[4] On the mesoscopic scale (micrometer to millimeter),[3] mesoscale analysis seeks to capture anatomically distinct populations of typically 80-120 neurons (e.g. cortical columns) across different brain regions.
[7] Structural connectivity describes how regions in the brain can communicate through anatomical pathways such as synaptic coupling between cells and axonal projections between neurons at the micro-scale and meso-scale and white matter fiber bundles at the macro scale.
[7] Optogenetic functional MRI (ofMRI) allows selective mapping of brain regions based on genetic markers, anatomic location, and axonal projections.
[13] Graph theory methods, when applied properly, can offer important new insights into the structure and function of networked brain systems, including their architecture, evolution, development, and clinical disorders.
[14] It describes meaningful information about the topological architecture of human brain networks, such as small-worldness, modular organization, and highly connected or centralized hubs.
[13] For example, in a study hypothesizing that aging processes modulate brain connectivity networks, 170 healthy elderly volunteers were submitted to EEG recordings in order to define age-related normative limits.
[15] Graph theory functions were applied to exact low-resolution electromagnetic tomography on cortical sources in order to evaluate the small-world parameter as a representative model of network architecture.
Key components include:[16] The degree of a node is the number of connections that link with the rest of the network, which is one of the fundamental measures for defining the model.
It is more actively utilized than the path length due to its easier numerical use and interpretation - for instance, estimating topological distances between elements of disconnected graphs.
Network science is largely built on the tools of graph theory, which focuses on the dyad (a single connection between two nodes) as the fundamental unit of interest.
However, the major difficulty of this cross-species network analysis is devising the measure to access the different connectome data from a range of species as each specimen has a unique biological baseline or structure.
[39] One study used novel methods such as Latent Dirichlet Association (LDA) combined with Independent Components Analysis (ICA) to generate multiple overlapping networks.
[44] Emotional representation in the brain has been proposed to be a functionally integrated system that involve large-scale cortical-subcortical networks tuned by bodily signals.
The key consequence of using network representations is that they can describe and uncover higher-level complexity in terms of the interaction perspective and further identify the overall processes of neural-behavioral activity.
For instance, the spatial distribution of network modules in auditory and visual cortex and of hub-like areas became more constrained to traditional anatomical boundaries in a multisensory task and displayed less variability across subjects.
Such approaches suggest that tasks with a heavy emphasis on sensory processing and integration appear to depend on tightly communicating cognitive hubs and sensorimotor regions.
[49][51] Research in the psychological and brain sciences has long sought to understand the nature of individual differences in human intelligence, examining the stunning breadth and diversity of intellectual abilities and the remarkable cognitive and neurobiological mechanisms from which they emerge.
elucidate how g – reflected in the positive manifold and the hierarchical pattern of correlations among tests – emerges from individual differences in the network topology and dynamics of the human brain.
In this viewpoint, the small-world topology of brain networks enables the rapid reconfiguration of their modular community structure, creating globally coordinated mental representations of a desired goal-state and the sequence of operations required to achieve it.
[62] Previous studies have identified the connection between personality factors and certain structures, functional brain networks and regions and how these interactions are crucial to emotional and cognitive processes.
[75] Studies have also shown that increased activation in the anterior insula and the frontal operculum in the SN is correlated with experiences of auditory verbal hallucinations in schizophrenic patients.
[82] Bipolar disorder is also thought to be characterized by abnormal functional connectivity between the FPN and motivational networks, with the DMN playing a mediation role.
The Central Executive Network, which helps maintain information in working memory and aids in decision making and problem solving, has been shown to be hypoactive in individuals with depression.
[91] Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease of upper and lower motor neurons, leading to respiratory issues and death in 3–5 years.
[107] A subnetwork that was centralized at the right angular gyrus and included frontal, temporal, and subcortical regions, showed enhanced connectivity in patients with insomnia.
[112] Several recent studies have suggested that AD patients have disruptive neuronal integrity in large-scale structural and functional brain systems underlying high-level cognition, as demonstrated by a loss of small-world network characteristics.
[116] Simple focal seizures with motor symptoms will affect muscle activity, causing jerking movements of a foot, the face, an arm or another part of the body.
When experiencing a complex focal seizure, patients may stare blankly into space, or experience automatisms (non-purposeful, repetitive movements such as lip smacking, blinking, grunting, gulping or shouting).
It is shown that neurological deficits do not only arise from focal tissue damage but also from local and remote changes in white-matter tracts and in neural interactions among widespread networks.
The results show that OCPD patients presented an increased functional connectivity in the precuneus (i.e., a posterior node of the DMN), known to be involved in the retrieval manipulation of past events in order to solve current problems and develop plans for the future.