Reproducibility of Swallow Induced Cortical fMRI Activity and Role of Negative BOLD Signal.

Am J Physiol Gastrointest Liver Physiol. 2012 Jul 5;

Authors: Babaei A, Ward BD, Ahmad S, Patel A, Nencka A, Li SJ, Hyde JS, Shaker R

Abstract
Background & Aim: fMRI studies have demonstrated that a number of brain regions (cingulate, insula, prefrontal and sensory/motor cortices) display blood oxygen level dependent (BOLD) positive activity during swallow. Negative BOLD activations and reproducibility of these activations have not been systematically studied. The aim of our study was to investigate the reproducibility of swallow related cortical positive and negative BOLD activity across different fMRI sessions. Methods: We studied 16 healthy volunteers utilizing an fMRI event-related analysis. Individual analysis using general linear model was used to remove undesirable signal changes correlated with motion, white matter and cerebrospinal fluid. The group analysis used mixed-effects multilevel model to identify active cortical regions. The volume and magnitude of BOLD signal within each cluster was compared between the two study sessions. Results: All subjects showed significant clustered BOLD activity within the known areas of cortical swallowing network (CSN) across both sessions. The cross correlation coefficient of percent fMRI signal change and the number of activated voxels across both positive and negative BOLD networks were similar between the two studies (r ≥ 0.87, p<0.0001). Swallow associated negative BOLD activity was comparable to the well-defined "default-mode" network, and positive BOLD activity had noticeable overlap with previously described "task-positive" network. Conclusions: Swallow activates two parallel cortical networks. These include a positive and a negative BOLD network respectively correlated and anti-correlated with swallow stimulus. Group cortical activity maps as well as extent and amplitude of activity induced by volitional swallowing in the CSN are reproducible between study sessions. Key Words: reliability, deglutition, test-retest, default mode network.

PMID: 22766854 [PubMed - as supplied by publisher]