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The Salience Network Of The Human Brain

The salience network of the human brain is a large scale brain network that is primarily composed of the anterior insula (AI) and dorsal anterior cingulate cortex (dACC). It is involved in detecting and filtering salient stimuli, as well as in recruiting relevant functional networks.

Together with its interconnected brain networks, the salience network (SN) contributes to a variety of complex functions, including communication, social behavior, and self-awareness through the integration of sensory, emotional, and cognitive information.

The network is detectable through independent component analysis of resting state fMRI images, as well as seed based functional connectivity analysis. In addition to the AI and dACC, the salience network also consists of the substantia nigra, ventral tegmental area, ventral striatum, amygdala, dorsomedial thalamus, and hypothalamus.

The functional connectivity has been linked with structural connectivity through diffusion tensor imaging, which reveals white matter tracts between the AI and dACC.

Function Of The Salience Network

While the function of the salience network is not exactly known, it has been implicated in the detection and integration of emotional and sensory stimuli, as well as in modulating the switch between the internally directed cognition of the default mode network and the externally directed cognition of the central executive network.

Evidence that the salience network mediates a switch between the default mode network and CEN comes from granger causality analysis and studies utilizing transcranial magnetic stimulation.

The timing of electrophysiological responses during the oddball task is consistent with interaction, as after the initial mismatch negativity response is transmitted “bottom-up” from sensory regions, a “top-down” signal localized to the AI and dACC occurs before a widespread evoked potential that corresponds to attentional shifting.

Anatomy

The salience network is primarily anchored at the AI and dACC. The node in the AI corresponds with the dorsal-anterior division distinguished in meta analyses of task-positive network related neuroimaging studies.

salience network of the human brain
The salience network is theorized to mediate switching between the default mode network and central executive network
Credit: Nekovarova, Fajnerova, Horacek, Spaniel CC BY 3.0

The AI and dACC are linked via a white matter tract along the uncinate fasciculus.

The subcortical nodes have yet to be structurally linked to the AI and dACC, however both seed based and resting state studies have observed intrinsic connectivity of the cortical nodes with subcortical nodes consisting of the sublenticular extended amygdala, the putamen, the dorsomedial thalamus, the ventral striatum, and the substantia nigra/ventral tegmental area.

The salience network is also distinguished by distinct cellular components, including von Economo neurons in the AI/dACC. Cortico-striatal-thalamic loop circuits contribute to the salience network.