FIG. 1.

From the fluctuating patterns of intrinsic activity seen in the human brain with fMRI BOLD imaging, striking patterns of spatial coherence within known brain systems can be extracted. A single-subject example of data from which these patterns are derived is shown (A). These data were obtained continuously over a period of 5 min (each row is 1 min, each frame is 2.3 sec). We have found it instructive to view the data occasionally in this way as it helps one understand the slowly moving, ever-changing nature of the activity. An interpolated version of these data in a movie format may be downloaded from ftp://imaging.wustl.edu/pub/raichlab/restless_brain. The patterns of spatial coherence shown on the bottom are obtained by placing a seed region in a single focus within a system (in this case, in the sensorimotor cortex) and extracting the resulting BOLD time series (B). This time series is then used as a regressor to search the brain for correlated time series. The results are brain-network–specific images of spatial coherence in the ongoing activity of the brain (C). This strategy has been applied with ever-increasing sophistication to systems throughout the human brain. A more complete description of the data-processing steps leading to such images is presented elsewhere along with alternate strategies (Zhang and Raichle, 2010). (D) Seven major brain networks analyzed in this way are shown. BOLD, blood oxygen level dependent; fMRI, functional magnetic resonance imaging.