  We study the topological properties of functional connectivity patterns among
cortical areas in the frequency domain. The cortical networks were estimated
from high-resolution EEG recordings in a group of spinal cord injured patients
and in a group of healthy subjects, during the preparation of a limb movement.
We first evaluate global and local efficiency, as indicators of the structural
connectivity respectively at a global and local scale. Then, we use the Markov
Clustering method to analyse the division of the network into community
structures. The results indicate large differences between the injured patients
and the healthy subjects. In particular, the networks of spinal cord injured
patient exhibited a higher density of efficient clusters. In the Alpha (7-12
Hz) frequency band, the two observed largest communities were mainly composed
by the cingulate motor areas with the supplementary motor areas, and by the
pre-motor areas with the right primary motor area of the foot. This functional
separation strengthens the hypothesis of a compensative mechanism due to the
partial alteration in the primary motor areas because of the effects of the
spinal cord injury.
