Psy 136 Large-Scale Brain Networks

What measures can one use to describe a dysfunctional brain organization? The author mentions five of them

1. abnormal small-world architecture 2. Dysfunctional subsystems 3. Compensatory subsystems 4. Identification of dysfunctional hubs 5. Disease identification, onset and progression In summary, graph-theoretical network matrices help to uncover loci of altered local and global network connectivity in psychopathology and help identify specific nodes for more targeted structural and functional connectivity analysis

What is the small-world architecture? Is it present in the brain? How about social networks?

A small world network is a type of mathematical graph in which most nodes are not neighbors of one another, but most nodes can be reached from every other node by a small number of hops to steps It is a dense local clustering of connections between neighboring nodes and a short path length between nodes, due to the low frequency of long length connections This exists in the brain because it is cost effective wiring without losing any data

What are the three core neurocognitive networks (according to Vinod Menon)? What brain structures are they anchored in?

Central Executive Network (CEN): a frontoparietal system anchored in dlPFC and the lateral PPC Default Mode Network (DMN): anchored in the PCC and the mPFC, with prominent nodes in the medial temporal lobe (MTL) and the angular gyrus Salience Network (SN): a cingulate-frontal operculum system anchored in the dorsal anterior cingulate cortex (dACC) and frontoinsular cotex (FIC), and is involved in detecting, integrating and filtering relevant interoceptive, autonomic and emotional information

Dysfunctional subsystems

Examine functional organization in key subdivisions Examining the global connectivity of regions with known structural pathology such as the posterior cingulate cortex (PCC) and hippocampus (in autism), or the insular cortex in FTD, can help identify disrupted subnetworks and cognitive systems differentially impacted by each disorder

What is the recent paradigm shift in the study of brain dysfunction?

Focuses on understanding how disturbances in distributed brain areas operating within large-scale networks contribute to cognitive and affective dysfunction Large scale networks and the discovery that the human brain is intrinsically organized into coherent functional networks

Identification of dysfunctional hubs

Identifying vulnerable hubs that are crucial for integrating information from many other brain areas

What is unique about the insula from the network perspective? Where is it located?

It is unique in that it is situated at the interface of the cognitive, homeostatic and affective systems of the human brain, providing a link between stimulus-driven processing and brain regions involved in monitoring the internal milieu and interoceptice awareness of physiological changes in the body

Disease identification, onset and progression

Network matrices can potentially be used as biomarkers to distinguish between disease stages

Abnormal small-world architecture

Measure path length between nodes Clustering coefficient Cumulative metric sigma (the ratio of normalized clustering coefficient to the characteristic path length, a measure of small-world organization)

What are the nodes and edges in a brain network?

Nodes (vertices) = brain regions Edges = the connections between the nodes Dysfunctional nodes or edges result in aberrant signaling which can then propagate to the whole network or subnetwork across the brain

Compensatory subsystems

Regional and subnetwork analyses can provide evidence for compensatory subsystems

Which of the three networks may act as a switch for the other two?

Salience Network (SN)

Which of the three networks is closely associated with the amygdala, the substantia nigra, and the ventral tegmental area (VTA)?

Salience Network (SN): because important for detecting emotion and reward saliency

Which of the three networks is involved in the processing of pain and the empathy for pain?

Salience network (SN)

What is graph theory?

The study of graphs, which are mathematical structures used to model pairwise relations between objects It can be used to analyze any large-scale networks

From the network perspective, what is the fundamental difference between the anterior cingulate cortex (ACC) and the posterior cingulate cortex (PCC), and between the dorsolateral PFC (dlPFC) and the ventromedial PFC (vmPFC)?

the ACC is in the SN, the PCC is in the DMN the dlPFC is in the CEN, the vmPFC is in the DMN They are in different systems