SummaryData analysis workflows in many scientific domains have become increasingly complex and flexible. To assess the impact of this flexibility on functional magnetic resonance imaging (fMRI) results, the same dataset was independently analyzed by 70 teams, testing nine ex-ante hypotheses. The flexibility of analytic approaches is exemplified by the fact that no two teams chose identical workflows to analyze the data. This flexibility resulted in sizeable variation in hypothesis test results, even for teams whose statistical maps were highly correlated at intermediate stages of their analysis pipeline. Variation in reported results was related to several aspects of analysis methodology. Importantly, meta-analytic approaches that aggregated information across teams yielded significant consensus in activated regions across teams. Furthermore, prediction markets of researchers in the field revealed an overestimation of the likelihood of significant findings, even by researchers with direct knowledge of the dataset. Our findings show that analytic flexibility can have substantial effects on scientific conclusions, and demonstrate factors related to variability in fMRI. The results emphasize the importance of validating and sharing complex analysis workflows, and demonstrate the need for multiple analyses of the same data. Potential approaches to mitigate issues related to analytical variability are discussed.
The G-protein subunit ␣-gustducin, which is similar to rod transducin, has been implicated in the transduction of both sweet-and bitter-tasting substances. In rodents, there are differences in sensitivity to sweet and bitter stimuli in different populations of taste buds. Rat fungiform taste buds are more responsive to salts than to sweet stimuli, whereas those on the palate respond predominantly to sweet substances. In contrast, hamster fungiform taste buds are more sensitive to sweet-tasting stimuli. Taste buds in the vallate and foliate papillae of both species are sensitive to bitter compounds. These differences in sensitivity should be reflected in the numbers of gustducin-containing cells in different taste bud populations. We examined taste buds in the rat and hamster for immunoreactivity to an antibody against ␣-gustducin. Immunofluorescence of labeled taste cells was examined by confocal microscopy, and the cells were counted. Gustducin-positive cells were seen in all taste bud regions; they were spindleshaped, with circular cross-sections and apical processes that extended to the taste pore. Cells with this characteristic shape in rat vallate taste buds are Type II (light) cells. In the rat, taste buds of the fungiform papillae had fewer gustducin-positive cells (3.1/taste bud) than those of other regions, including the posterior tongue and palate (Ͼ8.9/taste bud). Hamster fungiform taste buds contained twice as many gustducin-expressing cells (6.8/taste bud) as those of the rat. These data support the hypothesis that ␣-gustducin is involved in the transduction of both sweet-and bitter-tasting stimuli by mammalian taste receptor cells.
Key words: taste receptors; gustation; fungiform papillae; vallate papilla; palate; epiglottis; ␣-gustducin; G-protein; taste budsThe transduction of both sweet-and bitter-tasting substances is thought to involve membrane-bound receptors coupled to secondmessenger systems (Kinnamon and Cummings, 1992). Gustducin is an ␣-subunit of a G-protein closely related to the transducins that is expressed in taste tissue (McLaughlin et al., 1992). Studies with gustducin knockout mice implicate gustducin in the detection of both sweet-and bitter-tasting compounds. In both behavioral and electrophysiological experiments, mice homozygous for the null gustducin allele were much less responsive than wild-type mice to bitter and sweet stimuli, but not to salts or acids (Wong et al., 1996).Taste buds are specialized epithelial structures containing gustatory receptor cells. Taste buds in the rat are grouped into several populations: in fungiform papillae on the anterior portion of the tongue, in vallate and foliate papillae on the posterior tongue, in the epithelia of the nasoincisor ducts (NIDs) and "geschmacksstreifen" (GS) of the palate, and on the laryngeal surface of the epiglottis (Miller et al., 1978;Travers and Nicklas, 1990;Smith et al., 1993). These populations differ in their gustatory sensitivities, as shown by electrophysiological studies of peripheral taste fibers. In rats, ...
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