Epoch-specific functional networks involved in working memory

Woodward, T. S., Feredoes, E., Metzak, P. D., Takane, Y. and Manoach, D. S. (2013) Epoch-specific functional networks involved in working memory. NeuroImage, 65. pp. 529-539. ISSN 1053-8119 doi: 10.1016/j.neuroimage.2012.09.070

Abstract/Summary

Working memory (WM) is not a unitary construct. There are distinct processes involved in encoding information, maintaining it on-line, and using it to guide responses. The anatomical configurations of these processes are more accurately analyzed as functionally connected networks than collections of individual regions. In the current study we analyzed event-related functional magnetic resonance imaging (fMRI) data from a Sternberg Item Recognition Paradigm WM task using a multivariate analysis method that allowed the linking of functional networks to temporally-separated WM epochs. The length of the delay epochs was varied to optimize isolation of the hemodynamic response (HDR) for each task epoch. All extracted functional networks displayed statistically significant sensitivity to delay length. Novel information extracted from these networks that was not apparent in the univariate analysis of these data included involvement of the hippocampus in encoding/probe, and decreases in BOLD signal in the superior temporal gyrus (STG), along with default-mode regions, during encoding/delay. The bilateral hippocampal activity during encoding/delay fits with theoretical models of WM in which memoranda held across the short term are activated long-term memory representations. The BOLD signal decreases in the STG were unexpected, and may reflect repetition suppression effects invoked by internal repetition of letter stimuli. Thus, analysis methods focusing on how network dynamics relate to experimental conditions allowed extraction of novel information not apparent in univariate analyses, and are particularly recommended for WM experiments for which task epochs cannot be randomized.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/29608
Item Type	Article
Refereed	Yes
Divisions	Life Sciences > School of Psychology and Clinical Language Sciences > Department of Psychology Life Sciences > School of Psychology and Clinical Language Sciences > Neuroscience Life Sciences > School of Psychology and Clinical Language Sciences > Language and Cognition
Publisher	Elsevier
Download/View statistics	View download statistics for this item