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Coarse-to-fine construction for high-resolution representation in visual working memory.

Gao Z, Ding X, Yang T, Liang J, Shui R - PLoS ONE (2013)

Bottom Line: No CDA difference was found between two and four objects, even in an easy-comparison condition.Thus, Experiment 2 manipulated the memory array's exposure time under the easy-comparison condition and found a significant CDA difference at 100 ms while replicating Experiment 1's results at 500 ms.In Experiment 3, the 500-ms memory array was blurred to block the detailed information; this manipulation reestablished a significant CDA difference.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology and Behavioral Sciences, Zhejiang University, Hangzhou, China.

ABSTRACT

Background: This study explored whether the high-resolution representations created by visual working memory (VWM) are constructed in a coarse-to-fine or all-or-none manner. The coarse-to-fine hypothesis suggests that coarse information precedes detailed information in entering VWM and that its resolution increases along with the processing time of the memory array, whereas the all-or-none hypothesis claims that either both enter into VWM simultaneously, or neither does.

Methodology/principal findings: We tested the two hypotheses by asking participants to remember two or four complex objects. An ERP component, contralateral delay activity (CDA), was used as the neural marker. CDA is higher for four objects than for two objects when coarse information is primarily extracted; yet, this CDA difference vanishes when detailed information is encoded. Experiment 1 manipulated the comparison difficulty of the task under a 500-ms exposure time to determine a condition in which the detailed information was maintained. No CDA difference was found between two and four objects, even in an easy-comparison condition. Thus, Experiment 2 manipulated the memory array's exposure time under the easy-comparison condition and found a significant CDA difference at 100 ms while replicating Experiment 1's results at 500 ms. In Experiment 3, the 500-ms memory array was blurred to block the detailed information; this manipulation reestablished a significant CDA difference.

Conclusions/significance: These findings suggest that the creation of high-resolution representations in VWM is a coarse-to-fine process.

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Related in: MedlinePlus

Results of Experiments 1.The mean accuracy (A), CDA waveforms (B), and averaged CDA amplitudes of the tested time window (C) for the simple shape change, cross-category change and within-category change. Error bars in Fig. 3A, and 3C denote standard error. The CDA is a difference wave, constructed by subtracting the ipsilateral from the contralateral activity according to the cued hemifield. *indicates the difference between the two conditions was significant; whereas n.s. indicates the difference between the two conditions was non-significant. Grey areas of the CDA waveforms denote the tested time window.
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pone-0057913-g003: Results of Experiments 1.The mean accuracy (A), CDA waveforms (B), and averaged CDA amplitudes of the tested time window (C) for the simple shape change, cross-category change and within-category change. Error bars in Fig. 3A, and 3C denote standard error. The CDA is a difference wave, constructed by subtracting the ipsilateral from the contralateral activity according to the cued hemifield. *indicates the difference between the two conditions was significant; whereas n.s. indicates the difference between the two conditions was non-significant. Grey areas of the CDA waveforms denote the tested time window.

Mentions: As shown in Fig. 3A, the accuracy of change detection declines as array size increased in all three conditions. Importantly, accuracy also drops as comparison difficulty rose, suggesting that comparison difficulty modulated performance. Confirming these observations, a one-way ANOVA restricted to the simple shape change condition yielded a significant main effect of Set Size, F(1,11) = 55.70, p<.001. A two-way ANOVA restricted to the complex shape group with Comparison Difficulty (cross-category change vs. within-category change) and Set Size (two vs. four objects) as within-subjects factors yielded significant main effects of Set Size, F(1,13) = 239.68, p<.001, and Comparison Difficulty, F(1,13) = 265.14, p<.001. The interaction between Comparison Difficulty and Set Size was non-significant, F(1,13) = .14, p>.2. Furthermore, a mixed ANOVA taking Shape (complex shape vs. simple shape) as a between-subjects factor and Set Size (two vs. four objects) as a within-subjects factor for the two easy comparison conditions showed that only the main effect of Set Size was significant, F(1,24) = 214.08, p<.001; both the main effect of Shape and the interaction between the two factors were non-significant, ps >.2, suggesting that there was no difference in task difficulty between the simple shape change condition and cross-category change condition of the complex objects.


