空间距离对视觉工作记忆巩固的影响

Effects of spatial distance on visual working memory consolidation

以往研究发现,个体对不同类型的视觉信息进行视觉工作记忆巩固的模式存在差异,如对于方向信息,一次只能有一个项目被巩固进入视觉工作记忆系统,而对于颜色信息,个体则可以一次巩固两个项目进入视觉工作记忆系统。但对于视觉信息的巩固模式是否会受其他因素的影响,目前仍然没有明确的定论。本研究将探讨视觉信息的巩固模式是否可能受到记忆项目空间距离因素的影响。研究采用变化觉察范式、序列-同时呈现操作及控制记忆项目呈现间距的方法,通过3个实验考察记忆项目之间的空间距离是否能够影响个体对颜色信息和方向信息的巩固模式。在三种空间距离水平上序列呈现或同时呈现两个记忆项目,实验结果一致发现记忆项目之间的空间距离会对视觉工作记忆巩固模式产生明显影响,个体在同时呈现条件下的正确率会随着空间距离的增大而降低。这些结果表明对同一类视觉信息进行巩固的过程中所存在的项目数量限制并不是固定的,个体可以采用序列模式或有限容量的并行模式对同一类信息进行巩固,巩固的模式可能与视觉空间注意的分配以及视觉信息所能获得的注意资源有关。

During past years, visual working memory （VWM） consolidation has been studied extensively. Consolidation of visual information into VWM is widely considered to occur with capacity limit. Previous studies have demonstrated that two colors could be consolidated in parallel and two oriented gratings could be consolidated only in serial. Some researchers provided a bandwidth hypothesis for these results： because of the difference between the informational demands for color and for oriented grating, two colors could be consolidated in parallel without exceeding the bandwidth limit, whereas two oriented gratings could only be consolidated in serial because of exceeding the bandwidth limit. But other researchers recently realized that different positions of stimulus could affect the VWM consolidation as well. In the present study, we used change detection paradigm and sequential-simultaneous manipulation to examine whether the spatial distance between memory items could affect the VWM consolidation. In Experiment 1, we briefly presented two masked color patches （targets） within one of three levels of spatial distance （4.6°, 8.5° and 11.1°）. A probe color then appeared, and participants needed to judge whether the probe color matched any one of the targets. The results showed that no difference was found between sequential and simultaneous presentations in 4.6° and 8.5° spatial distance conditions, while the performance for sequential presentation was better than simultaneous presentation in 11.1° spatial distance condition. These results suggested that two colors were consolidated in parallel in 4.6° and 8.5° spatial distance conditions, but in serial in 11.1 o spatial distance condition. In Experiment 2, we presented a color target firstly, and then two masked color patches appeared and the participants needed to judge whether the color target matched any one of the two masked color patches. As a result, no difference was found in the three given spatial distance conditions, eliminating the possibility that perceptual encoding led to the results in Experiment 1. Considering that the consolidation for oriented grating was different from the process for color and color might also be a unique visual feature, we attempted to use oriented grating to replicate the results of Experiment 1. In Experiment 3, we briefly presented two masked oriented gratings （targets） within three levels of spatial distance （4.6°, 8.5° and 11.1°）. A probe cue then appeared, and participants needed to judge whether the cued sinusoidal grating had been oriented in a cardinal （horizontal or vertical） or an oblique （±45°） orientation. Despite superior performance for sequential over simultaneous presentations in all three spatial distance conditions, we found that the performance for parallel presentation was better than the accuracy＇in 4.6° spatial distance condition. The results suggested that parallel consolidation of oriented gratings into WVM was possible when the spatial distance between memory items was short enough. According to the results, we speculated that consolidation into VWM might be related to the distribution of the visual spatial attention, and the consolidation bandwidth increased with increasing resources of attention which memory items could get.