Efficient Coding Theory Predicts a Tilt Aftereffect from Viewing Untilted Patterns

The brain is bombarded with a continuous stream of sensory information, but biological limitations on the data-transmission rate require this information to be encoded very efficiently [1]. Li and Atick [2] proposed that the two eyes? signals are coded efficiently in the brain using mutually decorrelated binocular summation and differencing channels; when a channel is strongly stimulated by the visual input, such that sensory noise is negligible, the channel should undergo temporary desensitization (known as adaptation). To date, the evidence for this theory has been limited [3 and 4], and the binocular differencing channel is missing from many models of binocular integration [5, 6, 7, 8, 9 and 10]. Li and Atick?s theory makes the remarkable prediction that perceived direction of tilt (clockwise or counterclockwise) of a test pattern can be controlled by pre-exposing observers to visual adaptation patterns that are untilted or even have no orientation signal. Here, we confirm this prediction. Each test pattern consisted of different images presented to the two eyes such that the binocular summation and difference signals were tilted in opposite directions, to give ambiguous information about tilt; by selectively desensitizing one or other of the binocular channels using untilted or non-oriented binocular adaptation patterns, we controlled the perceived tilt of the test pattern. Our results provide compelling evidence that the brain contains binocular summation and differencing channels that adapt to the prevailing binocular statistics

An Automated Method for the Determination of Intestinal Disaccharidase and Glucoamylase Activities

Determination of disaccharidase and glucoamylase activities is important for the diagnosis of intestinal diseases. We adapted a widely accepted manual method to an automated system that uses the same reagents reaction volumes, incubation times, and biopsy size as the manual method. A dye was added to the homogenates as the internal quality control to monitor the pipetting precision of the automated system. When the automated system was tested using human intestinal homogenates, the activities of all the routinely tested disaccharidases, including lactase, maltase, sucrase, and palatinase, as well as the activity of glucoamylase, showed perfect agreement with the manual method and were highly reproducible. The automated analyzer can perform the same routine assays of disaccharidases and glucoamylase with high consistency and accuracy and reduce testing costs by performing a larger sample size with the same number of staff. Additional developments, such as barcoding and built-in plate reading, would result in a completely automated system

Plasma Clearance of Lovastatin Versus Chinese Red Yeast Rice in Healthy Volunteers

Objectives: It is now accepted that inhibition of cholesterol biosynthesis is effective in the primary and secondary prevention of heart disease. However, the perceived side-effects on muscle and liver reduce the general acceptance of statin drug therapy as well as compliance over the long term, which is necessary for prevention efforts to be successful. Chinese red yeast rice (CRYR) is a supplement containing lovastatin (monacolin K), eight other monacolins, pigments, tannins, and other phytochemicals. The authors previously reported on a double- blind placebo-controlled trial of CRYR supplement in 80 individuals demonstrating a significant decrease in cholesterol levels from 250 mg/dL to 210 mg/dL over 8 weeks independent of diet. The current study compared the pharmacokinetics of CRYR with lovastatin at the same bioeffective dose for lowering cholesterol. Methods: Eleven (11) healthy volunteers were randomized to a crossover study taking 2400 mg CRYR or 20 mg of lovastatin. Results: The Cmax and area under the curve (AUC) of lovastatin were 22.42 ng/mL, and 80.47 higher than CRYR (p = 0.001 and 0.002, respectively). The Cmax for lovastatin hydroxy-acid was 36.63 ng/mL higher than the Cmax of CRYR hydroxy-acid (p = 0.001). The AUC of lovastatin hydroxy-acid was 258.5 greater than that of CRYR (p = 0.001). Conclusions: The results suggested that the effect of CRYR on the cholesterol concentration might be caused by the additive and/or synergistic effects of monacolin K with other monacolins and substances in CRYR. It may lead to the ultimate development of a botanical supplement based on CRYR

Staged characteristics analysis of a severe convection over the Dongting Lake area based on dual-polarization Doppler weather radar data

The multi-cell storm stage and squall line stage of a severe convective weather process over the Dongting Lake on 15 May 2021 in this study are analyzed mainly based on S-band dual-polarized doppler weather radar data. The study focuses on the analysis of the supercell storm I2 in the multi-cell storm stage. The results are as follows. (1) During the initial period of the I2, the strong echo area (the horizontal reflectivity factor, ZH > 55 dBz) and the differential reflectivity factor (ZDR) column (ZDR > 2.5 dB) extend to Wet Blub Zero (WBZ) level, corresponding to the areas with large specific differential phase (KDP) (> 1.7 °·km-1) and large correlation coefficient (CC) (0.9-0.99). It indicates that during this period, the precipitation phase is dominated by water condensate mingled with large raindrops, and these supercooled raindrops provide hail embryos for the later hail development. (2) During the hail colliding-growth period of the I2, ZH intensity and height increase rapidly, and vertically integrated liquid water content (VIL) shows an obvious leap increase. The strong-echo center (ZH > 60 dBz) extends to the level of above -10 ℃. In the corresponding regions, the ZDR drops below 0, the ZDR column (ZDR> 2.5 dB) extends to the level of -10 ℃, CC drops, and a "hole" appears in the KDP value area. These indicate that the precipitation during this period is dominated by solid particles and these solid particles are in an increasing period. (3) During the mature hailfall period of the I2, the bottom of the ZH intensity center (ZH > 60 dBz) drops below the WBZ level and the CC is locally as low as 0.8. There are ZDR negative areas and KDP voids in the corresponding area. These means that the dragging effect of the falling hail further weakens the strength of the updraft, which means that the hail is about to land. Then comes the squall line stage. (4) Unlike the multi-cell storm stage, the squall line stage has anomalously large KDP values and ZDR values greater than 1. (5) Before the occurrence of extreme gales of the squall line stage, the areas with strong echo greater than 55 dBz and velocity larger than 27 m·s-1 extend below 1 km, and the KDP in the strong echo area is obviously large, corresponding to the strong downdraft. Besides, the strong precipitation dragging effect caused by the melting of descending precipitation particles intensifies the generation of extreme gales

