Laminar fMRI of long-range connections : Methods and contrast mechanisms

The nerve cells (neurons) in the human brain are organized into layers and these layers have different roles in signal transduction. Using functional MRI (fMRI) at high spatial resolutions opens up the possibility to non-invasively study the directionality of information flow throughout the human brain. However, the vascular system determines the fMRI signal and the workhorse fMRI contrast being used is highly sensitive to larger veins which do not co-locate well with the nerve cells’ architecture. Furthermore, as the image acquisition process in MRI is sequential rather than parallel, acquiring whole brain data at high spatial and temporal resolution is challenging. In this work, methods and contrast mechanisms were investigated to measure signals of long-range connections co-located to the neuronal system at a temporal resolution acceptable for neuroscience. It was shown that widely spaced regions can be simultaneously acquired at a high spatio-temporal resolution and that contrast mechanisms alternative to the most widely used contrast can provide signals more specific to the locus of brain activity when taking the characteristics of the signal readout into account