“Neural and Behavioral Indices of Online Visual Memory”
Faculty Host: Ken Norman
Working memory (WM) enables the “online” maintenance of information in a readily accessed and easily updated state that is often referred to as the “focus of attention”. Individual differences in WM ability exhibit robust correlations with a broad range of intellectual functions such as fluid intelligence and scholastic achievement. Thus, there has been a longstanding effort to elucidate the nature of capacity limits in this system, and to characterize the neural processes that mediate storage. I’ll present clear evidence for the hypothesis that storage in working memory is subject to an item limit that precludes the storage of more than 3-4 individuated representations, and I’ll review ongoing work that employs EEG signals to track the active contents of visual working memory. I’ll argue that neural signals tracking the focus of attention in working memory can be separated into at least two distinct components. On the one hand, rhythmic brain activity in the alpha frequency band provides a temporally-resolved and precise index of the spatial position of remembered items. On the other hand, the amplitude of slow wave EEG activity tracks the number of individuated representations stored in working memory. Thus, while delay period activity has often been treated as a monolith in WM research, these findings highlight an ensemble of distinct processes that support maintenance in visual working memory.