Psychology

Nicotinic acetylcholine receptors (nAChRs) in the muscle, autonomic ganglia, and brain are targets for pharmacologically administered nicotine. Several of the subunits that combine to form neuronal nicotinic receptors have been deleted by knockout or mutated by knockin in mice using homologous recombination. We will review the biochemical, pharmacological, anatomical, physiological, and behavioral phenotypes of mice with genetically altered neuronal nAChR subunits. Clinically relevant mutations in nAChR genes will also be discussed. In addition, some of the signal transduction pathways activated through nAChRs will be described in order to delineate the longer-term changes that might result from persistent activation or inactivation of nAChRs. Genetically manipulated mice have greatly increased our understanding of the subunit composition and physiological properties of nAChRs in vivo. In addition, these mice have provided a model system to determine the molecular basis for many of the pharmacological actions of nicotine on neurotransmitter release and behavior. Genetic manipulations in mice have also elucidated the role of nAChR subunits in various disease states, and suggest several avenues for drug development. D

Adult hippocampal neurogenesis declines with age in parallel with decreased performance on a variety of hippocampal-dependent tasks. We measured the rate of cellular proliferation in the hippocampus of mice lacking the β2-subunit of the nicotinic acetylcholine receptor (β2−/− mice) at three ages: young adult (3 months old), fully adult (7–10 months old), and aged (22–24 months old). Consistent with previous studies, we observed an age-related decline in hippocampal proliferation in both groups. However, in fully adult β2−/− mice a 43% reduction of granule cell proliferation was detected compared to age-matched controls. This was accompanied by a significant decrease in dentate gyrus area/section and the length of the granule cell layer in β2−/− mice. These alterations were not the result of a change in plasma corticosterone levels or expression of the neurotrophic factor BDNF in the dentate gyrus, two known regulators of hippocampal cell proliferation. Similarly, there was no increase in gliosis, abnormal myelination, or apoptotic cell death in the β2−/− animals, although there was a significant shift in the location of apoptotic cells in the dentate gyrus indicative of a change in neuronal survival. These results suggest that the β2-subunit containing nicotinic acetylcholine receptors play an important role in regulating cell proliferation in the hippocampus and that endogenous acetylcholine may act to oppose the negative effects of normal aging and stress on cellular proliferation. Synapse 54:200–206, 2004. © 2004 Wiley-Liss, Inc.

Prenatal nicotine exposure has been linked to attention deficit hyperactivity disorder and cognitive impairment, but the sites of action for these effects of nicotine are still under investigation. High-affinity nicotinic acetylcholine receptors (nAChRs) contain the ␤2 subunit and modulate passive avoidance (PA) learning in mice. Using an inducible, tetracycline-regulated transgenic system, we generated lines of mice with expression of high-affinity nicotinic receptors restored in specific neuronal populations. One line of mice shows functional ␤2 subunit-containing nAChRs localized exclusively in corticothalamic efferents. Functional, presynaptic nAChRs are present in the thalamus of these mice as detected by nicotine-elicited rubidium efflux assays from synaptosomes. Knock-out mice lacking high-affinity nAChRs show elevated baseline PA learning, whereas normal baseline PA behavior is restored in mice with corticothalamic expression of these nAChRs. In contrast, nicotine can enhance PA learning in adult wild-type animals but not in corticothalamic-expressing transgenic mice. When these transgenic mice are treated with doxycycline in adulthood to switch off nAChR expression, baseline PA is maintained even after transgene expression is abolished. These data suggest that high-affinity nAChRs expressed on corticothalamic neurons during development are critical for baseline PA performance and provide a potential neuroanatomical substrate for changes induced by prenatal nicotine exposure leading to long-term behavioral and cognitive deficits.

The present paper examines the tie between knowledge and behavior in a noun generalization context. An experiment directly comparing noun generalizations of children at the same point in development in forced choice and yes/no tasks reveals task-specific differences in the way children's knowledge of nominal categories is brought to bear in a moment. To understand the cognitive system that produced these differences, the real-time decision processes in these tasks were instantiated in a dynamic field model. The model captures both qualitative and quantitative differences in performance across tasks and reveals constraints on the nature of children's accumulated knowledge. Additional simulations of developmental change in the yes/no task between 2 and 4 years of age illustrate how changes in children's representations translate into developmental changes in behavior. Together, the empirical data and model demonstrate the dynamic nature of knowledge and are consistent with the perspective that knowledge cannot be separated from the task-specific processes that create behavior in the moment.

The acquisition of word meaning is often partially attributed to fast mapping. However, recent research suggests that fast mapping and word learning may represent distinct components of language acquisition. Here we examine their interaction with a Hebbian Normalized Recurrence Network, a connectionist architecture that captures both online processing and long-term statistical learning. After training on a small lexicon, the model performed well above chance on a fast mapping task. Careful analyses of the weight changes, however, suggest that the fast mapping task can be solved with minimal learning. Thus, this model not only captures both long-term learning and online processes, but also provides unique insights regarding the relationship between fast mapping and word learning and that the two should be carefully distinguished.

