Edward K. Vogel, Geoffrey F. Woodman, Steven J. Luck; The rapid time-course of visual working memory consolidation. Journal of Vision 2002;2(7):270. doi: 10.1167/2.7.270.
How long does it take to form a durable representation in visual working memory? Several theorists have proposed that this consolidation process is highly limited in capacity and very slow —taking upwards of 500 ms per item. However, these estimates of the “slow” consolidation process have been inferred from dual-task paradigms, and these paradigms may overestimate the duration of consolidation by including processes other than consolidation. In the present study, we sought to measure the time-course of the encoding process more directly, using a procedure in which consolidation is interrupted at various time points. This procedure allowed us to quantify the rate of information accrual in visual working memory. Specifically, observers performed a variation of a common change detection task, in which they were asked to remember an array of simple objects (colored squares) and compare them with a subsequent array. Shortly after the presentation of the first array, pattern masks were presented at the locations of each of the memory items. The masks were intended to disrupt representations that had not yet been consolidated, and the timing parameters were adjusted so that the initial identification of the squares was not impaired by the masks. Performance on this memory task revealed that encoding larger memory arrays required longer amounts of uninterrupted processing time than smaller arrays to reach asymptotic levels, which supports the general proposal that consolidation is highly capacity limited. However, the specific rate of consolidation was calculated to be near 50 ms per item, which is approximately an order of magnitude faster than previous estimates. These results indicate that forming a durable visual working memory representation is actually a relatively rapid process, and they pose a challenge to “slow” consolidation models.
This study was supported by grants from the National Institute of Mental Health (MH56877), the National Science Foundation (SBR 98-09126), and the Human Frontier Science Program (RG0136).