Files

Abstract

Past work has shown that storage in working memory elicits stimulus-specific neural activity that tracks the stored content. Here, we present evidence for a distinct class of load-sensitive neural activity that indexes items without representing their contents per se. We recorded electroencephalogram (EEG) activity while adult human subjects stored varying numbers of items in visual working memory. Multivariate analysis of the scalp topography of EEG voltage enabled precise tracking of the number of individuated items stored and robustly predicted individual differences in working memory capacity. In Chapters 1 and 2 we present evidence that this signature of working memory load generalized across variations in both the type and number of visual features stored about each item, suggesting that it tracked the number of individuated memory representations and not the content of those memories. We hypothesize that these findings reflect the operation of a capacity-limited pointer system that supports on-line storage and attentive tracking. In Chapter 3, we present evidence that spatial attention and working memory are distinct forms of voluntary attentional control. Spatial attention and working memory (WM) are closely intertwined. For example, spatial attention is deployed towards the position of items stored in WM, even when location is irrelevant to the memory task. But is focusing spatial attention on an item tantamount to encoding it into working memory? We examined this question by using EEG activity to track spatial attention and WM storage while observers saw displays that contained either one target and one irrelevant distractor, or two targets. Alpha oscillations tracked the locus of covert spatial attention, and revealed equally precise orienting towards targets and distractors. Nevertheless, at the same moment in time, EEG signatures of WM encoding showed that targets were far more likely to be stored in WM than distractors. Thus, spatial selective attention may be a persistent partner for visual working memory, but it can be dissociated from the operations that gate WM storage.

Details

Actions

PDF

from
to
Export
Download Full History