Mark Pagel, contributor
GIULIO TONONI'S charming book Phi is an account of consciousness that nods in its style to the writings of a fellow Italian. Yet while Dante had the poet Virgil to guide him on his journey through the circles of hell in the Divine Comedy, Tononi's elderly traveller Galileo draws on the expertise of three great scientific minds. Journeying into the nature of consciousness he is led by a Francis-Crick-like character, someone who must be Alan Turing and finally Charles Darwin.
Is Tononi trying to tell us that the vast philosophical morass of consciousness - what it is, where it resides, how it arises from a purely physical brain - is a kind of hell? And, like hell, is the scientific and philosophical study of consciousness a place from which few ever return?
In spite of having acquired a vastly improved understanding of the physical, chemical and neuronal structures of the brain, we seem little advanced over the ancient Greeks in our subjective understanding of this mysterious feature of our existence.
It is still the case, for example, that each of us knows we have consciousness but can't be sure anyone or anything else does. Mindful of this, Tononi, a neuroscientist at the University of Wisconsin-Madison, avoids the usual traps and lays out a computational theory that describes consciousness as arising from "integrated information", a quantity he denotes with the Greek character Φ of his title.
Think of it this way: your digital camera has a prodigious memory capacity but its millions of pixels never "see" a photo. Your mind can because your brain actively constructs scenarios, tableaux and even simple perceptions from the integrated inputs of myriad specialised circuits. So Φ is a measure of that integration.
Tononi's approach can explain some curious phenomenology of consciousness. Why do we lose consciousness when we go to sleep? He would say that this is a time when information from the brain's specialised circuits is no longer integrated. Why are brain seizures associated with a loss of consciousness? Again, seizures seem to block complex informational exchange.
These ideas move us closer to grasping what consciousness is because, if Tononi is right, he can in principle measure varying degrees of consciousness among different people, or even different organisms. But what about bats - those famous subjects of debates on consciousness? Are we any closer to knowing what it is like to be one? Not yet, it seems, but perhaps now Tononi at least has students of consciousness travelling along the path to Paradise.
Mark Pagel is an evolutionary biologist at the University of Reading, UK. His latest book isWired for Culture (Allen Lane/W. W. Norton)
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