Spatial Cognitive Abilities Research Articles

Effect of Balance Training Versus Stretching Relaxation Exercise in Memory and Spatial Cognition Enhancement on Healthy Adults

Abstract Background Physical exercise has been shown to improve cognitive functions. However, it is still unknown which type of exercise affects cognition. In the present study, we tested the hypothesis that demanding balance training program improves memory and spatial cognition. Objective To test the effect of balance training versus stretching relaxation exercise on memory and spatial cognition in cognitive enhancement. Patients and Methods Participants randomly assigned into 2 groups, 40 participants in balance training group and 40 participants in stretching relaxation training group: Participants trained in groups of 10–12 individuals. Each group trained four times a week for 6 weeks. Each session lasts for 50 minutes. Training groups instructed by the same professional trainers. Each participant took part in 24 training sessions in total. All participants advised not to change their habitual level of physical activity throughout the intervention period. Results Balance performance improved only in the balance group from pre- to post-training from 85.8±3.0 to 95.0±2.2. Only the balance group improved in memory in wechsler IQ test from 94.6±2.6 to 108.0±4.5 and spatial cognitive abilities in spatial reasoning from 17.5±5.0 to 26.2±5.2. Finally, none of the two groups displayed changes in mismatch negativity test. The findings suggest that systematic balance training is capable of enhancing some cognitive functions, such as memory and spatial cognition. Conclusion In sum, we are able to conclude that 6 weeks of balance training in healthy adults has positive effects on memory and spatial cognition, and an increase in cardiorespiratory fitness does not seem to be necessary to induce beneficial effects of physical exercise on cognition. From an applied perspective, balance training might represent a promising alternative intervention for individuals who are not able to participate in aerobic training following health restrictions.

Resting State EEG Related to Mathematical Improvement After Spatial Training in Children.

Spatial cognitive abilities, including mental rotation (MR) and visuo-spatial working memory (vsWM) are correlated with mathematical performance, and several studies have shown that training of these abilities can enhance mathematical performance. Here, we investigated the behavioral and neural correlates of MR and vsWM training combined with number line (NL) training. Fifty-seven children, aged 6–7, performed 25 days of NL training combined with either vsWM or MR and participated in an Electroencephalography (EEG)-session in school to measure resting state activity and steady-state visual evoked potentials during a vsWM task before and after training. Fifty children, aged 6–7, received usual teaching and acted as a control group. Compared to the control group, both training groups improved on a combined measure of mathematics. Cognitive improvement was specific to the training. Significant pre-post changes in resting state-EEG (rs-EEG), common to both training groups, were found for power as well as for coherence, with no significant differences in rs-EEG-changes between the vsWM and MR groups. Two of the common rs-EEG changes were correlated with mathematical improvement: (1) an increase in coherence between the central frontal lobe and the right parietal lobe in frequencies ranging from 16 to 25 Hz, and (2) an increase in coherence between the left frontal lobe and the right parietal lobe ranging from 23 to 25 Hz. These results indicate that changes in fronto-parietal coherence are related to an increase in mathematical performance, which thus might be a useful measure in further investigations of mathematical interventions in children.

Barren environment damages cognitive abilities in fish: Behavioral and transcriptome mechanisms

The surrounding environments that animals inhabit shape their behavioral phenotypes, physiological status and molecular processes. As one of the driving forces for the adaptation and evolution of marine animals, environmental complexity has been shown to affect several behavioral characteristics in fish. However, little is known about the effects of environmental complexity on fish spatial cognition and about the relevant regulatory mechanisms. To address this theoretical gap, black rockfish Sebastes schlegelii, which is a typical rock fish species, were exposed to laboratory-based small-scale contrasting environments (i.e., spatially complex environment vs. spatially barren environment) for seven weeks. Subsequently, the spatial cognitive abilities and behavioral performance during captive period were determined, and transcriptome sequencing and analyses for fish telencephalon were conducted. In general, the fish from barren environment had significantly lower spatial learning and memory abilities compared with the fish from complex environment (i.e., the complex fish exited the maze faster). During the whole captive period, the frequency of aggressive behavior among barren fish was significantly higher than complex fish. And meanwhile, the group dispersion index of barren group was also significantly higher than complex group, which indicated that complex fish tended to distribute in a more homogeneous pattern than barren fish. Through transcriptomic analyses, a series of differentially expressed genes and pathways which may underpin the damaged effects of barren environment on fish spatial cognition were identified, and these genes mainly related to stress response, metabolism, organism systems and neural plasticity. However, no significant differences in growth performance, locomotor activity (indicated by swimming behavior and rotatory behavior) between treatments were detected. Based on these results, mechanisms in the levels of behavior and molecule were proposed to explain the environmental effects on fish cognition. This study may provide fundamental information for deeply understanding the environmental effects on marine animals.

