Faculty Bibliography

Consumer valuations are shaped by choice sets, exemplified by patterns of substitution between alternatives as choice sets are varied. Building on recent neuroeconomic evidence that valuations are transformed during the choice process, we incorporate the canonical divisive normalization computation into a discrete choice model and characterize how choice behaviour depends on both size and composition of the choice set. We then examine evidence for such behaviour from two choice experiments that vary the size and composition of the choice set. We find that divisive normalization more accurately captures observed behaviour than alternative models, including an example range normalization model. These results are robust across experimental paradigms. Finally, we demonstrate that Divisive Normalization implements an efficient means for the brain to represent valuations given neurobiological constraints, yielding the fewest choice errors possible given those constraints.

OBJECTIVE:Global Maxwell Tomography (GMT) is a recently introduced volumetric technique for noninvasive estimation of electrical properties (EP) from magnetic resonance measurements. Previous work evaluated GMT using ideal radiofrequency (RF) excitations. The aim of this simulation study was to assess GMT performance with a realistic RF coil. METHODS:) inside heterogeneous head models for different RF shimming approaches, and used them as input for GMT to reconstruct EP for all voxels. RESULTS:) and absorbed power could be predicted with less than 0.5% error over the entire head. GMT could accurately detect a numerically inserted tumor. CONCLUSION/CONCLUSIONS:This work demonstrates that GMT can reliably reconstruct EP in realistic simulated scenarios using a tailored 8-channel RF coil design at 7T. Future work will focus on construction of the coil and optimization of GMT's robustness to noise, to enable in vivo GMT experiments. SIGNIFICANCE/CONCLUSIONS:GMT could provide accurate estimations of tissue EP, which could be used as biomarkers and could enable patient-specific estimation of RF power deposition, which is an unsolved problem for ultra-high-field magnetic resonance imaging.

OBJECTIVE:We conducted a meta-analysis of resting state functional magnetic resonance imaging (R-fMRI) studies in children/adolescents and adults with ADHD to assess spatial convergence of findings from available studies. METHOD/METHODS:, 2019, with no language/type-of-document restrictions. Study authors were systematically contacted for additional unpublished information/data. R-fMRI studies using seed-based connectivity (SBC) or any other method (non-SBC) reporting whole-brain results of group comparisons between individuals with ADHD and typically developing controls were eligible. Voxel-wise meta-analysis via activation likelihood estimation with cluster-level Family Wise Error (FWE) (voxel-level: p < 0.001; cluster-level: p < 0.05) was used. The full dataset used for analyses will be freely available online in an open source platform (http://anima.fz-juelich.de/). RESULTS:30 studies (18 SBC and 12 non-SBC), including a total of 1978 participants (1094 ADHD; 884 controls) were retained. The meta-analysis focused on SBC studies found no significant spatial convergence of ADHD-related hyper- or hypo-connectivity across studies. This non-significant finding remained after integrating 12 non-SBC studies into the main-analysis and in sensitivity analyses limited to studies including only children or only non-medication naïve patients. CONCLUSION/CONCLUSIONS:The lack of significant spatial convergence may be accounted for by heterogeneity in study participants, experimental procedures and analytic flexibility, as well as in ADHD pathophysiology. Alongside other neuroimaging meta-analyses in other psychiatric conditions, our results should inform the conduct and publication of future neuroimaging studies of psychiatric disorders.

The immune microenvironment of tumors can play a critical role in promoting or inhibiting tumor progression depending on the context. We present evidence that tumor-associated macrophages/microglia (TAMs) can promote tumor progression in the sonic hedgehog subgroup of medulloblastoma (SHH-MB). By combining longitudinal manganese-enhanced magnetic resonance imaging (MEMRI) and immune profiling of a sporadic mouse model of SHH-MB, we found the density of TAMs is higher in the ~50% of tumors that progress to lethal disease. Furthermore, reducing regulatory T cells or eliminating B and T cells in Rag1 mutants does not alter SHH-MB tumor progression. As TAMs are a dominant immune component in tumors and are normally dependent on colony-stimulating factor 1 receptor (CSF1R), we treated mice with a CSF1R inhibitor, PLX5622. Significantly, PLX5622 reduces a subset of TAMs, prolongs mouse survival, and reduces the volume of most tumors within 4 weeks of treatment. Moreover, concomitant with a reduction in TAMs the percentage of infiltrating cytotoxic T cells is increased, indicating a change in the tumor environment. Our studies in an immunocompetent preclinical mouse model demonstrate TAMs can have a functional role in promoting SHH-MB progression. Thus, CSF1R inhibition could have therapeutic potential for a subset of SHH-MB patients.