Roles of hippocampal GABA(A) and muscarinic receptors in consolidation of context memory and context-shock association in contextual fear conditioning: a double dissociation study

Contextual fear conditioning involves forming a context representation and associating it to a shock, both of which involved the dorsal hippocampus (DH) according to our recent findings. This study tested further whether the two processes may rely on different neurotransmitter systems in the DH. Male Wistar rats with cannula implanted into the DH were subjected to a two-phase training paradigm of contextual fear conditioning to separate context learning from context-shock association in two consecutive days. Immediately after each training phase, different groups of rats received bilateral intra-DH infusion of the GABA(A) agonist muscimol, 5HT(1A) agonist 8-OH-DPAT, NMDA antagonist APV or muscarinic antagonist scopolamine at various doses. On the third day, freezing behavior was tested in the conditioning context. Results showed that intra-DH infusion of muscimol impaired conditioned freezing only if it was given after context learning. In contrast, scopolamine impaired conditioned freezing only if it was given after context-shock training. Posttraining infusion of 8-OH-DPAT or APV had no effect on conditioned freezing when the drug was given at either phase. These results showed double dissociation for the hippocampal GABAergic and cholinergic systems in memory consolidation of contextual fear conditioning: forming context memory required deactivation of the GABA(A) receptors, while forming context-shock memory involved activation of the muscarinic receptors.     

Comparing single-pool and multiple-pool designs regarding test security in computerized testing

This article compares the use of single- and multiple-item pools with respect to test security against item sharing among some examinees in computerized testing. A simulation study was conducted to make a comparison among different pool designs using the item selection method of maximum item information with the Sympson-Hetter exposure control and content balance. The results from the simulation study indicate that two-pool designs have a better degree of resistance to item sharing than do the single-pool design in terms of measurement precision in ability estimation. This article further characterizes the conditions under which employing a multiple-pool design is better than using a single, whole pool in terms of minimizing the number of compromised items encountered by examinees under a randomized item selection method. Although no current computerized testing program endorses the randomized item selection method, the results derived in this study can shed some light on item pool designs regarding test security for all item selection algorithms, especially those that try to equalize or balance item exposure rates by employing a randomized item selection method locally, such as the a-stratified-with-b-blocking method.     

Combining CAT with cognitive diagnosis: A weighted item selection approach

Computerized adaptive testing (CAT) was originally proposed to measure θ, usually a latent trait, with greater precision by sequentially selecting items according to the student’s responses to previously administered items. Although the application of CAT is promising for many educational testing programs, most of the current CAT systems were not designed to provide diagnostic information. This article discusses item selection strategies specifically tailored for cognitive diagnostic tests. Our goal is to identify an effective item selection algorithm that not only estimates θ efficiently, but also classifies the student’s knowledge status α accurately. A single-stage item selection method with a dual purpose will be introduced. The main idea is to treat diagnostic criteria as constraints: Using the maximum priority index method to meet these constraints, the CAT system is able to generate cognitive diagnostic feedback in a fairly straightforward fashion. Different priority functions are proposed. Some of them are based on certain information measures, such as Kullback–Leibler information, and others utilize only the information provided by the Q-matrix. An extensive simulation study is conducted, and the results indicate that the information-based method not only yields higher classification rates for cognitive diagnosis, but also achieves more accurate θ estimation. Other constraint controls, such as item exposure rates, are also considered for all the competing methods.     

Beauty is better pursued: effects of attractiveness in multiple-face tracking

Using the multiple-object tracking paradigm, this study examines how spontaneous appraisal for facial beauty affects distributed attention to multiple faces in dynamic displays. Observers tracked attractive faces more effectively than unattractive faces in this task. Tracking performance was only affected by target attractiveness, suggesting an absence of appraisal for distractor attractiveness. Attractive male faces also produced stronger binding of face identity and location for female participants. Together, the results suggest that facial attractiveness was appraised during tracking even though this was task irrelevant. Contrary to the theory that multiple-object tracking is driven by encapsulated low-level vision, our results show that the content of target representation is not only penetrable by social cognition but also modulates the course of tracking operations.     

