On the participation of mTOR in recognition memory

Evidence indicates that activation of the neuronal protein synthesis machinery is required in areas of the brain relevant to memory for consolidation and persistence of the mnemonic trace. Here, we report that inhibition of hippocampal mTOR, a protein kinase involved in the initiation of mRNA translation, immediately or 180min but not 540min after training impairs consolidation of long-term object recognition memory without affecting short-term memory retention or exploratory behavior. When infused into dorsal CA1 after long-term memory reactivation in the presence of familiar objects the mTOR inhibitor rapamycin (RAP) did not affect retention. However, when given immediately after exposing animals to a novel and a familiar object, RAP impaired memory for both of them. The amnesic effect of the post-retrieval administration of RAP was long-lasting, did not happen after exposure to two novel objects or following exploration of the training arena in the absence of other stimuli, suggesting that it was contingent with reactivation of the consolidated trace in the presence of a behaviorally relevant and novel cue. Our results indicate that mTOR activity is required in the dorsal hippocampus for consolidation of object recognition memory and suggest that inhibition of this kinase after memory retrieval in the presence of a particular set of cues hinders persistence of the original recognition memory trace.     

Prediction of university students' academic achievement by linear and logistic models

University students' academic achievement measured by means of academic progress is modeled through linear and logistic regression, employing prior achievement and demographic factors as predictors. The main aim of the present paper is to compare results yielded by both statistical procedures, in order to identify the most suitable approach in terms of goodness of fit and predictive power. Grades awarded in basic scientific courses and demographic variables were entered into the models at the first step. Two hypotheses are proposed: (a) Grades in basic courses as well as demographic factors are directly related to academic progress, and (b) Logistic regression is more appropriate than linear regression due to its higher predictive power. Results partially confirm the first prediction, as grades are positively related to progress. However, not all demographic factors considered proved to be good predictors. With regard to the second hypothesis, logistic regression was shown to be a better approach than linear regression, yielding more stable estimates with regard to the presence of ill-fitting patterns.     

Reputation, loneliness, satisfaction with life and aggressive behavior in adolescence

The present study analyses the relationship between adolescents' perception of reputation and aggressive behavior among peers. The sample is made up of 1319 adolescents aged 11 to 16-years-old. Statistical analyses with structural equation modeling were carried out to examine the direct and indirect effect of perception of reputation (real and ideal) on aggressive behavior. Results indicate that adolescents' real and ideal reputations are related both directly and indirectly to aggressive behavior. The indirect effects suggest that loneliness and life satisfaction mediate the relationship between adolescents' reputation and their aggressive behavior. These findings and their implications are discussed.     

A comparison of the peers method and traditional methodologies, and risk behaviors in studies of the prevalence of drug consumption in a population of female, Chilean students

The present study investigates drug consumption and risk behaviors among female students between 8th and 12th grade in two communities in the city of Santiago, Chile. Based on studies of university populations, we hypothesize that the students' reports of their consumption of licit drugs will tend to be consistent with their actual use of said drugs using two methods to investigate consumption, while their consumption of illicit drugs will be susceptible, and will tend to be under-reported when evaluated through traditional self-report measures. In order to compare the two methods, a cross-sectional study was designed that would compare reported drug consumption, first using the peers method, and then by means of traditional self-report in a group of 350 students. The results show that women's reports of licit drug consumption converge using the two methods, while as earlier suggested, women's illicit drug consumption was found to be under-reported when traditional methodologies were used.     

Comparison of single- and double-stage designs in the prevalence estimation of eating disorders in community samples

The aim of this research was to compare two different case-identification designs: (a) a one-stage anonymous design using the Eating Disorders Examination-Questionnaire (EDE-Q; Fairburn & Beglin, 1994) as diagnostic instrument and (b) a two-stage-non-anonymous design using the Eating Attitudes Test (EAT; Garner & Garfinkel, 1979) and the EDE-Q as screening instruments and the clinical interview Eating Disorders Examination (EDE; Fairbumrn & Cooper, 1993) as diagnostic instrument, in the estimation of eating disorders prevalence in community samples. Both epidemiological designs were compared in: eating disorders prevalence, population at risk, and weekly frequency of associated symptomatology (binge eating episodes, self-vomiting) within a sample of 559 scholars (14 to 18 year-old males and females) studying in the region of Madrid. Eating disorders prevalence estimation using single-stage design was 6.2%, and 3% using the two-stage design; however, these differences were not significant (p = .067). No significant differences between the two procedures were found either in population at risk or in weekly frequency of reported self-vomiting. Reported binge eating episodes were higher in the one-stage design. The use of a two-stage procedure with clinical interview (vs. questionnaire) leads to a better understanding of the items (specially the most ambiguous ones) and thus, to a more accurate prevalence estimation.     

