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http://banban.blogbus.com/logs/34364278.html

It's excellent! It was a random page I turned to before reading the chapter in my reading list. I like the thoughts.

From book chapter Historical and Physiological Perspective in the second edition of Handbook of Functional Neuroimaging of Cognition (eds. Cabeza & Kingstone, 2005):

The Brain's Dark Energy

[As has been known long ago,] the brain represents about 2% of the total body weight but accounts about 20% of the energy consumed, 10 times that predicted by its weight alone (Clark & Sokoloff, 1999).

[One might expect that the energy are used by the neural activities evoked by the environmental events. Surprisingly, not much.] Regional changes in absolute blood flow are rarely more than 5-10% of the resting blood flow of the brain in the areas typically affected by the cognitive tasks. ... [Not] even the most vigorous sensory and motor activity (Fox et al., 1987; Fox et al., 1985; Sokoloff et al., 1955).

... well more than 50% of this energy support the ongoing activity of neurotransmitters. This remarkable fact should alert all who do functional brain imaging and neurophysiology as well to the fact that much of what the brain is actually doing is being ignored.

A published experiment in cat visual cortex [directly demonstrated that] in the absence of any sensory input the cat visual cortex appeared to be creating, in its spontaneous activity, representations of anticipated visual stimuli (Kenet et al., 2003). [Recent paper in Nature (Sirotin & Das, 2009) stated that, "Electrical signalling among brain cells summons the local delivery of extra blood — the basis of functional brain imaging. Yet sometimes, blood is sent in anticipation of neural events that never take place." They found "an increase in blood flow in the visual cortices of monkeys when the animals looked at a dot on a screen — but also when they were simply expecting the dot to appear". There is no a corresponding electrode signal in the later condition.]

[Raichle M. E. concluded in this book chapter, which I think is brilliant, that] the brain develops and maintains a probabilistic model of anticipated events and that the majority of ongoing neuronal activity is an internal representation of that model against which sensory information is compared.