Figure 8

Orientation discrimination task. In each trial, a bar oriented at an angle x is presented while the subject fixates; the stimulus disappears; two targets appear (gray dots), and the subject indicates whether the bar was tilted to the left or to the right by making an eye movement (horizontal arrow). Vertical bars correspond to x = 0°. a: The bar is tilted to the left (x < 0). With a red fixation spot (y = 1), responses to left- and right-tilted bars should be to the left and right targets, respectively. The correct response is thus to the left. b: With a green fixation spot (y = 2), left- and right-tilted bars correspond to right and left targets, respectively. The correct response is now to the right. A no-go condition (y = 3; not shown) is included in the simulations in addition to the two go conditions. Orientation is in degrees, with x between -8° and +8°.