Figure 4.

Attentional modulation effects across visual areas. (a) Activation map of a representative subject, displayed on the flattened cortical surface with visual areas delineated. Attention to peripheral gratings activated peripheral retinotopic regions (yellow-red) whereas attention to the central letters activated foveal regions (green-blue) more strongly. Asterisks indicate the location of the foveal cortical representation. Magnitude of attentional modulation averaged across subjects in retinotopic regions corresponding to the blank gap (b) and the surrounding gratings (c). Ordinate axis shows the difference in fMRI activity levels for the attend gratings condition minus the attend letters condition. Gray bars indicate the vertical grating condition; white bars indicate the horizontal grating condition (error bars, ±1 s.e.m.). Retinotopic regions in each visual area showed highly significant attentional modulation effects (P < 0.0001), and modulations were significantly stronger in higher visual areas (F_4,34 = 6.9, P < 0.0005).