Brain–Computer Interfaces - Index of

84 G. Pfurtscheller et al.
A
B
C
1 s
z = –32 z = 56 z = 70 z = 74
Fig. 4 (a) Examples of induced beta oscillations during foot MI at electrode position Cz.
Activation patterns through the blood oxygenation level-dependent BOLD signal during right (b,
d) and left foot movement imagination (c, e) in the tetraplegic patient. Strong activation was
found in the contralateral primary motor foot area. Right side on the image corresponds to the
left hemisphere. Z-coordinates correspond to Talairach space [64]
movement was 30 s long, with five blocks of each type of foot MI. Significant
activation with imagery versus rest was detected in the primary foot area contralateral
to imagery, premotor and supplementary motor areas, and in the cerebellum
ipsilaterally (Fig. 4). This strong activation is at first glance surprising, but may be
explained by the long-lasting MI practice and the vividness of MI by the tetraplegic
patient.
3.3 The Beta Rebound (ERS) and its Importance for BCI
Of importance for the BCI community is that the beta rebound is not only characteristic
for the termination of movement execution but also of MI (for further
details see Chapter 3 in this book). Self-paced finger movements induce such a
beta rebound not only in the contralateral hand representation area but also with
slightly higher frequencies and an earlier onset in midcentral areas overlaying the
supplementary motor area (SMA) [52]. This midcentrally induced beta rebound is
especially dominant following voluntary foot movement [33] and foot MI [49]. We
speculate, therefore, that the termination of motor cortex activation after execution
or imagination of a body part movement may involve at least two neural networks,
one in the primary motor area and another in the SMA. Foot movement may involve
D
E
13.2
2.66