Imagine a future where nobody dies — instead, our minds are uploaded to a digital world. They might live on in a realistic, simulated environment with avatar bodies, and could still call in and contribute to the biological world.
Mind uploading has powerful appeal, but what would it actually take to scan a person's brain and upload their mind? The main challenges are scanning a brain in enough detail to capture the mind and perfectly recreating that detail artificially.
But first, we have to know what to scan. The human brain contains about 86 billion neurons, connected by at least a hundred trillion synapses.
The pattern of connectivity among the brain's neurons, that is, all of the neurons and all their connections to each other, is called the connectome. We haven't yet mapped the connectome, and there's also a lot more to neural signaling.
There are hundreds, possibly thousands of different kinds of connections, or synapses. Each functions in a slightly different way.
Some work faster, some slower. Some grow or shrink rapidly in the process of learning; some are more stable over time.
And beyond the trillions of precise, 1-to-1 connections between neurons, some neurons also spray out neurotransmitters that affect many other neurons at once. All of these different kinds of interactions would need to be mapped in order to copy a person's mind.
There are also a lot of influences on neural signaling that are poorly understood or undiscovered. To name just one example, patterns of activity between neurons are likely influenced by a type of cell called glia.
Glia surround neurons and, according to some scientists, may even outnumber them by as many as ten to one. Glia were once thought to be purely for structural support, and their functions are still poorly understood, but at least some of them can generate their own signals that influence information processing.
Our understanding of the brain isn't good enough to determine what we'd need to scan in order to replicate the mind, but assuming our knowledge does advance to that point, how would we scan it? Currently, we can accurately scan a living human brain with resolutions of about half a millimeter using our best non-invasive scanning method, MRI.