Effect of partial occlusion on newborns' face preference and recognition

Many studies have shown that newborns prefer (e.g. Goren, Sarty & Wu, 1975; Valenza, Simion, Macchi Cassia & Umiltà, 1996) and recognize (e.g. Bushnell, Say & Mullin, 1989; Pascalis & de Schonen, 1994) faces. However, it is not known whether, at birth, faces are still preferred and recognized when some of their parts are not visible because hindered by other configurations, that is when faces are partly occluded. Also, it is not known whether newborns' preference for an upright over an inverted face and newborns' face recognition are differentially affected depending on the salience of the occluded face features. Seventy-seven newborns (mean age of 43.5 hrs) were tested using the preferential looking (Experiment 1) and the habituation techniques (Experiment 2). Results demonstrated that newborns prefer and recognize occluded faces even if some portions of them are not available, at least when the hindered features are not salient. On the contrary, these abilities are affected by obscuring high salience facial features (i.e. eyes). However, while in the case of face detection, eyes occlusion completely prevented newborns' face detection, in the case of face recognition an analogous stimulus manipulation heavily impaired, but did not totally preclude, newborns' recognition performance. The data collected improve our comprehension of newborns' way of processing and encoding information to detect and recognize faces.     

Analysis of effects of distribution of practice in learning and retention of a continuous and a discrete skill presented on a computer

This investigation examined the effects of distributed and massed practice on the learning and retention of a discrete computerized skill (Exp. 1) and a continuous computerized skill (Exp. 2). 40 men were randomly assigned to one of four groups, of which two groups took part in Exp. 1 and two groups in Exp. 2. Performance was assessed at various points during acquisition and then on 8 retention tests conducted at varying times after acquisition. Learning curves for practice were highly similar for the two conditions. Participants in the distributed-practice group performed significantly better than those in the massed-practice group at the end of practice on both the discrete and continuous skills. However, participants in the distributed-practice group performed significantly more poorly on retention during 24 hr. and after acquisition. Participants in the massed-practice condition performed significantly better on retention tests than did those who learned in the distributed-practice condition.     

Influence of articulation rate on two memory tasks in young and older adults

This study investigated the relation between phonological loop functioning and age. Phonological loop is a time-based subsystem of the Working Memory Model of Baddeley and Wilson, which uses rehearsal of information as an active process to avoid phonological decay. Performance differences were examined between young and older adults in two speech-based memory tasks, such as the immediate serial recall of words and the Digit Ordering Task. Analysis showed that performance on both tasks was lower for the older group. Articulation rate was also measured to test the hypothesis that the impairment of some cognitive functions in adults can be associated to their slowness or the greater time needed by older adults for the rehearsal process. A significant negative correlation was found for articulation rate with age. When the effect of articulation rate on Serial Recall and Digit Ordering Tasks was partialled out, the difference between the two groups was eliminated.     

On the Relationships between Sum Score Based Estimation and Joint Maximum Likelihood Estimation

This paper analyzes the sum score based (SSB) formulation of the Rasch model, where items and sum scores of persons are considered as factors in a logit model. After reviewing the evolution leading to the equality between their maximum likelihood estimates, the SSB model is then discussed from the point of view of pseudo-likelihood and of misspecified models. This is then employed to provide new insights into the origin of the known inconsistency of the difficulty parameter estimates in the Rasch model. The main results consist of exact relationships between the estimated standard errors for both models; and, for the ability parameters, an upper bound for the estimated standard errors of the Rasch model in terms of those for the SSB model, which are more easily available. The authors acknowledge partial financial support from the FONDECYT Project No. 1060722 from the Chilean Government, and the BIL05/03 grant to P. De Boeck, E. Lesaffre and G. Molenberghs (Flanders) for a collaboration with G. del Pino, E. San Martín, F. Quintana and J. Manzi (Chile).