Poster Session C, Sunday, March 24, 5:00 – 7:00 pm, Pacific Concourse
Independent representation of active and latent decision boundaries in working-memory-guided behavior
Paul Muhle-Karbe1,2, Mark G. Stokes1,2, Nicholas E. Myers1,2,3; 1Department of Experimental Psychology, University of Oxford, 2Oxford Centre for Human Brain Activity, Wellcome Centre for Integrative Neuroimaging, University of Oxford, 3Helen Wills Neuroscience Institute, UC Berkeley
Recent evidence suggests that working memories (WM) are encoded in qualitatively different states depending on their momentary task-relevance. Relevant items are thought to be encoded in spiking activity that is primed to drive behavior, whereas currently irrelevant items can be held in a latent state that minimizes interference but is accessible later. It is unclear how latent working memories are transformed to drive active decision circuits when behavioral priorities change. We used time-resolved decoding of WM items using electroencephalography (EEG) in a task that required cued priority switches between decision boundaries, permitting independent decoding of active and latent boundaries on trials when their priority status switched (requiring transfer from a latent to an active state) vs. when the priority status was repeated. WM switches created transient performance costs that recovered after a single trial. EEG revealed that this behavioral cost is driven by lingering over-representation of the latent item. On priority switch trials, both the newly active and the previously active item could be decoded. Intriguingly, active and latent items were represented in distinct neural patterns: training a decoder on the active item did not permit decoding of the latent one, and vice versa. Importantly, the magnitude of latent item decoding tracked participants’ performance cost after switches. On priority repeat trials, only the active item could be recovered from EEG activity, with decoding of the latent item returning to chance. These findings suggest that priority shifts incur transient competition between items for active representation.
Topic Area: EXECUTIVE PROCESSES: Working memory