Previous research suggests that competition among the objects present during referent selection influences young children's ability to learn words in fast mapping tasks. The present study systematically explored this issue with 30-month-old children. Children first received referent selection trials with a target object and either two, three or four competitor objects. Then, after a short delay, children were tested on their ability to retain the newly fast-mapped names. Overall, the number of competitors did not affect children's ability to form the initial name-object mappings. However, only children who encountered few competitors during referent selection demonstrated significant levels of retention. Results and implications are discussed in terms of the role of competition in studies of children's fast mapping. The relationship between referent selection and full word learning is also discussed.

A B S T R A C T Young children learning English are biased to attend to the shape of solid rigid objects when learning novel names. This study seeks further understanding of the processes that support this behavior by examining a previous finding that three-year-old children are also biased to generalize novel names for objects made from deformable materials by shape, even after the materials are made salient. In two experiments, we examined the noun generalizations of 72 two-, three-and fouryear-old children with rigid and deformable stimuli. Data reveal that three-year-old, but not two-or four-year-old, children generalize

Despite a large literature on infants' memory for visually presented stimuli, the processes underlying visual memory are not well understood. Two studies with 4-month-olds (N = 60) examined the effects of providing opportunities for comparison of items on infants' memory for those items. Experiment 1 revealed that 4month-olds failed to show evidence of memory for an item presented during familiarization in a standard task (i.e., when only one item was presented during familiarization). In Experiment 2, infants showed robust memory for one of two different items presented during familiarization. Thus, infants' memory for the distinctive features of individual items was enhanced when they could compare items.

Studies of cognitive development often find that children's abilities shift across age and task. The present paper examines an example of such developmental décalage: the same pattern of performance in novel noun generalization occurring at two points in development across forced choice and yes/no tasks. A formal model of these tasks, and an experiment directly comparing performance of children at the same developmental level in each task, demonstrate the importance of understanding how knowledge interacts with the specifics of the task to create behavior and development.

Although shared storybook reading is a common activity believed to improve the language skills of preschool children, how children learn new vocabulary from such experiences has been largely neglected in the literature. The current study systematically explores the effects of repeatedly reading the same storybooks on both young children's fast and slow mapping abilities. Specially created storybooks were read to 3-year-old children three times during the course of 1 week. Each of the nine storybooks contained two novel name–object pairs. At each session, children either heard three different stories with the same two novel name–object pairs or the same story three times. Importantly, all children heard each novel name the same number of times. Both immediate recall and retention were tested with a four-alternative forced-choice task with pictures of the novel objects. Children who heard the same stories repeatedly were very accurate on both the immediate recall and retention tasks. In contrast, children who heard different stories were only accurate on immediate recall during the last two sessions and failed to learn any of the new words. Overall, then, we found a dramatic increase in children's ability to both recall and retain novel name–object associations encountered during shared storybook reading when they heard the same stories multiple times in succession. Results are discussed in terms of contextual cueing effects observed in other cognitive domains.

Determining the referent of a novel name is a critical task for young language learners. The majority of studies on children's referent selection focus on manipulating the sources of information (linguistic, contextual and pragmatic) that children can use to solve the referent mapping problem. Here, we take a step back and explore how children's endogenous biases towards novelty and their own familiarity with novel objects influence their performance in such a task. We familiarized 2-year-old children with previously novel objects. Then, on novel name referent selection trials children were asked to select the referent from three novel objects: two previously seen and one completely novel object. Children demonstrated a clear bias to select the most novel object. A second experiment controls for pragmatic responding and replicates this finding. We conclude, therefore, that children's referent selection is biased by previous exposure and children's endogenous bias to novelty.

Purpose This study was designed to compare quality of life (QoL) outcomes after uterine artery embolization (UAE) or myomectomy. Methods Women with symptomatic fibroids diagnosed by ultrasound who wished to preserve their uterus were randomized to myomectomy (n = 81) or UAE (n = 82). Endpoints at 1 year were QoL measured by a validated questionnaire, hospital stay, rates of complications, and need for reintervention. Results UAE patients had shorter hospitalization (2 vs. 6 days, p \ 0.001). By 1 year postintervention, significant and equal improvements in QoL scores had occurred in both groups (myomectomy n = 59; UAE n = 61). There had been two (2.9%) major complications among UAE versus 6 (8%) among myomectomy patients (not significant). By 2 years, among UAE patients (n = 57) there were eight (14.0%) reinterventions for inadequate symptom control compared with one (2.7%) among myomectomy patients (n = 37). Half of the women who required hysterectomy had concomitant adenomyosis missed by US.

