Limits...
Feature-Based Change Detection Reveals Inconsistent Individual Differences in Visual Working Memory Capacity.

Ambrose JP, Wijeakumar S, Buss AT, Spencer JP - Front Syst Neurosci (2016)

Bottom Line: As expected, capacity was significantly lower for the shape dimension.Similarly, participants with a stronger BOLD response for color also showed a strong neural response for shape within the lateral occipital cortex, intraparietal sulcus (IPS), and superior IPS.Although there were robust individual differences in the behavioral and neural measures, we found little evidence of systematic brain-behavior correlations across feature dimensions.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Mathematics and Computational Sciences, University of Iowa, Iowa City IA, USA.

ABSTRACT
Visual working memory (VWM) is a key cognitive system that enables people to hold visual information in mind after a stimulus has been removed and compare past and present to detect changes that have occurred. VWM is severely capacity limited to around 3-4 items, although there are robust individual differences in this limit. Importantly, these individual differences are evident in neural measures of VWM capacity. Here, we capitalized on recent work showing that capacity is lower for more complex stimulus dimension. In particular, we asked whether individual differences in capacity remain consistent if capacity is shifted by a more demanding task, and, further, whether the correspondence between behavioral and neural measures holds across a shift in VWM capacity. Participants completed a change detection (CD) task with simple colors and complex shapes in an fMRI experiment. As expected, capacity was significantly lower for the shape dimension. Moreover, there were robust individual differences in behavioral estimates of VWM capacity across dimensions. Similarly, participants with a stronger BOLD response for color also showed a strong neural response for shape within the lateral occipital cortex, intraparietal sulcus (IPS), and superior IPS. Although there were robust individual differences in the behavioral and neural measures, we found little evidence of systematic brain-behavior correlations across feature dimensions. This suggests that behavioral and neural measures of capacity provide different views onto the processes that underlie VWM and CD. Recent theoretical approaches that attempt to bridge between behavioral and neural measures are well positioned to address these findings in future work.

No MeSH data available.


K values for each subject across set size for color (A) and shape (B) trials. The solid black line shows the average K values over subjects.
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Figure 1: K values for each subject across set size for color (A) and shape (B) trials. The solid black line shows the average K values over subjects.

Mentions: K values were estimated for each set size, participant, and stimulus dimension. Figure 1 shows these K values across participants for the color (left panel) and shape (right panel) dimensions. As is evident, there were differences across stimulus dimensions. In the Color CD task, participants generally had higher K values (note that we scaled the panels differently to highlight the individual differences across participants). Indeed, across the sample, the Max K value for color was significantly greater than the Max K for Shape, t(19) = 13.495, p < 0.001. The Color K values were also less variable across set sizes showing a clear increasing and then decreasing pattern. By contrast, performance in Shape CD declined less at higher set sizes, reflecting the difficulty participants had with the Shape CD task beyond the lowest set sizes.


Feature-Based Change Detection Reveals Inconsistent Individual Differences in Visual Working Memory Capacity.

Ambrose JP, Wijeakumar S, Buss AT, Spencer JP - Front Syst Neurosci (2016)

K values for each subject across set size for color (A) and shape (B) trials. The solid black line shows the average K values over subjects.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835449&req=5

Figure 1: K values for each subject across set size for color (A) and shape (B) trials. The solid black line shows the average K values over subjects.
Mentions: K values were estimated for each set size, participant, and stimulus dimension. Figure 1 shows these K values across participants for the color (left panel) and shape (right panel) dimensions. As is evident, there were differences across stimulus dimensions. In the Color CD task, participants generally had higher K values (note that we scaled the panels differently to highlight the individual differences across participants). Indeed, across the sample, the Max K value for color was significantly greater than the Max K for Shape, t(19) = 13.495, p < 0.001. The Color K values were also less variable across set sizes showing a clear increasing and then decreasing pattern. By contrast, performance in Shape CD declined less at higher set sizes, reflecting the difficulty participants had with the Shape CD task beyond the lowest set sizes.

Bottom Line: As expected, capacity was significantly lower for the shape dimension.Similarly, participants with a stronger BOLD response for color also showed a strong neural response for shape within the lateral occipital cortex, intraparietal sulcus (IPS), and superior IPS.Although there were robust individual differences in the behavioral and neural measures, we found little evidence of systematic brain-behavior correlations across feature dimensions.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Mathematics and Computational Sciences, University of Iowa, Iowa City IA, USA.

ABSTRACT
Visual working memory (VWM) is a key cognitive system that enables people to hold visual information in mind after a stimulus has been removed and compare past and present to detect changes that have occurred. VWM is severely capacity limited to around 3-4 items, although there are robust individual differences in this limit. Importantly, these individual differences are evident in neural measures of VWM capacity. Here, we capitalized on recent work showing that capacity is lower for more complex stimulus dimension. In particular, we asked whether individual differences in capacity remain consistent if capacity is shifted by a more demanding task, and, further, whether the correspondence between behavioral and neural measures holds across a shift in VWM capacity. Participants completed a change detection (CD) task with simple colors and complex shapes in an fMRI experiment. As expected, capacity was significantly lower for the shape dimension. Moreover, there were robust individual differences in behavioral estimates of VWM capacity across dimensions. Similarly, participants with a stronger BOLD response for color also showed a strong neural response for shape within the lateral occipital cortex, intraparietal sulcus (IPS), and superior IPS. Although there were robust individual differences in the behavioral and neural measures, we found little evidence of systematic brain-behavior correlations across feature dimensions. This suggests that behavioral and neural measures of capacity provide different views onto the processes that underlie VWM and CD. Recent theoretical approaches that attempt to bridge between behavioral and neural measures are well positioned to address these findings in future work.

No MeSH data available.