Saving Science Through Replication Studies.

The scientific enterprise has long been based on the presumption of replication, although scientists have recently become aware of various corruptions of the enterprise that have hurt replicability. In this article, we begin by considering three illustrations of research paradigms that have all been subject to intense scrutiny through replications and theoretical concerns. The three paradigms are one for which the corpus of research points to a real finding, one for which the corpus of research points to a significantly attenuated effect, and one for which the debate is ongoing. We then discuss what scientists can learn-and how science can be improved-through replications more generally. From there, we discuss what we believe needs to be done to improve scientific inquiry with regard to replication moving forward. Finally, we conclude by providing readers with several different approaches to replication and how these approaches progress science. The approaches discussed include multilab replications of many effects, multilab replications of specific effects, adversarial collaborations, and stand-alone applications.

Magnesium deficiency reduces fear-induced conditional lick suppression in mice.

The consequences of broad-scale alterations in magnesium (Mg2+) levels on learning and memory are poorly understood. We have recently demonstrated that adult male mice maintained on an Mg2+-deficient diet exhibit reduced conditional freezing behavior. The purpose of the present study was to determine if the detrimental effect of Mg2+ deficiency in mice extended to another measure of conditional fear, conditioned lick suppression (CLS), as well as to another form of learning, spatial learning in the swim maze task. Adult male C57Bl/6J mice were provided with a normal or Mg2+-deficient diet and were trained and tested ten days later for conditional fear, using CLS and freezing as indicators of learning. Learning in the swim maze was tested in a separate cohort of mice during days 14-18 of diet exposure. Mg2+-deficient mice showed reduced CLS as well as conditional freezing behavior in comparison to control mice. However, learning in the swim maze task was normal in Mg2+-deficient mice. These studies indicate that the detrimental effects of Mg2+ deficiency extend to other measures of conditional fear but not to all forms of learning.

Race, gender, and clinical risk index for babies (CRIB) score as predictors of severe retinopathy of prematurity.

PURPOSE: To determine whether race, gender, and the Clinical Risk Index for Babies (CRIB) illness severity score are predictors of threshold or severe prethreshold retinopathy of prematurity warranting surgery (ROP warranting surgery) and whether racial and gender differences in ROP are correlated with racial and gender differences in illness severity. METHODS: This was a retrospective analysis of premature infants 401-1250 g at birth that were admitted to the University Hospital of Cincinnati (January 1998 to May 2003). Birth weight, gestational age, multiple birth, birth in the study hospital or elsewhere, race, gender, CRIB score, and eye findings were abstracted. The outcome variable was ROP warranting surgery. RESULTS: Of 299 patients (596 eyes) with adequate eye and CRIB data, 35 patients (11.7%) [66 eyes; 11.1%] developed ROP warranting surgery. Multiple logistic regression analysis showed that higher CRIB score (P < 0.0001; odds ratio [OR] 1.21), male gender (P < 0.005; OR: 2.68), nonblack race (P < 0.0005; OR: 4.32), lower gestational age, and multiple birth are predictive factors for ROP warranting surgery. Because birth weight and gestational age comprise 2 of the 6 components of the CRIB score, a CRIB subscore (CRIBSUB) consisting of the remaining 4 components was tested and remained a significant predictor (P < 0.00001). Birth weight was a significant predictor when CRIBSUB was in the model but not when the CRIB score was used. The CRIB score was a predictor of neonatal mortality, but race and gender did not predict the CRIB score or neonatal mortality. CONCLUSIONS: Nonblack race, male gender, and higher CRIB illness severity scores are predictors of ROP warranting surgery. In our population, there were no racial or gender differences in neonatal mortality or CRIB scores to explain the racial and gender differences in severity of ROP.

Magnesium deficiency impairs fear conditioning in mice.

Magnesium (Mg2+) is one of the most abundant cations found in the body. In the central nervous system, Mg2+ plays an important role in the function of N-methyl-D-aspartate (NMDA)-type glutamate receptors, which are centrally involved in memory processing. Despite the relatively large concentration of Mg2+ in the CNS, little is known about the behavioral consequences of Mg2+ deficiency. The purpose of this study was to address this issue by assessing fear conditioning and related behaviors in mice maintained on normal or Mg(2+)-deficient diets. Young adult male C57Bl/6J mice were placed on a control or Mg(2+)-deficient diet, and testing was conducted between 10 and 21 days later. Magnesium-deficient mice exhibited impairments in contextual and cued fear conditioning. These impairments could not be attributed to changes in locomotor activity, exploration, or pain sensitivity. Furthermore, Mg(2+)-deficient mice were more sensitive to the convulsant effects of a peripheral injection of NMDA (100 mg/kg, IP). The results suggest that magnesium deficiency can lead to specific impairments in emotional memory. Such impairments may be related to hypersensitivity of NMDA-type glutamate receptors in Mg(2+)-deficient mice.