Differential control by context in the inflation and reinstatement paradigms.

Examined, in 5 conditioned suppression experiments, the influence of summation between fear of the CS and the context in experimental paradigms in which the rat is exposed to UCSs following conditioning or extinction. Context-preference tests assessed contextual fear. In Exps I–III with 88 female Wistar rats, the inflation paradigm, in which fear of a CS paired with a weak UCS is enhanced by exposure to intense UCS alone, was investigated. Results show that the contextual fear that was present when the target CS was tested was reduced by presenting the intense UCSs in a different context, by exposing Ss to the context following their presentation, and by signaling the intense UCSs with a 2nd CS. In Exp IV with 32 female Wistar rats, UCS exposures following conditioning or extinction both produced contextual fear, but only fear of the extinguished CS was reinstated by that fear. In Exp V with 32 female Wistar rats, identical amounts of contextual fear reinstated fear of an extinguished CS, but not a nonextinguished CS, when the 2 types of CSs were arranged to evoke comparable amounts of fear prior to testing. It is suggested that contextual fear plays a role in the reinstatement paradigm but not in the inflation paradigm. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of bed nucleus of the stria terminalis lesions on conditioned anxiety: Aversive conditioning with long-duration conditional stimuli and reinstatement of extinguished fear.

Four experiments investigated the effects of lesions of the bed nucleus of the stria terminalis (BNST) on conditioned fear and anxiety. Though BNST lesions did not disrupt fear conditioning with a short-duration conditional stimulus (CS; Experiments 1 and 3), the lesion attenuated conditioning with a longer duration CS (Experiments 1 and 2). Experiment 3 found that lesions attenuated reinstatement of extinguished fear, which relies on contextual conditioning. Experiment 4 confirmed that the lesion reduced unconditioned anxiety in an elevated zero maze. The authors suggest that long-duration CSs, whether explicit cues or contexts, evoke anxiety conditioned responses, which are dissociable from fear responses to shorter CSs. Results are consistent with behavioral and anatomical distinctions between fear and anxiety and with a behavior-systems view of defensive conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Study of the oxidation kinetics of finely-divided magnetites III — Influence of chromium and aluminum surstitution

The oxidation kinetics of aluminum and chromium-substituted magnetites (Fe²⁺Cr³⁺_xAl³⁺_2?x)O^2?₄ (0< x < 2) into the γ defect phase of type $\text{γ(}\text{Fe}{}^{\mathrm{3+}}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Al}{}^{\mathrm{3+}}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext><mtext>?</mtext><mtext>y</mtext>}}\text{Cr}{}^{\mathrm{3+}}{}_{\mathrm{<mtext>y</mtext>}}\text{)}{}_2\text{O}{}^{\mathrm{2?}}{}_3$ is found to be governed by the diffusion under variable working conditions for samples prepared at 700°C and whose size is less than 400 Å. When particle size is caused to increase by annealing the kinetic curves are sigmoidal but only for specimens with high chromium substitution. For compounds rich in chromium observations of morphology show facetting during oxidation but no fracturing was observed.     

Associative control of tolerance to the sedative effects of a short-acting benzodiazepine.

The role of Pavlovian conditioning in tolerance to the depressant effect of a benzodiazepine (midazolam) on the ambulatory activity of rats was examined. The depression of activity by low doses (1.0 and 4.0 mg/kg, ip) of midazolam diminished quickly over repeated doses given at 48-hr intervals (Experiment 1). Equivalent tolerance was observed in groups measured at 2 min and 30 min after drug injection. When challenged with saline, however, drug-tolerant animals tested immediately after injection were hyperactive in comparison with nontolerant controls, whereas equivalent groups tested 30 min after injection were not. A second context was designed, and its discriminability from the original was established by assessing context-specific suppression of activity following exposure to mild electric shock (Experiment 2). In Experiment 3A, although tolerant animals tested in the drug-associated context remained fully tolerant, a second group demonstrated a complete loss of tolerance when given the drug in a saline-associated context. Both groups were fully tolerant when tested again in the drug-associated context after 14 drug-free days. In Experiment 3B, tolerance was significantly reduced by 14 extinction exposures to the drug-associated environment without the drug. These results are uniquely predicted by associative models of drug tolerance and may have implications for the clinical use of this class of drugs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Context-specificity of target versus feature inhibition in a feature-negative discrimination.

