Functional mapping of the human visual cortex at 4 and 1.5 tesla using deoxygenation contrast EPI

Turner, Robert; Jezzard, Peter; Wen, H.; Kwong, Kenneth K.; Bihan, Denis Le; Zeffiro, Thomas A.; Balaban, R. S.

doi:10.1002/mrm.1910290221

Cited by 435 publications

(233 citation statements)

References 12 publications

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“…5). The combination of the high spatial resolution of the fMRI data, increased BOLD sensitivity and specificity available from higher field strengths Turner et al, 1993;van der Zwaag et al, 2009a,b;Yacoub et al, 2001) in combination with a wavelet-based analysis (Van De Ville et al, 2007;Van De Ville and Unser, 2008) of the functional images avoided a reduction of the spatial resolution. As a result, the distinction between the primary and non-primary auditory areas in fMRI data was possible and the used spatial resolution was sufficient to distinguish between areas which were sensitive to differences in presented sound location and those which were not.…”

Section: Discussionmentioning

confidence: 99%

Where sound position influences sound object representations: A 7-T fMRI study

et al. 2011

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Section: Discussionmentioning

confidence: 99%

Where sound position influences sound object representations: A 7-T fMRI study

et al. 2011

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“…Most of the existing fMRI data has been collected using gradient echo (GE) sequences [Bandettini et al, 1992;Belliveau et al, 1991;Blamire et al, 1992;Frahm et al, 1992;Kwong et al, 1992;Ogawa et al, 1992;Turner et al, 1993]. This technique, however, is very Output of the Phase-Only Filter for the retinotopic maps with/without EEG electrodes (Fig.…”

Section: Discussionmentioning

confidence: 99%

Influence of EEG electrodes on the BOLD fMRI signal

Bonmassar¹,

Hadjikhani²,

Ives³

et al. 2001

Human Brain Mapping

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Measurement of the EEG during fMRI scanning can give rise to image distortions due to magnetic susceptibility, eddy currents or chemical shift artifacts caused by certain types of EEG electrodes, cream, leads, or amplifiers. Two different creams were tested using MRS and T2* measurements, and we found that the one with higher water content was superior. This study introduces an index that quantifies the influence of EEG equipment on the BOLD fMRI signal. This index can also be used more generally to measure the changes in the fMRI signal due to the presence of any type of device inside (or outside) of the field of view (e.g., with fMRI and diffuse optical tomography, infrared imaging, transcranial magnetic stimulation, ultrasound imaging, etc.). Quantitative noise measurements are hampered by the normal variability of functional activation within the same subject and by the different slice profiles obtained when inserting a subject multiple times inside a MR imaging system. Our measurements account for these problems by using a matched filtering of cortical surface maps of functional activations. The results demonstrate that the BOLD signal is not influenced by the presence of EEG electrodes when using a properly constructed MRI compatible recording cap.

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“…Simultaneous acquisitions also avoid differences in spurious stimuli (Novitski et al, 2003), training or habituation effects (Debener et al, 2002) and other differences in subject performance (Boly et al, 2007). Considering fMRI, it is well known that a stronger static field B 0 results both in increased magnetization and in an accentuated BOLD effect, leading to super-linear gains in functional sensitivity (Turner et al, 1993;van der Zwaag et al, 2009). As a result, in recent years, fMRI studies conducted at ultra-high field have achieved sub-millimeter spatial resolution (Yacoub et al, 2008), and higher field strengths continue to be pursued (Deelchand et al, 2010;Duyn, 2012).…”

Section: Introductionmentioning

confidence: 99%

Simultaneous EEG–fMRI at ultra-high field: Artifact prevention and safety assessment

et al. 2015

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The simultaneous recording of scalp electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) can provide unique insights into the dynamics of human brain function, and the increased functional sensitivity offered by ultra-high field fMRI opens exciting perspectives for the future of this multimodal approach. However, simultaneous recordings are susceptible to various types of artifacts, many of which scale with magnetic field strength and can seriously compromise both EEG and fMRI data quality in recordings above 3 T. The aim of the present study was to implement and characterize an optimized setup for simultaneous EEG-fMRI in humans at 7 T. The effects of EEG cable length and geometry for signal transmission between the cap and amplifiers were assessed in a phantom model, with specific attention to noise contributions from the MR scanner coldheads. Cable shortening (down to 12 cm from cap to amplifiers) and bundling effectively reduced environment noise by up to 84% in average power and 91% in inter-channel power variability. Subject safety was assessed and confirmed via numerical simulations of RF power distribution and temperature measurements on a phantom model, building on the limited existing literature at ultra-high field. MRI data degradation effects due to the EEG system were characterized via B 0 and B 1 + field mapping on a human volunteer, demonstrating important, although not prohibitive, B 1 disruption effects. With the optimized setup, simultaneous EEG-fMRI acquisitions were performed on 5 healthy volunteers undergoing two visual paradigms: an eyes-open/eyes-closed task, and a visual evoked potential (VEP) paradigm using reversing-checkerboard stimulation. EEG data exhibited clear occipital alpha modulation and average VEPs, respectively, with concomitant BOLD signal changes. On a single-trial level, alpha power variations could be observed with relative confidence on all trials; VEP detection was more limited, although statistically significant responses could be detected in more than 50% of trials for every subject. Overall, we conclude that the proposed setup is well suited for simultaneous EEG-fMRI at 7 T.

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Functional mapping of the human visual cortex at 4 and 1.5 tesla using deoxygenation contrast EPI

Cited by 435 publications

References 12 publications

Where sound position influences sound object representations: A 7-T fMRI study

Where sound position influences sound object representations: A 7-T fMRI study

Influence of EEG electrodes on the BOLD fMRI signal

Simultaneous EEG–fMRI at ultra-high field: Artifact prevention and safety assessment

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