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Hum Brain Mapp. 2014 Sep;35(9):4932-43. doi: 10.1002/hbm.22523. Epub 2014 Apr 16.

Respiration phase-locks to fast stimulus presentations: implications for the interpretation of posterior midline "deactivations".

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  • 1Harvard Medical School, Martinos Center for Biomedical Imaging, Brigham and Women's Hospital, Boston, Massachusetts; Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands.

Abstract

The posterior midline region (PMR)-considered a core of the default mode network-is deactivated during successful performance in different cognitive tasks. The extent of PMR-deactivations is correlated with task-demands and associated with successful performance in various cognitive domains. In the domain of episodic memory, functional MRI (fMRI) studies found that PMR-deactivations reliably predict learning (successful encoding). Yet it is unclear what explains this relation. One intriguing possibility is that PMR-deactivations are partially mediated by respiratory artifacts. There is evidence that the fMRI signal in PMR is particularly prone to respiratory artifacts, because of its large surrounding blood vessels. As respiratory fluctuations have been shown to track changes in attention, it is critical for the general interpretation of fMRI results to clarify the relation between respiratory fluctuations, cognitive performance, and fMRI signal. Here, we investigated this issue by measuring respiration during word encoding, together with a breath-holding condition during fMRI-scanning. Stimulus-locked respiratory analyses showed that respiratory fluctuations predicted successful encoding via a respiratory phase-locking mechanism. At the same time, the fMRI analyses showed that PMR-deactivations associated with learning were reduced during breath-holding and correlated with individual differences in the respiratory phase-locking effect during normal breathing. A left frontal region--used as a control region--did not show these effects. These findings indicate that respiration is a critical factor in explaining the link between PMR-deactivation and successful cognitive performance. Further research is necessary to demonstrate whether our findings are restricted to episodic memory encoding, or also extend to other cognitive domains.

Copyright © 2014 Wiley Periodicals, Inc.

KEYWORDS:

attention; episodic memory; fMRI; posterior midline region; respiration

PMID:
24737724
[PubMed - indexed for MEDLINE]
PMCID:
PMC4445359
Free PMC Article
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