The effects of hippocampal and fimbria–fornix lesions on prepulse inhibition.

The present experiments tested the effects of conventional (dorsal aspiration and electrolytic) and excitotoxic (N-methyl-{d}-aspartate [NMDA]) hippocampal lesions and fimbria-fornix (FF) transection on prepulse inhibition (PPI) of startle response and on open-field activity. Activity was increased by FF transection and by conventional but not excitotoxic hippocampal lesions; complete NMDA lesion increased amphetamine-induced activity. Whereas dorsal hippocampal aspiration lesion disrupted PPI, the phenomenon was not affected by dorsal hippocampal. electrolytic lesion, partial or complete excitotoxic (NMDA) hippocampal lesions, or complete FF transection, which interrupted the cholinergic input to the hippocampus as well as the hippocampal-subicular input to the nucleus accumbens. Systemic apomorphine disrupted PPI in both FF-transected rats and their controls. It is suggested that the hippocampus is essential for PPI disruption rather than for PPI expression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Understanding Scribe Profile and Tool Type Effects on Visual Corrosion Assessments

Visual analysis is the most common evaluation of accelerated corrosion performance after exposure using a scribed protective coating on a metal substrate. Although the scribed-coating visual inspection is standardized, the specificity of initial conditions relative to the final performance has never been unified between laboratories, scribing tools, nor by published testing standards. To validate the initial state of the coating performance based on the selected tool, salt spray corrosion tests ASTM B117 and GM14872 were performed on 60 epoxy-amine primer coated UNS 10080/10100 steel test panels with nine different scribes (3 test panels each with 3 non-scribed control panels). The width of the initial scribe greatly impacted the visual corrosion assessment of the test results during ASTM B117, while the initial scribe width had little impact during GM14872. These results suggest that correlating the initial scribe with the final corrosion evaluation of the coating defect resulted in a better inter-comparable evaluation of coatings subjected to visual analysis by accelerated corrosion or electrolyte corrosion.     

Microstructure and Crystallography of Titanium Nitride Whiskers Grown by a Vapor–Liquid–Solid Process

Titanium nitride whiskers having diameters of 0.5 to 1.5 μm and aspect ratios in the range of 20 to 50 have been produced by a new commercially scalable vapor–liquid–solid process. Electron microscopy studies have shown that most of the whiskers can be classified into two types based upon structure and morphology. The whiskers of one type are single crystals and have a growth direction of (100). Whiskers of the second type are comprised of two crystals having a common (110) growth direction. Both types have smooth surfaces and relatively few internal defects. Additionally, a small percentage of whiskers have considerable internal structure related to significant magnesium impurities.     

Asymptotics of a right-angled impedance wedge

The asymptotics of the wave field scattered by a right-angled impedance wedge is considered. The exact complex Sommerfeld-type integral solution for the problem of the diffraction of a plane wave by a right-angled impedance wedge is transformed into a new representation. This new representation is in a form suitable for the asymptotic behaviour to be derived across the specular and shadow boundaries where the usual diffraction coefficient becomes infinite.     

Lamellar organisation in the rat hippocampus

A series of experiments was conducted in the urethane anaesthetised rat to determine the organisation of some hippocampal pathways in this species, using stimulating and recording microelectrodes to elicit and record pupulation spikes. It was found that the mossy fibres, alvear fibres and perforant path were clearly arranged in a lamellar fashion. Lamellar organisation could not be demonstrated for the afferents in the stratum radiatum which include the Schaffer collaterals. It was concluded that hippocampal organisation in this species essentially resembles that in the rabbit and cat.     

Targeted deletion of the GluR-1 AMPA receptor in mice dissociates general and outcome-specific influences of appetitive rewards on learning.

The authors assessed the hypothesis that deletion of the GluR-1 subtype of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor in mice disrupts the associative activation of a sensory-specific representation of an appetitive reward. In Experiment 1, mice received training on a Pavlovian-instrumental transfer task. In the test stage, conditioned stimulus (CS) presentations enhanced instrumental actions in both groups. However, this effect was specific to the action that shared the same outcome as the CS in wild-type (WT), but not GluR-1-/-, mice. In Experiment 2, the mice were trained on a heterogeneous instrumental chain in which rewards were obtained for emitting 1 response (R1, that was distal to reward delivery), followed by a 2nd response (R2, that was proximal to reward delivery). A change in general motivational state (from hungry to sated) reduced the number of R2 responses in both groups. In contrast, an outcome-specific satiety treatment produced a selective decline in R1 responding only in WT mice. The results support the hypothesis that GluR-1 deletion impairs the associative activation of a representation of the sensory-specific incentive motivational properties of an appetitive reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Doubts concerning primacy in rats' nonspatial recognition memory: Reply to Gaffan and Gaffan (1992).

E. A. Gaffan and D. Gaffan (see record 1992-37974-001) drew attention to an alarming lack of variability in a previous report (P. Reed et al; see record 1991-11847-001) of primacy and recency in recognition memory for nonspatial lists in rats. Their analysis, and the doubts raised by it, are accepted in the present article. Further analysis of the original data suggests that the low variability in the Reed et al data may have stemmed partly from experimenter effects. Equivalent analyses of other experiments conducted using the same apparatus and the same kinds of stimuli showed variances in line with a priori expectation. A new experiment modeled on the original one (but differing in some respects) showed recency but no primacy. It is concluded that the previous report of Reed et al should, for the present, be regarded as potentially flawed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estimation of ozone with total ozone portable spectroradiometer instruments. II. Practical operation and comparisons

We used a microcomputer-controlled total ozone portable spectroradiometer instrument #21 (MTOPS21) to measure solar radiation at 298, 304 and 310 nm in Greenbelt, Md., during 1995. One day's ozone measurements from a Brewer instrument (B105) were used to calibrate the 304- and 310-nm channel ratios to a theoretical model. Total ozone estimates were then determined for the entire MTOPS21 data set. Differences between individual B105 and MTOPS21 ozone estimates show a 1% drop as solar zenith angles increase and depend on atmospheric attenuation and SO(2) variation at the ±2% level. Daily average values agree well (<0.5% average offset, 2% standard deviation).     

Involvement of the entorhinal cortex in a process of attentional modulation: Evidence from a novel variant of an IDS/EDS procedure.

Novel behavioral assays were used to assess the role of the entorhinal cortex in modulating attention to components of stimulus compounds. In Stage 1, rats received discrimination training with compounds constructed from 3 dimensions (auditory, visual, and tactile); in each compound the combination of components from 2 dimensions (e.g., auditory and visual) were relevant to the solution of the discrimination, and the remaining dimension (e.g., tactile) was irrelevant. In Stage 2, rats received a different discrimination in which the relevant dimensions were either congruent (auditory and visual) or incongruent (auditory and tactile) with those that were relevant in Stage 1. Sham-operated rats acquired the congruent discrimination more rapidly than the incongruent discrimination—a finding indicative of a process of attentional modulation—whereas rats with excitotoxic lesions of the entorhinal cortex acquired both discriminations equally readily. (PsycINFO Database Record (c) 2010 APA, all rights reserved)