Functional Brain Imaging of Swallowing: An Activation Likelihood Meta-Analysis
    Peter
    1
    
    P 375
    
    1,2, S¨ r¨ s oo
    
    Yoko
    
    1,3, Inamoto
    
    Ruth
    
    1 Martin
    
    School of Communication Sciences & Disorders, The University of Western Ontario, London, Ontario, Canada 2 Department of Communication Sciences & Disorders, University of South Carolina, Columbia, SC, U.S.A. 3 Department of Physical Medicine and Rehabilitation, Johns Hopkins University, Baltimore, MD, U.S.A.
    
    soros@mailbox.sc.edu
    
    Introduction
    The neuroanatomy and functional significance of swallowingrelated networks in humans are not entirely clear. Activation likelihood estimation (ALE), a novel quantitative metaanalysis technique, was employed to pool the results of functional brain imaging studies for the investigation of the cortical control of swallowing (S¨ r¨ s et al. 2009). oo
    
    Conclusion
    This meta-analysis emphasizes the distributed and partly overlapping cortical networks involved in the control of water and saliva swallowing. Water swallowing is associated with right inferior parietal activation, likely reflecting the sensory processing of intraoral water stimulation. Saliva swallowing more strongly involves premotor areas, which are crucial for the initiation and control of movements.
    
    Methods
    Studies that were included in the meta-analysis 1) examined water swallowing, saliva swallowing, or both, and 2) reported brain activation as coordinates in standard space. Using these criteria, a systematic literature search identified 7 studies that examined water swallowing, and 5 studies of saliva swallowing. A quantitative voxel-wise ALE meta-analysis of these studies was done with GingerALE (http://brainmap.org). The following steps were performed: 1. The ALE value of each voxel of the brain in Talairach space was calculated (2 × 2 × 2 mm matrix, 10 mm FWHM). 2. A permutation test with 5000 permutations was performed to determine the significance of the ALE statistic at each voxel, returning an ALE map with a P value for each voxel. 3. This ALE map was thresholded using the false discovery rate algorithm with a false discovery rate of 0.05. 4. A cluster analysis of the thresholded maps was performed with a minimum cluster size of 100 mm3. Anatomical labels for these clusters were provided by the Talairach Daemon (http://www.talairach.org/) F IGURE 2: ALE meta-analysis of brain activity associated with saliva swallowing versus rest. Significant activation clusters included: • right medial frontal gyrus (1a), • right (1b) and left cingulate gyrus, • left postcentral gyrus (2a) • left precentral gyrus (2b), and • right insula (3).
    
    References
    1. Fraser C et al. (2002): Driving plasticity in human adult motor cortex is associated with improved motor function after brain injury. Neuron 34:831–840. 2. Furlong P et al. (2004): Dissociating the spatio-temporal characteristics of cortical neuronal activity associated with human volitional swallowing in the healthy adult brain. Neuroimage 22:1447–1455. 3. Hamdy S et al. (1999a): Cortical activation during human volitional swallowing: An event-related fMRI study. Am J Physiol 277:G219–G225. 4. Hamdy S et al. (1999b): Identication of the cerebral loci processing human swallowing with H215O PET activation. J Neurophysiol 81:1917–1926. 5. Harris M et al. (2005): Mapping metabolic brain activation during human volitional swallowing: A positron emission tomography study using 18Fluorodeoxyglucose. J Cereb Blood Flow Metab 25:520–526. 6. Martin R et al. (2001): Cerebral cortical representation of automatic and volitional swallowing in humans. J Neurophysiol 85:938–950. 7. Martin R et al. (2004): Cerebral areas processing swallowing and tongue movement are overlapping but distinct: A functional magnetic resonance imaging study. J Neurophysiol 92:2428–2443. F IGURE 3: Comparison between the ALE maps for water swallowing versus rest (see Fig. 1) and saliva swallowing versus rest (see Fig. 2). Clusters with significantly higher activation likelihood for water swallowing versus rest are shown in blue, including: • right inferior parietal lobule (1), • right postcentral gyrus (2), and • right insula (3). Clusters with significantly higher activation likelihood for saliva swallowing versus rest are shown in red, including: • right cingulate gyrus (6a), • left cingulate gyrus (6b), • right medial frontal gyrus (6c), • left precentral gyrus (7), and • right precentral gyrus (8). 8. Martin R et al. (2007): Cerebral cortical processing of swallowing in older adults. Exp Brain Res 176:12–22. 9. S¨ r¨ s P et al. (2009): Functional brain imaging of swallowoo ing: An activation likelihood estimation meta-analysis. Hum Brain Mapp. 10. Suzuki M et al. (2003): Activation of cerebellum and basal ganglia on volitional swallowing detected by functional magnetic resonance imaging. Dysphagia 18:71–77. 11. Zald D, Pardo J (1999): The functional neuroanatomy of voluntary swallowing. Ann Neurol 46:281–286.
    
    Results
    
    F IGURE 1: Activation likelihood estimation (ALE) metaanalysis of brain activity associated with water swallowing versus rest. Significant activation clusters included: • left precentral gyrus (1), • right post-central gyrus (2a), • inferior frontal gyrus (2b), • right inferior parietal lobule (3), • left cingulate gyrus (4), and • right insula (6).
    
    Acknowledgments
    Supported by: Heart and Stroke Foundation of Ontario, Natural Sciences and Engineering Research Council of Canada, Ontario Ministry of Health and Long-Term Care Salary Support, Premiers Research Excellence Award.
    A Typeset in L TEX on Mac OS X. Download this poster at: http://neuroactivity.org
    
    TABLE 1: A RTICLES INCLUDED IN THE META - ANALYSIS .
    Article Water swallow Fraser et al., 2002 Hamdy et al., 1999a Martin et al., 2001 Martin et al., 2007 Furlong et al., 2004 Hamdy et al., 1999b Harris et al., 2005 Saliva swallow Martin et al., 2001 Martin et al., 2004 Martin et al., 2007 Suzuki et al., 2003 Zald and Pardo, 1999 Imaging modality n Mean age (yrs, range) Cue Number of swallows Foci
    
    fMRI (1.5 T) fMRI (1.5 T) fMRI (4 T) fMRI (4 T) MEG H2O PET FDG PET
    
    8 10 14 9 8 8 8
    
    26 (23-34) 32 (22-61) 28 74 NA (26–45) 48 (35-65) NA (29-37)
    
    Visual Self-paced Self-paced Visual Visual Visual Visual
    
    96 20 5-17 10 20 180 90
    
    8 24 9 32 5 9 17
    
    fMRI (4 T) fMRI (4 T) fMRI (4 T) fMRI (1.5 T) H2O PET
    
    14 14 9 11 8
    
    28 28 74 NA (24-42) 30 (20-51)
    
    Self-paced Visual Visual Auditory Sef-paced
    
    4-12 18 10 15 22
    
    6 16 24 5 21

Add Comment

To add a comment, you need to login or signup (you can signup without leaving this page)