and an eye-less brain can see! Stimulate the somatosensory cortex and the bodiless brain can feel! Provide appendages that read signals from the motor cortex, and the brain-bot can shake your hand, walk or dance! While this may sound like the plot for a 60’s horror movie, neuroscientists have actually been doing similar experiments on humans since the 1950’s 2.

If a brain could interface with this world, who’s to say it couldn’t exist in any world, as real or illusory as we choose to imagine? Delivering to a brain visual input that represents a fire-breathing dragon is just as feasible as signaling the “real-life” table upon which the brain resides.

Do you have an evil demon?

The Matrix

If scientists could overcome the technical challenges to construct a brain-in-jar, cyborg or Neo, it’s arguable whether such existences would be qualitatively equivalent to our subjective life experience. If our stream of experience boils down to a sequence of neural inputs and outputs, does it matter if the brain-world interface is organic, or if our surroundings are “real”? Would we even be aware of the artificiality of a virtual existence?

What is real? How do you define real? If you’re talking about what you can feel, what you can smell, what you can taste and see, then real is simply electrical signals interpreted by your brain. – Morpheus

These are not novel questions, but have been pondered by philosophers since the time of Descartes, who posited the existence of an evil demon who dupes us into perceiving a non-existent external environment 3. With our evolving understanding of the brain as the mind’s abode, a modern philosopher, Hilary Putnam, later expanded upon this theory 4. If a brain in a vat can be deluded into believing illusory experiences, can we be certain our own existence is any more real?

Have you ever had a dream, Neo, that you were so sure was real? What if you were unable to wake from that dream? How would you know the difference between the dream world and the real world? – Morpheus

While a bodiless brain could most certainly sustain “life”, bathing in oxygenated cerebral spinal fluid may not be the most thrilling existence. Replace that jar with the brain-world interface of your choosing, and such a life just might be tolerable.

Cypher: If I had to choose between that and the Matrix, I’d choose the Matrix.
Trinity: The Matrix isn’t real.
Cypher: I disagree, Trinity. I think that the Matrix can be more real than this world.

So if you one day discover a glitch in the Matrix, at least take comfort in being more than just a brain in a jar.


1. Attwell D. & Laughlin SB. (2001). An energy budget for signaling in the grey matter of the brain. J Cereb Blood Flow Metab. 21:1133-45.

2. Penfield W. & Jasper H. (1954). Epilepsy and the functional anatomy of the human brain. Little, Brown & Co: Oxford, England.

3. Descartes R. (1641). Meditations on First Philosophy.

4. Putnam, H. (1981). Brains in Vat. In Reason, Truth and History, Cambridge Univ. Press: Cambridge. 1–21.