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Fig. 10.12. (a) Time-varying persistence of the bilateral connections in the cortical network. On
y-axes all the 120 possible reciprocal connections while time in seconds on x-axes. The colour of
the line corresponding to a particular link codes the number of subjects that actually hold such
a connection. (b) Average time-varying 3-motif spectra. On y-axes all the 13 possible directed
3-motifs are listed while time in seconds is displayed on x-axes.
In Figure 10.12(b), we compared the 3-motif properties of real brain networks
with random networks and we identified some motif classes that occurred more
frequently during particular stages of the movement. Of particular interest is the
involvement of the feed-forward-loop motif (the fifth in the Figure 10.4) that
tends to significantly (p < 0.01) increase during the proper movement execution
(from about 0 to +1 s ). This type of building block is known to play an important
functional role in information processing. In fact, one possible function of this
circuit is to activate output only if the input signal is persistent and to allow a
rapid deactivation when the input goes off. In the cortical context, a possible
interpretation of such a motif would make a particular ROI act as a “switch” for
the communication between the others two ROIs composing the triad. Another
interesting aspect was revealed by the significant (p<<0.01) “persistence” of the
single-input motif (the third in the Figure 10.4) that represented the highest
recurrent pattern of interconnections during the entire evolution of the foot
movement. The main function of this motif is known to involve the “activation”
of several parallel pathways by a single activator. Thus, since the single-input
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