Go-no go avoidance discriminations in rats with simple “go” and compound “no go” signals: Stimulus modality and stimulus intensity

Four groups of 16 rats were trained in a go-no go discrimination with symmetrical negative reinforcement (active-passive avoidance task). A 2 by 2 design was used with stimulus combinations as one factor [light-go, noise/light-no go, (L⁺ NL^?) vs noise-go, light/noise-no go (N⁺ LN^?)] and noise intensity as the other factor (90 dB, high, vs 70 dB, low). The two N⁺ LN^? groups learned both active and passive avoidance responses much more rapidly than the L⁺ NL^? groups. In later phases of training, high noise intensity facilitated passive avoidance in the L⁺ NL^? condition and exerted a slight effect in the opposite direction in the other condition. While the differences in active avoidance learning were the same as in previous work on light and noise CSs, the interactions between stimuli of different modalities appeared to be more important than stimulus modality or stimulus intensity per se in determining rate of passive avoidance learning.     

Value transfer in a simultaneous discrimination by pigeons: The value of the S+ is not specific to the simultaneous discrimination context

During simultaneous discrimination training, there is evidence that some of the value of the S⁺ transfers to the S^?. When the value of the S+ is altered outside the context of the simultaneous discrimination, two very different predictions are made concerning its effect on its S^?, depending on whether one views the S⁺ as an occasion setter or as a stimulus capable of transferring value. In four experiments, pigeons were trained with two similar simultaneous discriminations, A⁺B^? and C⁺D^?, and two single-stimulus trial types, A and C, (in which A always had greater nominal value than C). According to value transfer theory, on test trials, B should always be preferred over D, because B and D should be affected by the net values of A and C, respectively. According to an occasion setting account, however, D should be preferred over B because the presence of D signals a higher probability of reinforcement for responding to C than when C is alone, and/or the presence of B signals a lower probability of reinforcement for responding to A than when A is alone. In all four experiments, the pigeons preferred B over D, a result consistent with value transfer theory. Thus, an S^? can acquire value from an S⁺ even when that value is conditioned in a “context” different from that of the simultaneous discrimination.     

Which instructional models influence more on perceived exertion,affective valence,physical activity level,and class time in physical education?

Abstract

The aim of this study was to examine the effects of two different instructional models (i.e. direct instructional model (DIM) and tactical games model (TGM)) with primary education students. Perceived exertion, affective valence, physical activity (PA) level, instruction time, active learning time, and relation of instruction/active learning time were measured with 256 primary education students during DIM and TGM 8 weeks’ intervention programs. Significant differences were found between the DIM and TGM in perceived exertion, PA level, instruction time and in the relation between instruction/active learning time (p?<?.01, ES=?0.4 to 1.1). By age group, the DIM had significantly higher PA level in students of 3^rd grade of primary education (G3), 4^th grade (G4) and 6^th grade (G6) (p?<?.05 or p?<?.01, ES=?0.8 to ?0.4). The instructional model used during physical education classes can affect perceived exertion, PA level, instruction time, and the relation instruction/active learning time.     

Alternative accounts are preferable to value transfer theory: Commentary on Dorrance, Kaiser, and Zentall (1998)

Dorrance, Kaiser, and Zentall (1998) trained pigeons on two concurrent simultaneous discriminations (A₊B_?; C₊D_?), with interspersed single-stimulus trials in which responding to the two positive discriminanda was differentially reinforced (A₊; C_±). In each of four separate experiments, the birds showed a preference for stimulus B over stimulus D. Dorrance et al. concluded that the results of these experiments were best described in terms of value transfer theory (VTT; Fersen, Wynne, Delius, & Staddon, 1991). They reject the possibility that the results of these experiments might have been caused by differential nonreinforced experience with the test stimuli (B and D) on the basis of correlational analyses within each experiment. However, differences between experiments in choice of B over D are well predicted by differences in their history of reinforcement. Previous findings that were thought to favor VTT are also entirely consistent with a simpler associative analysis.     

