Data-driven clustering reveals a fundamental subdivision of the human cortex into two global systems

Abstract

Global organizational principles are critical for understanding cortical functionality. Recently we proposed a global sub-division of the posterior cortex into two large-scale systems. One system, labeled extrinsic, comprises the sensory-motor cortex, and is associated with the external environment. The second system, labeled intrinsic, overlaps substantially with the previously described "default-mode" network, and is likely associated with inner-oriented processing. This global partition of the cerebral cortex emerged from hemodynamic imaging data the analysis of which was constrained by pre-determined hypotheses. Here we applied a hypothesis-free, unsupervised two-class clustering algorithm (k-means) to a large set of fMRI data. The two clusters delineated by this unsupervised hypothesis-free procedure showed high anatomical consistency across individuals, and their cortical topography coincided largely with the previously determined extrinsic and intrinsic systems. These new clustering-based results confirm that the intrinsic-extrinsic subdivision constitutes a fundamental cortical divide.

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

“…complex | graph | modularity | rest | connectome I ncreasing evidence points to a fundamental distinction between two large-scale functional systems in the brain (1)(2)(3)(4). One system, comprising regions of lateral prefrontal and parietal cortex, dorsal anterior cingulate, and anterior insula/frontoopercular regions, typically shows increased activation during performance of challenging cognitive tasks and has been implicated in attentional and cognitive control functions (5,6).…”

“…One system, comprising regions of lateral prefrontal and parietal cortex, dorsal anterior cingulate, and anterior insula/frontoopercular regions, typically shows increased activation during performance of challenging cognitive tasks and has been implicated in attentional and cognitive control functions (5,6). It may thus be generally referred to as an external attention system (EAS), but it has also been labeled the task-positive and extrinsic network (3,4). 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).…”

“…The apparent antagonism between these two systems is mirrored in their spontaneous dynamics, which are often strongly anticorrelated (2). These competitive interactions are thought to promote adaptive and efficient alternation between DMN-dominated introspective thought and EAS-mediated processing of external stimuli (1)(2)(3)(4).…”

Brain activity at rest: a multiscale hierarchical functional organization

“…More recently, Golland et al (2008) generalized this partition to the whole brain using an unsupervised approach. They revealed an intrinsic system exhibiting an inner-oriented mental activity and overlapping the DMN and an extrinsic system driven by external inputs and activated during sensory stimulations, including the attentional network and the sensory-motor cortex.…”

The epileptogenic network: the relationship between resting state and pre-spike related perturbations

“…RSNs represent the organization of ongoing baseline neural activity of distinct, highly specialized networks that are functionally identified (Golland et al, 2008, Yeo et al, 2011. At rest, the human brain consumes about 50% of its metabolic energy in intrinsic signalling and processing, while only 5% of its energy is utilized in response to neural activity of external stimuli (Buzsaki et al, 2007, Liao et al, 2010a, Raichle et al, 2001).…”