55 resultados para shape memory effect
Resumo:
In general, fiscal adjustments are associated with significant reductions in social spending. Hence, the welfare state is not spared from austerity. Because the welfare state is still central to party competition, this is electorally risky. The paper addresses the following questions: Do left parties differ from their centrist and rightist competitors in the design of austerity measures? And does government type has an impact on the extent to which austerity policies rely on social spending cuts? By comparing 17 OECD countries between 1982 and 2009 we show that if governments embark on a path to austerity, their ideology does not have a significant effect on the magnitude of welfare state retrenchment. However, if major opposition parties and interest groups rally against social spending cuts, a broad pro-reform coalition is a crucial precondition for large fiscal consolidation programs to rely on substantial cuts to social security.
Resumo:
Background: Semantic memory processes have been well described in literature. However, the available findings are mostly based on relatively young subjects and concrete word material (e.g. tree). Comparatively little information exists about semantic memory for abstract words (e.g. mind) and possible age related changes in semantic retrieval. In this respect, we developed a paradigm that is useful to investigate the implicit (i.e. attentionindependent) access to concrete and abstract semantic memory. These processes were then compared between young and elderly healthy subjects. Methods: A well established tool for investigating semantic memory processes is the semantic priming paradigm, which consists both of semantically unrelated and related word pairs. In our behavioral task these noun-noun word pairs were further divided into concrete, abstract and matched pronounceable non-word conditions. With this premise, the young and elderly participants performed a lexical decision task: they were asked to press a choice of two buttons as an indication for whether the word pair contained a non-word or not. In order to minimize controlled (i.e. attention-dependent) retrieval strategies, a short stimulus onset asynchrony (SOA) of 150ms was set. Reaction time (RT) changes and accuracy to related and unrelated words (priming effect) in the abstract vs. concrete condition (concreteness effect) were the dependent variables of interest. Results and Discussion: Statistical analysis confirmed both a significant priming effect (i.e. shorter RTs in semantically related compared to unrelated words) and a concreteness effect (i.e. RT decrease for concrete compared to abstract words) in the young and elderly subjects. There was no age difference in accuracy. The only age effect was a commonly known general slowing in RT over all conditions. In conclusion, age is not a critical factor in the implicit access to abstract and concrete semantic memory.
Resumo:
Pneumococcal meningitis is associated with high morbidity and mortality rates. Brain damage caused by this disease is characterized by apoptosis in the hippocampal dentate gyrus, a morphological correlate of learning deficits in experimental paradigms. The mood stabilizer lithium has previously been found to attenuate brain damage in ischemic and inflammatory diseases of the brain. An infant rat model of pneumococcal meningitis was used to investigate the neuroprotective and neuroregenerative potential of lithium. To assess an effect on the acute disease, LiCl was administered starting five days prior to intracisternal infection with live Streptococcus pneumoniae. Clinical parameters were recorded, cerebrospinal fluid (CSF) was sampled, and the animals were sacrificed 42 hours after infection to harvest the brain and serum. Cryosections of the brains were stained for Nissl substance to quantify brain injury. Hippocampal gene expression of Bcl-2, Bax, p53, and BDNF was analyzed. Lithium concentrations were measured in serum and CSF. The effect of chronic lithium treatment on spatial memory function and cell survival in the dentate gyrus was evaluated in a Morris water maze and by quantification of BrdU incorporation after LiCl treatment during 3 weeks following infection. In the hippocampus, LiCl significantly reduced apoptosis and gene expression of Bax and p53 while it increased expression of Bcl-2. IL-10, MCP-1, and TNF were significantly increased in animals treated with LiCl compared to NaCl. Chronic LiCl treatment improved spatial memory in infected animals. The mood stabilizer lithium may thus be a therapeutic alternative to attenuate neurofunctional deficits as a result of pneumococcal meningitis.
