Abstract
For different functional magnetic resonance imaging experiments using blood oxygenation level-dependent (BOLD) contrast, the acquisition of T 2*-weighted scans at a high spatial resolution may be advantageous in terms of time-course signal-to-noise ratio and of BOLD sensitivity when the regions are prone to susceptibility artifacts. In this study, we explore this solution by examining how spatial resolution influences activations elicited when appetizing food pictures are viewed. Twenty subjects were imaged at 3 T with two different voxel volumes, 3.4 μl and 27 μl. Despite the diminution of brain coverage, we found that high-resolution acquisition led to a better detection of activations. Though known to suffer to different degrees from susceptibility artifacts, the activations detected by high spatial resolution were notably consistent with those reported in published activation likelihood estimation meta-analyses, corresponding to taste-responsive regions. Furthermore, these regions were found activated bilaterally, in contrast with previous findings. Both the reduction of partial volume effect, which improves BOLD contrast, and the mitigation of susceptibility artifact, which boosts the signal to noise ratio in certain regions, explained the better detection noted with high resolution. The present study provides further evidences that high spatial resolution is a valuable solution for human BOLD fMRI, especially for studying food-related stimuli.
Highlights
With the widespread use of high magnetic fields, interest in increasing the spatial resolution in fMRI is constantly developing
The brain regions activated at the group level for the contrast between viewing food and nonfood pictures are represented in Table 2 for both low resolution (LR) and high spatial resolution (HR) conditions, and visually compared x, y, z t
In conditions of similar resolutions (LR), the activations detected in our study recover only a part of the activations described by the meta-analyses [28, 29], in particular no activation was found in left amygdala, left lateral orbitofrontal cortex (OFC), and right insula
Summary
With the widespread use of high magnetic fields, interest in increasing the spatial resolution in fMRI is constantly developing. When voxel size is reduced isotropically, its efficiency is not prone to the orientation of magnetic field gradients, known to change rapidly over the brain. It may be advantageous in terms of time-course signal-to-noise ratio (tSNR) to acquire images with a reduced voxel volume, in which thermal noise dominates. In this regime, tSNR comes closer to what can be expected from the SNR of an individual image. TSNR increases steadily with the degree of smoothing, rather than being limited when physiological fluctuations with time dominate [9,10,11]
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