A test of Rescorla and Wagner’s (1972) prediction of nonlinear effects in contingency learning

According to most theories, in a simple contingency learning situation, excitatory learning occurs when the probability of the unconditioned stimulus in the presence of the conditioned stimulus (p₁) is higher than the probability of the unconditioned stimulus in the absence of the conditioned stimulus (p₂). In Rescorla and Wagner??s (1972) model, this prediction varies, depending on the parameters used. In the following experiments, we evaluated whether the difference between p₁ and p₂ that is required to produce excitatory conditioning is the same, independent of the specific value of p₁, or whether this difference varies proportionally to p₁??s value. To do so, an appetitive procedure of Pavlovian conditioning with rats was used. In four experiments, we compared different levels of contingency (low, medium and high) and found that the difference between p₁ and p₂ that is required to produce excitatory conditioning increases when the value of p₁ is higher. The possibility of analyzing contingency learning as a discrimination between p₁ and p₂ is also discussed.     

Replacement of event-generated memories of nonreinforcement with signal-generated memories of reinforcement during partial reinforcement training: Effect on resistance to extinction

Event-generated memory refers to the memory of a reinforcement (R) or nonreinforcement (N) event from an immediately preceding trial;signal-generated memory refers to the memory of a temporally remote R or N, retrieval of which is generated by presentation of a signal with which the memory is associated (Haggbloom, 1988). In each of three experiments, Group Signal-R received runway discrimination training in Phase 1 to establish a stimulus as a signal for R, and partial reinforcement training in Phase 2. An extinction test measured learning about the memory of nonreward (S^N)—learning that occurs when S^N is retrieved on R trials that follow N trials. In Group Signal-H, those R trials were accompanied by the signal for R, a treatment we hypothesized would generate retrieval of the memory of reinforcement (S^R) so that signal-generated S^R would replace event-generated S^N as the operative memory, thereby eliminating the increased resistance to extinction normally produced by PRF training. In each experiment, Group Signal-R was less resistant to extinction than was a control group conditioned to respond to-event-generated S^N. Extinction was as rapid in Group Signal-R as it was in a consistent reinforcement control group (Experiment 1) and in a group given intertrial reinforcements to interfere with learning about S^N (Experiment 3). Experiment 2 tested two alternative interpretations of the failure to learn about S^N in Group Signal-R. Those alternatives were found to be less viable than the hypothesis that the signal for R actively recruited retrieval of a competing memory.     

Contextual cues and the retrieval of competing memories of goal events

In Experiment 1, four groups of rats were initially trained on a discrimination which established a stimulus as a signal for reinforcement. That signal was then presented during subsequent partial reinforcement training in a way that could potentially interfere with retrieval of the memory of nonreinforcement (S^N) on the preceding trial either because (1) thestorage and retrieval contexts for S^N were different (retrieval failure hypothesis), or (2) the memory of reinforcement produced by the signal acted as a competing memory (competing memory hypothesis). Experiment 1 supported the competing memory hypothesis. In Experiment 2, we investigated the effect of stimulus change on the capacity of the context to retrieve a competing memory of a temporally remote reinforcement event with which the context was strongly associated. Retrieval of a competing memory was impaired by differences between the storage and retrieval contexts in a manner analogous to the effect of context on retrieval of a reinforcement event memory from an immediately preceding trial.     

Evaluation of spatial and vertical variability of nitrogen and phosphorus in sewage-irrigated soil in Tongliao, China

The reuse of wastewater for the irrigation of farmlands is gaining popularity, and the nutrient leaching associated with wastewater irrigation is becoming a matter of concern. The variability of nitrogen and phosphorus fractions in wastewater-irrigated soil was investigated in both horizontal and vertical directions in Kongjiaxiang, Tongliao, Inner Mongolia, China. The results showed that wastewater irrigation resulted in the concentrations of available N and P being 40.36% and 66.49% higher, respectively, than those with groundwater irrigation. Different forms of N and P exhibited significantly different distribution patterns. Higher concentrations of NO3- and total available N, as well as of those of Ca-P and total available P were observed near wastewater irrigation channels. Ca-P has a spatial distribution pattern similar to that of available P. The concentrations of NO3- and NH4+ were the highest in top soil and decreased with depth. The complex interactions between nitrate leaching and nitrogen transformation processes (e.g., nitrification, denitrification, and mineralization) determined the vertical profile of NO3- . The significant amount of NH4+ loss inhibited its deep seepage. The Ca-bound compound contained more P than other inorganic fractions as a result of high Ca levels throughout the soil profile. The differences in the concentrations of Ca-bound P at different depths could be due to the upward flux or translocation of Ca from subsurface to surface soil and the sequestration of P.     

