Temporal discrimination learning by pigeons

Memory for time by animals appears to undergo a systematic shortening. This so-called choose-short effect can be seen in a conditional temporal discrimination when a delay is inserted between the sample and comparison stimuli. We have proposed that this temporal shortening may result from a procedural artifact in which the delay appears similar to the intertrial interval and thus, produces an inadvertent ambiguity or 'instructional failure'. When this ambiguity is avoided by distinguishing the intertrial interval from the delay, as well as the samples from the delay, the temporal shortening effect and other asymmetries often disappear. By avoiding artifacts that can lead to a misinterpretation of results, we may understand better how animals represent time. An alternative procedure for studying temporal discriminations is with the psychophysical bisection procedure in which following conditional discrimination training, intermediate durations are presented and the point of subjective equality is determined. Research using the bisection procedure has shown that pigeons represent temporal durations not only as their absolute value but also relative to durations from which they must be discriminated. Using this procedure, we have also found that time passes subjectively slower when animals are required to respond to the to-be-timed stimulus.     

Assessing the Default Assumption That Children Are Always at Risk

This paper establishes that non-elderly healthy adult animal models commonly display greater susceptibility than young animals to both acute and a wide range of chronic toxic effects from agents representing numerous chemical classes, including pharmaceutical agents and agents typically regulated as environmental/occupational pollutants. While the general belief that the young are likely to be at enhanced risk compared to adults remains the predominant perspective, the not-infrequent occurrence of greater susceptibility in adults raises questions about the utility of a generic default uncertainty factor (UF) for the young and suggests consideration of categorical UFs.     

Non‐genetic polymorphisms in rotifers: environmental and endogenous controls,development, and features for predictable or unpredictable environments

Pronounced non‐genetic polymorphisms, or polyphenisms, occur in some monogonont rotifers reproducing by diploid, female parthenogenesis. In many brachionids, there is great variation in spine length. In trimorphic species of Asplanchna, females can vary in size and shape, from a small saccate morph to giant cruciform and campanulate morphs. In species that also reproduce sexually, diploid eggs can develop into two types of females. Amictic females produce diploid eggs that develop parthenogenetically into females; mictic females produce haploid eggs that develop parthenogenetically into males or, if fertilized, into resting eggs. In a species of Synchaeta, amictic females produce diploid eggs that can be either thin‐shelled and subitaneous or thicker‐shelled and diapausing. In all cases, morph determination occurs during the oogenesis or embryological development of diploid eggs in the maternal body cavity. For the first time, these polymorphisms are reviewed together and compared regarding a number of features associated with transitions from default to induced morphs: (i) type of variation (morphological, physiological, or both; continuous or discrete); (ii) inducing signal (environmental, endogenous, or both); (iii) universality of response to that signal (all or only some individuals); (iv) fitness cost; (v) reversibility; and (vi) ecological significance. Most of the polymorphisms fall into two major categories regarding these features. Transitions suitable for predictable environments involve: universal responses to environmental signals; continuous morphological variation; low reproductive cost; rapid reversibility; and adaptations for defence, hydrodynamics or prey ingestion. Transitions suitable for unpredictable environments are bet‐hedging strategies and usually involve: partial (stochastic) responses to environmental or endogenous signals; discontinuous physiological variation; initiation of diapause, and thus high reproductive cost and slow reversibility. Two cases of morphological variation also involve the simultaneous production of different morphs and likely are adaptations for an uncertain future: continuous spine‐length variation due to maternal age in Brachionus calyciflorus, and production of discrete cruciform and campanulate females in Asplanchna spp.     

A cautionary note on Bayesian estimation of population size by removal sampling with diffuse priors

We consider the problem of estimating a population size by removal sampling when the sampling rate is unknown. Bayesian methods are now widespread and allow to include prior knowledge in the analysis. However, we show that Bayes estimates based on default improper priors lead to improper posteriors or infinite estimates. Similarly, weakly informative priors give unstable estimators that are sensitive to the choice of hyperparameters. By examining the likelihood, we show that population size estimates can be stabilized by penalizing small values of the sampling rate or large value of the population size. Based on theoretical results and simulation studies, we propose some recommendations on the choice of the prior. Then, we applied our results to real datasets.     

Which women default from follow‐up cervical cytology tests? A cohort study within the TOMBOLA trial

L. Sharp, S. Cotton, A. Thornton, N. Gray, D. Whynes, L. Smart, N. Waugh, I. Duncan, M. Cruickshank and J. Little, on behalf of the TOMBOLA Group Which women default from follow‐up cervical cytology tests? A cohort study within the TOMBOLA trial Objective: To identify factors associated with default from follow‐up cervical cytology tests. Methods: A cohort study was conducted involving 2166 women, aged 20–59, with recent low‐grade cervical cytology taken within the NHS Cervical Screening Programmes in Scotland and England, and managed by 6‐monthly cytology in primary care. For the first (6‐month) and second (12‐month) surveillance cytology tests separately, women were categorized as ‘on‐time attendees’ (attended ≤6 months of test being due), ‘late attendees’ (attended greater than 6 months after test was due) or ‘non‐attendees’ (failed to attend). Multivariate odds ratios (ORs) were computed for factors associated with late and non‐attendance. Results: For the first surveillance test, risk of non‐attendance was significantly higher in younger women, those without post‐secondary education, and non‐users of prescribed contraception. Factors significantly associated with late attendance for the first test were the same as for non‐attendance, plus current smoking and having children. The most important predictor of non‐attendance for the second surveillance test was late attendance for the first test (OR = 9.65; 95% CI, 6.60–16.62). Non‐attendance for the second test was also significantly higher among women who were younger, smokers and had negative cytology on the first surveillance test. Late attendance for the second surveillance test was higher in women who were younger, smokers, had children and attended late for the first test. Conclusions: Women at highest risk of default from follow‐up cytology tend to be young, smoke, lack post‐secondary education, and have defaulted from a previous surveillance appointment. Tackling default will require development of targeted strategies to encourage attendance and research to better understand the reasons underpinning default.     

