This is talk 11 (of 31) at the Conference on Brain Network Dynamics held at the University of California at Berkeley on January 26-27, 2007. Speaker is Marcus E. Raichle, Departments of Radiology, Neurology, and Anatomy and Neurobiology, Washington University School of Medicine St Louis, Missouri. http://www.nil.wustl.edu/labs/raichle/.

Abstract:
Functional neuroimaging has played a dominant role in the development of cognitive neuroscience. The overwhelming majority of this work has focused on studies of the response of the brain to controlled stimuli and carefully controlled tasks. This approach reflects a long-standing view of the brain as primarily reflexive, driven by the momentary demands of the environment. An alternative view of brain function is that the brain’s operations are mainly intrinsic involving the maintenance of information for interpreting, responding to and even predicting environmental demands. The former has motivated most neuroscience research including that with functional neuroimaging. This is likely the case because experiments designed to measure brain responses to controlled stimuli and carefully designed tasks can be very productive whereas evaluating the behavioral relevance of intrinsic brain activity can be an illusive enterprise.

Motivation for studies of the brain’s intrinsic activity has come, in part, from the realization that it commands most of the brain’s enormous energy budget, upwards of 80% by some estimates. Evoked activity on the other hand represents a very small fraction (~ 1-5%). The challenge is how to evaluate intrinsic activity. Neurophysiologists have focused on spontaneous activity in the form of oscillations in various frequency bands. Neuroimaging with fMRI provides an important extension of that work as revealed by spatial patterns of coherence in the spontaneous fluctuations of the fMRI BOLD signal. This presentation will focus on the nature and significance of these observations and their possible relevance to the underlying neurophysiology.

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