Conditioned avoidance responses survive contingency degradation in the garden slug,Lehmannia valentiana

Joint presentations of a conditioned stimulus (CS) and an unconditioned stimulus (US) strengthen the contingency between them, whereas presentations of one stimulus without the other degrade this contingency. For example, the CS can be presented without the US either before conditioning (CS–no US and then CS–US; latent inhibition) or after conditioning (CS–US and then CS–no US; extinction). In vertebrate subjects and several invertebrate species, a time lapse usually results in a return of the conditioned response, or spontaneous recovery. However, in land mollusks, spontaneous recovery from extinction has only recently been reported, and response recovery after latent inhibition has not been reported. In two experiments, using conditioned aversion to a food odor as a measure of learning and memory retention, we observed contingency degradation via latent inhibition (Experiment 1) and extinction (Experiment 2) in the common garden slug, Lehmannia valentiana. In both situations, the contingency degradation procedure successfully attenuated conditioned responding, and delaying testing by several days resulted in recovery of the conditioned response. This suggests that the CS–US association survived the degradation manipulation and was retained over an interval of several days.     

Uptake,transport and distribution of molybdenum in two oilseed rape (<Emphasis Type="Italic">Brassica napus</Emphasis> L.) cultivars under different nitrate/ammonium ratios

Objectives

To investigate the effects of different nitrate sources on the uptake, transport, and distribution of molybdenum (Mo) between two oilseed rape (Brassica napus L.) cultivars, L0917 and ZS11.

Methods

A hydroponic culture experiment was conducted with four nitrate/ammonium (NO₃ ^?:NH₄ ⁺) ratios (14:1, 9:6, 7.5:7.5, and 1:14) at a constant nitrogen concentration of 15 mmol/L. We examined Mo concentrations in roots, shoots, xylem and phloem sap, and subcellular fractions of leaves to contrast Mo uptake, transport, and subcellular distribution between ZS11 and L0917.

Results

Both the cultivars showed maximum biomass and Mo accumulation at the 7.5:7.5 ratio of NO₃ ^?:NH₄ ⁺ while those were decreased by the 14:1 and 1:14 treatments. However, the percentages of root Mo (14.8% and 15.0% for L0917 and ZS11, respectively) were low under the 7.5:7.5 treatment, suggesting that the equal NO₃ ^?:NH₄ ⁺ ratio promoted Mo transportation from root to shoot. The xylem sap Mo concentration and phloem sap Mo accumulation of L0917 were lower than those of ZS11 under the 1:14 treatment, which suggests that higher NO₃ ^?:NH₄ ⁺ ratio was more beneficial for L0917. On the contrary, a lower NO₃ ^?:NH₄ ⁺ ratio was more beneficial for ZS11 to transport and remobilize Mo. Furthermore, the Mo concentrations of both the cultivars’ leaf organelles were increased but the Mo accumulations of the cell wall and soluble fraction were reduced significantly under the 14:1 treatment, meaning that more Mo was accumulated in organelles under the highest NO₃ ^?:NH₄ ⁺ ratio.

Conclusions

This investigation demonstrated that the capacities of Mo absorption, transportation and subcellular distribution play an important role in genotype-dependent differences in Mo accumulation under low or high NO₃ ^?:NH₄ ⁺ ratio conditions.

     

Preference for signaled shock: A test of two hypotheses

In a test of safety signal and preparatory response explanations of the preference for signaled vs. unsignaled shock, three groups of rats were exposed to a different light-tone-shock contingency on each of the two sides of a shuttlebox. One contingency (S/P) provided both a safety signal and a warning stimulus, another (NS/NP) provided neither, and a third (S/NP) provided a safety period but no warning stimulus. Rats preferred either the S/P or the S/NP side of the shuttlebox when the alternate side provided neither safety signal nor warning stimulus. When the safety signal was available on both sides, the side without the warning stimulus was preferred. Results are interpreted as supporting the safety signal hypothesis.     

