FIGURE 2.

Schematic block diagram of the visual stimuli. The checkerboard paradigm consisted of 15 s active blocks of contrast-reversing (8 Hz) checkerboards interleaved with 15 s presentation of a blank screen as rest blocks (R). Active blocks were comprised of 3 blocks for each contrast that were randomly presented for high (H), medium (M), and low (L) contrasts interspersed with 9 rest blocks (Ashtari et al., 2011).