Why It’s So Hard to Build a Human Brain

Now there’s a tough question to ask. Biologists, neuroscientists, and computer scientists will all give you slightly different answers, but in the end, one theme unites them: the brain is really, really, really complex.

Biology has made progress in brain-building — in late 2020, scientists at Cambridge announced they had grown artificial tissues known as organoids that behaved neurobiologically like brain tissue. This step marks a milestone for understanding how the brain develops over the course of a lifespan since we can now learn from “test-tube brains”.

Computer scientists tell a different story, one of AI and the push to recapitulate human intelligence in computer programs. Efforts here have been fruitful, but progress is slowing. To truly build a human brain needs a little bit of something we don’t have yet — new knowledge about the brain, its parts, and the mysterious ways it works.

The old days of neuroscience: what have we learned so far

Psychologists, neurobiologists, physicians, and neuroscientists alike were once most interested in understanding the brain as a human organ. How does a lump of pink flesh autonomously control most of our daily functions, while also serving as a center for conscious thought, communication, and memory storage? There was (and still is) so much we didn’t know about the brain.

At a time when technology like fMRI was unavailable, and locations of the brain could not be directly mapped to physiological functions, the brain was essentially a black box. We knew nothing about it — only that it took input signals from the rest of the body and coordinated output signals to control the body’s responses.

As neurotechnology progressed over the last century, we began to get clearer pictures of the brain, its physiology, and its many mysteries. The more we learn, the more we realize we didn’t know before. Where does conscious thought originate? How does neural architecture give way to the complex cognitive processes we employ each and every day?

There’s research underway to get at the heart of some of these questions. One such project is a spinoff of the famous Human Genome Project, called the Human Connectome Project (HCP). In a collaborative effort, the HCP hopes to map each…