Consistency and functional specialization in the default mode brain network - PubMed (original) (raw)

Consistency and functional specialization in the default mode brain network

Ben J Harrison et al. Proc Natl Acad Sci U S A. 2008.

Abstract

The notion of a "default mode of brain function" has taken on certain relevance in human neuroimaging studies and in relation to a network of lateral parietal and midline cortical regions that show prominent activity fluctuations during passive imaging states, such as rest. In this study, we perform three fMRI experiments that demonstrate consistency and specialization in the default mode network. Correlated activity fluctuations of default mode network regions are identified during (i) eyes-closed spontaneous rest, (ii) activation by moral dilemma, and (iii) deactivation by Stroop task performance. Across these imaging states, striking uniformity is shown in the basic anatomy of the default mode network, but with both tasks clearly and differentially modulating this activity compared with spontaneous fluctuations of the network at rest. Against rest, moral dilemma is further shown to evoke regionally specific activity increases of hypothesized functional relevance. Mapping spontaneous and task-related brain activity will help to constrain the meaning of the default mode network. These findings are discussed in relation to recent debate on the topic of default modes of brain function.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.

Fig. 1.

Default mode network activities across the three imaging states. (A) Spontaneous activity in the default mode network during rest and the associated time course of a representative subject (z score range = 3.5 to 7). (B) Task-related activity of the default mode network during the moral dilemma experiment and the associated mean (solid line) and standard error (dotted line) time course estimated across all subjects (z score range = 3.5 to >8). (C) Task-related activity of the default mode network during the Stroop task experiment and the associated mean (solid line) and standard error (dotted line) time course estimated across all subjects (z score range = 3.5 to 7). Diamonds located below this time course correspond to the approximate middle point of each Stroop task block. White diamonds, rest-fixation periods; green diamonds, congruent trials; red diamonds, incongruent trials. Image display: left = right.

Fig. 2.

Fig. 2.

Anatomical overlap of default mode network activities. (A) Representative axial slices showing the moral dilemma activation map (color) overlaid with the corresponding anatomy of the default mode network at rest (white contour lines). (B) Representative axial slices showing the Stroop task deactivation map (color) overlaid with the corresponding functional anatomy of the default mode network at rest (white contour lines). Image display: left = right.

Fig. 3.

Fig. 3.

Functional specialization in the default mode network. (A) Default mode network regions that showed relatively greater spatially correlated activity during the moral dilemma task compared with rest. (B) Default mode network regions whose spatially correlated activity at rest predicted their strength of correlated activity during the moral dilemma task. White circles and arrows indicate posterior and anterior cingulate cortex regions. Image display: left = right.

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