Figure 1.
High-resolution fMRI activity evoked by scotopic stimuli, relative to the border of retinotopic visual areas and motion-selective columns in the inflated right hemisphere of one subject, shown from a posterior-ventral-lateral viewpoint. Panel A shows BOLD activity produced by a high contrast, moving achromatic grating at scotopic luminance levels, compared to a uniform gray stimulus at equal luminance level. The foveal representation shows negative BOLD responses in V1 and V2. The color activity scale shows P-values, with minimum and maximum thresholds = 10–2.5 and 10−5, respectively. Positive and negative values are indicated by red/yellow and blue/cyan, respectively. Panel B shows the activity map evoked by contrasting the response to stimulation of horizontal (red/yellow) versus vertical (blue/cyan) meridians (minimum and maximum thresholds = 0.05 and 10−3, respectively). Activity produced by the horizontal versus vertical meridians define the borders between retinotopic visual areas. Panel C shows only the positive BOLD changes, to more clearly illustrate the regularly spaced patchy stripes evoked by the scotopic grating (white arrowheads), which occur outside the very central visual field representation in area V2. Panel D shows the patchy (sometimes stripe-shaped) activation produced by achromatic moving versus stationary gratings, at photopic levels. In all panels, the black line shows the border between areas V1 and V2, based on independent retinotopic scans (e.g., panel B). The location of the white arrowheads (from panel C) is duplicated in panel D.