Protective effects of krill oil on high fat diet-induced cognitive impairment by regulation of oxidative stress

Consumption of high fat diet (HFD) increases risk of cognitive impairment and memory deficit by elevation of oxidative stress in the brain. In this study, we investigated the protective effects of krill oil (KO) against HFD-induced cognitive impairment in mice. The mice were fed with HFD for 10 weeks, and then KO was orally administered at doses of 100, 200, or 500 mg/kg/d for 4 weeks. To evaluate the cognitive abilities, we carried out the behavior tests, such as T-maze, novel object recognition test, and Morris water maze test. The HFD-induced cognitive impairment mice showed impairments in both spatial memory and novel object cognitive abilities. However, administration of KO at doses of 100, 200, or 500 mg/kg/d improved spatial memory ability and novel object cognition by increase of the exploration of new route and novel object. In addition, KO-administered group improved learning and memory abilities, showing shorter latency to reach hidden platform compared with control group. Furthermore, levels of reactive oxygen species (ROS), lipid peroxidation, and nitric oxide (NO) were significantly elevated by consumption of HFD, indicating that consumption of HFD induces oxidative stress in the brain. However, administration of KO attenuated oxidative stress by decrease of the ROS levels, lipid peroxidation, and NO. This study suggests that KO improves HFD-induced cognitive impairment by attenuation of oxidative stress in the brain. Therefore, KO may play as a promising agent in treatment and prevention of HFD-induced cognitive impairment.

Sexual Dimorphism in Language, and the Gender Shift Hypothesis of Homosexuality.

Psychological sex differences have been studied scientifically for more than a century, yet linguists still debate about the existence, magnitude, and causes of such differences in language use. Advances in psychology and cognitive neuroscience have shown the importance of sex and sexual orientation for various psychobehavioural traits, but the extent to which such differences manifest in language use is largely unexplored. Using computerised text analysis (Linguistic Inquiry and Word Count: LIWC 2015), this study found substantial psycholinguistic sexual dimorphism in a large corpus of English-language novels (n = 304) by heterosexual authors. The psycholinguistic sex differences largely aligned with known psychological sex differences, such as empathising–systemising, people–things orientation, and men’s more pronounced spatial cognitive styles and abilities. Furthermore, consistent with predictions from cognitive neuroscience, novels (n = 158) by lesbian authors showed minor signs of psycholinguistic masculinisation, while novels (n = 167) by homosexual men had a female-typical psycholinguistic pattern, supporting the gender shift hypothesis of homosexuality. The findings on this large corpus of 66.9 million words indicate how psychological group differences based on sex and sexual orientation manifest in language use in two centuries of literary art.

Spatial and attentional aftereffects of virtual reality and relations to cybersickness

Cybersickness describes the nausea and discomfort that frequently emerges upon exposure to a virtual reality (VR) environment. The extent to which cybersickness leads to temporary constraints in cognitive functioning after VR exposure is a critical aspect of evaluating the risk to human safety where VR tasks are used for workforce training. Here, we examined whether VR exposure results in deteriorated cognitive spatial ability and attention, and if this possible deterioration is related to cybersickness. A standardized cognitive test battery consisting of Corsi blocks task (CBT), Manikin spatial task (MST), and color trails test (CTT-A and -B) was administered before and after participants were exposed to virtual reality (VR group), or engaged in interactive board games (control group). The performance of participants in CBT remained unchanged from pre-test to post-test in both groups, while performance in MST improved in the control and remained stable in VR group. Response times in CTT-A remained stable in the VR group but reduced significantly in the control group. Regarding CTT-B, participants from both groups became significantly faster in post-test. We did not observe any significant sex differences, or effects of past VR experience, across measures of cognitive performance or cybersickness. Crucially, no significant correlations were found between cognitive performance changes and cybersickness scores in any cases. The results provide encouragement for the use of VR in professional settings, suggesting that VR and cybersickness may minimally limit subsequent cognitive processing. However, it will be crucial to further examine the aftereffects in other cognitive functions.

