Aging and the perception of depth and 3-D shape from motion parallax

The ability of younger and older observers to perceive 3-D shape and depth from motion parallax was investigated. In Experiment 1, the observers discriminated among differently curved 3-dimensional (3-D) surfaces in the presence of noise. In Experiment 2, the surfaces' shape was held constant and the amount of front-to-back depth was varied; the observers estimated the amount of depth they perceived. The effects of age were strongly task dependent. The younger observers' performance in Experiment 1 was almost 60% higher than that of the older observers. In contrast, no age effect was obtained in Experiment 2. Older observers can effectively perceive variations in depth from patterns of motion parallax, but their ability to discriminate 3-D shape is significantly compromised.     

Memory enhancement of classical fear conditioning by post-training injections of corticosterone in rats

There is extensive evidence that post-training administration of the adrenocortical hormone corticosterone facilitates memory consolidation processes in a variety of contextual and spatial-dependent learning situations. The present experiments examine whether corticosterone can modulate memory of auditory-cue classical fear conditioning, a learning task that is not contingent on contextual or spatial representations. Male Sprague-Dawley rats received three pairings of a single-frequency auditory stimulus and footshock, followed immediately by a post-training subcutaneous injection of either corticosterone (1.0 or 3.0mg/kg) or vehicle. Retention was tested 24h later in a novel test chamber and suppression of ongoing motor behavior served as the measure of conditioned fear. Corticosterone dose-dependently facilitated suppression of motor activity during the 10-s presentation of the auditory cue. As corticosterone administration did not alter responding after unpaired presentations of tone and shock, tone alone, shock alone or absence of tone/shock, the findings indicated that corticosterone selectively facilitated memory of the tone-shock association. Furthermore, injections of corticosterone given 3h after training did not alter motor activity during retention testing, demonstrating that corticosterone enhanced time-dependent memory consolidation processes. These findings provide evidence that corticosterone modulates the consolidation of memory for auditory-cue classical fear conditioning and are consistent with a wealth of data indicating that glucocorticoids can modulate a wide variety of emotionally influenced memories.     

Contextual conditioning in infants, but not older animals, is facilitated by CS conditioning

Context conditioning in infant Sprague-Dawley rats (postnatal days [PD] 15, 17, and 19), juveniles (PD 25), adolescents (PD 35), and adults (PD 71-89) was compared when CS conditioning did or did not occur in the context. Degree of CS conditioning within that context was equated across age, and separate groups at each age were given unpaired presentations of the CS and US within that context. Infants conditioned more effectively to context when CS-US pairings occurred in that context than when they did not, juveniles conditioned to context about equally with and without CS-US pairings in the context, and adolescents and adults conditioned less effectively to context when CS and US were paired than when unpaired. Adolescents had significant context conditioning despite CS-US pairings in the context but adults did not, and overall, context conditioning was strongest for adolescents. Supplementary experiments indicated that with more extensive conditioning experience, the infants' pattern of context conditioning became more similar to that of older animals, and with less conditioning experience the pattern of context conditioning by adults became more similar to that of younger animals, but infants never attained the adult pattern of context conditioning nor did adults attain the infant pattern. The potentiation of context conditioning by CS conditioning observed in infants is consistent with previous evidence derived from compound conditioning. Alternative explanations place common emphasis on infant-specific amodal processing. One views potentiation as a result of the greater perceived intensity of the stimulus compound (CS and context, in this case) during conditioning and the lesser generalization decrement in infants than adults when tested with a single element after conditioning with a compound. The other explanation emphasizes consequences of the redundancy inherent in intersensory compounds, within the theory of Bahrick and Lickliter.     

The relevance of the nature of learned associations for the differentiation of human memory systems

In a previous functional magnetic resonance imaging (fMRI) study we demonstrated an involvement of the medial temporal lobe (MTL) during an implicit learning task. We concluded that the MTL was engaged because of the complex contingencies that were implicitly learned. In addition, the basal ganglia demonstrated effects of a paralleled proceduralization of fixed stimulus-response associations. In the present study we directly tested the hypothesis that the MTL activation depends upon implementing the complex regularity in task material, whereas activation of basal ganglia does not. Therefore, we rearranged task material such that it did not contain any complex regularity. The statistical comparison of behavioral and fMRI data between the materials allowed for isolating effects that were directly related to the implicit learning process regarding the complex regularity. The results showed a reliable difference of fMRI signal limited to the MTL, indicating a specific functional role of the MTL in implicit learning of complex contingencies. Furthermore, no difference of BOLD (Blood-Oxygenation Level Dependent) signal in the basal ganglia and cerebellum were detected, supporting the assumption of a functional involvement of the structures in proceduralization of simple stimulus-response associations but not in implicitly learning complex relations. We therefore conclude that the nature of the learned associations is relevant for determining the neuronal focus of learning, rather than the accompanying awareness.     

