A Neuroscientist’s Radical Theory of How Networks Become Conscious

What do you mean?

Koch: My consciousness is an undeniable fact. One can only infer facts about the universe, such as physics, indirectly, but the one thing I’m utterly certain of is that I’m conscious. I might be confused about the state of my consciousness, but I’m not confused about having it. Then, looking at the biology, all animals have complex physiology, not just humans. And at the level of a grain of brain matter, there’s nothing exceptional about human brains.

Only experts can tell, under a microscope, whether a chunk of brain matter is mouse or monkey or human — and animals have very complicated behaviors. Even honeybees recognize individual faces, communicate the quality and location of food sources via waggle dances, and navigate complex mazes with the aid of cues stored in their short-term memory. If you blow a scent into their hive, they return to where they’ve previously encountered the odor. That’s associative memory. What is the simplest explanation for it? That consciousness extends to all these creatures, that it’s an immanent property of highly organized pieces of matter, such as brains.

That’s pretty fuzzy. How does consciousness arise? How can you quantify it?

Koch: There’s a theory, called Integrated Information Theory, developed by Giulio Tononi at the University of Wisconsin, that assigns to any one brain, or any complex system, a number — denoted by the Greek symbol of Φ — that tells you how integrated a system is, how much more the system is than the union of its parts. Φ gives you an information-theoretical measure of consciousness. Any system with integrated information different from zero has consciousness. Any integration feels like something

Ecosystems are interconnected. Can a forest be conscious?

Koch: In the case of the brain, it’s the whole system that’s conscious, not the individual nerve cells. For any one ecosystem, it’s a question of how richly the individual components, such as the trees in a forest, are integrated within themselves as compared to causal interactions between trees.

The philosopher John Searle, in his review of Consciousness, asked, “Why isn’t America conscious?” After all, there are 300 million Americans, interacting in very complicated ways. Why doesn’t consciousness extend to all of America? It’s because integrated information theory postulates that consciousness is a local maximum. You and me, for example: We’re interacting right now, but vastly less than the cells in my brain interact with each other. While you and I are conscious as individuals, there’s no conscious Übermind that unites us in a single entity. You and I are not collectively conscious. It’s the same thing with ecosystems. In each case, it’s a question of the degree and extent of causal interactions among all components making up the system.

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