Novel Cultivation of six-year-old Korean Ginseng (Panax ginseng) in pot: From Non-Agrochemical Management to Increased Ginsenoside

BackgroundGinseng (Panax ginseng Meyer) is a perennial plant belonging to the Araliaceae family that is known to have various beneficial effects including improving memory loss and spatial cognitive ability, and anti-cancer and anti-diabetes activity. Its functional benefits also include improving liver function, regulating blood pressure, stress, and providing antioxidant activity. Usually, various agrochemicals are used in cultivating ginseng preventing from many diseases. MethodsFCGP (field cultivated ginseng in pot) was implemented by imitating MCWG (mountain cultivated wild ginseng). Pesticide analysis of pot cultivation was carried out and the contents of bioactive components such as ginsenoside were also analyzed. ResultsFCGP ginsenoside content was higher than that of FCG (field cultivated ginseng) and MCWG. FCGP has been shown to have a relatively high antioxidant effect compared with cultivated ginseng. ConclusionIt was confirmed that ginseng can be grown for 6 years without resorting to use of pesticides. In addition, it was confirmed that effective accumulation of physiologically active ingredients such as ginsenoside is possible. Our result represents FCGP is a novel method of pesticide-free ginseng cultivation

Ratiometric and reversible detection of endogenous SO2 and HCHO in living cells and mice by a near-infrared and dual-emission fluorescent probe

Abstract The small signal transmitters SO2 can elaborately modulate signal transduction pathways. Endogenous formaldehyde (FA) can toxify protein and DNA as a crosslinking agent besides functions in the aspect of spatial memory and cognitive ability. Both SO2 and FA are tightly associated with neurological disorders, cardiovascular diseases. Therefore, it is significant and challenging to monitor the real-time dynamic fluctuation of SO2 and FA in cells or animals. Toward this end, for the first time, a near-infrared (NIR) dual-emission fluorescent probe (BCou-BP) for SO2 and FA was developed based on the rational combination of benzypylium and benzo[g]coumarin cores through tuning the conjugation and rigidity of the fluorophore units. Thus, this rational design affords the new cationic probe the ratiometric detection ability (F604/F694) toward mitochondrial SO2 with a fast response time of 10 s, as well as toward FA in 170 s. Endogenous FA could restore the fluorescence at 694 nm of BCou-BP due to the capture of SO2 from decomposition of the adduct BCou-BP-SO3H. The powerful probe succeeded in real-time visualizing the dynamic change of endogenous mitochondrial SO2 and FA in living cells and mice.

Influence of individual characteristics on spatial cognitive ability in desktop virtual environment and real scene

Influence of individual characteristics on spatial cognitive ability in desktop virtual environment and real scene

Individual-Level Memory Is Sufficient to Create Spatial Segregation among Neighboring Colonies of Central Place Foragers.

AbstractCentral place foragers often segregate in space, even without signs of direct agonistic interactions. Using parsimonious individual-based simulations, we show that for species with spatial cognitive abilities, individual-level memory of resource availability can be sufficient to cause spatial segregation in the foraging ranges of colonial animals. The shapes of the foraging distributions are governed by commuting costs, the emerging distribution of depleted resources, and the fidelity of foragers to their colonies. When colony fidelity is weak and foragers can easily switch to colonies located closer to favorable foraging grounds, this leads to space partitioning with equidistant borders between neighboring colonies. In contrast, when colony fidelity is strong-for example, because larger colonies provide safety in numbers or individuals are unable to leave-it can create a regional imbalance between resource requirements and resource availability. This leads to nontrivial space-use patterns that propagate through the landscape. Interestingly, while better spatial memory creates more defined boundaries between neighboring colonies, it can lower the average intake rate of the population, suggesting a potential trade-off between an individual's attempt for increased intake and population growth rates.

