Age-related changes in memory and in acetylcholine functions in the hippocampus in the Ts65Dn mouse, a model of Down syndrome

Spatial working memory and the ability of a cholinesterase inhibitor to enhance memory were assessed at 4, 10, and 16 months of ages in control and Ts65Dn mice, a partial trisomy model of Down syndrome, with possibly significant relationships to Alzheimer's disease as well. In addition, ACh release during memory testing was measured in samples collected from the hippocampus using in vivo microdialysis at 4, 10, and 22-25 months of age. When tested on a four-arm spontaneous alternation task, the Ts65Dn mice exhibited impaired memory scores at both 4 and 10 months. At 16 months, control performance had declined toward that of the Ts65Dn mice and the difference in scores across genotypes was not significant. Physostigmine (50 microg/kg) fully reversed memory deficits in the Ts65Dn mice in the 4-month-old group but not in older mice. Ts65Dn and control mice exhibited comparable baseline levels of ACh release at all ages tested; these levels did not decline significantly across age in either genotype. ACh release increased significantly during alternation testing only in the young Ts65Dn and control mice. However, the increase in ACh release during alternation testing was significantly greater in control than Ts65Dn mice at this age. The controls exhibited a significant age-related decline in the testing-related increase in ACh release. With only a small increase during testing in young Ts65Dn mice, the age-related decline in responsiveness of ACh release to testing was not significant in these mice. Overall, these results suggest that diminished responsiveness of ACh release in the hippocampus to behavioral testing may contribute memory impairments in Ts65Dn mice.     

Eye-tracking the cancellation and focus model for preference judgments

By means of a relatively new eye-tracking method that allows for a test situation much closer to reality, we recorded and examined gaze time and fixation number within the cancellation and focus paradigm, a feature-matching model for preference judgments between two alternatives. In line with the cancellation and focus model we found that when subjects encountered the second option in each pair, shared features were canceled out and thus given less consideration whereas unique features were focused on more. We also investigated the role of feature attractiveness as a second important factor in preference judgments and found a U-shaped relationship between attractiveness and visual consideration intensity; that is, attractive and unattractive features received more attention than did those of intermediate attractiveness. Finally, we tested the ability of two models, Franklin’s rule and the WReSt (Weighted Recalled Stepwise Comparing) heuristic, to predict the preference ratings.     

The efficiency of biological motion perception

Humans can readily perceive biological motion from point-light (PL) animations, which create an image of a moving human figure by tracing the trajectories of a small number of light points affixed to a moving human body. We have applied ideal observer analysis to a standard biological motion discrimination task involving either full-figure or PL displays. Contrary to current dogma, we find that PL animations can be rich inpotential stimulus information but that human observers are remarkably inefficient at exploiting this information. Although our findings do not discount the utility of PL animation, they do provide a realistic measure of the computational challenge posed by biological motion perception.     

Unrealistic optimism and event threat

Individuals typically exhibit "unrealistic optimism" (UO), the belief that they are less likely than the average person to experience a negative event. This may be because, fearing the event, they try to reassure themselves by distorting their reasoning to conclude that they are at comparatively little risk. If this is so, the greater the "event threat" (i.e., the more serious the event's consequences and/or the greater the likelihood that those consequences will be experienced), the more reassurance should be required, and the greater the UO that should be observed. This prediction was tested in a study in which students (N = 148) were informed about a type of heart disease that could develop in later life due to inadequate diet when young. The risk attributable to diet was stated to be either slight (low-threat condition) or great (high-threat condition). Participants were asked to rate their own risk and that of the average student of developing the disease; question order was counterbalanced. The effects of event threat and question order were found to interact: event threat affected UO in the predicted way, but only when the question about own risk came first. The results are explained in motivational terms. Implications for health education are discussed.     

Intrinsic-Extrinsic Religiosity and University Students' Willingness to Donate Organs Posthumously

This research focuses on the links between intrinsic and extrinsic religious orientations as they relate to willingness to donate organs posthumously. Participants responded to a factual test of their knowledge about organ donation, indicated their degree of willingness to donate organs, and filled out personality inventories measuring their intrinsic and extrinsic orientations. The data indicated a high level of factual knowledge about organ donation. Also, contrary to Allport's (1966) arguments, people with an intrinsic religious orientation were not more likely to donate their organs, nor were people with an extrinsic religious orientation less likely to do so. Instead, it was found that intrinsic religiosity was unrelated to willingness to donate organs and that extrinsics with strong social orientations were more willing to donate their organs. Discussion centers on the need to develop more psy-chometrically sound measures of mature religiosity as a means of conducting a fairer test of Allport's original theorizing about intrinsic religiosity.     

