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. 2017 Oct:42:123-129.
doi: 10.1016/j.mri.2017.06.009. Epub 2017 Jun 17.

Activation volume vs BOLD signal change as measures of fMRI activation - Its impact on GABA - fMRI activation correlation

Pallab K Bhattacharyya  1 , Micheal D Phillips  2 , Lael A Stone  3 , Mark J Lowe  2
Affiliations

Activation volume vs BOLD signal change as measures of fMRI activation - Its impact on GABA - fMRI activation correlation

Pallab K Bhattacharyya et al. Magn Reson Imaging. 2017 Oct.

Abstract

Purpose: To explore the relative robustness of functional MRI (fMRI) activation volume and blood oxygen level-dependent (BOLD) signal change as fMRI metric, and to study the effect of relative robustness on the correlation between fMRI activation and cortical gamma amino butyric acid (GABA) in healthy controls and patients with multiple sclerosis (MS).

Methods: fMRI data were acquired from healthy controls and patients with MS, with the subjects peforming self paced bilateral finger tapping in block design. GABA spectroscopy was performed with voxel placed on the area of maximum activation during fMRI. Activation volume and BOLD signal changes at primary motor cortex (M1), as well as GABA concentration were calculated for each patient.

Results: Activation volume correlated with BOLD signal change in healthy controls, but no such correlation was observed in patients with MS. This difference was likely the result of higher intersubject noise variance in the patient population. GABA concentration correlated with M1 activation volume in patients but not in controls, and did not correlate with any fMRI metric in patients or controls.

Conclusion: Our data suggest that activation volume is a more robust measure than BOLD signal change in a group with high intersubject noise variance as in patients with MS. Additionally, this study demonstrated difference in correlation behavior between GABA concentration and the 2 fMRI metrics in patients with MS, suggesting that GABA - activation volume correlation is more appropriate measure in the patient group.

Keywords: Activation volume; BOLD signal; GABA; fMRI.

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Figures

Fig. 1
Fig. 1
Example of fMRI activation map showing percent BOLD signal change and activation volume within M1 ROI. M1 ROIs from HMAT displayed on 1-mm thick slices without any gap; right M1 in blue and left M1 in red (a); BOLD signal change within the M1 ROI (Student t > 3.5, 1-sided, uncorrected P < 3 × 10−4) (b); zoomed version of BOLD signal change (c).
Fig. 2
Fig. 2
Representative single subject edited spectrum. Co-edited glutamate (Glu) and glutamine (Gln) are also seen in the spectrum.
Fig. 3
Fig. 3
M1 activation volume correlates with percent BOLD signal change in healthy controls (a) but not in patients with MS (b).
Fig. 4
Fig. 4
M1 GABA level ([GABA]) correlates with activation volume (a) but not with percent BOLD signal change (b) in patients with MS.
Fig. 5
Fig. 5
M1 GABA level ([GABA]) does not correlate with percent BOLD signal change (a) or activation volume (b) in healthy controls.
See this image and copyright information in PMC

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