Motor and Visual-spatial Cognitive Abilities in Children Treated for Infantile Esotropia.

While many studies have investigated links between motor and visual spatial cognitive abilities in typically developing children, only a few studies have tested this link among children with innate handicaps. Therefore, we assessed motor abilities (using the M-ABC-2) and visual spatial cognitive skills (using the Block Design subtest of the WPPSI-III and a picture mental rotation task, PRT) of 5-7 year old typically developing children (n= 17) and same-aged children with severe deficits in stereopsis due to infantile esotropia (n= 17). Compared to the typically developing children, children with esotropia showed significantly poorer motor performances, especially in manual dexterity and ball skills, and significantly poorer and slower performance on the visual spatial cognitive tasks. Especially the girls treated for infantile esotropia needed more time to mentally rotate the pictures of the PRT correctly. Overall, this study showed that perceptual, motor and cognitive processes are interconnected and that children treated for infantile esotropia had an increased risk of motor and visual spatial cognitive deficits.

Genetic variants of the type-3 metabotropic glutamate receptor gene associated with human spatial localization ability

People present and transform spatial information through spatial cognitive abilities to learn and adapt to the environment. Accumulating evidence exhibits individual difference in spatial cognition, which is ascribed to environmental and genetic factors. The detail knowledge remains to be investigated. In this study, 941 healthy college students were recruited, and their spatial localization ability, an essential symbol of spatial cognitive ability, was measured. We analyzed the individual difference in spatial localization and relative influence factors. We selected the type-3 metabotropic glutamate receptor (GRM3) gene to dissect the genetic role in spatial cognition. In this study, both individual general cognitive ability and spatial localization were influenced by age, birthplace, growing environment, occupation and educational level of parent, and genetic variants of GRM3. The variants of GRM3 were significantly associated with spatial localization, and not associated with general cognitive ability. The carriers of the AA of rs6465084 or the TT of rs1468412 exhibited a weak spatial localization ability, and even the relative non-genetic factors above-mentioned were well controlled. Conclusion: Our results suggest that genetic variants of GRM3 are significantly associated with the spatial localization ability in the healthy people.

Spatial cognitive abilities of a tide-pool fish show resilience to noise pollution

Noise pollution may impair the cognitive performances of several animal species, producing suboptimal behavioral responses. Involuntary shifts in attention from noise pollution (an irrelevant stimulus) may account for this outcome, specifically, by reducing the available cognitive processing capacity to conduct relevant tasks; the ‘distracted prey hypothesis’. Many reef fish mediate predation risks by pairing with conspecifics and using refuges; two crucially important resources that are often heterogeneously distributed in space. In a T-maze, we tested the cognitive performances of wild-caught tide-pool fish, Sergeant Major (Abudefduf saxatilis), exposed to control (45 dBA) or noise playbacks (100 dBA). After exposure to a model predator, fish could reach an area containing a refuge and conspecifics (target area), located in one arm of the maze. We posited that fish exposed to noise playbacks would require additional time to reach this target, because of impaired cognitive performances (i.e., learning, remembering). While fish learned to reach the target, no statistical difference existed between acoustic treatments. However, fish exposed to additional noise increased their time spent under shelter and reduced their exploratory behavior. As tide-pools are inherently noisy and structurally complex, residents of these habitats may have cognitive abilities that are resilient to acoustic disturbances.

Spatial cognitive ability is associated with transitory movement speed but not straightness during the early stages of exploration.

Memories about the spatial environment, such as the locations of foraging patches, are expected to affect how individuals move around the landscape. However, individuals differ in the ability to remember spatial locations (spatial cognitive ability) and evidence is growing that these inter-individual differences influence a range of fitness proxies. Yet empirical evaluations directly linking inter-individual variation in spatial cognitive ability and the development and structure of movement paths are lacking. We assessed the performance of young pheasants (Phasianus colchicus) on a spatial cognition task before releasing them into a novel, rural landscape and tracking their movements. We quantified changes in the straightness and speed of their transitory paths over one month. Birds with better performances on the task initially made slower transitory paths than poor performers but by the end of the month, there was no difference in speed. In general, birds increased the straightness of their path over time, indicating improved efficiency independent of speed, but this was not related to performance on the cognitive task. We suggest that initial slow movements may facilitate more detailed information gathering by better performers and indicates a potential link between an individual's spatial cognitive ability and their movement behaviour.

