Abstract
How do working memory circuits store multiple spatial locations for the control of planned sequences of eye movements? How does using rank-sensitive coding contribute to sequence storage and recall when the same movement repeats at multiple list positions, or ranks, during the sequence? We develop a competitive queuing model of working memory to explain and simulate microstimulation, behavioral, electrophysiological, and anatomical data that clarify these processes. The model utilizes rank-sensitive prefrontal working memory representations (Averbeck et al, 2003), which depend upon rank-related activity in parietal cortex (Sawamura et al., 2002, see also Grossberg & Pearson, 2008), to produce spatial sequences in which the same action is repeated several times. The model shows how the supplementary eye fields (SEF; Schlag & Schlag-Rey, 1987) could mediate the selection of saccade plans from sequential working memory by simulating both behavioral results and a number of SEF cell types (Isoda & Tanji, 2002, Lu et al., 2002). In addition, model simulations illustrate how microstimulation (Histed & Miller, 2006; Yang et al., 2008) may alter the order of performance of sequences of eye movements stored in spatial working memory, but not which movements (items) are generated. Finally, the model proposes how SEF interacts with downstream regions such as the frontal eye fields (FEF), during memory-guided sequential saccade tasks. The model explicates a functional role for the SEF and its interactions with interconnected cortical areas, and makes predictions for novel experimental conditions. The explicit circuit model clarifies how rank-order sensitive working memories may solve the problem of representing sequential plans in which component actions repeat at later points in the sequence.
Supported in part by CELEST, an NSF Science of Learning Center (SBE-0354378) and the SyNAPSE program of DARPA (HR001109-03-0001, HR001-09-C-0011).