Bifactor and item response theory analyses of interviewer report scales of cognitive impairment in schizophrenia

A psychometric analysis of 2 interview-based measures of cognitive deficits was conducted: the 21-item Clinical Global Impression of Cognition in Schizophrenia (CGI-CogS; Ventura et al., 2008), and the 20-item Schizophrenia Cognition Rating Scale (SCoRS; Keefe et al., 2006), which were administered on 2 occasions to a sample of people with schizophrenia. Traditional psychometrics, bifactor analysis, and item response theory methods were used to explore item functioning and dimensionality and to compare instruments. Despite containing similar item content, responses to the CGI-CogS demonstrated superior psychometric properties (e.g., higher item intercorrelations, better spread of ratings across response categories) relative to the SCoRS. The authors argue that these differences arise mainly from the differential use of prompts and how the items are phrased and scored. Bifactor analysis demonstrated that although both measures capture a broad range of cognitive functioning (e.g., working memory, social cognition), the common variance on each is overwhelmingly explained by a single general factor. Item response theory analyses of the combined pool of 41 items showed that measurement precision is peaked in the mild to moderate range of cognitive impairment. Finally, simulated adaptive testing revealed that only about 10 to 12 items are necessary to achieve latent trait level estimates with reasonably small standard errors for most individuals. This suggests that these interview-based measures of cognitive deficits could be shortened without loss of measurement precision.     

Lidocaine attenuates anisomycin-induced amnesia and release of norepinephrine in the amygdala

When administered near the time of training, protein synthesis inhibitors such as anisomycin impair later memory. A common interpretation of these findings is that memory consolidation requires new protein synthesis initiated by training. However, recent findings support an alternative interpretation that abnormally large increases in neurotransmitter release after injections of anisomycin may be responsible for producing amnesia. In the present study, a local anesthetic was administered prior to anisomycin injections in an attempt to mitigate neurotransmitter actions and thereby attenuate the resulting amnesia. Rats received lidocaine and anisomycin injections into the amygdala 130 and 120 min, respectively, prior to inhibitory avoidance training. Memory tests 48 h later revealed that lidocaine attenuated anisomycin-induced amnesia. In other rats, in vivo microdialysis was performed at the site of amygdala infusion of lidocaine and anisomycin. As seen previously, anisomycin injections produced large increases in release of norepinephrine in the amygdala. Lidocaine attenuated the anisomycin-induced increase in release of norepinephrine but did not reverse anisomycin inhibition of protein synthesis, as assessed by c-Fos immunohistochemistry. These findings are consistent with past evidence suggesting that anisomycin causes amnesia by initiating abnormal release of neurotransmitters in response to the inhibition of protein synthesis.     

Imagining the future: degraded representations of future rewards and events in schizophrenia

Over the course of life, most people work toward temporally distant rewards such as university degrees or work-related promotions. In contrast, many people with schizophrenia show deficits in behavior oriented toward long-term rewards, although they function adequately when rewards are more immediately present. Moreover, when asked about possible future events, individuals with schizophrenia show foreshortened future time perspectives relative to healthy individuals. Here, we take the view that these deficits are related and can be explained by cognitive deficits. We compared the performance of participants with schizophrenia (n = 39) and healthy participants (n = 25) on tasks measuring reward discounting and future event representations. Consistent with previous research, we found that relative to healthy participants, those with schizophrenia discounted the value of future rewards more steeply. Furthermore, when asked about future events, their responses were biased toward events in the near future, relative to healthy participants' responses. Although discounting and future representations were unrelated in healthy participants, we found significant correlations across the tasks among participants with schizophrenia, as well as correlations with cognitive variables and symptoms. Further analysis showed that statistically controlling working memory eliminated group differences in task performance. Together these results suggest that the motivational deficits characteristic of schizophrenia relate to cognitive deficits affecting the ability to represent and/or evaluate distant outcomes, a finding with important implications for promoting recovery from schizophrenia.