High-resolution functional magnetic resonance imaging (fMRI) and image analysis performed on a model system in the rat: Localisation of tactile input-projections in the cerebellum

Since its introduction in 1973, Magnetic Resonance Imaging has developed into one of the most powerful techniques in diagnostic medical and biomedical research. Besides the registration of structural characteristics, during the last 10 year, the possibilities of the technique have expanded towards the assessment of functional information of organs and tissues. MRI has also been extensively used to investigate brain function. The most recent development of MRI-technology for the non-invasive assessment of human brain functioning uses the influence of the oxygenation status of the blood on the MR image contrast. This is called BOLD imaging (BOLD = Blood Oxygenation Level Dependent Contrast). In this work we used BOLD fMRI to map to brain activity of the rat, in particular tactile stimulation projections in the cerebellum.; With the use of the BOLD technique we mapped the activation in the cerebellum as a result of electrical stimulation of the paws. Different bilateral activated patches were found in a mosaic-like organisation. In the meanwhile optimisation steps were taken to create the possibility to detect very small activated areas (200 micron).; These optimisation techniques are the following: (1) Enhancement of the electrical and hemodynamic response of the animal to a stimulus by optimising its physiological condition with the use of an awake animal. (2) Enhancing the contrast changes during activation by using a contrast agent which ameliorates the sensitivity of the fMRI technique. (3) Eliminating the global disturbing signal changes by using a data post-processing algorithm.; All these results contribute to the amelioration of the resulting fMRI technique, which will undoubtedly help to gain a better insight in the brain mechanisms.