Resumo:
Recently, many studies about a network active during rest and deactivated during tasks emerged in the literature: the default mode network (DMN). Spatial and temporal DMN features are important markers for psychiatric diseases. Another prominent indicator of cognitive functioning, yielding information about the mental condition in health and disease, is working memory (WM) processing. In EEG studies, frontal-midline theta power has been shown to increase with load during WM retention in healthy subjects. From these findings, the conclusion can be drawn that an increase in resting state DMN activity may go along with an increase in theta power in high-load WM conditions. We followed this hypothesis in a study on 17 healthy subjects performing a visual Sternberg WM task. The DMN was obtained by a BOLD-ICA approach and its dynamics represented by the percent-strength during pre-stimulus periods. DMN dynamics were temporally correlated with EEG theta spectral power from retention intervals. This so-called covariance mapping yielded the spatial distribution of the theta EEG fluctuations associated with the dynamics of the DMN. In line with previous findings, theta power was increased at frontal-midline electrodes in high- versus low-load conditions during early WM retention. However, load-dependent correlations of DMN with theta power resulted in primarily positive correlations in low-load conditions, while during high-load conditions negative correlations of DMN activity and theta power were observed at frontal-midline electrodes. This DMN-dependent load effect reached significance during later retention. Our results show a complex and load-dependent interaction of pre-stimulus DMN activity and theta power during retention, varying over the course of the retention period. Since both, WM performance and DMN activity, are markers of mental health, our results could be important for further investigations of psychiatric populations.
Resumo:
Recently, multiple studies showed that spatial and temporal features of a task-negative default mode network (DMN) (Greicius et al., 2003) are important markers for psychiatric diseases (Balsters et al., 2013). Another prominent indicator of cognitive functioning, yielding information about the mental condition in health and disease, is working memory (WM) processing. In EEG and MEG studies, frontal-midline theta power has been shown to increase with load during WM retention in healthy subjects (Brookes et al., 2011). Negative correlations between DMN activity and theta amplitude have been found during resting state (Jann et al., 2010) as well as during WM (Michels et al., 2010). Likewise, WM training resulted in higher resting state theta power as well as increased small-worldness of the resting brain (Langer et al., 2013). Further, increased fMRI connectivity between nodes of the DMN correlated with better WM performance (Hampson et al., 2006). Hence, the brain’s default state might influence it’s functioning during task. We therefore hypothesized correlations between pre-stimulus DMN activity and EEG-theta power during WM maintenance, depending on the WM load. 17 healthy subjects performed a Sternberg WM task while being measured simultaneously with EEG and fMRI. Data was recorded within a multicenter-study: 12 subjects were measured in Zurich with a 64-channels MR-compatible system (Brain Products) in a 3T Philips scanner, 5 subjects with a 96-channel MR-compatible system (Brain Products) in a 3T Siemens Scanner in Bern. The DMN components was obtained by a group BOLD-ICA approach over the full task duration (figure 1). The subject-wise dynamics were obtained by back-reconstructed onto each subject’s fMRI data and normalized to percent signal change values. The single trial pre-stimulus-DMN activation was then temporally correlated with the single trial EEG-theta (3-8 Hz) spectral power during retention intervals. This so-called covariance mapping (Jann et al., 2010) yielded the spatial distribution of the theta EEG fluctuations during retention associated with the dynamics of the pre-stimulus DMN. In line with previous findings, theta power was increased at frontal-midline electrodes in high- versus low-load conditions during early WM retention (figure 2). However, correlations of DMN with theta power resulted in primarily positive correlations in low-load conditions, while during high-load conditions negative correlations of DMN activity and theta power were observed at frontal-midline electrodes. This DMN-dependent load effect reached significance in the middle of the retention period (TANOVA, p<0.05) (figure 3). Our results show a complex and load-dependent interaction of pre-stimulus DMN activity and theta power during retention, varying over time. While at a more global, load-independent view pre-stimulus DMN activity correlated positively with theta power during retention, the correlation was inversed during certain time windows in high-load trials, meaning that in trials with enhanced pre-stimulus DMN activity theta power decreases during retention. Since both WM performance and DMN activity are markers of mental health our results could be important for further investigations of psychiatric populations.
Resumo:
BACKGROUND Cognitive problems can have a negative effect on a person's education, but little is known about cognitive problems in young childhood cancer survivors (survivors). This study compared cognitive problems between survivors and their siblings, determined if cognitive problems decreased during recent treatment periods and identified characteristics associated with the presence of a cognitive problem in survivors. METHODS As part of the Swiss Childhood Cancer Survivor Study, a questionnaire was sent to all survivors, aged 8-20 years, registered in the Swiss Childhood Cancer Registry, diagnosed at age <16 years, who had survived ≥5 years. Parent-reported (aged 8-15 years) and self-reported (aged 16-20 years) cognitive problems (concentration, working speed, memory) were compared between survivors and siblings. Multivariable logistic regression was used to identify characteristics associated with cognitive problems in survivors. RESULTS Data from 840 survivors and 247 siblings were analyzed. More often than their siblings, survivors reported problems with concentration (12% vs. 6%; P = 0.020), slow working speed (20% vs. 8%; P = 0.001) or memory (33% vs. 15%; P < 0.001). Survivors from all treatment periods were more likely to report a cognitive problem than were siblings. Survivors of CNS tumors (OR = 2.82 compared to leukemia survivors, P < 0.001) and those who had received cranial irradiation (OR = 2.10, P = 0.010) were most severely affected. CONCLUSION Childhood cancer survivors, even those treated recently (2001-2005), remain at risk to develop cognitive problems, suggesting a need to improve therapies. Survivors with cognitive problems should be given the opportunity to enter special education programs. Pediatr Blood Cancer © 2014 Wiley Periodicals, Inc.
