Observed Age Differences Research Articles

Female Rat Behavior Effects from Low Levels of Hexavalent Chromium (Cr[VI]) in Drinking Water Evaluated with a Toxic Aging Coin Approach

We are facing a critical aging crisis, with geriatric populations (65+) growing to unprecedented proportions and ~4 million people (a 6.5-fold increase) expected to become centenarians by 2050. This is compounded by environmental pollution, which affects individuals of all ages and contributes to age-related diseases. As we have a limited understanding of how environmental pollutants affect older populations distinctly from younger populations, these longer-lived geriatric populations present a key knowledge gap. To address this knowledge gap, we employ a “Toxic Aging Coin” approach: heads consider how age impacts chemical toxicity, and tails consider how chemicals act as gerontogens—or how they accelerate biological aging. We employed this approach to investigate hexavalent chromium (Cr[VI]) impacts on female rats exposed to 0.05 or 0.1 mg Cr(VI)/L in drinking water for 90 days; these are the maximum contaminant levels (i.e., the highest levels permitted) from the World Health Organization and U.S. Environmental Protection Agency, respectively. During exposure, rats performed a battery of behavior assays to assess grip strength, locomotor coordination, anxiety, spatial memory, sociability, and social novelty preference. We observed age differences in Cr(VI) neurotoxicity, with grip strength, locomotor function, and spatial memory in middle-aged females being particularly affected. We further compared these results in females to results in males, noting many sex differences, especially in middle-aged rats. These data emphasize the need to consider age and sex as variables in toxicology and to revisit drinking water regulations for Cr(VI).

Semantic details in autobiographical memory narratives increase with age among younger adults

ABSTRACT It is well documented that older adults, compared to younger adults, produce fewer episodic details and more semantic details when recalling autobiographical memories. However, group comparisons have provided limited insight into the trajectories of detail generation across the lifespan. Utilising an open source dataset [Clark, I. A., & Maguire, E. A. (2023). Release of cognitive and multimodal MRI data including real-world tasks and hippocampal subfield segmentations. Scientific Data, 10(1), 1–29. https://doi.org/10.1038/s41597-022-01899-x], we examined how episodic and semantic detail generation varied with age among 194 younger adults, ages 20-41. We tested whether age differences were mediated by hippocampal subfield volumes and MTL resting-state functional connectivity. Results indicated that semantic details increased with age, while episodic details remained stable. We observed age differences in hippocampal subfield volumes and MTL connectivity, but these measures did not mediate age effects on semantic detail. Based on these and prior findings [Matijevic, S., Andrews-Hanna, J. R., Wank, A. A., Ryan, L., & Grilli, M. D. (2022). Individual differences in the relationship between episodic detail generation and resting state functional connectivity vary with age. Neuropsychologia, 166, 108138. https://doi.org/10.1016/j.neuropsychologia.2021.108138], we suggest a model of diverging episodic and semantic detail generation trajectories across the adult lifespan.

Distress Signals: Age Differences in Psychological Distress before and during the COVID-19 Pandemic.

Psychological distress reached historically high levels in 2020, but why, and why were there pronounced age differences? We address these questions using a relatively novel, multipronged approach, part narrative review and part new data analyses. We first updated previous analyses of national surveys that showed distress was increasing in the US and Australia through 2017 and then re-analyzed data from the UK, comparing periods with and without lockdowns. We also analyzed the effects of age and personality on distress in the US during the pandemic. Results showed distress levels and age differences in distress were still increasing through 2019 in the US, UK, and Australia. The effects of lockdowns in 2020 revealed the roles of social deprivation and fear of infection. Finally, age-related differences in emotional stability accounted for the observed age differences in distress. These findings reveal the limitations of analyses comparing pre-pandemic and pandemic periods without accounting for ongoing trends. They also suggest that differences in personality traits such as emotional stability modulate responses to stressors. This could explain age and individual differences in both increases and decreases in distress in response to changes in the level of stressors such as those occurring prior to and during the COVID-19 pandemic.

