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Therefore, it is interesting to note that the optimal organization of the functional
links among the cortical areas during the preparation of the foot movement is not
correlated to the need of a high level of overall connectivity.
Fig. 10.11. (a) Average time-varying “weighted-density” in the Beta band. (b)
Average time-
varying “reciprocity” during the period of interest in the Beta band. On y-axes the correlation
coefficient
ρ
while time in seconds on x-axes.
The analysis of the average time-varying reciprocity index revealed an
interesting behavior during the preparation (from about -1 to 0
s
) of the
movement in the Beta frequency band. In such a period, the functional network
moved from a reciprocal (r = 0.1) to an anti-reciprocal (r = -0.1) state. This aspect
emphasizes the role of the early preparation in which a high level of mutual
exchange of information is required to speed up the cortical process in
expectation of the execution. Moreover, by tracking the evolving involvement of
each single reciprocal connection (see Fig. 10.12(a)) it is possible to observe their
“persistence” during the entire period of interest. In particular, the persistent
bilateral links between the cingulate motor areas and the supplementary motor
areas (they correspond to the rows 58 and 69) in the Beta band reveals a novel
aspect of such a connection that anyway was expected in a self-paced modality of
movement generation, as in our experimental condition.
