The developmental neural substrates of item and serial order components of verbal working memory

Abstract

Behavioral and developmental studies have made a critical distinction between item and serial order processing components of verbal working memory (WM). This functional magnetic resonance imaging (fMRI) study determined the extent to which item and serial order WM components are characterized by specialized neural networks already in young children or whether this specialization emerges at a later developmental stage. Total of 59 children aged 7-12 years performed item and serial order short-term probe recognition tasks in an fMRI experiment. While a left frontoparietal network was recruited in both item and serial order WM conditions, the right intraparietal sulcus was selectively involved in the serial order WM condition. This neural segregation was modulated by age, with both networks becoming increasingly separated in older children. Our results indicate a progressive specialization of networks involved in item and order WM processes during cognitive development.

Keywords: development; neuroimaging; serial order; short-term memory; working memory.

Figure 1

Experimental design and timing of the two WM tasks. For each condition, a negative probe trial is illustrated

Figure 2

Error rate and RTs (mean and SE) for behavioral performance as a function of item and order WM conditions

Figure 3

Scatterplot of performance in item and order WM tasks as a function of age in months [Color figure can be viewed at http://wileyonlinelibrary.com]

Figure 4

Activity foci for the (a) encoding and (b) recognition phase as a function of WM task (item vs. order). LH = left hemisphere; RH = right hemisphere. All activity foci displayed here are significant at p < .001 (uncorrected) and are mapped onto an inflated brain template using caret 5.64 with the PALS‐B12 atlas (Van Essen et al., 2001) [Color figure can be viewed at http://wileyonlinelibrary.com]

Figure 5

Correlation between age and parameter estimates (beta values) during the recognition phase for both WM tasks in the parietal ROI. Values identified as outside of the sensitive cutoff (<.071) by means of Cook's distance are circled [Color figure can be viewed at http://wileyonlinelibrary.com]

Figure 6

Brain regions activated in the (a) encoding and (b) recognition phase from the two WM tasks (item vs. order) × 2 WM phases (encoding vs. recognition) × 2 groups (young vs. old) factorial design. Below, parameter estimates (beta values) for each group, WM task and phase are showed at the parietal and frontal ROI level. LH = left hemisphere; RH = right hemisphere. All brain activations showed are significant at p < .001 (uncorrected) and are mapped onto an inflated brain template using Caret 5.64 with the PALSB12 atlas (Van Essen et al., 2001) [Color figure can be viewed at http://wileyonlinelibrary.com]