Carl Zimmer has a piece in the New York Times on Guilio Tononi’s theory of consciousness (here). Tononi is trying to quantify consciousness in terms of ‘phi’, the amount of integrated information in networks. In simplistic terms, the higher the ‘phi’ – the higher the consciousness. My reaction to the theory is lukewarm but the attempt to measure the amount of consciousness in people is a great step forward for medicine. This is Zimmer’s description of the technique:
…he and his colleagues placed a small magnetic coil on the heads of volunteers. The coil delivered a pulse of magnetism lasting a tenth of a second. The burst causes neurons in a small patch of the brain to fire, and they in turn send signals to other neurons, making them fire as well.
To track these reverberations, Dr. Tononi and his colleagues recorded brain activity with a mesh of scalp electrodes. They found that the brain reverberated like a ringing bell, with neurons firing in a complex pattern across large areas of the brain for 295 milliseconds.
Then the scientists gave the subjects a sedative called midazolam and delivered another pulse. In the anesthetized brain, the reverberations produced a much simpler response in a much smaller region, lasting just 110 milliseconds. As the midazolam started to wear off, the pulses began to produce richer, longer echoes. Dr. Tononi has gotten similar results when he has delivered pulses to sleeping people or at least people in dream-free stages of sleep. he and his colleagues reported that dreaming brains respond more like wakeful ones. Dr. Tononi is now collaborating with Dr. Steven Laureys of the University of Liège in Belgium to test his theory on people in persistent vegetative states. That would give us a consciousness index, Dr. Laureys said.
What a fabulous tool that would be, with so many uses. If it comes to be, then we will have to remember that it gives us the ‘how much’ and ‘when’ of consciousness but not the ‘how’ or ‘why’. It does not help us with what information is being integrated, how the integration is done and what the brain does with the result.