Association of monocyte/high-density lipoprotein cholesterol ratio and the carotid intima-media thickness in diabetic patients

ObjectivesThe goal of this study was to see whether there was a link between the monocyte/high-density lipoprotein cholesterol ratio (MHR) and carotid intima-media thickness (CIMT) in people with type 2 diabetes.MethodsDuplex ultrasonography parameters and demographic, physical, and paraclinical assessments were recorded. Using the t-test, the MHR and CIMT were compared between the two groups. Regression models were also constructed.ResultsA total of 118 diabetics and 126 non-diabetics were included in the cross-sectional research. According to the stated diabetes duration, the observed age difference of 7 years might be considered. The MHR and CIMT were not substantially different between the two groups. In the DM and non-DM groups, the Spearman correlations between MHR and CIMT were 0.32 and − 0.08, respectively (p-values = 0.001 and 0.379). Thus, regression models (stratified for DM/non-DM and male/female) revealed that the MHR is a significant predictor of CIMT, but only in the case of male DM individuals, when crudely adjusted for confounders.ConclusionsIn diabetes mellitus, the current investigation found a direct link between MHR and CIMT. In addition, in male diabetic subjects, MHR was demonstrated to be a predictor of CIMT.

Chronostratigraphic and geomorphologic challenges of last glacial loess in Poland in the light of new luminescence ages

Abstract. The aim of this study is to check the validity of luminescence ages obtained from last glacial–interglacial Polish loess palaeosol sequences (LPSs) by several established current protocols, with respect to sound geomorphological and chronostratigraphic interpretations. We report 38 new optically stimulated luminescence (OSL) ages from fine-grained (4–11 µm) quartz separates extracted from four loess palaeosol sequences in Poland, measured in the Bayreuth Luminescence Laboratory, Germany. The investigated sections are situated in Lower Silesia in the southwest (Zaprężyn, Trzebnica Hills, and Biały Kościół, Strzelin Hills), the Sandomierz Upland (Złota) in central Poland, and the Volhynian Upland (Tyszowce) in the east, allowing for regional comparison. From one Silesian section (Biały Kościół) 12 new post-infrared infrared stimulated luminescence (pIRIR) ages are presented in addition to the quartz ages of identical sample material. The obtained ages are compared to already published independently elaborated middle-grain (45–63 µm) and coarse-grain (90–125 µm) quartz ages and pIRIR ages from fine grains produced in the Gliwice Luminescence Laboratory (Poland). This comparison shows that in many cases the middle- and coarse-grain quartz ages underestimate the fine-grain quartz ages, but a general rule has not been able to be established so far, likely due to different geological origin of the quartz grains. Even fine-grain quartz ages ≥∼ 50 ka may be underestimated with respect to lithostratigraphic expectations. For pIRIR ages, however, no evidence for age underestimates has been found in the studied sections, but they are more easily prone to age overestimates due to unknown residual doses at deposition in a periglacial environment. Basic agreement between the luminescence-based chronologies elaborated in the two involved laboratories can be stated for the first time in contrast to other previous studies. The observed age differences are, however, critical for the accurate time bracketing of geomorphologic and pedostratigraphic features such as ice wedging, thermokarst erosion events, and interstadial soil formations and for their attribution to marine isotope stages. Alternative interpretations are discussed including possible periglacial mirroring of pre-LGM ice advances (Ristinge and Klintholm advances) in the southwestern Baltic Sea area. The uncertainty in luminescence ages from pre-Holocene loess due to fossil ice during permafrost conditions is the major systematic error source which will be addressed but at present is far from an unambiguous solution. The present study focuses on a complex of interstadial soils now labelled L1SS1 and on harsh periglacial climate afterwards and before, yielding some unexpected results for the timing of ice wedging and thermokarst processes. In order not to leave the users alone with the decision about the most credible dating, the suggested way forwards is to simultaneously apply various luminescence dating protocols including different quartz grain sizes and pIRIR from fine polymineral grains, as an honest approach to reliable time bracketing of geomorphological processes and stratigraphic events under debate. A refinement of this approach remains challenging as far as the sole reliable dating protocol is not ensured.

Seizing the opportunity: Lifespan differences in the effects of the opportunity cost of time on cognitive control

Previous work suggests that lifespan developmental differences in cognitive control reflect maturational and aging-related changes in prefrontal cortex functioning. However, complementary explanations exist: It could be that children and older adults differ from younger adults in how they balance the effort of engaging in control against its potential benefits. Here we test whether the degree of cognitive effort expenditure depends on the opportunity cost of time (average reward rate per unit time): if the average reward rate is high, participants should withhold cognitive effort whereas if it is low, they should invest more. In Experiment 1, we examine this hypothesis in children, adolescents, younger, and older adults, by applying a reward rate manipulation in two cognitive control tasks: a modified Erikson Flanker and a task-switching paradigm. We found that young adults and adolescents reflexively withheld effort when the opportunity cost of time was high, whereas older adults and, to a lesser degree children, invested more resources to accumulate reward as quickly as possible. We tentatively interpret these results in terms of age- and task-specific differences in the processing of the opportunity cost of time. We qualify our findings in a second experiment in younger adults in which we address an alternative explanation of our results and show that the observed age differences in effort expenditure may not result from differences in task difficulty.To conclude, we think that our results present an interesting first step at relating opportunity costs to motivational processes across the lifespan. We frame the implications of further work in this area within a recent developmental model of resource-rationality, which points to developmental sweet spots in cognitive control.

