Memory Age-based Stereotype Threat: Role of Locus of Control and Anxiety.

Background: Age-related stereotype threat impacts episodic memory performance. This study compared the predictors of memory performance in older adults with and without exposure to age-related stereotype threat, hypothesizing that activating the stereotype threat modulates the relative weight of metamemory predictors of memory performance.Methods: Participants were 80 older adults (aged 60-84 years) divided into two groups, one with stereotype threat activation and one without; both groups performed an episodic memory task. To activate the stereotype threat, the memory component of the task was emphasized in the instruction given to the threatened group. Both groups also completed two scales of the MIA questionnaire (locus of control and anxiety) to identify potential predictors of memory performance.Results: Results indicated that the non-threatened group performed better than the threatened group on the episodic memory task. They also indicated that factors predicting episodic memory performance varied according to the group. In the non-threatened group, both control and anxiety were involved in memory performance and interacted whereas in the threatened group only anxiety was involved.Conclusion: This study confirms that aging stereotype threat impairs episodic memory performance; it also suggests that stereotype threat disrupts mechanisms underlying memory performance abolishing the role of control over memory regardless of the level of anxiety.

Profiling the onset of somatic embryogenesis in Arabidopsis.

BACKGROUND: Totipotency is the ability of a cell to regenerate a whole organism. Plant somatic embryogenesis (SE) is a remarkable example of totipotency because somatic cells reverse differentiation, respond to an appropriate stimulus and initiate embryo development. Although SE is an ideal system to investigate de-differentiation and differentiation, we still lack a deep molecular understanding of the phenomenon due to experimental restraints. RESULTS: We applied the INTACT method to specifically isolate the nuclei of those cells undergoing SE among the majority of non-embryogenic cells that make up a callus. We compared the transcriptome of embryogenic cells to the one of proliferating callus cells. Our analyses revealed that embryogenic cells are transcriptionally rather than metabolically active. Embryogenic cells shut off biochemical pathways involved in carbohydrate and lipid metabolism and activate the transcriptional machinery. Furthermore, we show how early in SE, ground tissue and leaf primordia specification are switched on before the specification of a shoot apical meristem. CONCLUSIONS: This is the first attempt to specifically profile embryogenic cells among the different cell types that constitute plant in vitro tissue cultures. Our comparative analyses provide insights in the gene networks regulating SE and open new research avenues in the field of plant regeneration.

Live imaging of DORNRÖSCHEN and DORNRÖSCHEN-LIKE promoter activity reveals dynamic changes in cell identity at the microcallus surface of Arabidopsis embryonic suspensions.

KEY MESSAGE : Transgenic DRN::erGFP and DRNL::erGFP reporters access the window from explanting Arabidopsis embryos to callus formation and provide evidence for the acquisition of shoot meristem cell fates at the microcalli surface. The DORNRÖSCHEN (DRN) and DORNRÖSCHEN-LIKE (DRNL) genes encode AP2-type transcription factors, which are activated shortly after fertilisation in the zygotic Arabidopsis embryo. We have monitored established transgenic DRN::erGFP and DRNL::erGFP reporter lines using live imaging, for expression in embryonic suspension cultures and our data show that transgenic fluorophore markers are suitable to resolve dynamic changes of cellular identity at the surface of microcalli and enable fluorescence-activated cell sorting. Although DRN::erGFP and DRNL::erGFP are both activated in surface cells, their promoter activity marks different cell identities based on real-time PCR experiments and whole transcriptome microarray data. These transcriptome analyses provide no evidence for the maintenance of embryogenic identity under callus-inducing high-auxin tissue culture conditions but are compatible with the acquisition of shoot meristem cell fates at the surface of suspension calli.

[Episodic memory, frontal functioning, and aging]. / Mémoire épisodique, fonctionnement frontal et vieillissement.

Episodic memory is commonly defined as the kind of memory that renders possible conscious recollection of personal happenings and events from one's personal past. Although it is classically assumed that episodic memory is subserved by a distinct neurocognitive system including mediotemporal cortex and hippocampus, recent evidence also supports the idea of a close relationship between episodic memory and frontal cortex. This view assumes that the frontal cortex plays a critical supervisory role in empowering encoding and retrieval episodic memory operations. In recent years, this view had significantly influenced research in the field of normal memory aging. Indeed, different data have highlighted that age-related cognitive differences, most particularly age-related memory differences, might be explained by the decline of executive-frontal functioning that accompanies aging. In this article, we provide studies on aging and episodic memory that, in support of the executive hypothesis of aging episodic memory, have provided evidence that age-related differences in strategies implemented at encoding and retrieval in this type of memory are mediated by the executive functioning difficulties of older adults.

Genome-wide transcriptome profiling of the early cadmium response of Arabidopsis roots and shoots.

Transcriptional regulation in response to cadmium treatment was investigated in both roots and leaves of Arabidopsis, using the whole genome CATMA microarray containing at least 24,576 independent probe sets. Arabidopsis plants were hydroponically treated with low (5 microM) or high (50 microM) cadmium concentrations during 2, 6, and 30 hours. At each time point, Cd level was determined using ICP-AES showing that both plant tissues are able to accumulate the heavy metal. RT-PCR of eight randomly selected genes confirmed the reliability of our microarray results. Analyses of response profiles demonstrate the existence of a regulatory network that differentially modulates gene expression in a tissue- and kinetic-specific manner in response to cadmium. One of the main response observed in roots was the induction of genes involved in sulfur assimilation-reduction and glutathione (GSH) metabolism. In addition, HPLC analysis of GSH and phytochelatin (PC) content shows a transient decrease of GSH after 2 and 6 h of metal treatment in roots correlated with an increase of PC contents. Altogether, our results suggest that to cope with cadmium, plants activate the sulfur assimilation pathway by increasing transcription of related genes to provide an enhanced supply of GSH for PC biosynthesis. Interestingly, in leaves an early induction of several genes encoding enzymes involved in the biosynthesis of phenylpropanoids was observed. Finally, our results provide new insights to understand the molecular mechanisms involved in transcriptional regulation in response to cadmium exposure in plants.

Aging and encoding in memory: false alarms and decision criteria in a word-pair recognition task.

Employing a false alarm recognition procedure with learning of highly associated word pairs, an experiment was conducted to examine the hypothesis of an age-related deficit in the distinctiveness of encoding. The evolution of the false alarm rate and of the C decision criteria was observed across three age groups, young adults, older adults, and older-older adults. The results show 1) no age differences on C decision criteria, indicating that the increase in FA with age is not related to a subject compensation strategy but is probably due to a failure in memory strength, and 2) that older respondents produced significantly more false alarms to distractors related to target items than the young respondents did but that they did not differ in their false alarm rate for unrelated distractors. This finding is interpreted as supporting the hypothesis of a failure with age to encode target items in a sufficiently elaborate or distinctive fashion. For the older-older respondents the data showed an increase in all false alarms indexes, suggesting that the encoding deficit gets worse in late adulthood.