L^p-estimates on a ratio involving a Bessel process

INTRODUCTION Throughout this paper, we shall work with a filtered complete probability space (?,F,(Ft),P) sat-isfying the usual conditions. Let B=(Bt)t≥0 be a stan-dard Brownian motion with B0=0. Denote by ú the set of all non-negative real numbers. Recall that a diffusion process X starting at x≥0 is called the square of a Bessel process of dimension δ>0 if d X t = δd t 2 | X t |d Bt , X 0= x, (1) Clearly, this equation has a unique non-negative strong solution X, i.e., …     

Effects of sample duration,retention interval,and passage of time in the test on pigeons’ matching-to-sample performance

Four pigeons served as subjects in an experiment using the go/no-go delayed matching-to-sample paradigm. The go/no-go method was used because it permits the experimenter to track the time course of discriminative performance throughout the test period, unlike the conventional choice matching procedure. It was found that discriminative test performance increased with longer sample durations; performance decreased with longer retention intervals and also as time passed in the test period. The rate of forgetting was virtually the same when either the retention interval was lengthened or time elapsed in the test. These findings support a modified trace theory, which proposes that the sample stimulus trace decays at a constant rate from the point of sample offset, and that the decaying memory trace is repeatedly compared with the prevailing test stimulus as time passes in the test period.     

Precise asymptotics in the law of the logarithm for random fields in Hilbert space

Consider the positive d-dimensional lattice d (d≥2) with partial ordering ≤, let {XK; K ∈ d } be i.i.d. random vari- ables taking values in a real separable Hilbert space (H, ||·||) with mean zero and covariance operator ∑, and set partial sums SN =∑K≤NXK, K , N ∈ d . Under some moment conditions, we obtain the precise asymptotics of a kind of weighted infinite series for partial sums SN as ε 0 by using the truncation and approximation methods. The results are related to the convergence rates of the law of the logarithm in Hilbert space, and they also extend the results of (Gut and Spǎtaru, 2003).     

Electrochemical study on semiconductive properties of the passive film on rebar in concrete

INTRODUCTION Steel rebar embedded in concrete is protectedagainst corrosion by the thin passive film on its sur-face and the physical protection from concrete. Thealkaline environment (pH≥12.5) of the concrete poresolution triggers passivation on the rebar surface andformation of the protective oxide film. The physicaprotection of concrete coverage hinders the invasionof aggressive agents. However, this passivity can bebroken down by local pH loss as a result of concretecracking or the…     

Effects of self-assessment and peer-assessment interventions on academic performance: A meta-analysis

This meta-analysis examined the effects of self-assessment (SA) and/or peer-assessment (PA) interventions on academic performance. The synthesis included 626 effect sizes from 175 independent studies, either using an experimental/quasi-experimental design or a repeated measures design, and involved 19,383 participants in total. Results indicated that SA (g = 0.585), PA (g = 0.606), and SA + PA (mixed) intervention (g = 0.448) had meaningful effects on academic performance. The difference between the effects of SA and PA interventions, conducted on different groups within the same study, was not statistically significant. The use of online technology increased the effect of PA interventions but not for SA. Participants with a higher mean age had more performance gains from the SA + PA (mixed) intervention. For both SA and PA, the studies that used a repeated measures design generated larger effect sizes than those with an experimental/quasi-experimental design. Overall, the findings from this meta-analysis demonstrated the benefits of SA and PA interventions on academic performance in different contexts. Implications for practice and directions for future research are discussed.     

Effects of nitrogen form on growth,CO2 assimilation,chlorophyll fluorescence,and photosynthetic electron allocation in cucumber and rice plants