Resumo:
A large body of research suggests that when we retrieve visual information from memory, we look back to the location where we encoded these objects. It has been proposed that the oculomotor trace we act out during encoding is stored in long-term memory, along other contents of the episodic representation. If memory recall triggers the eyes to revisit the location where the stimulus was encoded, is there also an effect in the reverse direction? Can eye movements trigger memory recall? In Experiment 1 participants encoded two faces at two different locations on the computer screen. Then, the average face (morph) of these two faces appeared in either of the two encoding locations and participants had to indicate whether it resembles more the first or second face. In Experiment 2 the morph appeared in a new location, but participants had to repeat one of the oculomotor traces that was used during encoding. Participants’ morph perception was influenced both by the location and the eye-movement it was presented with. Our results suggest that eye-movements can bias memory recall, but only in a short-lasting and rather fragile way.
Resumo:
Introduction. Erroneous answers in studies on the misinformation effect (ME) can be reduced in different ways. In some studies, ME was reduced by SM questions, warnings, or a low credibility of the source of post-event information (PEI). Results are inconsistent, however. Of course, a participant can deliberately decide to refrain from reporting a critical item only when the difference between the original event and the PEI is distinguishable in principle. We were interested in the question to what extent the influence of erroneous information on a central aspect of the original event can be reduced by different means applied singly or in combination. Method. With a 2 (credibility; high vs. low) x 2 (warning; present vs. absent) between subjects design and an additional control group that received neither misinformation nor a warning (N = 116), we examined the above-mentioned factors’ influence on the ME. Participants viewed a short video of a robbery. The critical item suggested in the PEI was that the victim was given a kick by the perpetrator (which he was actually not). The memory test consisted of a two-forced-choice recognition test followed by a SM test. Results. To our surprise, neither a main effect of erroneous PEI nor a main effect of credibility was found. The error rates for the critical item in the control group (50%) as well as in the high (65%) and low (52%) credibility condition without warning did not significantly differ. A warning about possible misleading information in the PEI significantly reduced the influence of misinformation in both credibility conditions by 32-37%. Using a SM question significantly reduced the error rate too, but only in the high credibility no warning condition. Conclusion and Future Research. Our results show that, contrary to a warning or the use of a SM question, low source credibility did not reduce the ME. The most striking finding was, however, the absence of a main effect of erroneous PEI. Due to the high error rate in the control group, we suspect that the wrong answers might have been caused either by the response format (recognition test) or by autosuggestion possibly promoted by the high schema-consistency of the critical item. First results of a post-study in which we used open-ended questions before the recognition test support the former assumption. Results of a replication of this study using open-ended questions prior to the recognition test will be available by June.
Resumo:
According to the intention superiority effect, people remember more future intentions than past events. Moreover, several studies have shown a facilitation of retrieving positive compared to negative or neutral events. The aim of the present study was to investigate the influence of age on the intention superiority effect for positive, negative and neutral events. We asked a group of young and a group of older adults to report their future intentions and their memories of past events from a specific time-window (i.e., day, week or year). Additionally, we prompted them to rate each intention/memory as positive, negative or neutral. The results showed more positive than negative or neutral future and past events in both age-groups and more negative events of young adults compared with reported negative events of older adults. Critically, there was an intention superiority effect for positive events in both age-groups, but only in the “year” time-window. These results suggest that the retrieval of positive future events is facilitated, at least for a large time-perspective, and independent of age-effects.
