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Brain–Computer Interfaces - Index of

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Neur<strong>of</strong>eedback Training for BCI Control 73<br />

Fig. 3 Effect <strong>of</strong> different BCI feedback displays on oscillatory activity and heart rate. The top<br />

images depict a horizontal bar feedback condition, and the bottom images present a virtual street<br />

feedback condition. The two left panels each show the monitor or VR display. The middle panels<br />

display the corresponding ERD maps computed at electrode position Cz for hand motor imagery<br />

during bar and VR feedback. The right panels show corresponding changes in the heart rate<br />

(modified from Pfurtscheller et al. [54])<br />

presentation types, namely abstract versus realistic feedback, to two experimental<br />

groups, while keeping the amount <strong>of</strong> information provided by the feedback equivalent.<br />

The “abstract feedback” group was trained to use left or right hand motor<br />

imagery to control a moving bar (varying in size) on a computer monitor. This is the<br />

standard protocol <strong>of</strong> the Graz-BCI, cf. [37, 40]. The “realistic feedback group”, in<br />

contrast, used their online EEG parameters to control a video presentation showing<br />

an object-directed grasp from the actor’s perspective. The results suggest that, when<br />

feedback provides comparable information on the continuous and final outcomes<br />

<strong>of</strong> mental actions, the type <strong>of</strong> feedback (abstract vs. realistic) does not influence<br />

performance. Considering the task-related EEG changes (i.e. ERD/ERS patterns),<br />

there was a significant difference between screening and feedback sessions in both<br />

groups, but the “realistic feedback” group showed more significant effects due to<br />

the feedback. Another important question is whether VR can reduce the number <strong>of</strong><br />

training sessions [50].<br />

4 Final Considerations<br />

The BCI paradigm (see Fig. 4) basically corresponds to an operant conditioning<br />

neur<strong>of</strong>eedback paradigm. However, important differences exist between the training<br />

(e.g. with the basket paradigm) and the application (e.g. controlling a hand orthosis)

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