The ICBM project has seen new developments in functional research. We completed the first neuroreceptor PET study examining serotonin (5-HT 2A) receptors using PET and probabilistic maps of cytoarchitectonic cortical regions. These also were related to post mortem tritium labeled ketanserin autoradiographs for multiple cytoarchitectural areas. Additionally, all technical and methodological developments and tests regarding radiosynthesis, metabolite analysis, scanning procedures, and modeling of [ 18F]-altanserin have been completed and is ready for routine application in serotonin receptor PET studies on humans.
Application of Cytoarchitectonic Maps for Analyzing Brain Function
Combination of cytoarchitectonic probabilistic maps and fMRI for the analysis of the parieto-insular vestibular cortex
The parieto-insular vestibular cortex (PIVC) plays a central role in the cortical vestibular network. While this region was first defined and subsequently extensively studied in non-human primates, there is also ample evidence for a human analogue in the posterior parietal operculum. We have functionally and anatomically characterized the putative human equivalent to macaque area PIVC by combining human functional MR imaging of the cortical response to galvanic vestibular stimulation with probabilistic cytoarchitectonic maps of the human parietal operculum.
Combination of Cytoarchitectonic Probabilistic Maps and fMRI for the Analysis of Visual Word Recognition and Broca's Region
We investigated the influence of the task (lexical decision or phonological decision) on activation in the left Brodmann's areas (BA) 44 and 45 using fMRI and probabilistic cytoarchitectonic maps of BA 44 and 45 in a paradigm for visual word recognition. By combining the fMRI data with the cytoarchitectonic anatomical probability maps of BA 44 and
BA 45, we demonstrated that the left BA 44 and BA 45 were more strongly activated for pseudo-words than for words.
Combination of Cytoarchitectonic Probabilistic Maps and MEG for the Analysis of the Visual System
In several magnetoencephalography (MEG) studies a three-phasic pattern of the visual pattern reversal evoked field has been reported (N75m-P100m-N145m). For the first time, we used probabilistic cytoarchitectonic maps that are based on observer-independent mapping in 10 post mortem brains, in order to anatomically identify active generators as revealed by MEG.
Combination of Cytoarchitectonic Probabilistic Maps and Neuroreceptor rPET Data. A Feasibility Study
Three-dimensional maximum probability maps of cytoarchitectonically defined cortical regions based on post mortem histological studies have recently been made available in the stereotaxic reference space of the ICBM single subject template. This permits the use of cytoarchitectonic maps for the analysis of functional in vivo data sets, including receptor positron emission tomography (PET) studies. In a feasibility study, we used PET of 5-hydroxytryptamine 2A (5-HT2A) receptors to test the applicability of maximum cytoarchitectonic probability maps for quantitative analysis.
Serotonin Receptor PET
We are now employing the [18F]-altanserin method in serotonin receptor PET studies on humans.
[18F]-altanserin is highly metabolized in vivo with a terminal elimination half-life time of about 80 minutes. We have developed, tested and implemented a simple and robust method to measure the fraction of parent compound and metabolites at different time points throughout the scanning procedure.
Scan Protocol of [18F]-Altanserin and PET
PET measurements were set up as bolus/infusion equilibrium paradigms. Using this paradigm, volunteers were successfully investigated to establish age-dependent alterations of the cerebral 5-HT 2A receptor.
Displacement Studies with KETENSINŠ
A series of in vivo displacement studies with KETENSINŠ were performed demonstrating that there is very little displaceable binding in the cerebellum. This confirms that the cerebellum can be chosen as reference region for graphical analysis of [18F]-altanserin binding.