Rats exhibit asymmetrical retention functions for hedonic samples

Rats were trained in a symbolic delayed matching-to-sample task to discriminate hedonic sample stimuli that consisted of food or no food. Retention functions decreased more rapidly on trials initiated by a food sample than on trials initiated by a no-food sample when retention intervals were manipulated within session. The asymmetrical functions could not be explained in terms of mediation of choice responding by magazine head-entry behavior during the retention interval. Unlike within-session changes in retention interval, between-session changes did not result in steeper forgetting functions for food samples. These results in rats are consistent with previous findings reported for the presence and absence of visual samples in pigeons (Wixted, 1993).     

Genetic interaction is associated with lower metabolic connectivity and memory impairment in clinically mild Alzheimer's disease

Metabolic connectivity as showed by [18F] fluorodeoxyglucose (FDG) positron emission tomography (FDG‐PET) reflects neuronal connectivity. The aim of this study was to investigate the genetic impact on metabolic connectivity in default mode subnetworks and its clinical‐pathological relationships in patients with Alzheimer's disease (AD). We separately investigated the modulation of 2 default mode subnetworks, as identified with independent component analysis, by comparing APOE‐ε4 carriers to noncarriers with AD. We further analyzed the interaction effects of APOE (APOE‐ε4 carriers vs noncarriers) with PICALM (rs3851179‐GG vs rs3851179‐A‐allele carriers) on episodic memory (EM) deficits, reduction in cerebral metabolic rate for glucose (CMRgl) and decreased metabolic connectivity in default mode subnetworks. The metabolic connectivity in the ventral default mode network (vDMN) was positively correlated with EM scores (β =0.441, P < .001). The APOE‐ε4 carriers had significantly lower metabolic connectivity in the vDMN than the APOE‐ε4 carriers (t(96) = ?2.233, P = .028). There was an effect of the APOE‐PICALM (rs3851179) interactions on reduced CMRgl in regions of vDMN (P < .001), and on memory deficits (F_3,93 =5.568, P = .020). This study identified that PICALM may modulates memory deficits, reduced CMRgl and decreased metabolic connectivity in the vDMN in APOE‐ε4 carriers. [18F] FDG‐PET‐based metabolic connectivity may serve a useful tool to elucidate the neural networks underlying clinical‐pathological relationships in AD.     

Comprehensive Realism's Weight-of-Evidence Based Distributional Dose-Response Characterization

Challenges to low-dose linearity and other default assumptions in cancer risk assessment and the limitations associated with NOAELs, LOAELs, and constant uncertainty factor values in the evaluation of noncancer health effects have stimulated the continued evolution of risk assessment methodologies. The increasing need for more realistic estimates of the dose-response relationship, better uncertainty characterization, and greater utilization of cost-benefit analyses have also contributed to this evolution. “Comprehensive Realism” is an emerging quantitative weight-of-evidence based risk assessment methodology for both cancer and noncancer health effects which utilizes probability distributions and decision analysis techniques to reflect more of the relevant human exposure data, more of the available and pertinent human and animal dose-response data, and the current state of knowledge about the relative plausibility of alternative dose-response analyses. A tree (like a decision tree and a probability tree) is used to decompose the dose-response assessment into component factors, to provide a structure for explicitly considering multiple alternatives for each factor, and to explicitly incorporate the current state of knowledge about the relative plausibility of these alternatives. Groundbreaking work has demonstrated the feasibility of weight-of-evidence based distributional characterizations, and provided initial examples. Computer software implementations are also available.     

An audit of colposcopy appointment processes in women with abnormal cervical cytology

C. Kietpeerakool, M. Manopunya, P. Phuprasertsak, T. Jaijit and J. Srisomboon An audit of colposcopy appointment processes in women with abnormal cervical cytology Objectives: This study was conducted to audit the waiting times and default rates of colposcopy using the standard requirements of the National Health Service Cervical Screening Programme (NHSCSP) 2004 guidelines. Methods: The records of 291 women with abnormal cervical smears referred to the colposcopy clinic between January and December 2008 at Chiang Mai University Hospital, Thailand, were reviewed. Results: The proportion of women with abnormal cervical smears of any grade receiving colposcopy appointments within 8 weeks of referral (96.9%) achieved the minimum requirements (≥ 90%). However, the waiting times for women with high‐grade squamous intraepithelial lesion, glandular cell abnormality and invasive lesion smears were longer than recommended by NHSCSP guidelines. The default rate of 15.8% in this study was slightly higher than recommended by the guidelines (< 15%). Having no health insurance, being known to have HIV infection and waiting times longer than 4 weeks were independent predictors of default from an initial colposcopy appointment. Conclusion: The waiting times for colposcopy among women with high‐grade smear abnormality and the default rate failed to meet standard requirements. Designing an effective protocol for colposcopy appointment processes is warranted.