Four experiments with rats examined the effects of a context switch on inhibition that was acquired during a feature-negative discrimination. A target CS was paired with food when it was presented alone but occurred without food when it was combined with a feature stimulus. A context switch following training did not disrupt inhibition conditioned to the feature. However, responding to the target was more difficult to inhibit when it was tested in a different context. It is suggested that both the target and the feature acquired inhibition, as well as the target's inhibition, were especially sensitive to the context. The feature may inhibit responding to the target by directly suppressing the representation of the food and by activating the target's own inhibitory association with food, which is at least partly context-specific. Implications for theories of inhibition and negative occasion-setting are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preschoolers' strategies of attention on a same-different task.

Forty-six preschoolers were asked to decide whether two rows of drawings, objects were exactly the same by opening the doors that covered the drawings. Four-year-olds, but generally not 3-year-olds, used the most efficient strategy, opening vertically aligned pairs of doors to compare spatially corresponding parts of the rows. Producing this strategy was associated with more accurate same–different judgments. Furthermore, the 4-year-olds improved their strategies significantly, although modestly, over some of the six trials. Earlier phases of strategy development were seen in the use of inefficient, but systematic, spatial strategies in 3-year-olds and partial use of efficient or inefficient strategies in both 3- and 4-year-olds. Children rarely gathered information randomly. Results are discussed in terms of a multifaceted change in strategy production and utilization that extends over several years. Several limitations of 4-year-olds' strategic behavior were also identified. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tyrosine phosphorylation of focal adhesion kinase (p125FAK): regulation by cAMP and thrombin in mesangial cells

This study aimed at evaluating the influence of submaximal isometric contraction on pressure pain thresholds (PPTs) in 14 fibromyalgia (FM) patients and 14 healthy volunteers, before and after skin hypoesthesia. PPTs were determined with pressure algometry over m. quadriceps femoris before, during and following an isometric contraction. Maximum voluntary contraction (MVC) was assessed using a computerized dynamometer. A contraction of 22% MVC on average was held until exhaustion (max. 5 min) and PPTs were assessed every 30 sec. A local anesthetic cream and a control cream were applied following a double-blind design and PPTs were reassessed. In healthy volunteers PPTs increased during contraction (P < 0.001), then decreased after the end of contraction (P < 0.001) but remained above precontraction values during the 5 min of post-contraction assessments (P < 0.001). In FM patients PPTs decreased in the middle of the contraction period (P < 0.05) and remained below precontraction levels during the rest of the contraction period (P < 0.05) and during the 5 min of post-contraction assessment (immediately post-contraction NS; 2.5 min post-contraction P < 0.01; 5 min post-contraction P < 0.05). The normalized PPTs were significantly lower in patients than in controls during contraction (start P < 0.01; middle P < 0.001; end P < 0.001) and at all times during post-contraction assessments (P < 0.001). Anesthetic cream raised PPTs at rest in controls (P < 0.01) but not in FM patients, and did not influence contraction or post-contraction PPTs in either group. Therefore, the increased pressure pain sensibility in FM patients is more pronounced deep to the skin. The observed decrease of PPTs during isometric contraction in FM patients could be due to sensitization of mechanonociceptors caused by muscle ischemia and/or dysfunction in pain modulation during muscle contraction.     

Thermal stability of “living” polymer–lithium systems

The thermal stabilities of polybutadienyllithium, polyisoprenyllithium, and polystyryllithium solutions have been determined in hydrocarbon solvents. Kinetic analysis indicated that a complex mechanism was involved in the thermolysis of polybutadienyllithium. The thermal stability was observed to increase with increasing lithium concentration, suggesting the presence of competitive reactions in addition to the expected elimination of lithium hydride. The thermal stability of the three systems studied was consistent with their reported degrees of association: dimeric polystyryllithium was less stable than tetrameric polyisoprenyllithium or hexameric polybutadienyllithium.     

Comparison of some properties of meat from normal steers and steers heterozygous for muscular hypertrophy

Carcase characteristics and meat properties of 19 normal steers and 14 steers heterozygous for muscular hypertrophy (HMH), killed at a liveweight of circa 360 kg and 500 days of age, were compared. Carcases of the HMH animals had less subcutaneous fat and a greater eye muscle area. It was considered that HMH animals were no more stress susceptible than control animals as plasma glucose concentrations at slaughter and ultimate pH values of the M. semitendinosus (ST) did not differ. ST sarcomere length and cooking losses did not differ between control and HMH animals. ST Warner-Bratzler (peak) shear force values and adhesion values were less in the HMH animals; these lower values would indicate that the ST of the HMH animals was more tender. These differences may have resulted from the difference in the mean age of the normal (527 days) and the HMH groups (489 days) at slaughter. However, other workers have found a reduced hydroxyproline content in muscles of homozygous double-muscled animals and the lower adhesion values of animals heterozygous for muscular hypertrophy may reflect the fact that they also have a lower connective tissue content in their muscles compared with normal animals.