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Sensitivity of BOLD response to increasing visual contrast: spin echo versus gradient echo EPI.
MedLine Citation:
PMID:  23707589     Owner:  NLM     Status:  Publisher    
Previous evidence showed that spin-echo (SE) BOLD signals offer an increased linearity and promptness with respect to gradient-echo (GE) acquisition, possibly providing a more accurate estimate of the amplitude of neuronal activity. However there is no evidence that the two sequences differ in representing different activation levels due to changes in stimulus intensity. In this study at 3T we compared GE and SE BOLD responses to visual stimuli at increasing contrast levels (5%, 20%, 60%, 100%). Both sequences showed a monotonic increase of the BOLD response with stimulus contrast. While the larger sensitivity of GE yielded overall larger signal changes, step-wise increase in activation for GE was significant only when comparing 20% with 5% contrast, whereas for SE a significant increase was observed also when comparing 60% with 20% contrast. Moreover, BOLD responses normalized to the lowest contrast showed that relative increases of SE fMRI signal with increasing stimulus strength are larger with respect to the corresponding values of GE signal. This difference was observed also when excluding voxels attributed to large vessels, suggesting a non negligible role of the extravascular contribution to the modulation of SE fMRI signal with stimulus intensity. These results are shown to be in agreement with theoretical predictions that we derived from a recently proposed model of GE and SE functional signals. The present findings suggest that, despite the limited increase in functional localization accuracy at low field, SE fMRI might offer a potential advantage in distinguishing different levels of stimulus-evoked brain activity.
Piero Chiacchiaretta; Gian Luca Romani; Antonio Ferretti
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-5-23
Journal Detail:
Title:  NeuroImage     Volume:  -     ISSN:  1095-9572     ISO Abbreviation:  Neuroimage     Publication Date:  2013 May 
Date Detail:
Created Date:  2013-5-27     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9215515     Medline TA:  Neuroimage     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2013. Published by Elsevier Inc.
Department of Neuroscience and Imaging, University "G. d'Annunzio" of Chieti, Italy; Institute for Advanced Biomedical Technologies (ITAB), University "G. d'Annunzio" Foundation, Chieti, Italy. Electronic address:
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