Associative memory persistence in 3- to 5-year-olds.

Adults struggle to recollect episodic memories from early life. This phenomenon-referred to as "infantile" and "childhood amnesia"-has been widely observed across species and is characterized by rapid forgetting from birth until early childhood. While a number of studies have focused on infancy, few studies have examined the persistence of memory for newly learned associations during the putative period of childhood amnesia. In this study, we investigated forgetting in 137 children ages 3-5years old by using an interactive storybook task. We assessed associative memory between subjects after 5-min, 24-h, and 1-week delay periods. Across all delays, we observed a significant increase in memory performance with age. While all ages demonstrated above-chance memory performance after 5-min and 24-h delays, we observed chance-level memory accuracy in 3-year-olds following a 1-week delay. The observed age differences in associative memory support the proposal that hippocampal-dependent memory systems undergo rapid development during the preschool years. These data have the potential to inform future work translating memory persistence and malleability research from rodent models to humans by establishing timescales at which we expect young children to forget newly learned associations.

Human aging alters social inference about others’ changing intentions

Decoding others’ intentions accurately in order to adapt one's own behavior is pivotal throughout life. In this study, we asked how younger and older adults deal with uncertainty in dynamic social environments. We used an advice-taking paradigm together with Bayesian modeling to characterize effects of aging on learning about others’ time-varying intentions. We observed age differences when comparing learning on two levels of social uncertainty: the fidelity of the adviser and the volatility of intentions. Older adults expected the adviser to change his/her intentions more frequently (i.e., a higher volatility of the adviser). They also showed higher confidence (i.e., precision) in their volatility beliefs and were less willing to change their beliefs about volatility over the course of the experiment. This led them to update their predictions about the fidelity of the adviser more quickly. Potentially indicative of stereotype effects, we observed that older advisers were perceived as more volatile, but also more faithful than younger advisers. This offers new insights into adult age differences in response to social uncertainty.

The GOGREEN survey: post-infall environmental quenching fails to predict the observed age difference between quiescent field and cluster galaxies at z > 1

ABSTRACT We study the star formation histories (SFHs) and mass-weighted ages of 331 UVJ-selected quiescent galaxies in 11 galaxy clusters and in the field at 1 < z < 1.5 from the Gemini Observations of Galaxies in Rich Early ENvironments (GOGREEN) survey. We determine the SFHs of individual galaxies by simultaneously fitting rest-frame optical spectroscopy and broad-band photometry to stellar population models. We confirm that the SFHs are consistent with more massive galaxies having on average earlier formation times. Comparing galaxies found in massive clusters with those in the field, we find galaxies with M* < 1011.3 M⊙ in the field have more extended SFHs. From the SFHs we calculate the mass-weighted ages, and compare age distributions of galaxies between the two environments, at fixed mass. We constrain the difference in mass-weighted ages between field and cluster galaxies to $0.31_{^{-0.33}}^{_{+0.51}}$ Gyr, in the sense that cluster galaxies are older. We place this result in the context of two simple quenching models and show that neither environmental quenching based on time since infall (without pre-processing) nor a difference in formation times alone can reproduce both the average age difference and relative quenched fractions. This is distinctly different from local clusters, for which the majority of the quenched population is consistent with having been environmentally quenched upon infall. Our results suggest that quenched population in galaxy clusters at z > 1 has been driven by different physical processes than those at play at z = 0.

Cognitive and Affective Theory of Mind in Healthy Aging

ABSTRACT Background Previous studies on the effect of healthy aging on Theory of Mind (ToM) have produced mixed results. A possible explanation may be that different ToM components and types of inference have not systematically been considered. This study examined the effect of aging on ToM by assessing both first and second order cognitive and affective components within a single task. Methods We compared performance of young (M = 18.3y) and older adults (M = 61.0y) on the Yoni task. This task allows for a within-subject assessment of both first and second order cognitive and affective ToM. Results We observed that older adults had longer reaction times than young adults across cognitive and affective first order items. For second order items, this age difference was larger for affective than cognitive items. Results showed no indications that these findings could be explained by age differences in speed/accuracy trade-offs. Conclusion Our findings suggest that decision processes underlying ToM are slower in older adults on both first and second order inferences, but that age differences in these processes between cognitive and affective ToM are selective to second order inferences. We propose that the observed age differences may be associated with cortical and mental changes that occur with aging.