Properties of V1 Neurons Tuned to Conjunctions of Visual Features: Application of the V1 Saliency Hypothesis to Visual Search behavior

From a computational theory of V1, we formulate an optimization problem to investigate neural properties in the primary visual cortex (V1) from human reaction times (RTs) in visual search. The theory is the V1 saliency hypothesis that the bottom-up saliency of any visual location is represented by the highest V1 response to it relative to the background responses. The neural properties probed are those associated with the less known V1 neurons tuned simultaneously or conjunctively in two feature dimensions. The visual search is to find a target bar unique in color (C), orientation (O), motion direction (M), or redundantly in combinations of these features (e.g., CO, MO, or CM) among uniform background bars. A feature singleton target is salient because its evoked V1 response largely escapes the iso-feature suppression on responses to the background bars. The responses of the conjunctively tuned cells are manifested in the shortening of the RT for a redundant feature target (e.g., a CO target) from that predicted by a race between the RTs for the two corresponding single feature targets (e.g., C and O targets). Our investigation enables the following testable predictions. Contextual suppression on the response of a CO-tuned or MO-tuned conjunctive cell is weaker when the contextual inputs differ from the direct inputs in both feature dimensions, rather than just one. Additionally, CO-tuned cells and MO-tuned cells are often more active than the single feature tuned cells in response to the redundant feature targets, and this occurs more frequently for the MO-tuned cells such that the MO-tuned cells are no less likely than either the M-tuned or O-tuned neurons to be the most responsive neuron to dictate saliency for an MO target

Cortical Surround Interactions and Perceptual Salience via Natural Scene Statistics

Spatial context in images induces perceptual phenomena associated with salience and modulates the responses of neurons in primary visual cortex (V1). However, the computational and ecological principles underlying contextual effects are incompletely understood. We introduce a model of natural images that includes grouping and segmentation of neighboring features based on their joint statistics, and we interpret the firing rates of V1 neurons as performing optimal recognition in this model. We show that this leads to a substantial generalization of divisive normalization, a computation that is ubiquitous in many neural areas and systems. A main novelty in our model is that the influence of the context on a target stimulus is determined by their degree of statistical dependence. We optimized the parameters of the model on natural image patches, and then simulated neural and perceptual responses on stimuli used in classical experiments. The model reproduces some rich and complex response patterns observed in V1, such as the contrast dependence, orientation tuning and spatial asymmetry of surround suppression, while also allowing for surround facilitation under conditions of weak stimulation. It also mimics the perceptual salience produced by simple displays, and leads to readily testable predictions. Our results provide a principled account of orientation-based contextual modulation in early vision and its sensitivity to the homogeneity and spatial arrangement of inputs, and lends statistical support to the theory that V1 computes visual salience

A controlled trial of protein enrichment of meal replacements for weight reduction with retention of lean body mass

<p>Abstract</p> <p>Background</p> <p>While high protein diets have been shown to improve satiety and retention of lean body mass (LBM), this study was designed to determine effects of a protein-enriched meal replacement (MR) on weight loss and LBM retention by comparison to an isocaloric carbohydrate-enriched MR within customized diet plans utilizing MR to achieve high protein or standard protein intakes.</p> <p>Methods</p> <p>Single blind, placebo-controlled, randomized outpatient weight loss trial in 100 obese men and women comparing two isocaloric meal plans utilizing a standard MR to which was added supplementary protein or carbohydrate powder. MR was used twice daily (one meal, one snack). One additional meal was included in the meal plan designed to achieve individualized protein intakes of either 1) 2.2 g protein/kg of LBM per day [high protein diet (HP)] or 2) 1.1 g protein/kg LBM/day standard protein diet (SP). LBM was determined using bioelectrical impedance analysis (BIA). Body weight, body composition, and lipid profiles were measured at baseline and 12 weeks.</p> <p>Results</p> <p>Eighty-five subjects completed the study. Both HP and SP MR were well tolerated, with no adverse effects. There were no differences in weight loss at 12 weeks (-4.19 ± 0.5 kg for HP group and -3.72 ± 0.7 kg for SP group, p > 0.1). Subjects in the HP group lost significantly more fat weight than the SP group (HP = -1.65 ± 0.63 kg; SP = -0.64 ± 0.79 kg, P = 0.05) as estimated by BIA. There were no significant differences in lipids nor fasting blood glucose between groups, but within the HP group a significant decrease in cholesterol and LDL cholesterol was noted at 12 weeks. This was not seen in the SP group.</p> <p>Conclusion</p> <p>Higher protein MR within a higher protein diet resulted in similar overall weight loss as the standard protein MR plan over 12 weeks. However, there was significantly more fat loss in the HP group but no significant difference in lean body mass. In this trial, subject compliance with both the standard and protein-enriched MR strategy for weight loss may have obscured any effect of increased protein on weight loss demonstrated in prior weight loss studies using whole food diets.</p