Cucumber and rice plants with varying ammonium (NH₄ ⁺) sensitivities were used to examine the effects of different nitrogen (N) sources on gas exchange, chlorophyll (Chl) fluorescence quenching, and photosynthetic electron allocation. Compared to nitrate (NO₃ ⁻)-grown plants, cucumber plants grown under NH₄ ⁺-nutrition showed decreased plant growth, net photosynthetic rate, stomatal conductance, intercellular carbon dioxide (CO₂) level, transpiration rate, maximum photochemical efficiency of photosystem II, and O₂-independent alternative electron flux, and increased O₂-dependent alternative electron flux. However, the N source had little effect on gas exchange, Chl a fluorescence parameters, and photosynthetic electron allocation in rice plants, except that NH₄ ⁺-grown plants had a higher O₂-independent alternative electron flux than NO₃ ⁻-grown plants. NO₃ ⁻ reduction activity was rarely detected in leaves of NH₄ ⁺-grown cucumber plants, but was high in NH₄ ⁺-grown rice plants. These results demonstrate that significant amounts of photosynthetic electron transport were coupled to NO₃ ⁻ assimilation, an effect more significant in NO₃ ⁻-grown plants than in NH₄ ⁺-grown plants. Meanwhile, NH₄ ⁺-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) for NO₃ ⁻ reduction, regardless of the N form supplied, while NH₄ ⁺-sensitive plants had a high water-water cycle activity when NH₄ ⁺ was supplied as the sole N source.     

Understanding active metal reaction kinetics with Cu-Mg replacement reaction

Metal substitution reactions are simple redox reactions. These reactions demonstrate the relative activity and the electrochemical series of metals. In particular, the purpose of this study is to help students comprehend the displacement reaction among, Mg metal and solutions containing Cu⁺², Ni⁺², Pb⁺², Cd⁺², Co⁺². This study is an important experiment towards understanding reaction kinetics.     

Synergistic effects of tea polyphenols and ascorbic acid on human lung adenocarcinoma SPC-A-1 cells

Tea polyphenols have been shown to have anticancer activity in many studies.In the present study,we investigated effects of theaflavin-3-3'-digallate(TF3),one of the major theaflavin monomers in black tea,in combination with ascorbic acid(AA),a reducing agent,and(-)-epigallocatechin-3-gallate(EGCG),the main polyphenol presented in green tea,in combination with AA on cellular viability and cell cycles of the human lung adenocarcinoma SPC-A-1 cells.The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide(MTT) assay showed that the 50% inhibition concentrations(IC50) of TF3,EGCG,and AA on SPC-A-1 cells were 4.78,4.90,and 30.62 μmol/L,respectively.The inhibitory rates of TF3 combined with AA(TF3+AA) and EGCG combined with AA(EGCG+AA) at a molar ratio of 1:6 on SPC-A-1 cells were 54.4% and 45.5%,respectively.Flow cytometry analysis showed that TF3+AA and EGCG+AA obviously increased the cell population in the G0/G1 phase of the SPC-A-1 cell cycle from 53.9% to 62.8% and 60.0%,respectively.TF3-treated cells exhibited 65.3% of the G0/G1 phase at the concentration of its IC50.Therefore,TF3+AA and EGCG+AA had synergistic inhibition effects on the proliferation of SPC-A-1 cells,and significantly held SPC-A-1 cells in G0/G1 phase.The results suggest that the combination of TF3 with AA or EGCG with AA enhances their anticancer activity.     

Preschooler's physical activity levels and associations with lesson context,teacher's behavior,and environment during preschool physical education

Preschools offer two main opportunities, recess and physical education (PE), for preschool children to participate in physical activity (PA) and are considered a suitable institution for PA promotion given the large number of children enrolled. Although PE can have a meaningful effect on preschoolers’ PA levels, preschool PE characteristics associated with increased PA have, to the best of our knowledge, not been identified. Therefore, the purpose of the present study was to examine preschooler's PA levels and the associations with lesson context, teacher behavior, and environment during preschool physical education. A random sample of 573 preschoolers (288 boys; M_age = 5.4 years, SD = 0.4) from 35 preschools was examined during one PE class. Findings indicated that preschoolers accumulated 12 min (33%) of moderate-to-vigorous PA (MVPA), 5 min (13%) of light PA, and 20 min (54%) of sedentary behavior during PE. Forty-seven percent of the variance in pupils’ MVPA may be attributed to differences between PE classes. Less knowledge content, less promotion, less management, less preschoolers per 100 m², using obstruction material, and not using throwing equipment were significantly associated with higher MVPA levels. These predictors explained 56% of the variance in MVPA at the PE class-level. To conclude, PE in its current format contributes only a small amount to the PA requirements of preschoolers. Preschoolers’ MVPA levels were related to modifiable PE characteristics indicating that preschool PE can be restructured to increase MVPA.