Abstract
It is well established that Visual Working Memory is capacity limited. Recent behavioral research has demonstrated that perceptual grouping can facilitate the retrieval of items stored in working memory. At what stage and by what mechanism are these grouping effects manifesting? In order to answer this question we used high-density electroencephalography (hdEEG) to examine neural correlates of perceptual grouping during the encoding phase of a standard change detection working memory recognition task. Specifically, we used an EEG technique, known as frequency tagging. This technique takes advantage of the fact that flickering stimuli will elicit a steady-state oscillation at a corresponding frequency in the EEG data. Using this technique we designed an experiment in which participants were presented with sets of four novel shapes, each flickering at one of four chosen frequencies: 3Hz, 5Hz, 12Hz and 20Hz, between black and a randomly chosen color on a grey background. The experiment consisted of two conditions: grouped and non-grouped. In the grouped condition two of the four shapes were the same, had the same color and were always presented on the same side of the screen. In the non-grouped condition, all shapes and colors were different. Behaviorally, we found that participants were significantly more accurate in performing the task in the grouping condition. This grouping benefit was accompanied by a significant increase in two non-linear harmonics of the grouped items. Conclusion: our data demonstrate that the grouping benefit observed in visual working memory tasks arises in part at the time of encoding from a non-linear neural interaction between the items comprising the group.
Meeting abstract presented at VSS 2015