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Tahedl, M.

Publications and source records attributed to Tahedl, M..

2 recordsLinked to original sources

An updated and extended atlas for corresponding brain activation during task and rest

The complexity of our actions and thinking is likely reflected in functional brain networks. Independent component analysis (ICA) is a popular data-driven method to compute group differences between such networks. To aid interpretation of functional network analyses, Smith and colleagues proposed a template of ten functional networks identified in 36 healthy participants. They labeled them those components according to their similarity with statistical parameter maps from a metaanalysis of task-based functional magnetic resonance imaging studies (Smith et al., 2009). However, those original templates show substantial distortion with respect to what up-to date correction methods can achieve, such that trying to capture relevant effects within several cortical regions, especially the sensorimotor and orbitofrontal cortices, as well as the cerebellum may yield suboptimal results. Here, we provide a technical update and extension to the original templates. Using correlation analyses, we identified the best matching maps of each of the original ten templates to ICA maps from the Human Connectome Project (HCP). The HCP provides group-parcellations of a large dataset (n = 1003) with high-quality data. This approach yields a better fit of spatial component maps with anatomical borders and gray-/white-matter-boundaries. Additionally, we provide a version of the updated templates in CIFTI file-format, an emerging format in the neuroimaging community that combines surface-based data with subcortical/cerebellar data in volumetric space. The two formats we provide here offer an improvement on the templates by Smith et al., which should enhance sensitivity and interpretability of future research that compares functional networks between groups.

neuroscience↗

Temporal signal-to-noise changes in combined multiband- and slice-accelerated echo-planar imaging with a 20- and 64-channel coil

Echo planar imaging (EPI) is the most common method of functional magnetic resonance imaging for acquiring the blood oxygenation level-dependent (BOLD) contrast. One of the primary benefits of using EPI is that an entire volume of the brain can be acquired on the order of two seconds. However, this speed benefit comes with a cost. Because imaging protocols are limited by hardware (e.g., fast gradient switching), researchers are forced to compromise between spatial resolution, temporal resolution, or whole-brain coverage. Earlier attempts to circumvent this problem included developing protocols in which slices of a volume were acquired faster (i.e., slice (S) acceleration), while more recent protocols allow for multiple slices to be acquired simultaneously (i.e., multiband (MB) acceleration). However, applying such acceleration methods can lead to a reduction in the temporal signal-to-noise ratio (tSNR), which is a critical measure of the stability of the signal over time. Here we show, in five healthy subjects, using a 20- and 64-channel receiver coil, that enabling S-acceleration consistently yielded, as expected, a substantial decrease in tSNR, regardless of the receiver coil employed, whereas tSNR decrease resulting from MB acceleration was less pronounced. Specifically, with the 20-channel coil, tSNR of upto 4-fold MB-acceleration is comparable to that of no acceleration, while up to 6-fold MB-acceleration with the 64-channel coil yields comparable tSNR to that of no acceleration. Moreover, observed tSNR losses tended to be localized to temporal, insular, and medial brain regions and were more noticeable in the 20-than in the 64-channel coil. Conversely, with the 64-channel coil, the tSNR in lateral frontoparietal regions remained relatively stable with increasing MB factors. Such methodological explorations can inform researchers and clinicians as to how they can optimize imaging protocols depending on the available hardware and the brain regions they want to investigate.

neuroscience↗