Visual Working Memory Capacity Does Not Modulate the Feature-Based Information Filtering in Visual Working Memory

Background: The limited capacity of visual working memory (VWM) requires us to select the task relevant information and filter out the irrelevant information efficiently. Previous studies showed that the individual differences in VWM capacity dramatically influenced the way we filtered out the distracters displayed in distinct spatial-locations: low-capacity individuals were poorer at filtering them out than the high-capacity ones. However, when the target and distracting information pertain to the same object (i.e., multiple-featured object), whether the VWM capacity modulates the featurebased filtering remains unknown. Methodology/Principal Findings: We explored this issue mainly based on one of our recent studies, in which we asked the participants to remember three colors of colored-shapes or colored-landolt-Cs while using two types of task irrelevant information. We found that the irrelevant high-discriminable information could not be filtered out during the extraction of VWM but the irrelevant fine-grained information could be. We added 8 extra participants to the original 16 participants and then split the overall 24 participants into low- and high-VWM capacity groups. We found that regardless of the VWM capacity, the irrelevant high-discriminable information was selected into VWM, whereas the irrelevant fine-grained information was filtered out. The latter finding was further corroborated in a second experiment in which the participants were required to remember one colored-landolt-C and a more strict control was exerted over the VWM capacity

Dissociated Mechanisms of Extracting Perceptual Information into Visual Working Memory

The processing mechanisms of visual working memory (VWM) have been extensively explored in the recent decade. However, how the perceptual information is extracted into VWM remains largely unclear. The current study investigated this issue by testing whether the perceptual information was extracted into VWM via an integrated-object manner so that all the irrelevant information would be extracted (object hypothesis), or via a feature-based manner so that only the target-relevant information would be extracted (feature hypothesis), or via an analogous processing manner as that in visual perception (analogy hypothesis).High-discriminable information which is processed at the parallel stage of visual perception and fine-grained information which is processed via focal attention were selected as the representatives of perceptual information. The analogy hypothesis predicted that whereas high-discriminable information is extracted into VWM automatically, fine-grained information will be extracted only if it is task-relevant. By manipulating the information type of the irrelevant dimension in a change-detection task, we found that the performance was affected and the ERP component N270 was enhanced if a change between the probe and the memorized stimulus consisted of irrelevant high-discriminable information, but not if it consisted of irrelevant fine-grained information.We conclude that dissociated extraction mechanisms exist in VWM for information resolved via dissociated processes in visual perception (at least for the information tested in the current study), supporting the analogy hypothesis

Selectively Maintaining Object Features within Visual Working Memory: An ERP Study

PURPOSE: The manipulation of visual working memory (VWM) has received increasing interest, by focusing on the underlying mechanisms of manipulation for objects presented at distinct locations. However, no study has explored the manipulation mechanisms for the content of a stored multi-featured object (e.g., retaining color while discarding polygon for a colored-polygon). The current study examined whether participants can selectively retain task-relevant information of a dual-featured object after a retro-cue was presented at the maintenance interval. We hypothesized that the processing nature of a feature at the perceptual stage affected its manipulation in VWM, and tested this hypothesis by adopting two types of dual-featured objects. One is objects composed of highly-discriminable features (colored-oriented-bars) which can be processed via spread attention; the other type is objects containing fine-grained information (colored-polygons) which is processed via focal attention. We predicted that selective maintenance could not occur for the former type but occurred for the latter. METHODS: Contralateral delay activity (CDA) was adopted as a neural marker during a change detection task, in which two features of an object was initnally memorized. During the maintenance phase, we presented a retro-cue to inform participants to selectively retain color, polygon/orientation, or both. RESULTS: In line with our prediction, CDA amplitude was significantly lower for retain-color and retain-polygon conditions than for retain-both when colored-polygons were presented as stimuli; however, there was no significant difference between retain-color, retain-orientation, and retain-both conditions when colored-oriented-bars were used as stimuli (Experiment 1). Moreover, the findings cannot be explained by operations over independent objects (Experiment 2). CONCLUSIONS:we found that the selective maintenance manipulation was modulated by the nature of the constituent elements. In particular, for dual-featured representations containing fine-grained information which needs to be processed via focal attention, the constituent single features can be selectively retained according to the task requirement (e.g., colored polygon). In contrast, for dual-featured representations composed of highly-discriminable information which is processed via spread attention, the stable unit could not be broken to selectively maintain the individual elements (e.g., colored bar).</p

Line bisection performance in right-handed primary headache sufferers

Context : In previous studies, patients with migraine and tension-type headaches have shown asymmetries at the central nervous system level. Aims: Hence we would like to figure out whether the lateral cerebral dominance might be more pronounced in the line bisection performance with these patients. Settings and Design: Patients were enrolled in a specialized headache clinic and healthy volunteers from a community as controls. Materials and Methods: The visual line bisection is used to test the unilateral neglect of subjects. Altogether, we studied 28 patients with chronic tension-type, 16 frequent episodic tension-type headache, 31 migraine patients without aura between attacks and 146 healthy volunteers. Statistical Analysis: One-way ANOVA was applied to the mean Index and Net of line bisection errors and the Spearman rank order to the relationship between the Index, Net, subject′s age and time since onset of head pain. Results and Conclusions: As reflected by group means of Index of line bisection errors, healthy subjects and migraine patients bisected slightly rightward. Conversely, both forms of tension-type headache sufferers bisected significantly leftward compared to the healthy subjects as well as the migraine sufferers. The study indicates relatively strong right or weak left hemisphere activation or both in the two forms of tension-type headaches, confirming the central nervous system alterations in such patients