Hydrogenation of Ti50Zr25Co25 amorphous ribbons and its effect on their structural and mechanical properties

Changes in the structure and mechanical properties of Ti₅₀Zr₂₅Co₂₅ melt-spun ribbons upon electrolytic hydrogenation have been investigated. Structural analyses of the as-spun ribbons revealed the sporadic presence of icosahedral (i) quasicrystalline short-range order (SRO) in the amorphous structure. Upon cathodic charging with hydrogen, the i-SRO vanished for a hydrogen content of about 21 at.% (hydrogen-to-metal atom ratio, H/M: 0.26), resulting in a fully amorphous structure. Simultaneously, the fracture strength was found to increase while the ribbons preserved their bending ductility. However, a significant reduction in the fracture strength and ductility of the ribbons was observed for hydrogen concentrations larger than 26 at.%. Variations in the mechanical stability are discussed based on a structure-property correlation.     

Electronegativity difference as a factor for evaluating the thermal stability of Al-rich metallic glasses

This article proposes a factor, the critical electronegativity difference Δx _cri, to correlate alloy composition with thermal stability and glass-forming ability of Al–Ni–RE (RE: Rare Earth element) ternary metallic glasses. The Al-rich metallic glasses with Δx > Δx _cri exhibit glassy behavior, whereas alloys with Δx < Δx _cri are nanocrystalline. Nanoglassy alloys occur when Δx ≈ Δx _cri. The best glass formers are located near Δx _cri. Furthermore, an equation has been deduced to calculate Δx _cri with varying RE covalent atomic radius.     

Efficient atomic packing clusters and glass formation in ternary Al-based metallic glasses

In this article, we propose an efficient atomic packing cluster-based composition protocol to help design Al-based metallic glasses. Its validity is verified by some typical experimental data from the literatures. Furthermore, with this understanding, the Al–Ni–Y alloy system is re-evaluated. As a result, the best glass former Al₈₆Ni₉Y₅ in this system, with the critical thickness of about 500 µm, is successfully fabricated by wedge casting.     

Nucleation of the C40-to-C11 b transformation in magnetron-sputtered MoSi 2 thin films

Transmission electron microscopy has been used to reveal the microstructure of metastable C40 MoSi 2 thin films produced by annealing amorphous magnetron-sputtered deposits at 700°C. The films contain nanoscale acicular grains elongated parallel to (0001), with extensive basal faulting. The faults are intrinsic with R ´ 1/3[0001] and correspond to thin slabs of the equilibrium C11 b phase. It is proposed that these faults may act as nuclei for the subsequent transformation from C40 to C11 b by a process akin to discontinuous coarsening.     

I Knew It All Along,Unless I Had to Work to Learn What I Know

After receiving knowledge regarding some topic, people usually overestimate their prior topic knowledge. Two experiments investigated whether people would claim less prior knowledge if they worked to earn their present knowledge. In Study 1, students finishing a psychology course claimed less precourse psychology knowledge if they reported devoting more effort toward the course. In Study 2, the knew-it-all-along effect was stronger for participants who were simply given the answers to questions than for participants who studied for 20 minutes to learn the answers. Both cognitive and motivational factors can account for the observed effects of effort investment on retrospective knowledge judgments.     

CONTROLLING TWO CONFOUNDING VARIABLES IN WORD LENGTH: "VANISHED WORD-LENGTH EFFECT"

Lee (1999) argued that there would be two possible confounding variables in the word length effect. This study attempted to control those two variables. A possible confounding variable in the word-length effect is the neighborhood size. A shortword usually has more neighbors than a long word.Another confounding variable is different perceptual availability between inside and outside letters in a long word. Inside letters are easier to perceive than outside letters. Controlling of these two confounding variables in the two experiments eliminated the wordlength effect.