Consistency and functional specialization in the default mode brain network

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.activation ͉ deactivation ͉ default mode ͉ functional MRI ͉ spontaneous activity

Competitive and cooperative dynamics of large-scale brain functional networks supporting recollection

“…The method is well-suited for characterizing the spatial anatomy and temporal dynamics of each network, while accounting for possible functional heterogeneity within either the DMN and/or EAS (5, 7, 21, 22, 24) (SI Text, section S.3). The DMN was identified as a single component with a characteristic functional anatomy consistent with prior work (7,10). The EAS was split into four distinct components: (i) a dorsal attention network (DAN) commonly associated with focusing attention on external stimuli (2, 6); (ii) a cinguloopercular network (CON) implicated in interoceptive awareness (35), salience processing of external stimuli (25), and maintenance of response set during cognitive task performance (5); and (iii and iv) left and (4) right frontoparietal networks (LFPN and RFPN, respectively) often implicated in top-down executive control processes (5,24).…”

“…First, the DMN and EAS do not always operate as functionally homogeneous entities, often splitting into distinct subnetworks depending on task demands (5,7,21,22). This finding is particularly true for the EAS, which has been functionally dissociated into a number of distinct subsystems (5,6,(22)(23)(24)(25)(26), although similar observations have been noted for the DMN (7,10,21). Second, local field potentials recorded from putative DMN and EAS regions in felines are more often positively than negatively correlated with each other, suggesting that these regions often interact cooperatively (27).…”

“…The other system, often called the default mode network (DMN), is localized primarily to midline posterior and anterior cortical regions, the angular gyri, and medial and lateral temporal cortices (7,8). It often shows decreased activity during tasks requiring attention to external stimuli (9,10) and increased activity during unconstrained thought, introspection, and self-related processing (7,11). The apparent antagonism between these two systems is mirrored in their spontaneous dynamics, which are often strongly anticorrelated (2).…”

Brain electrical activities of dancers and fast ball sports athletes are different

“…Spontaneous resting activity, measured by blood oxygen level-dependent (BOLD) in fMRI in the resting awake or anesthetized brain, is organized in multiple highly specific functional anatomical networks (resting state networks, RSNs), only one of which corresponds to the DMN (RSA 1) (De Luca et al 2006;Damoiseaux et al 2006). Those RSNs strongly overlap with sensorimotor, visual, auditory, attention, language, and default networks that are commonly modulated during active behavioral tasks (Fox et al 2006;Mantini et al 2007;Harrison et al 2008).…”

Topographic maps of multisensory attention

“…A separate interconnected network, the default mode, or task negative network (7)(8)(9), is comprised of brain regions more active during rest or attention to internal stimuli or narrative (10). We use here the nomenclature "attention control" and "default mode" networks rather than "task positive" or "task negative" networks because the positive or negative activation of each of these networks depends entirely on whether the task measures internal mentalization or attention to external stimuli (11), and both may be coactivated or have similar behavioral associations (12).…”