Demographic Effects on Longitudinal Semantic Processing, Working Memory, and Cognitive Speed.

ObjectivesTo better understand and compare effects of aging and education across domains of language and cognition, we investigated whether (a) these domains show different associations with age and education, (b) these domains show similar patterns of age-related change over time, and (c) education moderates the rate of decline in these domains.MethodWe analyzed data from 306 older adults aged 55–85 at baseline of whom 116 returned for follow-up 4–8 years later. An exploratory factor analysis identified domains of language and cognition across a range of tasks. A confirmatory factor analysis analyzed cross-sectional associations of age and education with these domains. Subsequently, mixed linear models analyzed longitudinal change as a function of age and moderation by education.ResultsWe identified 2 language domains, that is, semantic control and semantic memory efficiency, and 2 cognitive domains, that is, working memory and cognitive speed. Older age negatively affected all domains except semantic memory efficiency, and higher education positively affected all domains except cognitive speed at baseline. In language domains, a steeper age-related decline was observed after age 73–74 compared to younger ages, while cognition declined linearly with age. Greater educational attainment did not protect the rate of decline over time in any domain.DiscussionSeparate domains show varying effects of age and education at baseline, language versus cognitive domains show dissimilar patterns of age-related change over time, and education does not moderate the rate of decline in these domains. These findings broaden our understanding of age effects on cognitive and language abilities by placing observed age differences in context.

Hierarchical Development of Early Visual-Spatial Abilities - A Taxonomy Based Assessment Using the MaGrid App.

Visual-spatial abilities (VSA) are considered a building block of early numerical development. They are intuitively acquired in early childhood and differentiate in further development. However, when children enter school, there already are considerable individual differences in children’s visual-spatial and numerical abilities. To better understand this diversity, it is necessary to empirically evaluate the development as well as the latent structure of early VSA as proposed by the 2 by 2 taxonomy of Newcombe and Shipley (2015). In the present study, we report on a tablet-based assessment of VSA using the digital application (app) MaGrid in kindergarten children aged 4–6 years. We investigated whether the visual-spatial tasks implemented in MaGrid are sensitive to replicate previously observed age differences in VSA and thus a hierarchical development of VSA. Additionally, we evaluated whether the selected tasks conform to the taxonomy of VSA by Newcombe and Shipley (2015) applying a confirmatory factor analysis (CFA) approach. Our results indicated that the hierarchical development of VSA can be measured using MaGrid. Furthermore, the CFA substantiated the hypothesized factor structure of VSA in line with the dimensions proposed in the taxonomy of Newcombe and Shipley (2015). Taken together, the present results advance our knowledge to the (hierarchical) development as well as the latent structure of early VSA in kindergarten children.

The same with age: Evidence for age-related similarities in interpersonal accuracy.

Interpersonal accuracy refers to the ability to make accurate perceptions about others' social and emotional qualities. Despite this broad definition, the measurement of interpersonal accuracy remains narrow, as most studies focus on the accurate perception of others' emotional states. Moreover, previous research has relied primarily upon traditional tasks consisting of posed, prototypic expressions and behaviors as stimuli. These methodological limitations may constrain our understanding of how different interpersonal perception skills change in adulthood. The present study investigated the extent to which various interpersonal perception skills are worse, better, or remain the same with age using both traditional and nontraditional interpersonal accuracy tasks. One hundred fifty-one adults from 3 age groups (young, middle age, and older) completed a battery of interpersonal accuracy tasks that assessed eight different emotion perception skills and six different social perception skills. Analyses revealed age-related differences in accuracy for five interpersonal perception skills; differences were typically observed between younger and older adults on emotion perception accuracy and between younger and middle-age adults on social perception accuracy. In contrast, almost all remaining interpersonal perception skills-both emotional and social-revealed greater evidence for age-related similarities than differences in Bayesian analyses. Additional exploratory analyses indicated that the observed age differences in interpersonal accuracy may be attributable to individual differences in cognitive ability rather than age. Results provide a nuanced picture of how interpersonal perception skills change in adulthood and provide new methodological tools for a more complete and comprehensive assessment of interpersonal accuracy. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Anatomy of Non-Employment Risk

