Functional Brain Connectivity during Multiple Motor Imagery Tasks in Spinal Cord Injury

Table 3

Summary presentation and description of the most important models and connectivity metrics or measures that were used in the methodological section of this study.

Metric or model name	Acronym	Description
Current cortical density	CCD	Forward problem solution	A model that aims to explain the correspondence of cortical source activity to scalp electrical potentials, taking account of skull and scalp conductivity.
Weighted minimum norm estimate	wMNE	Inverse problem solution	An estimation of how signals captured at the scalp correspond to source activations, with their power limited by the cortical physiology.
Directed transfer function	DTF	Granger causality measure	A metric of effective network connectivity (functional connectivity that incorporates causal relations instead of statistical inference alone) that produces directed networks with weighted edges.
Characteristic path length	CPL	Network integration	A representative measure of shortest distances between network nodes that are connected to each other.
Clustering coefficient	CC	Network segregation	A measure of the tendency of network nodes to become organized into functionally separated clusters.
Density	D	Network density	A measure of existing connections against the theoretical maximum number of possible connections if the network was fully connected.
Small-worldness	SW	Overall network effectiveness	A model of network behavior, where short paths and increased forming of functional clusters lead to optimization and resilience of information transfer.
Out-strength and in-strength	OS and IS		The total nodal sum of weights from outgoing and incoming connections, respectively.