It is well established that spatial attention can modify processing in local regions of the visual field, and this is associated with corresponding retinotopically specific modulations of activity in primary and extrastriate visual cortex (e.g. Brefczynski & DeYoe,
1999; Gandhi, Heeger, & Boynton,
1999; Somers, Dale, Seiffert, & Tootell,
1999). Typically, the effect of spatial attention is characterized as strengthening the representation of a stimulus, enhancing its salience and potency in competitive interactions with cortical representations of other stimuli in the visual environment (Kastner, De Weerd, Desimone, & Ungerleider,
1998). Here, we found that spatial attention directed to an MIB target increased the probability of it disappearing. This appears counter-intuitive given the characterization of spatial attention as increasing the salience of a target; why should a more salient target be more likely to disappear? However, previous behavioral work suggests that increasing target salience increases the duration of MIB (Bonneh et al.,
2001). Specifically, disappearance of the target occurs for longer when the contrast between target and distracters is greater, presumably hampering the grouping of target and distracters (Hsu et al.,
2004). These findings have led to the proposal that MIB is unlikely to be caused by local adaptation, but rather that higher level attentional and grouping mechanisms play a role (Bonneh et al.,
2001). Thus, our findings of increased probability of disappearance with spatial attention are consistent with the notion that increased salience of the target (relative to distracters) is associated with enhanced disappearance. Moreover, this effect of attention might be different from a facilitation of adaptation, which is assumed to underlie perceptual filling-in (De Weerd, Smith, & Greenberg,
2006).