Physical health correlates of overprediction of physical discomfort during exercise

This study sought to determine if overprediction of physical discomfort prior to and following exercise was related to a number of self-report and objective measures of physical health status in a general population sample. Cross-sectional findings indicated a significant and specific relation between patterns of discomfort overprediction (vs under- or accurate prediction) and negative self-reported health status and attitudes to exercise, lower levels of physical activity, as well as poorer scores for resting heart rate, cardiorespiratory fitness and body mass index (but not waist:hip ratio). Females were more likely to overpredict discomfort, were less active and had poorer physical health than males. The potential usefulness of the prediction match-mismatch paradigm for studying exercise-related appraisal processes as proximal determinants of physical activity are discussed. Information obtained from such studies could prove useful in public health education campaigns aimed at increasing levels of physical activity in the general population, particularly among the less active.     

Bridging psychology and biology. The analysis of individuals in groups

Biological systems are particularly prone to variation, and the authors argue that such variation must be regarded as important data in its own right. The authors describe a method in which individual differences are studied within the framework of a general theory of the population as a whole and illustrate how this method can be used to address three types of issues: the nature of the mechanisms that give rise to a specific ability, such as mental imagery; the role of psychological or biological mediators of environmental challenges, such as the biological bases for differences in dispositional mood; and the existence of processes that have nonadditive effects with behavioral and physiological variables, such as factors that modulate the response to stress and its effects on the immune response.     

Conceptual representation of verbs in bilinguals: semantic field effects and a second-language performance paradox

It is well known that bilinguals perform better in their first language (L1) than in their second lanaguage (L2) in a wide range of linguistic tasks. In recent studies, however, the authors have found that bilingual participants can demonstrate faster response times to L1 stimuli than to L2 stimuli in one classification task and the reverse in a different classification task. In the current study, they investigated the reasons for this "L2-better-than-L1" effect. English-French bilinguals performed one word relatedness and two categorization tasks with verbs of motion (e.g., run) and psychological verbs (e.g., admire) in both languages. In the word relatedness task, participants judged how closely related pairs of verbs from both categories were. In a speeded semantic categorization task, participants classified the verbs according to their semantic category (psychological or motion). In an arbitrary classification task, participants had to learn how verbs had been assigned to two arbitrary categories. Participants performed better in L1 in the semantic classification task but paradoxically better in L2 in the arbitrary classification task. To account for these effects, the authors used the ratings from the word relatedness task to plot three-dimensional "semantic fields" for the verbs. Cross-language field differences were found to be significantly related to the paradoxical performance and to fluency levels. The results have implications for understanding of how bilinguals represent verbs in the mental lexicon.     

Personality disorders at the crossroads

Personality disorders are now at a crossroads with respect to theory, research, and conceptualization. In this article, we review relevant and current issues within the personality disorder field. After reviewing changes in the conception of personality disorders across the past half century (1952 to 2002), we focus on the issue of continuity versus discontinuity methodologies for assessing personality, interactionism, treatments, resolved and unresolved issues, and future directions. The issue of continuity versus discontinuity is a theme in this article. We conclude that the evidence is in favor of a reapprochment between a categorical classification system and a dimensional system and we also outline the difficulties in achieving this change.     

The perception and discrimination of local 3-D surface structure from deforming and disparate boundary contours

In a series of four experiments, we evaluated observers' abilities to perceive and discriminate ordinal depth relationships between separated local surface regions for objects depicted by static, deforming, and disparate boundary contours or silhouettes. Comparisons were also made between judgments made for silhouettes and for objects defined by surface texture, which permits judgment based on conventional static texture gradients, conventional stereopsis, and conventional structure-from-motion. In all the experiments, the observers were able to detect, with relatively high precision, ordinal depth relationships, an aspect of local three-dimensional (3-D) structure, from boundary contours or silhouettes. The results of the experiments clearly demonstrate that the static, disparate, and deforming boundary contours of solid objects are perceptually important optical sources of information about 3-D shape. Other factors that were found to affect performance were the amount of separation between the local surface regions, the proximity or closeness of the regions to the boundary contour itself, and for the conditions with deforming contours, the overall magnitude of the boundary deformation.     

Pubertal timing and substance use: associations between and within families across late adolescence

In the present study, between-family analyses of data from adolescent twin girls offer new evidence that early menarche is associated with earlier initiation and greater frequency of smoking and drinking. The role of personality factors and peer relationships in that association was investigated, and little support was found for their involvement. Novel within-family analyses replicating associations of substance use with pubertal timing in contrasts of twin sisters selected for extreme discordance for age at menarche are reported. Within-family replications demonstrated that the association of pubertal timing with substance use cannot be explained solely by between-family confounds. Within-family analyses demonstrated contextual modulation of the influence of pubertal timing: Its impact on drinking frequency is apparent only among girls in urban settings. Sibling comparisons illustrate a promising analytic tool for studying diverse developmental outcomes.