What are we, exactly? No line of enquiry has come as close to answering as neuroscience. When all our other organs are positioned roughly the same and perform the same tasks in everyone, the brain is obviously the seat of the self, but as we peer at ever-smaller pieces of our biological substrate we’re discovering things are remarkably similar in our brains too.
So how is it a complete stranger would never mistake you for your next door neighbour — unless you were identical twins? Why can’t you feel anyone else’s sense of self aside from your own? Genetics tells us we’re our genome, the code that will determine and influence everything from our hair colour to how easily we fall in love.
But if you like to think we’re more than a string of nucleic acid types, the theory of the connectome might be for you. You have 100 billion neurons made up of millions of kilometres (no, that’s not a misprint) of wiring packed neatly into your skull. Your continued sense of self, memories and feelings are encoded within and act upon the connections between them.
According to University of WA neuroscientist Mathew Martin-Iverson, it’s a new term for an old idea.
“The idea that your neurological connections determine who you are was advanced in the 1800s, well before the discovery of genes,” Professor Martin-Iverson from the school of Medicine and Pharmacology said. Professor Martin-Iverson and his team have been looking at the brain function behind the well-known rubber hand illusion, in which your brain can be momentarily tricked into thinking a fake hand belongs to you. Along with the nervous laughter it prompts it teaches us a lot about the way the brain processes our sense of body position in space, a critical aspect of our sense of self.
“Nobody seriously thinks genes determine who you are,” he said, “they play an integral role in the development of neurons but even that’s regulated by the environment. All genes do is code for what proteins are made in the cells.”
On that basis Sebastian Seung — professor of computational neuroscience at the Massachusetts Institute of Technology (MIT) — has taken investigation of the connectome to the next level. His team started with the scan of a tiny portion of a mouse’s brain. A computer ‘slices’ it into individual plates, and each neuron is isolated and colour coded on each plate. Putting the plates back together, the computer generates a 3D representation of each neuron and the neighbours it’s connected to (each connection is called a ‘synapse’).
As Professor Seung told a technology conference in Oxford last July, with a small leap of imagination and a near-unfathomable leap in technology we could do the same for an entire human brain.
Events in the environment and our feelings and thoughts that affected our brain’s neural activity would influence these connections between neurons that encoded our life experience — our connectome.
Once we have a map of our connectome, it could potentially be applied to help some urgent mental health problems, he suggested.
It might be possible to plot pathways to pinpoint “miswiring” that might contribute to conditions such as Alzheimer’s or schizophrenia and to prompt the optimal, correct firing pattern. In the latter condition, he suggested, the common symptom of auditory hallucinations could be little more than the sufferer not realising the voices were simply his or her own inner monologue — the same way the rubber hand illusion temporarily interfered with our sense of body ownership.
He also suggested we might one day have the ability to ‘read’ the content of a thought or memory independent of the brain owner’s experience of it.
Plotting a complete map of our connectome also raised the tantalising possibility of transplanting an entire neural framework to a new body or a computer with the consciousness intact indefinitely.
University of WA professor Martin-Iverson agrees it was logically possible to transplant a neural network given the technology, but says it remained a long way into the future.
“A map of Australia isn’t Australia,” he said, referring to the problem identified by many neuroscientists, that a brain counts for little without a body.
“A digital representation couldn’t be imposed on a machine or body, you’d have to recreate the brain’s unique cells, connections and functioning. (At the moment) we can’t even recreate a liver, a much less complex organ.”