Abstract This paper investigates how job separation and job-finding probabilities shape the non-employment risk across ages and working group characteristics. Improving on current methods, I estimate duration models for employment and non-employment separately. I then use the results to derive the individual age profiles of conditional transitions in and out of non-employment as well as the unconditional non-employment risk profile over the whole working life. This approach allows me to apply the decomposition of changes in individual non-employment risk. To date, this type of decomposition has only been used to study aggregate non-employment dynamics. I find that differences in job separation rates across ages underlie the observed age differences in non-employment risk. When differences between working groups are under consideration, the job finding probability is just as important as the job separation probability.

Age differences in everyday stressor-related negative affect: A coordinated analysis.

Advancing age is often characterized by preserved or even enhanced emotion regulation, which is thought to manifest in terms of age-related reductions in the within-person association between stressors and negative affect. Existing research from ecological momentary assessment and end-of-day daily diary studies examining such age-related benefits have yielded mixed results, potentially due to differences in samples, design, and measurement of everyday stressors and negative affect. We conducted a coordinated analysis of 5 ecological momentary assessments and 2 end-of-day daily diary studies to examine adult age differences in the within-person association between everyday stressors and negative affect. Reported stressor occurrences are robustly associated with higher negative affect, regardless of study design and sample characteristics. Across studies, interactions between age and everyday stressors predicting negative affect revealed a pattern of age-related decreases in the stressor-negative affect association, but this interaction was only significant for 2 studies. Further, examination of statistical power of the included studies suggests that, despite differences in the number of repeated assessments, power to detect within-person stressor-negative affect associations is quite good. In contrast, despite possessing wider age ranges, observed age differences were relatively small in magnitude, and studies are potentially underpowered to detect age differences in these within-person associations. We discuss the importance of study design, interval of repeated assessments and number of participants for examining age differences in everyday stressors and negative affect, as well as the virtue of coordinated analyses for detecting consistent direction of associations, but inconsistent patterns of statistical significance. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Changes in the spatial spread of attention with ageing

Spatial attention is a necessary cognitive process, allowing for the direction of limited capacity resources to varying locations in the visual field for improved visual processing. Thus, understanding how ageing influences these processes is vital. The current study explored the relationship between the spatial spread of attention and healthy ageing using an inhibition of return task to tap visual attention processing. This task allowed us to measure the spatial distribution of inhibition, and thus acted as a marker for attentional spread. Past research has indicated minimal age differences in inhibitory spread. However, these studies used placeholder stimuli, which may have restricted the range over which age differences could be reliably measured. To address this, in Experiment One, we measured the relationship between the spatial spread of inhibition and healthy ageing using a method which did not employ placeholders. In contrast to past research, an age difference in inhibitory spread was observed, where in comparison to younger adults, older adults exhibited a relatively restricted spread of attention. Experiment Two then confirmed these findings, by directly comparing inhibitory spread for placeholder present and placeholder absent conditions, across younger and older adults. Again, it was found that age differences in inhibitory spread emerged, but only in the placeholder absent condition. Possible reasons for the observed age differences in attention are discussed.

Effects of aging and text-stimulus quality on the word-frequency effect during Chinese reading.

Age-related reading difficulty is well established for alphabetic languages. Compared to young adults (18-30 years), older adults (65+ years) read more slowly, make more and longer fixations, make more regressions, and produce larger word-frequency effects. However, whether similar effects are observed for nonalphabetic languages like Chinese remains to be determined. In particular, recent research has suggested Chinese readers experience age-related reading difficulty but do not produce age differences in the word-frequency effect. This might represent an important qualitative difference in aging effects, so we investigated this further by presenting young and older adult Chinese readers with sentences that included high- or low-frequency target words. Additionally, to test theories that suggest reductions in text-stimulus quality differentially affect lexical processing by adult age groups, we presented either the target words (Experiment 1) or all characters in sentences (Experiment 2) normally or with stimulus quality reduced. Analyses based on mean eye-movement parameters and distributional analyses of fixation times for target words showed typical age-related reading difficulty. We also observed age differences in the word-frequency effect, predominantly in the tails of fixation-time distributions, consistent with an aging effect on the processing of high- and low-frequency words. Reducing stimulus quality disrupted eye movements more for the older readers, but the influence of stimulus quality on the word-frequency effect did not differ across age groups. This suggests Chinese older readers' lexical processing is resilient to reductions in stimulus quality, perhaps due to greater experience recognizing words from impoverished visual input. (PsycINFO Database Record

Effects of AMPA receptor antagonist, NBQX, and extrasynaptic GABAA agonist, THIP, on social behavior of adolescent and adult rats.

