Orientation-selective adaptation and tilt after-effect from invisible patterns

Exposure to visual patterns of high contrast (for example, gratings formed by alternating white and black bars) creates after-effects in perception. We become temporarily insensitive to faint test patterns that resemble the pre-exposed pattern (such as gratings of the same orientation), and we require more contrast to detect them. Moreover, if the test pattern is slightly tilted relative to the pre-exposed one, this tilt may be perceptually exaggerated: we experience a tilt after-effect. Here we show that these visual after-effects occur even if the pre-exposed grating is too fine to be perceptually resolved. After looking at a very fine grating, so high in spatial frequency that it was perceptually indistinguishable from a uniform field, observers required more contrast to detect a test grating presented at the same orientation than one presented at the orthogonal orientation. They also experienced a tilt after-effect that depended on the relation of the test pattern's tilt to the unseen orientation of the pre-exposed pattern. Because these after-effects are due to changes in orientation-sensitive mechanisms in visual cortex, our observations imply that extremely fine details, even those too fine to be seen, can penetrate the visual system as far as the cortex, where they are represented neurally without conscious awareness.     

Antidromic latency variations of nigral compacta neurones

Summary Variations in the antidromic latency of substantia nigra compacta neurones were commonly observed following striatal stimulation. These results provide electrophysiological evidence for a branched unmyelinated nigrostriatal pathway and demonstrate that the antidromic criterion of constant latency is not valid for this type of pathway.     

Photosynthesis inCuscuta

Zusammenfassung Die inCuscuta gronovii undC. Campestris bewiesene Photosynthese ist in ihrem Ausmass in beiden Arten gleichwertig und beträgt ungefähr ein Zehntel desjenigen von Pelargonium-Blättern. Als photosynthetisches Produkt wird in beiden Pflanzen grösstenteils Saccharose festgestellt.     

A photometric redshift of z = 6.39 +/- 0.12 for GRB 050904

Gamma-ray bursts (GRBs) and their afterglows are the most brilliant transient events in the Universe. Both the bursts themselves and their afterglows have been predicted to be visible out to redshifts of z approximately 20, and therefore to be powerful probes of the early Universe. The burst GRB 000131, at z = 4.50, was hitherto the most distant such event identified. Here we report the discovery of the bright near-infrared afterglow of GRB 050904 (ref. 4). From our measurements of the near-infrared afterglow, and our failure to detect the optical afterglow, we determine the photometric redshift of the burst to be z = 6.39 - 0.12 + 0.11 (refs 5-7). Subsequently, it was measured spectroscopically to be z = 6.29 +/- 0.01, in agreement with our photometric estimate. These results demonstrate that GRBs can be used to trace the star formation, metallicity, and reionization histories of the early Universe.     

Minisatellite repeat coding as a digital approach to DNA typing

Most DNA typing systems used in forensic and legal medicine assay allelic length variation at tandem repetitive DNA regions such as minisatellites. A simple alternative approach that displays patterns of variant repeat units along minisatellite alleles is described here. This produces DNA profiles as extraordinarily variable digital sequences appropriate for forensic investigations, including computer databasing, and for analysing allele diversity and the role of recombination in minisatellite instability.