The current study examines how focusing children’s attention immediately after fast mapping improves their ability to retain novel names. Previous research suggests that young children can only retain novel names presented via referent selection if ostensive naming is provided and that such explicit naming works by increasing children’s attention to the target and decreasing their attention to the competitor objects (Horst and Samuelson, 2008). This explanation of the function of ostensive naming after referent selection trials was tested by drawing 24-month-old children’s attention to the target either by illuminating the target, covering the competitors, or both. A control group was given a social pragmatic cue (pointing). Children given social pragmatic cue support did not demonstrate retention. However, children demonstrated retention if the target object was illuminated, and also when it was illuminated and the competitors simultaneously dampened. This suggests that drawing children’s attention to the target object in a manner that helps focus children’s attention is critical for word learning via referent selection. Directing attention away from competitors while also directing attention toward a target also aids in the retention of novel words.

Young children learn words from a variety of situations, including shared storybook reading. A recent study by Horst et al. (2011a) demonstrates that children learned more new words during shared storybook reading if they were read the same stories repeatedly than if they were read different stories that had the same number of target words. The current paper reviews this study and further examines the effect of contextual repetition on children's word learning in both shared storybook reading and other situations, including fast mapping by mutual exclusivity. The studies reviewed here suggest that the same cognitive mechanisms support word learning in a variety of situations. Both practical considerations for experimental design and directions for future research are discussed.

Reading the same storybooks repeatedly helps preschool children learn words. In addition, sleeping shortly after learning also facilitates memory consolidation and aids learning in older children and adults. The current study explored how sleep promotes word learning in preschool children using a shared storybook reading task. Children were either read the same story repeatedly or different stories and either napped after the stories or remained awake. Children's word retention were tested 2.5 h later, 24 h later, and 7 days later. Results demonstrate strong, persistent effects for both repeated readings and sleep consolidation on young children's word learning. A key finding is that children who read different stories before napping learned words as well as children who had the advantage of hearing the same story. In contrast, children who read different stories and remained awake never caught up to their peers on later word learning tests. Implications for educational practices are discussed.

Research demonstrates that within-category visual variability facilitates noun learning; however, the effect of visual variability on verb learning is unknown. We habituated 24-month-old children to a novel verb paired with an animated star-shaped actor. Across multiple trials, children saw either a single action from an action category (identical actions condition, for example, travelling while repeatedly changing into a circle shape) or multiple actions from that action category (variable actions condition, for example, travelling while changing into a circle shape, then a square shape, then a triangle shape). Four test trials followed habituation. One paired the habituated verb with a new action from the habituated category (e.g., ‘dacking’ + pentagon shape) and one with a completely novel action (e.g., ‘dacking’ + leg movement). The others paired a new verb with a new same-category action (e.g., ‘keefing’ + pentagon shape), or a completely novel category action (e.g., ‘keefing’ + leg movement). Although all children discriminated novel verb/action pairs, children in the identical actions condition discriminated trials that included the completely novel verb, while children in the variable actions condition discriminated the out-of-category action. These data suggest that – as in noun learning – visual variability affects verb learning and children's ability to form action categories.

Children develop in a real, messy world in which learning unfolds through time and space shared with others. Understanding how children develop in this complex environment will require a solid, theoretically-grounded understanding of how the child and environment interact—both within and beyond the laboratory. We as researchers understand the scientific value in testing children in carefully-controlled environments, but for our findings to have any impact on children's lives we must strive to understand how the processes we study in the lab operate in the real, busy environments in which children interact with peers and adults.

Many experimental research designs require images of novel objects. Here we introduce the Novel Object and Unusual Name (NOUN) Database. This database contains 64 primary novel object images and additional novel exemplars for ten basic- and nine global-level object categories. The objects' novelty was confirmed by both self-report and a lack of consensus on questions that required participants to name and identify the objects. We also found that object novelty correlated with qualifying naming responses pertaining to the objects' colors. The results from a similarity sorting task (and a subsequent multidimensional scaling analysis on the similarity ratings) demonstrated that the objects are complex and distinct entities that vary along several featural dimensions beyond simply shape and color. A final experiment confirmed that additional item exemplars comprised both sub- and superordinate categories. These images may be useful in a variety of settings, particularly for deve...

This paper reports two experiments which explore the nature of comprehension deficits in children with normal word recognition ability. In Experiment 1, skilled and less-skilled comprehenders listened to a series of stories. They were then given an unexpected recognition test comprised of some original sentences, some sentences that were valid inferences from the'original stories, and some that were invalid inferences. Both groups falsely identified more valid than invalid inference foils, but this difference was significantly larger for the skilled comprehenders. These results confirm and extend the findings of Oakhill (1982). They indicate that skilled comprehenders engage in more constructive processing, and that the effect does not depend on the subjects being given deliberate memorisation instructions. Experiment 2 investigated whether the difference between skilled and less-skilled comprehenders is related to their working memory capabilities, using the paradigm devised by Hitch and Halliday (1983). No difference between the groups was found. This result suggests that impairment in comprehension does not stem from a defective working memory. Other possible explanations for the differences between the groups are considered.