Figure 1
From: Brain-computer interfacing using modulations of alpha activity induced by covert shifts of attention
Covert attention task. After 1000 ms, a cue in form of a hexagon appeared. Participants had to attend to either the blue, red, or green face of the hexagon, and they had to covertly shift attention to the disc the face was pointing at. After a variable amount of time (500-2000 ms), a target ('+' or '×') appeared, followed by a masker ('*'). The participant indicated the perceived symbol by means of a button press with the right or left hand.