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

Abstract

Selective attention may be flexibly directed toward particular locations in the visual field (spatial attention) or to entire object configurations (object-based attention). A key question is whether spatial attention plays a direct role in the selection of objects, perhaps by spreading its facilitatory influence throughout the boundaries of an object. We studied the relationship between spatial and object-based attention in a design in which subjects attended to brief offsets of one corner of a real or illusory square form. Object-selective attention was indexed by differences in event-related potential (ERP) amplitudes and blood oxygen level-dependent (BOLD) activations to unattended corner offsets in conditions in which the objects were intact versus fragmented or absent. This design ensured that object-based attention effects were not an artifact of attention being guided by simple directional cues such as parallel lines, which may have occurred in previous studies. Both space-based and object-based attention were associated with enhanced negative ERPs (N1 component at 140 -180 ms) that were colocalized with BOLD activations in lateral occipital cortex (LOC). These results provide physiological evidence that directing spatial attention to one part of an object (whether real or illusory) facilitates the processing of the entire object at the level of the LOC and thus contributes directly to object-based selective attention.

Strategic Control of Attention to Objects and Locations

“…Meanwhile, the amplitude difference between cued and uncued stimuli reflects a concurrent space-based attentional modulation. However, the earlier P1 component indicated a purely space-based modulation: cued stimuli evoked the largest amplitude, but there was no effect of object configuration [Martinez et al (2007), their Fig. 3 (http://www.jneurosci.org/cgi/content/ full/27/30/7963/F3)].…”

“…Because locations and objects are more or less relevant depending on one's current goals, it is important to examine how and when processing resources are allocated to these different types of information. In their recent The Journal of Neuroscience paper, Martinez et al (2007) provide a window into the temporal profiles and the functional neuroanatomical correlates of space-based and object-based attention. They measured event-related potentials (ERPs), two components of which index attention: the P1 component (a positive deflection 80 -130 ms after stimulus presentation) and the N1 component (a negative deflection 150 -200 ms after stimulus presentation).…”

“…Martinez, personal communication). Martinez et al (2007) predicted a same-object neural advantage such that uncued stimuli would evoke larger neural responses in the IO condition than in the FO condition, because only in the IO condition did uncued stimuli occur on an object having a cued corner. This prediction was borne out in the N1 component: cued, uncued IO, and uncued FO stimuli evoked the largest, medium, and smallest amplitudes, respectively.…”

“…3 (http://www.jneurosci.org/cgi/content/ full/27/30/7963/F3)]. Accordingly, Martinez et al (2007) concluded that "spatially mediated selection began earlier than the object-selective effects." N1-component source analysis localized a combined object-based and spacebased attentional modulation of neural activity to the lateral occipital complex (LOC) contralateral to the offset-stimulus hemifield.…”

Object-Guided Spatial Selection in Touch Without Concurrent Changes in the Perceived Location of the Hands

“…In vision, several studies have demonstrated that these pathways interact with one another in spatial selective attention (e.g. Baylis & Driver, 1992;Egly, Driver, & Rafal, 1994;Hollingworth, Maxcey-Richard, & Vecera, 2012;Marino & Scholl, 2005;Martinez, Ramanathan, Foxe, Javitt, & Hillyard, 2007). For example, Egly et al (1994) presented long outline rectangles either above and below fixation (horizontal objects), or left and right of fixation (vertical objects).…”