Fig. 4.

Main effects of age-group on (A) BOLD, (B) relative CBF, (C) relative CMRO₂, and (D) NVC ratio, main effects of flicker frequency, and age-group × flicker frequency interaction effects on (E) BOLD, (F) relative CBF, and (G) relative CMRO₂. Both (A) BOLD and (D) NVC ratio were significantly higher in younger than in older adults, whereas relative (C) CMRO₂ was significantly higher in older than in younger adults, and no group difference was observed in (B) relative CBF. The effects of flicker frequency on both (E) BOLD and (F) relative CBF were significant, and the quadratic main effect of flicker frequency was significant on (G) relative CMRO₂. The only significant age-group × flicker frequency interaction effect was observed in NVC ratio (see Fig. 5B, top row).