blue skies from pain

Why does a clear blue sky feel so different from the screech of a badly tuned violin? - What Is Consciousness? by Christof Koch

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So, so you think you can tell
Heaven from Hell
Blue skies from pain
Can you tell a green field
From a cold steel rail
A smile from a veil
Do you think you can tell?

The scientists held a sheathed coil of wire against the scalp and “zapped” it—sent an intense pulse of magnetic energy into the skull — inducing a brief electric current in the neurons underneath. The perturbation, in turn, excited and inhibited the neurons’ partner cells in connected regions, in a chain reverberating across the cortex, until the activity died out. A network of electroencephalogram (EEG) sensors, positioned outside the skull, recorded these electrical signals. As they unfolded over time, these traces, each corresponding to a specific location in the brain below the skull, yielded a movie.

These unfolding records neither sketched a stereotypical pattern, nor were they completely random. Remarkably, the more predictable these waxing and waning rhythms were, the more likely the brain was unconscious. The researchers quantified this intuition by compressing the data in the movie with an algorithm commonly used to “zip” computer files. The zipping yielded an estimate of the complexity of the brain’s response. Volunteers who were awake turned out have a “perturbational complexity index” of between 0.31 and 0.70, dropping to below 0.31 when deeply asleep or anesthetized. Massimini and Tononi tested this zap-and-zip measure on 48 patients who were brain-injured but responsive and awake, finding that in every case, the method confirmed the behavioral evidence for consciousness.

via Mind-Body Problems, Introduction