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Haluk Ogmen, Christopher Shooner, Srimant Tripathy, Harold Bedell; Dual Memory Systems Store Direction of Motion Information for Multiple Moving Objects. Journal of Vision 2010;10(7):763. doi: 10.1167/10.7.763.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The ability to establish and maintain the identities of moving objects is essential to behavioral success, yet very little is known about the underlying mechanisms. The multiple-object tracking experimental paradigm (MOT-EP) has been used extensively for studying how attention, position and motion cues contribute to this task. Among the unresolved issues are the relative importance of motion information and the role of various memory mechanisms. We sought to quantify the capacity and the temporal dynamics of the memory systems involved in storing direction-of-motion information when viewing a multiple-object motion stimulus. Methods: Observers viewed three to nine objects in random linear motion and reported motion direction of a cued object after motion ended. In three experiments, we (1) measured performance as a function of set-size, (2) characterized the temporal dynamics of memory using seven cue delays ranging from 0ms to 3s, and (3) examined interactions between the dynamics of memory and the read-out processes by comparing performance with partial and full report. Results: Direction reports show a graded deterioration in performance with increased set size. This lends support to a flexible-capacity theory of MOT-EP. Temporal dynamics of memory follows an exponential function that decays within 1s to a steady-state plateau above chance performance. This outcome indicates the existence of two complementary memory systems, one transient with high-capacity and a second sustained with low-capacity. For the transient high-capacity memory, retention capacity was equally high whether object motion lasted 5s or 200ms. We found a significant partial-report advantage, which provides further support for a rapidly decaying high-capacity memory. Conclusions: Our results show that dual memory systems store direction of motion information for multiple moving objects. This finding provides a possible reconciliation to seemingly contradictory results previously published in the literature.
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