Intrinsic functional architecture in the anaesthetized

J. L. Vincent, G. H. Patel1, M. D. Fox, A. Z. Snyder, J. T. Baker, D. C. Van Essen, J. M. Zempel, L. H. Snyder, M. Corbetta, M. E. Raichle
Nature Vol 447| 3 May 2007| doi:10.1038/nature05758

The traditional approach to studying brain function is to measure
physiological responses to controlled sensory, motor and cognitive
paradigms. However, most of the brain’s energy consumption
is devoted to ongoing metabolic activity not clearly associated with
any particular stimulus or behaviour1. Functional magnetic resonance
imaging studies in humans aimed at understanding this
ongoing activity have shown that spontaneous fluctuations of the
blood-oxygen-level-dependent signal occur continuously in the
resting state. In humans, these fluctuations are temporally coherent
within widely distributed cortical systems that recapitulate the
functional architecture of responses evoked by experimentally
administered tasks2–6. Here, we show that the same phenomenon
is present in anaesthetized monkeys even at anaesthetic levels
known to induce profound loss of consciousness. We specifically
demonstrate coherent spontaneous fluctuations within three well
known systems (oculomotor, somatomotor and visual) and the
‘default’ system, a set of brain regions thought by some to support
uniquely human capabilities. Our results indicate that coherent
system fluctuations probably reflect an evolutionarily conserved
aspect of brain functional organization that transcends levels of
consciousness.