The human brain is intrinsically organized into dynamic, anticorrelated functional networks

Abstract

During performance of attention-demanding cognitive tasks, certain regions of the brain routinely increase activity, whereas others routinely decrease activity. In this study, we investigate the extent to which this task-related dichotomy is represented intrinsically in the resting human brain through examination of spontaneous fluctuations in the functional MRI blood oxygen level-dependent signal. We identify two diametrically opposed, widely distributed brain networks on the basis of both spontaneous correlations within each network and anticorrelations between networks. One network consists of regions routinely exhibiting task-related activations and the other of regions routinely exhibiting task-related deactivations. This intrinsic organization, featuring the presence of anticorrelated networks in the absence of overt task performance, provides a critical context in which to understand brain function. We suggest that both task-driven neuronal responses and behavior are reflections of this dynamic, ongoing, functional organization of the brain.

Figures

Fig. 1.

Intrinsic correlations between a seed region in the PCC and all other voxels in the brain for a single subject during resting fixation. The spatial distribution of correlation coefficients shows both correlations (positive values) and anticorrelations (negative values), thresholded at R = 0.3. The time course for a single run is shown for the seed region (PCC, yellow), a region positively correlated with this seed region in the MPF (orange), and a region negatively correlated with the seed region in the IPS (blue).

Fig. 2.

Population-based z-score maps showing nodes significantly correlated or anticorrelated with six seed regions (small circles). (Upper) (Left) Results from three task-negative seed regions: MPF, PCC, and LP. (Right) Results from three task-positive seed regions: IPS, FEF, and MT+. (Lower) The conjunction map is an average, including only nodes significantly correlated or anticorrelated with five of the six seed regions. White contours are drawn on the conjunction map and copied onto the other maps to facilitate comparison.

Fig. 3.

Intrinsically defined anticorrelated processing networks in the brain. Positive nodes are significantly correlated with seed regions involved in focused attention and working memory (task-positive seeds) and significantly anticorrelated with seed regions routinely deactivated during attention demanding cognitive tasks (task-negative seeds). Negative nodes are significantly correlated with task-negative seed regions and significantly anticorrelated with task-positive seed regions. (Left) Lateral and medial views of left hemisphere. (Center) Dorsal view. (Right) Lateral and medial views of right hemisphere.