Resumo:
Prospective memory (ProM) is the ability to remember and perform an intention in the future. If a prospective memory task is to be performed only once, it is episodic. If it is repeated, then it becomes habitual. Thus, with repetition, a task changes from episodic to habitual. The goal of this study was to investigate the transition from episodic to habitual prospective memory with event-related potentials (ERP). The ProM task was to respond to a target word which was embedded in an ongoing lexical decision task. 40 ProM trials were administered in each of two sessions that were separated by a week. The results revealed a behavioural consolidation effect with increased ProM performance after one week. The ERP-analyses showed that when the task became more habitual a difference occurred in a time-window between 450-650 ms post-stimulus in an ERP-component. In addition, a covariance analysis revealed that this transition is continued in the second session. These results demonstrate that the transition from episodic to habitual prospective memory is long-lasting and continuous.
Resumo:
The current study was designed to test for the effect of lateralized attention on prospective memory performance in a dichotic listening task. The practice phase of the experiment consisted of a semantic decision task during which the participants were presented with different words on either side via headphones. Depending on the experimental condition the participants were required to focus on the words presented on the left or right side and to decide if these words were abstract or concrete. Thereafter, the participants were informed about the prospective memory task. They were instructed to press a distinct key whenever they hear a word which denotes an animal in the same task later during the experiment. The participants were explicitly informed that the prospective memory cues could appear on either side of the headphones. This was followed by a retention interval which was filled with unrelated tasks. Next, the participants performed the prospective memory task. The results revealed more prospective hits for the attended side. The finding suggests that noticing a prospective memory cue is not an automatic process but requires attention.
Resumo:
Succeeding in everyday activities often requires executive functioning (EF), metacognitive abilities (MC) and memory skills such as prospective memory (PM) and retrospective memory (RM). These cognitive abilities seem to gradually develop in childhood, possibly influencing each other during development. From a theoretical point of view, it is likely that they are closely interrelated, especially in children. Their empirical relation, however, is less clear. A model that links these cognitive abilities can help to better understand the relation between PM and RM and other cognitive processes. In this project we studied the longitudinal development of PM, RM, EF, and MC in 7-8 year old elementary school children across half a year. 119 second graders (MT1 = 95 months, SDT1, = 4.8 months) completed the same PM, RM, EF and MC tasks twice with a time-lag of 7 months. The developmental progression was analysed using paired t-tests, the longitudinal relationships were analysed using confirmatory factor analysis and all fit indices are in accordance with Hu and Bentler (1998). In general, performance improved significantly (ps < .001) and effect sizes ranged from .45 to .62 (Cohen’s d). CFA revealed a good model fit, c2(227, 119) = 242.56, p = .23, TLI = .973, CFI = .979, RMSEA = .024. At T1, significant cross-sectional links were found between PM T1 and RM T1, between PM T1 and EF T1, and between EF T1 and MC T1. Moreover, significant longitudinal links were found between EFT1 and PMT2 and between EFT1 and MCT2; EF T1 and RM T2 were marginally linked. Results underline previous findings showing that PM, RM, EF, and MC develop significantly during childhood, even within this short time period. Results also indicate that these cognitive abilities are linked not only cross-sectionally, but longitudinally. Most relevant, however, is the predictive role of EF for both metacognition and memory.
Resumo:
Studies of memory-guided saccades in monkeys show an upward bias, while studies of antisaccades in humans show a diagonal effect, a deviation of endpoints toward the 45° diagonal. To determine if these two different spatial biases are specific to different types of saccades, we studied prosaccades, antisaccades and memory-guided saccades in humans. The diagonal effect occurred not with prosaccades but with antisaccades and memory-guided saccades with long intervals, consistent with hypotheses that it originates in computations of goal location under conditions of uncertainty. There was a small upward bias for memory-guided saccades but not prosaccades or antisaccades. Thus this bias is not a general effect of target uncertainty but a property specific to memory-guided saccades.
Resumo:
In prospective memory tasks different kinds of load can occur. Adding a prospective memory task can impose a load on ongoing task performance. Adding ongoing task load (OTL) can affect prospective memory performance. The existence of multiple target events increases prospective load (PL) and adding complexity to the to-be-remembered action increases retrospective load (RL). In two experiments, we systematically examined the effects of these different types of load on prospective memory performance. Results showed an effect of PL on costs in the ongoing task for categorical targets (Experiment 2), but not for specific targets (Experiment 1). RL and OTL both affected remembering the retrospective component of the prospective memory task. We suggest that PL can enhance costs in the ongoing task due to additional monitoring requirements. RL and OTL seem to impact the division of resources between the ongoing task and retrieval of the retrospective component, which may affect disengagement from the ongoing task. In general, the results demonstrate that the different types of load affect prospective memory differentially.