Spatial attention facilitates selection of illusory objects: Evidence from event-related brain potentials

Abstract

The relationship between spatial attention and object-based attention has long been debated. On the basis of behavioral evidence it has been hypothesized that these two forms of attention share a common mechanism, such that directing spatial attention to one part of an object facilitates the selection of the entire object. In a previous study (Martinez et al., 2006) we used recordings of eventrelated potentials (ERPs) during a paradigm modeled after that of Egly et al. (1994) to investigate this relationship. As reported in numerous studies of spatial attention, we found the typical pattern of enhanced neural activity in visual cortex elicited by attended stimuli. Unattended stimuli belonging to the same object as the attended stimuli elicited a very similar spatiotemporal pattern of enhanced neural activity that was localized to lateral occipital cortex (LOC). This similarity was taken as evidence that spatial-and object-selective attention share, at least in part, a common neural mechanism. In the present study we further investigate this relationship by examining whether this spread of spatial attention within attended objects can be guided by objects defined by illusory contours. Subjects viewed a display consisting of two illusory rectangular objects and directed attention to continuous sequences of stimuli (brief onsets) at one end of one of the objects. Stimuli ocurring at irrelevant locations but belonging to the same attended object elicited larger posterior N1 amplitudes than that elicited by unattended objects forming part of a different object. This objectselective N1 enhancement was localized to lateral occipital cortex. The present data support the hypothesis that the allocation of spatial attention can be guided by illusory object boundaries and that this allocation strengthens the perceptual representations of attended objects at the level of visual area LOC.

Object-based attention: A tutorial review

“…Since P1 is known to indicate the distribution of spatial attention (e.g., Hillyard et al, 1996;Luck, Heinze, Mangun, & Hillyard, 1990), this result, together with the results from other ERP studies (e.g., Martínez et al, 2007;Martínez et al, 2006) and fMRI and single-cell recording studies (e.g., Müller & Kleinschmidt, 2003;Roelfsema et al, 1998), provides physiological evidence supporting the location-mediated selection of object-based attention. Matsukura and Vecera (2011) recently proposed that a spatially invariant representation could occur under conditions when objects were clearly segregated.…”

“…Results in support of the sensory enhancement account can also be found in a number of other ERP experiments, including X. He et al (2004He et al ( , 2008, Martínez et al (2007;Martínez et al, 2006), and Weber et al (1997). Despite the differences in their methodology (e.g., using exogenous or endogenous cues or a postdisplay probe to measure the distribution of spatial attention), a common finding is that object-based attention is associated with an enhanced N1 component over the occipito-temporal areas (but see Weber et al, 1997, for a larger N1 amplitude in the different-object condition than in the same-object condition).…”

“…Whereas some studies have reported results consistent with object-based attention selecting a location-independent representation, where attention selects the features of an attended object, such as its shape, color, orientation, and texture, without selecting its spatial location (e.g., Awh, Dhaliwal, Christensen, & Matsukura, 2001;Matsukura & Vecera, 2011;O'Craven et al, 1999;Vecera & Farah, 1994), other studies have found that object-based attention selects from a location-mediated representation, where attention selects the regions of space occupied by the attended object (e.g., Kim & Cave, 1995;Martínez et al, 2007;Martínez et al, 2006;Müller & Kleinschmidt, 2003;Valdes-Sosa et al, 1998;Vecera & Farah, 1994;Weber et al, 1997). As was mentioned earlier, Vecera and Farah (see also Vecera, 1994) referred to these two types of selection as spatially invariant and grouped-array selection, respectively.…”

Are objects the same as groups? ERP correlates of spatial attentional guidance by irrelevant feature similarity

“…Many ERP studies have noted an enhancement of N1 in response to stimuli that belong to an unattended region of an attended object, both for spatial cueing and sustained-attention tasks using physical or illusory rectangles (He et al, 2004;Kasai, 2010;Martínez et al, 2006Martínez et al, , 2007aMartínez et al, , 2007b, or human-head geometry or connectedness (Verliger et al, 2008). This convergent evidence for an object-based N1 attention effect may indicate a single and general selection process for object-based attention, which is partly shared with spatial attention.…”

The Role of Spatial Attention in the Selection of Real and Illusory Objects

“…According to this view, spatial attention directed to one part of an object spreads throughout its boundaries and strengthens the sensory representation of the entire object. In support of this "objectguided spatial-selection mechanism," physiological studies using variants of the dual-rectangle paradigm of Egly et al (1994) have shown that neural activity patterns associated with spatial and object-based attention have much in common, as evidenced by functional magnetic resonance imaging (fMRI) (Müller and Kleinschmidt, 2003) and event-related potential (ERP) recordings (He et al, 2004;Martinez et al, 2006Martinez et al, , 2007.…”