Self-Reported Sense of Direction and Vestibular Function in the Baltimore Longitudinal Study of Aging (BLSA).

Sense of direction is an individual's ability to navigate within an environment and generate a mental map of novel environments. Although sense of direction is correlated with psychometric tests of spatial ability, it also reflects an individual's real-world spatial ability that is not fully captured by laboratory-based assessments. Sense of direction is known to vary widely in the population and has been shown to decline with age. However, other factors that contribute to an individual's sense of direction have not been well-characterized. Vestibular impairment has been linked to reduced spatial cognitive ability, which encompasses spatial memory and navigation skills. Several studies have shown that vestibular input is necessary for effective spatial cognition, notably accurate spatial navigation ability. These studies have typically considered laboratory-based spatial navigation assessments; however, the influence of vestibular function on variation in real-world sense of direction is unknown. In this study, we evaluated whether vestibular function is associated with self-reported sense of direction. Participants for this cross-sectional study were recruited from the Baltimore Longitudinal Study of Aging, a longstanding cohort study of healthy aging. In a modified version of the Santa Barbara Sense-of-Direction (SBSOD) Scale, participants rated statements about spatial and navigational abilities. A lower average score indicates poorer self-reported sense of direction. Vestibular function testing included cervical vestibular-evoked myogenic potential (VEMP) to assess saccular function, ocular VEMP to assess utricular function, and the video head-impulse test to assess semicircular canal function based on vestibular ocular reflex. The study sample included 82 participants with mean age of 71.0 (± 16.9) years and mean SBSOD score of 4.95(± 1.07). In a multivariate linear regression model, female sex and bilateral saccular loss were associated with a lower average SBSOD score. These data suggest that vestibular impairment contributes to the known variation in spatial navigation ability.

Visual Instruction to Enhance Teaching of Technical Subject to Design Students

AbstractVisual instruction complementing verbal lectures is known to promote learning among students. In this study, the role of visual instruction in engaging learners effectively via the simplification of technical concepts was examined. Different aspects of visualisation, such as order of presenting and dimensionality, were tested to observe their effect on students’ approach to learning and learning outcomes. In this mixed‐method quasi‐non‐experimental explanatory study, visual instruction was applied in one of the undergraduate architecture modules that teaches fundamentals of building systems, which students often find difficult to comprehend. Three key variables, including spatial cognitive ability, approach to learning and learning outcomes, were measured using statistically valid instruments along with students’ feedback and interviews. These factors were also measured for the control group that did not receive visual instruction (n = 32), to assess the effect of the intervention. When taught with visualisation, students (n = 69), showed a significant increase in deep approach to learning (e.g., deep motive: t = 2.584, p = 0.011). In interviews, students expressed a deeper interest in the subject and reported that the topic was engaging in class. Visualisation favours students with a higher spatial ability and, thus, is useful for design students who receive spatial ability training in the course. Two‐dimensional visuals must be followed and preceded by three‐dimensional visuals to provide advanced organisation and the connection of new knowledge with known organisational models to be made.

The role of user-centered AR instruction in improving novice spatial cognition in a high-precision procedural task

AR instruction is a kind of virtual information presented on a human–computer interface. It allows users to view the geometric state, spatial relationship, operation method, and other information involved in the physical task, to form the spatial cognition of the current interaction process. At present, AR instructions cannot support high-precision procedural tasks. The reason is that the existing research work is to use visual elements to express the spatial relationship of physical tasks, without considering transforming the long-term accumulated potential experience of advanced users into a series of effective visual features and interaction modes, to promote the new users to quickly conceive the task intention. In this paper, a user-centered AR instruction(UcAI) is defined and tested for the first time in a procedural task. The control experiment and behavior analysis of 30 participants designing two tasks with different operation precision show that UcAI is more beneficial to improve the user's spatial cognitive ability than conventional AR instruction. Especially in the high-precision operation task, UcAI plays an important role. Our research results have a certain guiding significance for advanced AR instruction design, which extends AR technology to physical tasks with high cognitive complexity.

