Title: Storage in working memory recruits a modality-independent pointer system
Henry Jones, doctoral student in the Awh/Vogel Lab, Department of Psychology, University of Chicago
Abstract: Prominent theories of working memory (WM) have proposed that distinct working memory systems may support the storage of different types of information. For example, distinct dorsal and ventral stream brain regions are activated during the storage of spatial and object information in visual WM. Although feature-specific activity is likely critical to WM storage, we hypothesize that a content-independent indexing process may also play a role. Specifically, spatiotemporal pointers may be required for the sustained indexing and tracking of items in space and time, even while features change, within an unfolding event. Past evidence for such a content-independent pointer operation includes the finding that signals tracking the number of individuated representations in WM (load) generalize across colors, orientations and conjunctions of those features. However, a common allocation or spatial attention, or an overlapping orientation and color codes in early visual cortices may mimic a generalizable signal. Here, I will present a stronger demonstration of content-independence. In experiment 1, I dissociate WM load from a common confound, spatial attention. By independently manipulating the two, we find signals which were selectively sensitive to WM load. In experiment 2, I replicate the previous finding of load signal generalization, after which I provide a stronger demonstration of content-independence by using pairs of features that are as cortically disparate as possible, color and motion coherence. We use RSA to simultaneously track both content-feature and content-independent load signals. Extending these observations, in the final experiment we apply similar analytic approaches to demonstrate a common load signature between auditory and visual sensory modalities, while controlling for modality-specific neural activity and the spatial extent of covert attention. Our findings suggest that content-independent pointers may play a fundamental role in the storage of information in working memory, and may contribute to its overall limited capacity.