Intrusive effects of semantic information on visual selective attention

Every object contains semantic information in extension to its low-level properties. It is well documented that such information biases attention when it is necessary for an ongoing task. However, whether semantic relationships influence attentional selection when they are irrelevant to the ongoing task remains an open question. The ubiquitous nature of semantic information suggests that it could bias attention even when these properties are irrelevant. In the present study, three objects appeared on screen, two of which were semantically related. After a varying time interval, a target or distractor appeared on top of each object. The objects’ semantic relationships never predicted target location. Despite this, a semantic bias on attentional allocation was observed with an initial, transient bias to semantically related objects. Further experiments demonstrated that this effect was contingent on the objects being attended: if an object never contained the target, it no longer exerted a semantic influence. In a final set of experiments, we demonstrate that semantic bias is robust and appears even in the presence of more predictive cues (spatial probability). The results suggest that as long as an object is attended, its semantic properties bias attention, even if it is irrelevant to an ongoing task and there are more predictive factors available

Intrusive effects of task-irrelevant information on visual selective attention: semantics and size

Attentional selection is a mechanism by which incoming sensory information is prioritized for further, detailed and more effective, processing. Given that attended information is privileged by the sensory system, understanding and predicting what information is granted prioritization becomes an important endeavor. It has been argued that salient events as well as information that is related to the current goal of the organism (i.e., task-relevant) receive such priority. Here, we propose that attentional prioritization is not limited to task-relevance, and discuss evidence showing that task-irrelevant, non-salient, high-level properties of unattended objects, namely object meaning and size, influence attentional allocation. Such intrusion of non-salient task-irrelevant high-level information points to the need to re-conceptualize and formally modify current models of attentional guidance

Task-irrelevant semantic properties of objects impinge on sensory representations within the early visual cortex

Objects can be described in terms of low-level (e.g., boundaries) and high-level properties (e.g., object semantics). While recent behavioral findings suggest that the influence of semantic relatedness between objects on attentional allocation can be independent of task-relevance, the underlying neural substrate of semantic influences on attention remains ill-defined. Here, we employ behavioral and functional magnetic resonance imaging (fMRI) measures to uncover the mechanism by which semantic information increases visual processing efficiency. We demonstrate that the strength of the semantic relatedness signal decoded from the left inferior frontal gyrus (IFG): (i) influences attention, producing behavioral semantic benefits; (ii) biases spatial attention maps in the intraparietal sulcus (IPS), subsequently modulating early visual cortex (EVC) activity; (iii) directly predicts the magnitude of behavioral semantic benefit. Together, these results identify a specific mechanism driving task-independent semantic influences on attention

Object-based attention in real-world scenes

We are continually confronted with more visual information than we can process in a given moment. In order to interact effectively with our environment, attentional mechanisms are used to select subsets of environmental properties for enhanced processing. Previous research demonstrated that spatial regions can be selected based on either their low-level feature or high-level semantic properties. However, the efficiency with which we interact with the world suggests that there must be an additional, midlevel, factor constraining effective attentional space. The present study investigates whether object-based attentional selection is one such midlevel factor that constrains visual attention in complex, real-world scenes. Participants viewed scene images while their eye movements were recorded. During viewing, a cue appeared on an object which participants were instructed to fixate. A target then appeared either on the same object as the cue, on a different object, or floating. Participants initiated saccades faster and had shorter response times to targets presented on the same object as the fixated cue. The results strongly suggest that when attending to a location on an object, the entire object benefits perceptually. This object-based effect on the distribution of spatial attention forms a critical link between low-and high-level factors that direct attention efficiently in complex real-world scenes

Cortical systems mediating visual attention to both objects and spatial locations

Natural visual scenes consist of many objects occupying a variety of spatial locations. Given that the plethora of information cannot be processed simultaneously, the multiplicity of inputs compete for representation. Using event-related functional MRI, we show that attention, the mechanism by which a subset of the input is selected, is mediated by the posterior parietal cortex (PPC). Of particular interest is that PPC activity is differentially sensitive to the object-based properties of the input, with enhanced activation for those locations bound by an attended object. Of great interest too is the ensuing modulation of activation in early cortical regions, reflected as differences in the temporal profile of the blood oxygenation level-dependent (BOLD) response for within-object versus between-object locations. These findings indicate that object-based selection results from an object-sensitive reorienting signal issued by the PPC. The dynamic circuit between the PPC and earlier sensory regions then enables observers to attend preferentially to objects of interest in complex scenes.</p