Fig 1.
Pathways of human visual cortex.
Fig 2.
Pattern of checkerboard paradigm.
The coordinate (x, y) in the formulas (1) and (2) refer to the coordinate position of each pixel of the pattern on the display screen.
Fig 3.
BCI lab table.
Fig 4.
Configuration of electrode locations used in this study.
Fig 5.
The process of experiment (a).
(a) The experiment process of task 1 and task 2. (b) The experiment process of task 3 and task 4.
Fig 6.
The process of experiment (b).
Fig 7.
The process of experiment (c).
Fig 8.
Average power spectrum density of subjects at different stimulation frequencies.
(a) Average power spectrum density of subjects at 11 Hz. Equal-luminance red-green checkerboard induced higher EEG SNR. (b) Average power spectrum density of subjects at 16 Hz. The differences of the two paradigms are not significant. (c) Average power spectrum density of subjects at 18 Hz. The differences of the two paradigms are not significant. (d) Average power spectrum density of subjects at 8 Hz. We shortened the stimulus duration per trial to 2 seconds and equal-luminance red-green checkerboard still induced higher SNR.
Fig 9.
Average power spectrum density variance maps of subjects at 11 Hz and 16 Hz.
(a) Average power spectrum density variance map of subjects at 11 Hz. The equal-luminance colored stimulus has a significant effect on the brain response than black-white. (b) Average power spectrum density variance map of subjects at 16 Hz. There is no significant difference on the brain response between black-white and red-green stimulus at middle frequency spectrum (16 Hz).
Fig 10.
Mean variance histogram of the recognition accuracy of subjects with different stimulation duration.
First, we calculated the accuracy of each subject with different stimulation duration. Then we averaged recognition accuracy of 9 subjects according to stimulation duration. The equal-luminance red-green checkerboard always has higher recognition accuracy than that of the black-white checkerboard.
Table 1.
Comparison of average recognition accuracy between Red-Green and Black-White paradigms.
Fig 11.
Power spectrum density of subjects at 10.5 Hz.
Fig 12.
The off-line recognition accuracy error bar chart of subjects.
Table 2.
Comparison of recognition accuracy between CCA and PSD.