Evidence suggests than human time perception is likely to reflect an ensemble of recent temporal experience. For example, prolonged exposure to consistent temporal patterns can adaptively realign the perception of event order, both within and between sensory modalities (e.g. Fujisaki et al., 2004 Nat. Neurosci., 7, 773-778). In addition, the observation that 'a watched pot never boils' serves to illustrate the fact that dynamic shifts in our attentional state can also produce marked distortions in our temporal estimates. In the current study we provide evidence for a hitherto unknown link between adaptation, temporal perception and our attentional state. We show that our ability to use recent sensory history as a perceptual baseline for ongoing temporal judgments is subject to striking top-down modulation via shifts in the observer's selective attention. Specifically, attending to the temporal structure of asynchronous auditory and visual adapting stimuli generates a substantial increase in the temporal recalibration induced by these stimuli. We propose a conceptual framework accounting for our findings whereby attention modulates the perceived salience of temporal patterns. This heightened salience allows the formation of audiovisual perceptual 'objects', defined solely by their temporal structure. Repeated exposure to these objects induces high-level pattern adaptation effects, akin to those found in visual and auditory domains (e.g. Leopold & Bondar (2005) Fitting the Mind to the World: Adaptation and Aftereffects in High-Level Vision. Oxford University Press, Oxford, 189-211; Schweinberger et al. (2008) Curr. Biol., 18, 684-688).

PURPOSE: Epidemiologic research has shown that multifocal spectacle wearers (bifocal and progressive addition lenses [PALs]) are more than twice as likely to fall than are nonmultifocal spectacle wearers, with this risk further increasing when negotiating stairs. The present study investigated whether step and stair descent safety is improved by using single-vision distance lenses. METHODS: From a stationary standing position on top of a block, 20 long-term multifocal wearers stepped down (from different block heights) onto a lower level wearing bifocal, progressive addition, or single-vision distance lenses. RESULTS: Use of single-vision distance spectacles led to an increased single-limb support time, a reduced ankle and knee angle and vertical center-of-mass velocity at contact with the lower level, and a reduced ankle angular velocity and vertical center-of-mass velocity during initial landing (P < 0.03). These findings indicate that landing occurred in a more controlled manner when the subjects wore single-vision distance spectacles, rather than tending to "drop" onto the lower level as occurred when wearing bifocals or PALs. CONCLUSIONS: Use of single-vision distance spectacles led to improvements in landing control, consistent with individuals' being more certain regarding the precise height of the lower floor level. This enhanced control was attributed to having a view of the foot, step edge, and immediate floor area that was not blurred, magnified, or doubled and that did not suffer from image jump or peripheral distortions. These findings provide further evidence that use of single-vision distance lenses in everyday locomotion may be advantageous for elderly multifocal wearers who have a high risk of falling.

We report here the genome sequence of an ancient human. Obtained from approximately 4,000-year-old permafrost-preserved hair, the genome represents a male individual from the first known culture to settle in Greenland. Sequenced to an average depth of 20x, we recover 79% of the diploid genome, an amount close to the practical limit of current sequencing technologies. We identify 353,151 high-confidence single-nucleotide polymorphisms (SNPs), of which 6.8% have not been reported previously. We estimate raw read contamination to be no higher than 0.8%. We use functional SNP assessment to assign possible phenotypic characteristics of the individual that belonged to a culture whose location has yielded only trace human remains. We compare the high-confidence SNPs to those of contemporary populations to find the populations most closely related to the individual. This provides evidence for a migration from Siberia into the New World some 5,500 years ago, independent of that giving rise to the modern Native Americans and Inuit.