The Storage Mechanism And Load Effect Of Different Feature Information In Visual-object Working Memory

It has been shown that we have a highly capacity-limited representational space with which to store objects in visual working memory. In order to perform more appropriate behaviors, our brain must choose the most relevant information to the current object and neglect the irrelevant information from the multitude of information in the present environment. Whereas, a majority of objects in actual environment does not consist of single feature but multiple features, are all features or just task-relevant features encoded into VWM when an object is present? To address the question, researchers are using different material or setup launched their own researches. Part of studies report that there exists an object-based processing benefit such that, when attention is directed to one object feature, all other features of that object may be registered, even when these unattended features are task irrelevant. Meanwhile, some other studies have failed to find this effect, and found that a task-irrelevant object feature might not be processed when observers were asked to encode another feature from the same object. At the time of the two major views debate, Shen et al.(2007) proposed dissociated mechanisms of extracting perceptual information into visual working memory, which try to reconcile these seemingly conflicting results. But, it still failed to explain the all phenomenon of the current study. Thus, what determines when object-based processing may or may not occur on earth?To address the question, the present study attempts to take the distinct basic feature (color and sample shape) which are processed via an automatic and parallel processing in visual perception and the fine-grained information (random polygons) which is serially encompassed into perception processing via focal attention as the experimental materials to rule out the interference of visual spatial location information, operate variables of the type of task-irrelevant feature and the demand of task-relevant feature in the same object, and ask the observers to remember the object colors via high temporal resolution event-related-potentials (ERPs) focusing on the component N2pc to explore the processing way of different feature information in visual-object working memory and the influence of the encoding demand of the task-relevant feature to the process of task-irrelevant feature.The results showed that, when the task-irrelevant feature is the basic feature-simple shape, the probe stimuli, matching the task-relevant color and the irrelevant shape, elicited the N2pc component, and the amplitude and the onset latency of the N2pc component was largely consistent across color-encoding loads in the range of capacity-limited; but as the remembering load of task-relevant increasing to six, the N2pc effect disappeared in task-irrelevant shape matching. When the task-irrelevant feature is the fine-grained feature-random polygons, only the probe stimuli, matching the task-relevant color, elicited the N2pc component regardless of the remembering load of task-relevant feature. These results indicated that when the task-irrelevant feature is the basic feature, object-based encoding processing of the task-irrelevant features does occur, as reported previously, but it is determined by the overall remembering load of the task-relevant object feature; moreover, there exist a dissociated processing mechanism for different object information in visual-object working memory. That is to say, not only the processing way of object information in visual perception but also the remembering load of the task-relevant determine whether the visual-object information can be processed into visual working memory via an integrated-object manner or via a feature-based manner.