Figure 1. The generic stimulus set used in this study.

All stimuli consisted of a fixation spot of radius 0.1 deg randomly changing from black to white throughout the presentation (A, B and D) and blank (C) periods. A, radial grating pattern: fixation radius, 0.1 deg; contrast, 50 %; field size, 5.4 or 26 deg; spatial frequency from 4 to 20 c.p.d.; contrast reversing at 8 Hz. B, concentrically oriented Gabors: 4 c.p.d.; σ= 0.1 deg; 50 % contrast; contrast reversing at 8 Hz; field size, 5.4 deg. C, blank period stimulus consisting of just a mean luminance screen and randomly changing fixation spot. D, the Gabors of stimulus B but with shuffled orientations.