EEG Recording and Online Signal Processing on Android: A Multiapp Framework for Brain-Computer Interfaces on Smartphone

Figure 4

Trial structure of the selective auditory attention paradigm. The upper time axis corresponds to the timing during training trials; the lower time axis corresponds to the timing during feedback trials. Each trial begins with a fixation cross which is shown for either 600 ms during the training or 400 ms during the feedback trials. Then, an arrow tip is presented for 500 ms, pointing to the left or right, indicating the sound direction to be attended. During the sound playback, which lasts 3000 ms, a fixation cross is shown. After the sound playback a break interval of 2400 ms is added. In the feedback trials, the classification outcome is fed back to the user by displaying the word left or right.