Figure 1.
(a) Experimental paradigm of one trial. (b) 64-electrode positions.
Figure 2.
Examples of group-level average time-frequency maps at typical electrode locations for six MI tasks.
LH, RH, F, BH, LH&RF, RH&LF indicate left hand, right hand, feet, both hands, left hand combined with right foot, right hand combined with left foot respectively. Blue indicates ERD and red indicates ERS, vertical dashed line indicates stimulus onset.
Figure 3.
The topographical distribution of ERD patterns within beta band for six MI tasks.
LH, RH, F, BH, LH&RF, RH&LF indicate left hand, right hand, feet, both hands, left hand combined with right foot, right hand combined with left foot respectively. Blue regions indicate the involved areas when ERD occurs during mental tasks.
Figure 4.
Source localization of induced beta ERD for six MI tasks.
LH, RH, F, BH, LH&RF, RH&LF indicate left hand, right hand, feet, both hands, left hand combined with right foot, right hand combined with left foot respectively. Red regions indicate the estimated sources during mental tasks. L indicates left hemisphere and R indicates right hemisphere.
Figure 5.
The networks of six different types of mental tasks.
LH, RH, F, BH, LH&RF, RH&LF indicate left hand, right hand, feet, both hands, left hand combined with right foot, right hand combined with left foot respectively. Green line represents the unidirectional connectivity whereas the red line represents the bi-directional connectivity. The green arrows' tips point toward electrodes to which the flows are directed with their bases at ‘source electrodes’.
Figure 6.
The mean positive causal flow of per electrode for six MI tasks.
LH, RH, F, BH, LH&RF, RH&LF indicate left hand, right hand, feet, both hands, left hand combined with right foot, right hand combined with left foot respectively. Horizontal axis represents all 21 selected channels.
Figure 7.
The mean causal density of per electrode for six MI tasks.
LH, RH, F, BH, LH&RF, RH&LF indicate left hand, right hand, feet, both hands, left hand combined with right foot, right hand combined with left foot respectively. Horizontal axis represents all 21 selected channels.
Table 1.
The electrodes with significant difference for the comparison of positive causal flow in six groups.
Table 2.
The comparison of causal density for all selected channels in six groups.
Figure 8.
The mean out-degree of the midfrontal electrodes under a 60% threshold (up) and under a 30% threshold (bottom) for six MI tasks.
Red bar indicates simple limb motor imagery, while blue bar indicates compound limb motor imagery. LH, RH, F, BH, LH&RF, RH&LF indicate left hand, right hand, feet, both hands, left hand combined with right foot, right hand combined with left foot respectively. Horizontal axis represents 5 selected channels.
Figure 9.
The comparison between connectivity number in the network of compound limb motor imagery and the summation of connectivity number in the networks of corresponding simple limb motor imagery.
Blue bar indicates compound limb motor imagery, while red bar indicates the summation of simple limb motor imagery. (LH+RH) indicates the summation of left hand imagery and right hand imagery. (LH+F) indicates the summation of left hand imagery and feet imagery. (RH+F) indicates the summation of right hand imagery and feet imagery. Condition pairs that significantly differ from each other are indicated by an asterisk (p<0.05) or two asterisks (p<0.01).
Figure 10.
The example of group-level average time-frequency map (up) and VEP (bottom) at electrode Cz for right hand combined with left foot imagery.
Blue indicates ERD and red indicates ERS. Vertical dashed line indicates stimulus onset.