Abstract
Identifying targets in a stream of items at a given constant spatial location relies on selection of aspects such as color, shape, or texture. Such attended (target) features of a stimulus elicit a negative-going event-related brain potential (ERP), termed Selection Negativity (SN), which has been used as an index of selective feature processing. In two experiments, participants viewed a series of Gabor patches in which targets were defined as a specific combination of color, orientation, and shape. Distracters were composed of different combinations of color, orientation, and shape of the target stimulus. This design allows comparisons of items with and without specific target features. Consistent with previous ERP research, SN deflections extended between 160–300 ms. Data from the subsequent P3 component (300–450 ms post-stimulus) were also examined, and were regarded as an index of target processing. In Experiment A, predominant effects of target color on SN and P3 amplitudes were found, along with smaller ERP differences in response to variations of orientation and shape. Manipulating color to be less salient while enhancing the saliency of the orientation of the Gabor patch (Experiment B) led to delayed color selection and enhanced orientation selection. Topographical analyses suggested that the location of SN on the scalp reliably varies with the nature of the to-be-attended feature. No interference of non-target features on the SN was observed. These results suggest that target feature selection operates by means of electrocortical facilitation of feature-specific sensory processes, and that selective electrocortical facilitation is more effective when stimulus saliency is heightened.
Highlights
When searching the visual environment for a specific target that is not defined by spatial location, humans often encounter complex, multi-feature stimuli that can be identified only by a combination of their visual properties
A variety of processes have been suggested to be involved in identifying a target object based on pre-defined features: First, the visual system needs to enhance the sensitivity to the target features at the cost of competing non-target features
Misses, and false alarms were compared across the 8 feature combinations
Summary
When searching the visual environment for a specific target that is not defined by spatial location, humans often encounter complex, multi-feature stimuli that can be identified only by a combination of their visual properties. The attentive selection of object features at the cost of visual information that does not match a specified multi-feature target has been studied in the laboratory and has been referred to as feature-based selective attention [1,2]. A variety of processes have been suggested to be involved in identifying a target object based on pre-defined features: First, the visual system needs to enhance the sensitivity to the target features at the cost of competing non-target features. Such object features (in the present study: color, orientation, and shape) must be integrated into cohesive entities, forming a percept
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