Adolescence is characterized by high significance of social interactions, along with a propensity to exhibit social facilitating effects of ethanol while being less sensitive than adults to the inhibition of social behavior that emerges at higher doses of ethanol. Among the neural characteristics of adolescence are generally enhanced levels of glutamatergic (especially NMDA receptor) activity relative to adults, whereas the GABA system is still developmentally immature. Activation of NMDA receptors likely plays a role in modulation of social behavior in adolescent animals as well as in socially facilitating and suppressing effects of ethanol. For instance, adolescent and adult rats differ in their sensitivities to the effects of NMDA antagonists and ethanol on social behavior, with adolescents but not adults demonstrating social facilitation at lower doses of both drugs and adults being more sensitive to the socially suppressing effects evident at higher doses of each. The roles of AMPA and extrasynaptic GABAA receptors in modulation of social behavior during adolescence and in adulthood are still unknown. The present study was designed to assess whether pharmacological blockade of AMPA receptors and/or activation of extrasynaptic GABAA receptors results in age-dependent alterations of social behavior. Adolescent and adult male and female Sprague-Dawley rats were injected with an assigned dose of either a selective AMPA antagonist, NBQX (Experiment 1) or extrasynaptic GABAA agonist, THIP (Experiment 2) and placed into a modified social interaction chamber for a 30-min habituation period prior to a 10-min social interaction test with a novel age- and sex-matched partner. Behaviors such as social investigation, contact behavior and play behavior were scored from video recordings of the interaction tests. In Experiment 1, NBQX produced similar social inhibition at higher doses in both age groups. In Experiment 2, THIP induced inhibition in adolescents, but not adults. No social facilitation was evident following low doses of either drug. Therefore, AMPA and extrasynaptic GABAA receptors appear to play little role if any in modulation of peer-directed social behavior in adolescence and adulthood and not likely to contribute to previously observed age differences in the social effects of acute ethanol.

Fluid intelligence and gross structural properties of the cerebral cortex in middle-aged and older adults: A multi-occasion longitudinal study

According to Parieto-Frontal Integration Theory (P-FIT, Jung and Haier, 2007), individual differences in a circumscribed set of brain regions account for variations in general intelligence (g). The components of g, fluid (Gf) and crystallized (Gc) reasoning, exhibit distinct trajectories of age-related change. Because the brain also ages differentially, we hypothesized that age-related cognitive and neural changes would be coupled. In a sample of healthy middle-aged and older adults, we examined changes in Gf (operationalized by Cattell Culture Fair Test) and Gc (indexed by two vocabulary tests) as well as in structural properties of 19 brain regions. We fitted linear mixed models to the data collected on 73 healthy adults who participated in baseline assessment, with 43 returning for at least one follow-up, and 16 of them contributing four repeated assessments over seven years. We observed age differences as well as longitudinal decline in Gf, contrasted to a lack of age differences and stability in Gc. Cortical thickness and cortical volume exhibited significant age differences and longitudinal declines, which were accelerated in P-FIT regions. Gf (but not Gc) was associated with cortical thickness, but no such relationship was found for cortical volume. Uniformity of cognitive change (lack of reliable individual differences) precluded examination of the coupling between cognitive and brain changes. Cortical shrinkage was greater in high-Gc individuals, whereas in participants with higher Gf cortical volume slower volume shrinkage was observed.

A dissociation between renewal and contextual fear conditioning in juvenile rats.

We investigated whether juvenile rats do not express renewal following extinction of conditioned fear due to their inability to form a long-term contextual fear memory. In experiment 1, postnatal day (P) 18 and 25 rats received 3 white-noise and footshock pairings, followed by 60 white-noise alone presentations the next day. When tested in a different context to extinction, P25 rats displayed renewal whereas P18 rats did not. Experiments 2A and 2B surprisingly showed that P18 and P25 rats do not show differences in contextual and cued fear, regardless of the conditioning-test intervals and the number of white-noise-footshock pairings received. Finally, we observed age differences in contextual fear when P25 rats were weaned at P21 in experiment 3. These results indicate that the developmental dissociation observed in renewal of extinguished fear is not related to the widely believed late emergence of contextual fear learning.