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Brain–Computer Interfaces - Index of

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122 B. Blankertz et al.<br />

Table 1 Results <strong>of</strong> a feedback study with six healthy volunteers (identification code in the first column).<br />

From the three classes used in the calibration measurement, the two chosen for feedback are<br />

indicated in the second column (L: left hand, R: right hand, F: right foot). The accuracies obtained<br />

online in cursor control are given in column 3. The average duration ± standard deviation <strong>of</strong> the<br />

feedback trials is provided in column 4 (duration from cue presentation to target hit). Participants<br />

are sorted according to feedback accuracy. Columns 5 and 6 report the information transfer rates<br />

(ITR) measured in bits per minute as obtained by Shannon’s formula, cf. (3). Here, the complete<br />

duration <strong>of</strong> each run was taken into account, i.e., also the inter-trial breaks from target hit to the<br />

presentation <strong>of</strong> the next cue. The column overall ITR (oITR) reports the average ITR <strong>of</strong> all runs (<strong>of</strong><br />

25 trials each), while column peak ITR (pITR) reports the peak ITR <strong>of</strong> all runs<br />

id classes accuracy [%] duration [s]<br />

oITR<br />

[b/m]<br />

pITR<br />

[b/m]<br />

al LF 98.0 ± 4.3 2.0 ± 0.9 24.4 35.4<br />

ay LR 95.0 ± 3.3 1.8 ± 0.8 22.6 31.5<br />

av LF 90.5 ± 10.2 3.5 ± 2.9 9.0 24.5<br />

aa LR 88.5 ± 8.1 1.5 ± 0.4 17.4 37.1<br />

aw RF 80.5 ± 5.8 2.6 ± 1.5 5.9 11.0<br />

mean 90.5 ± 7.6 2.3 ± 0.8 15.9 27.9<br />

3.2 Good Performance Without Subject Training<br />

The goal <strong>of</strong> our second feedback study was to investigate which proportion <strong>of</strong><br />

naive subjects could successfully use our system in the very first session [48].<br />

The design <strong>of</strong> this study was similar to the one described above. But here, the<br />

subjects were 14 individuals who never performed in a BCI experiment before.<br />

feedback accuracy [%]<br />

90<br />

80<br />

70<br />

60<br />

50<br />

cm ct cp zp cs cu ea at zr co eb cr cn<br />

90−100<br />

80−90<br />

70−80<br />

60−70<br />

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