Dissociation of first- and second-order motion systems by perceptual learning

Previous studies investigating transfer of perceptual learning between luminance-defined (LD) motion and texture-contrast-defined (CD) motion tasks have found little or no transfer from LD to CD motion tasks but nearly perfect transfer from CD to LD motion tasks. Here, we introduce a paradigm that yields a clean double dissociation: LD training yields no transfer to the CD task, but more interestingly, CD training yields no transfer to the LD task. Participants were trained in two variants of a global motion task. In one (LD) variant, motion was defined by tokens that differed from the background in mean luminance. In the other (CD) variant, motion was defined by tokens that had mean luminance equal to the background but differed from the background in texture contrast. The task was to judge whether the signal tokens were moving to the right or to the left. Task difficulty was varied by manipulating the proportion of tokens that moved coherently across the four frames of the stimulus display. Performance in each of the LD and CD variants of the task was measured as training proceeded. In each task, training produced substantial improvement in performance in the trained task; however, in neither case did this improvement show any significant transfer to the nontrained task

Clinical validation of cutoff target ranges in newborn screening of metabolic disorders by tandem mass spectrometry: A worldwide collaborative project.

Purpose: To achieve clinical validation of cutoff values for newborn screening by tandem mass 215 spectrometry through a worldwide collaboration. Methods: Cumulative percentiles of amino 216 acids and acylcarnitines in dried blood spots of approximately 30 million normal newborns and 217 10,615 true positive cases are compared to assign clinical significance, which is achieved when 218 the median of a disease range is either >99%ile or <1%ile of the normal population. The cutoff 219 target ranges of analytes and ratios are then defined as the interval between the limits of the two 220 populations. When overlaps occur, adjustments are made to maximize sensitivity and specificity 221 taking in consideration all available factors. Results: As of December 1, 2010, 129 sites in 45 222 countries have uploaded to the project website a total of 23,970 percentile data points, 558,168 223 analyte results of 10,615 true positive cases with 64 conditions, and 5,088 cutoff values. The 224 average rate of submission of true positive cases between December 1, 2008 and December 1, 225 2010 was 4.7 cases per day (3,418 cases). This cumulative evidence generated 91 and 23 high 226 and low target cutoff ranges, respectively. The overall proportion of cutoff values within the 227 respective target range was 43% (2,176/5,088). Conclusions: An unprecedented level of 228 cooperation and collaboration has allowed the objective definition of cutoff target ranges for 114 229 markers applied to newborn screening of rare metabolic disorders. This set of data could be used 230 as baseline for monitoring of future performance