Coarse-to-fine construction for high-resolution representation in visual working memory.

Gao Z, Ding X, Yang T, Liang J, Shui R - PLoS ONE (2013)

Results of Experiments 1.The mean accuracy (A), CDA waveforms (B), and averaged CDA amplitudes of the tested time window (C) for the simple shape change, cross-category change and within-category change. Error bars in Fig. 3A, and 3C denote standard error. The CDA is a difference wave, constructed by subtracting the ipsilateral from the contralateral activity according to the cued hemifield. *indicates the difference between the two conditions was significant; whereas n.s. indicates the difference between the two conditions was non-significant. Grey areas of the CDA waveforms denote the tested time window.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585254&req=5

pone-0057913-g003: Results of Experiments 1.The mean accuracy (A), CDA waveforms (B), and averaged CDA amplitudes of the tested time window (C) for the simple shape change, cross-category change and within-category change. Error bars in Fig. 3A, and 3C denote standard error. The CDA is a difference wave, constructed by subtracting the ipsilateral from the contralateral activity according to the cued hemifield. *indicates the difference between the two conditions was significant; whereas n.s. indicates the difference between the two conditions was non-significant. Grey areas of the CDA waveforms denote the tested time window.
Mentions: As shown in Fig. 3A, the accuracy of change detection declines as array size increased in all three conditions. Importantly, accuracy also drops as comparison difficulty rose, suggesting that comparison difficulty modulated performance. Confirming these observations, a one-way ANOVA restricted to the simple shape change condition yielded a significant main effect of Set Size, F(1,11) = 55.70, p<.001. A two-way ANOVA restricted to the complex shape group with Comparison Difficulty (cross-category change vs. within-category change) and Set Size (two vs. four objects) as within-subjects factors yielded significant main effects of Set Size, F(1,13) = 239.68, p<.001, and Comparison Difficulty, F(1,13) = 265.14, p<.001. The interaction between Comparison Difficulty and Set Size was non-significant, F(1,13) = .14, p>.2. Furthermore, a mixed ANOVA taking Shape (complex shape vs. simple shape) as a between-subjects factor and Set Size (two vs. four objects) as a within-subjects factor for the two easy comparison conditions showed that only the main effect of Set Size was significant, F(1,24) = 214.08, p<.001; both the main effect of Shape and the interaction between the two factors were non-significant, ps >.2, suggesting that there was no difference in task difficulty between the simple shape change condition and cross-category change condition of the complex objects.

Bottom Line: No CDA difference was found between two and four objects, even in an easy-comparison condition.Thus, Experiment 2 manipulated the memory array's exposure time under the easy-comparison condition and found a significant CDA difference at 100 ms while replicating Experiment 1's results at 500 ms.In Experiment 3, the 500-ms memory array was blurred to block the detailed information; this manipulation reestablished a significant CDA difference.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology and Behavioral Sciences, Zhejiang University, Hangzhou, China.

ABSTRACT

Background: This study explored whether the high-resolution representations created by visual working memory (VWM) are constructed in a coarse-to-fine or all-or-none manner. The coarse-to-fine hypothesis suggests that coarse information precedes detailed information in entering VWM and that its resolution increases along with the processing time of the memory array, whereas the all-or-none hypothesis claims that either both enter into VWM simultaneously, or neither does.

Methodology/principal findings: We tested the two hypotheses by asking participants to remember two or four complex objects. An ERP component, contralateral delay activity (CDA), was used as the neural marker. CDA is higher for four objects than for two objects when coarse information is primarily extracted; yet, this CDA difference vanishes when detailed information is encoded. Experiment 1 manipulated the comparison difficulty of the task under a 500-ms exposure time to determine a condition in which the detailed information was maintained. No CDA difference was found between two and four objects, even in an easy-comparison condition. Thus, Experiment 2 manipulated the memory array's exposure time under the easy-comparison condition and found a significant CDA difference at 100 ms while replicating Experiment 1's results at 500 ms. In Experiment 3, the 500-ms memory array was blurred to block the detailed information; this manipulation reestablished a significant CDA difference.

Conclusions/significance: These findings suggest that the creation of high-resolution representations in VWM is a coarse-to-fine process.

Show MeSH
Related in: MedlinePlus