The Construction Of Object Representation In Visual Working Memory

Visual working memory (VWM) maintains and manipulates a limited set of visual object representations. It is one of the most important components in human beings' visual system. Recently, a large quantity of work has been done on exploring the capacity of VWM, as well as the object storage fashion in VWM. The cpacity of VWM is like a 'bucket', and the object reprentation stored in VWM is like the 'water' or the 'ice' in a bucket. The operating mechanism of VWM should fit its function in visual perception, and the content it maintains depends on the interaction between visual perception and VWM. Therefore, based upon the function of VWM, here we focused on how these object representations are constructed in VWM. We hypothesized that how visual information is extracted during visual perception can directly influence how the information will be selected and retained in VWM. According to this hypothesis, there are two dissociated mechanisms in VWM for selecting and storing information extracted at different stages of visual perception (parallel or serial processing). Here we tested this prediction by conducting behavioral experiments and by recording event-related potentials, while two types of visual information (basic feature and detailed feature) were selected to represent two extremes of the perceptual processing.This study was composed of three parts. Adopting change detection paradigm, the first part investigated whether the basic feature (Experiment 1), detailed feature (Experiment 2), and the basic feature and detailed feature formed by the same type of feature (Experiment 3) can be automatically selected and stored into VWM when they were task-irrelevant features. In the second part, a delayed match-to-sample paradigm was used, while N270 was taken as an index, the amplitude which reflects conflict between representation in VWM and perceptual inputs. We explored whether the basic feature (Experiment 4), detailed feature (Experiment 5), and the basic feature and detailed feature formed by the same type of feature (Experiment 6) can elicit N270 when they were task-irrelevant features. In the third part, a change detection task was adopted while the amplitude of CDA was adopted as an index, the amplitude which represents the representation maintenance in VWM. By manipulating the type of remembered features (Experiment 7), the top-down task requirement (Experiment 8), and the stimuli encoding time (Experiment 9), the storage mechanisms of basic feature and detailed feature in VWM were explored.The main findings of this study were the follows:(1) There are dissociated mechanisms for representing information extracted at different stages of perceptual processing in VWM. The outputs of parallel processing are firstly automatically consolidated into VWM, and the detailed information is updated into VWM later at the top-down modulation of task demand.(2) The object construction in VWM is an accumulative encoding process, instead of an "all-or-none" one.