Information Technology Reference
In-Depth Information
Fig. 10.10. Average time-varying efficiency indexes. The lighter lines around the mean value
indicate the time courses of the 25
th
and 75
th
percentile. The latency from the movement onset is
shown on the x-axes.
Consequently the structure of the cortical networks tends to maximize the
interplay between the global integration and its local interactions. This particular
structure represents one of the best way in which the cortical areas communicate,
since the relevant network presents simultaneously short links between each pair
of ROIs and highly connected clusters (i.e. small-world architecture). After the
onset (from the onset to +0.5
s
), the estimated cortical networks show a typical
random organization of the functional links, with a high
E
g
and a low
E
l
,
reflecting the dense presence of wide-scope interactions among the ROIs, but a
low tendency of the same cortical regions to form functional clusters. In the last
period of the movement execution (from about +0.5 to +1
s
) the estimated
cortical networks mainly show high
E
l
values and low
E
g
values. The resulting
structure is known to reflect the properties of regular and ordered graphs in
which the local property of clustering is privileged with respect to the overall
communication. Figure 10.11(a) shows the average time-varying course of the
weighted-density
k
w
in the Beta band during the analyzed period of interest.
In particular, the average intensity of the network links during the preparation
(from -0.5
s
to the onset) is relatively low if compared with its maximum value
reached in the following movement execution. In correspondence with this
period the network structure presents the most efficient pattern of
communication, as revealed by the estimated small-world characteristic.
