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  Transient and sustained BOLD responses to sustained visual stimulation

Uludag, K. (2008). Transient and sustained BOLD responses to sustained visual stimulation. Magnetic Resonance Imaging, 26(7), 863-869. doi:10.1016/j.mri.2008.01.049.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0013-C721-0 Version Permalink: http://hdl.handle.net/21.11116/0000-0003-2FBE-4
Genre: Journal Article

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Uludag, K1, 2, Author              
Affiliations:
1Former Department MRZ, Max Planck Institute for Biological Cybernetics, Max Planck Society, Spemannstrasse 38, 72076 Tübingen, DE, ou_2528700              
2Max Planck Institute for Biological Cybernetics, Max Planck Society, Spemannstrasse 38, 72076 Tübingen, DE, ou_1497794              

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 Abstract: Examining the transients of the blood-oxygenation-level-dependent (BOLD) signal using functional magnetic resonance imaging is a tool to probe basic brain physiology. In addition to the so-called initial dip and poststimulus undershoot of the BOLD signal, occasionally, overshoot at the beginning and at the end of stimulation and stimulus onset and offset (‘phasic’) responses are observed. Hemifield visual stimulation was used in human subjects to study the latter transients. As expected, sustained (‘tonic’) stimulus-correlated contralateral activation in the visual cortex and LGN was observed. Interestingly, bilateral phasic responses were observed, which only partly overlapped with the tonic network and which would have been missed using a standard analysis. A biomechanical model of the BOLD signal (‘balloon model’) indicated that, in addition to phasic neuronal activity, vascular uncoupling can also give rise to phasic BOLD signals. Thus, additional physiological information (i.e., cerebral blood flow ) and examination of spatial distribution of the activity might help to assess the BOLD signal transients correctly. In the current study, although vascular uncoupled responses cannot be ruled out as an explanation of the observed phasic BOLD network, the spatial distribution argues that sustained hemifield visual stimulation evokes both bilateral phasic and contralateral sustained neuronal responses. As a consequence, in rapid event-related experimental designs, both the phasic and tonic networks cannot be separated, possibly confounding the interpretation of BOLD signal data. Furthermore, a combination of phasic and tonic responses in the same region of interest might also mimic a BOLD response typically observed in adaptation experiments.

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 Dates: 2008-09
 Publication Status: Published in print
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 Identifiers: DOI: 10.1016/j.mri.2008.01.049
BibTex Citekey: 5175
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Title: Magnetic Resonance Imaging
Source Genre: Journal
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Publ. Info: New York : Elsevier
Pages: - Volume / Issue: 26 (7) Sequence Number: - Start / End Page: 863 - 869 Identifier: ISSN: 0730-725X
CoNE: https://pure.mpg.de/cone/journals/resource/954925533026