Fingerprints of Neuronal Activation

A major line of our research is a more specific understanding of the measured MR signal during brain activation, the variability of this contrast across different cortical and subcortical regions, its dependence on the underlying structure and shape of the microvasculature, and the correlation of this contrast to neuronal activation as a function of spatial and temporal resolution. An important step towards a better understanding of MR signal formation in neuronal tissue will be achieved with multimodal integrated micro devices composed of MR detectors, optical and electrical detectors with a size of only a few hundreds of micrometers. Along these lines, we also try to assess the spatial limit of BOLD fMRI at ultra-high fields, and whether it is possible at all, to reliably detect subunits of the primary cortex such as layers or columns.

Arterial spin labeling (ASL) can benefit twofold from ultrahigh-field MRI. First, the higher field strength leads to an increase in the intrinsic signal-to-noise ratio (SNR), and second, a higher and longer-lasting perfusion-related signal change can be measured due to the longer longitudinal relaxation times. [more]
An increasing number of studies aim to perform functional MRI measurements acquired at ultra-high field (UHF) with voxel dimensions in the sub-millimeter scale. Such studies are possible primarily due to the stronger BOLD effect at higher fields, resulting in an increased contrast-to-noise ratio (CNR) in fMRI, as well as the superlinear increase of image signal-to-noise ratio with field strength. [more]
The superior colliculus (SC) is a layered structure located in the midbrain. We exploited the improved spatial resolution and BOLD signal strength available at 9.4 T to investigate the depth profile of visual BOLD responses in the human SC based on distortion-corrected EPI data with a 1 mm isotropic resolution. [more]
We investigate the superior colliculi to reveal how human sensory processing is managed by this small mid-brain structure. Ultra-high fields are central to enable detailed detection of  layer-specific fMRI signals. [more]
Magnetic Resonance Imaging at ultra high field strengths can help to increase the signal amplitude and thus to improve spatial or temporal resolution. But how much? And how does that affect the contrast? [more]
Though it is used in a large number of neuroscientific studies, the BOLD effect, arising due to a complex interplay of changes in blood volume, blood oxygenation and blood flow, is still not completely understood. Intrinsic optical imaging can help to disentangle the different contributions, being able to measure changes in oxygenation and blood volume separately and quantitatively. [more]
Widefield optical imaging is an important tool for neuroscientific research, either for directly observing changes in the oxygenation and blood volume during activation with intrinsic optical imaging, or for using dyes or genetically encoded indicators to look at calcium inflow or electrical cellular events. [more]
The primary visual cortex of humans contains patches of neurons responding preferentially to stimulation of one eye (the ocular dominance columns). Multiple previous studies attempted to detect their activity using fMRI. [more]
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