A motor signal and "visual" size perception

Recent models of the visual system in primates suggest that the mechanisms underlying visual perception and visuomotor control are implemented in separate functional streams in the cerebral cortex. However, a little-studied perceptual illusion demonstrates that a motor-related signal representing arm position can contribute to the visual perception of size. The illusion consists of an illusory size change in an afterimage of the hand when the hand is moved towards or away from the subject. The motor signal necessary for the illusion could be specified by feedforward and/or feedback sources (i.e. efference copy and/or proprioception/kinesthesis). We investigated the nature of this signal by measuring the illusion's magnitude when subjects moved their own arm (active condition, feedforward and feedback information available), and when arm movement was under the control of the experimenter (passive condition, feedback information available). Active and passive movements produced equivalent illusory size changes in the afterimages. However, the illusion was not obtained when an after-image of subject's hand was obtained prior to movement of the other hand from a very similar location in space. This evidence shows that proprioceptive/kinesthetic feedback was sufficient to drive the illusion and suggests that a specific three-dimensional registration of proprioceptive input and the initial afterimage is necessary for the illusion to occur.     

Oxidative stress following traumatic brain injury in rats

BACKGROUND: Free radicals may be involved in the pathophysiology of traumatic brain injury (TBI) through oxidative damage of neurovascular structures. Endogenous antioxidants, such as ascorbate and alpha-tocopherol, may play a critical role in combating these oxidative reactions and their oxidized products can serve as an important index of oxidative stress. METHODS: We used electron spin resonance (ESR) spectroscopy and in vivo spin trapping (reaction of an organic compound with free radical species) to detect the possible generation of free radicals after TBI. Injury was inflicted by a weight drop technique over the head (5.7 kg-cm). Rats were intravenously infused with either 1 mL, 0.1 M of the spin trap, alpha-phenyl-N-tert-butyl nitrone (PBN), or an equivalent volume of saline immediately before TBI or sham-injury. Animals were divided into four groups: (1) Group I: PBN-infused sham-injured, (2) Group II: PBN-infused injured, (3) Group III: saline-infused sham-injured, and (4) Group IV: saline-infused injured. Additional groups of saline-infused uninjured, saline-infused, and PBN-infused injured animals were used for histopathology. Sixty minutes after TBI or sham-injury, rats were again anesthetized and decapitated. The brains were removed within 1 minute, homogenized, and extracted for lipids. The extracts were analyzed by ESR spectroscopy. Brain ascorbic acid (AA) concentration was determined spectrophotometrically, using the ascorbate oxidase assay. RESULTS: No PBN spin adduct signals (indicating trapped free radical species) were visible 60 minutes after TBI. All groups of rats showed an ascorbyl free radical signal. The ascorbyl signal intensity (AI) was, however, significantly higher in the injured rats, while the brain (AA) was significantly reduced. In addition, the ratio of AI/AA, which eliminates the effect of variable ascorbate concentrations in the brain, was also significantly higher in the injured animals. CONCLUSIONS: We conclude that 60 minutes following TBI there was a significantly increased level of oxidative stress in the brain. This may reflect formation of free radical species with subsequent interaction with ascorbate (antioxidant) during the 60 minute period. The lack of PBN spin adduct signals 1 hour after TBI may indicate that free radical generation is time dependent and might be detectable earlier or later than the 60 minute period.     

Interactive Television Trials and Marketplace Experiences

This article provides a review of ITV trials and services from the 1970s through the mid 1990s. It presents an annotated history of ITV and draws a number of lessons about content, pricing, consumer appeal and advertising within an interactive television context. ITV has alternated between peaks of marketing hyperbole and valleys of skepticism. A realistic path of development may now be emerging.     

Carbohydrate deficient glycoprotein syndrome type I: a cause of cerebellar vermis hypoplasia

To determine element contents of auditory ossicles, the malleus and incus were removed from 27 subjects which died at the ages between 40 and 98 years old, and their elemental contents were analyzed by inductively coupled plasma atomic emission spectrometry. It was found that the relative contents (RCs) of calcium and phosphorus were very high in the malleus and incus. The RCs of calcium and phosphorus in the ossicles corresponded to one-and-a-half-fold amounts as compared with the spongy bone of human cervical vertebrae. The mass ratio of calcium per phosphorus in the ossicles was almost the same as that of crystalline calcium phosphate hydroxyapatite. Relationships between the aging and RCs of minerals and between both the sexes in the ossicle were examined. It was found that both the RCs of calcium and phosphorus in the malleus and incus were really constant at the age over 40 years old, and that there was no significant difference of the mineral contents between men and women.     

Viscous flow and transport with moving free and reactive surfaces

Transport of a chemical species through a viscous fluid with reaction at an interface is modelled by a quasi-static process in which the transient behaviour is dominated by motion of the reactive surface. The reaction is accompanied by a molar volume change which leads to motion of the free surface. A decoupled stream function-vorticity formulation is introduced in conjunction with a moving finite element method. This also permits convenient treatment of the free and reactive surface boundary conditions. The model is applied to the growth of oxide films on silicon surfaces and reveals the effect of surface curvature on film growth.     

Relationship of activity to depression in adolescents: Development of the Adolescent Activities Checklist.

Developed an adolescent activities checklist (AAC) consisting of 100 items that assess pleasant and unpleasant activities. In an initial study with 151 8th–12th graders, the AAC subscales demonstrated high internal consistency and homogeneity. In a validation study conducted on 145 Ss, Unpleasant Activities total scores were correlated with Beck Depression Inventory (BDI) scores and with the Pleasant Activities total scores. Analysis of Ss with extreme BDI scores indicated differences on Unpleasant but not on Pleasant Activities total scores. The AAC appears to be a reliable index of the frequency of pleasant and unpleasant activities reported by adolescents. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analytical modeling of bidirectional multi‐channel IEEE 802.11 MAC protocols

This paper presents an analytical approach to model the bi‐directional multi‐channel IEEE 802.11 MAC protocols (Bi‐MCMAC) for ad hoc networks. Extensive simulation work has been done for the performance evaluation of IEEE 802.11 MAC protocols. Since simulation has several limitations, this work is primarily based on the analytical approach. The objective of this paper is to show analytically the performance advantages of Bi‐MCMAC protocol over the classical IEEE 802.11 MAC protocol. The distributed coordination function (DCF) mode of medium access control (MAC) is considered in the modeling. Two different channel scheduling strategies, namely, random channel selection and fastest channel first selection strategy are also presented in the presence of multiple channels with different transmission rates. M/G/1 queue is used to model the protocols, and stochastic reward nets (SRNs) are employed as a modeling technique as it readily captures the synchronization between events in the DCF mode of access. The average system throughput, mean delay, and server utilization of each MAC protocol are evaluated using the SRN formalism. We also validate our analytical model by comparison with simulation results. The results obtained through the analytical modeling approach illustrate the performance advantages of Bi‐MCMAC protocols with the fastest channel first scheduling strategy over the classical IEEE 802.11 protocol for TCP traffic in wireless ad hoc networks. Copyright © 2010 John Wiley & Sons, Ltd.