Event-related potentials elicited by visual stimulus-duration discrimination tasks

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 feature-based 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.

Conclusions/Significance

We conclude that VWM capacity did not modulate the feature-based filtering in VWM.

Event-Related Potential N270 in Detecting Cognitive Impairment in Patients With Transient Ischemic Attack

Latency and amplitude of the visual P300 and N270 were examined in patients with transient ischemic attack (TIA) and in age-matched healthy control subjects to investigate the feasibility of N270 as a clinical examination method to evaluate the cognitive status of patients with TIA. Stimulus pairs with identical (match condition) or different (conflict condition) colors were randomly presented to subjects. Each pair consisted of two sequential stimuli (S1 and S2) that lasted for 300 ms; the onset interval between them was 700 ms. Thirty TIA patients without clinical dementia and 30 age-matched control subjects determined if the two stimuli in a pair had the same color. Subjects were required to press a button in the match condition and another button in the conflict condition. Event-related potentials (ERPs) were recorded from their scalp electrodes at the same time. N270 was evoked by the second stimulus (S2) of the conflict condition in either control subjects or patients. The patient group exhibited a delayed N270 than the control group. TIA patients as a group showed cognitive decline. N270 is an effective index to detect the cognitive impairment of TIA patients.