Effects of verbal working memory load on corticocortical connectivity modeled by path analysis of functional magnetic resonance imaging data

G. D. Honey, C. H. Y. Fu, J. Kim, M. J. Brammer, T. J. Croudace, J. Suckling, E. M. Pich, S. C. R. Williams, E. T. Bullmore (Lead / Corresponding author)

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    160 Citations (Scopus)

    Abstract

    We investigated the hypothesis that there are load-related changes in the integrated function of frontoparietal working memory networks. Functional magnetic resonance imaging time-series data from 10 healthy volunteers performing a graded n-back verbal working memory task were modeled using path analysis. Seven generically activated regions were included in the model: left/right middle frontal gyri (L/R MFG), left/right inferior frontal gyri (L/R IFG), left/right posterior parietal cortex (L/R PPC), and supplementary motor area (SMA). The model provided a good fit to the 1-back (χ2 = 7.04, df = 8, P = 0.53) and 2-back conditions (χ2 = 9.35, df = 8, P = 0.31) but not for the 3-back condition (χ2 = 20.60, df = 8, P = 0.008). Model parameter estimates were compared overall among conditions: there was a significant difference overall between 1-back and 2-back conditions (χ2diff = 74.77, df = 20, P <0.001) and also between 2-back and 3-back conditions (χ2diff = 96.28, df = 20, P <0.001). Path coefficients between LIFG and LPPC were significantly different from zero in both 1-back and 2-back conditions; in the 2-back condition, additional paths from LIFG to LPPC via SMA and to RMFG from LMFG and LPPC were also nonzero. This study demonstrated a significant change in functional integration of a neurocognitive network for working memory as a correlate of increased load. Enhanced inferior frontoparietal and prefrontoprefrontal connectivity was observed as a correlate of increasing memory load, which may reflect greater demand for maintenance and executive processes, respectively.
    Original languageEnglish
    Pages (from-to)573-582
    Number of pages10
    JournalNeuroImage
    Volume17
    Issue number2
    DOIs
    Publication statusPublished - Oct 2002

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