The attentional field has a Mexican hat distribution.

We assessed the interference by distracter letters on target discrimination as a function of the distance between incompatible distracters and target. The slope of the response time-distance function supports a Mexican hat pattern of attentional modulation in the visual field. We relate the results to our recent finding of neural activity suppression in primary visual cortex coding locations in the vicinity of an attended region [Muller, N. G., & Kleinschmidt, A. (2004). The attentional 'spotlight's' penumbra: Center-surround modulation in striate cortex. Neuroreport, 15(6), 977-980]. As behavioral performance parallels activity modulation of primary visual cortex but not other areas we propose that perceptual capacities are determined by attentional response properties of V1.