Intensive treadmill training promotes cognitive recovery after cerebral ischemia-reperfusion in juvenile rats

Rehabilitation training is routine for children who experience stroke, but its protective mechanism remains unclear. To study the effect of treadmill training intensity on hippocampal synaptic plasticity after cerebral ischemia, a model of middle cerebral artery occlusion (MCAO)/reperfusion was established in young rats to simulate childhood ischemic stroke. The rats were randomly allocated into five groups: sham operation, MCAO, low-intensity exercise and MCAO (5 m/min), medium-intensity exercise and MCAO (10 m/min), and high-intensity exercise and MCAO (15 m/min). Intervention was continued for 14 days, and a series of experimental tests were conducted.After MCAO, the juvenile rats exhibited a series of morphological and functional alterations, including changes in their neurobehavior and cerebral infarct volumes. Compared with control rats, MCAO rats had a longer escape latency and crossed fewer platforms in the water maze test and exhibited decreased hippocampal neuron density and Synapsin I and PSD95 expression. Furthermore, MCAO rats exhibited synapse morphology changes and abnormal serum levels of lactic acid and corticosterone. Treadmill training effectively reduced the neurobehavioral scores and cerebral infarction volumes, with medium-intensity training showing the best effect. Treadmill training shortened the escape latency, increased the number of platform crossings, and improved the spatial cognitive abilities of the rats, with the medium intensity training having the best effect on spatial learning/memory efficiency. Treadmill training increased the neuron density in the hippocampus, with the medium-intensity training resulting in the highest density. Treadmill training had a positive effect on the expression of Synapsin I and PSD95, with the medium-intensity training showing the strongest effect. Treadmill training improved the sub-microstructure synapse morphology, with the medium-intensity training demonstrating the best effect. Treadmill training increased the plasma levels of lactic acid and corticosterone, with the high-intensity training having the most obvious effect.Treadmill training can provide neuroprotection by promoting hippocampal synaptic plasticity, with medium-intensity training showing the most optimal effects.

Assessment of spatial reasoning in blind individuals using a haptic version of the Kohs Block Design Test

• Early blind individuals show difficulties in manipulating haptic spatial configurations. • Late blind and sighted individuals report efficient spatial reasoning capabilities. • Performance in spatial reasoning task is not related to duration of blindness. • Adapted neuropsychological tests are efficient tools to assess the cognitive functioning of blind people. Past research investigating the spatial abilities of visually impaired people, provided conflicting results. There is thus an urgent need to develop standardized tests for the evaluation of spatial cognition when vision is absent or disrupted. To this aim, we developed a haptic version of the Kohs Block Design Test and investigated the spatial non-verbal reasoning of early blind, late blind and sighted individuals. Participants reproduced 3D printed haptic configurations by assembling blocks with different textures, within a time limit. Results showed that early blind individuals reproduced fewer haptic designs than the other two groups correctly. Instead, the assembling time of the correct responses was similar among all groups. Moreover, blindness duration (in years) did not seem to affect the correctness of the performance: no significant correlation between the two variables was observed for early and late blind participants. Since only early blind individuals display difficulties in mentally representing the haptic configurations and manipulating multiple spatial information, we conclude that early visual deprivation may affect spatial reasoning capabilities. The present study adds new insights on the role of visual experience in the development of spatial skills and represents a first step in the adaptation of standardized tests for the assessment of spatial cognitive abilities in visually impaired people.

Anti-aging effects of Ribes meyeri anthocyanins on neural stem cells and aging mice.

Aging is associated with neurological impairment and cognitive decline. Flavonoids are very promising in anti-aging research in mouse models. Ribes meyeri anthocyanins are rich in abundant flavonoids, but their anti-aging biological activities remain unknown. In this study, we prepared an R. meyeri anthocyanin extract and analyzed its effects on neural stem cell (NSC) senescence in vivo and in vitro. We isolated mouse NSCs and used cell counting kit-8 (CCK-8), cell cycle, reactive oxygen species (ROS), and immunofluorescence methods to analyze the anti-aging effects of R. meyeri anthocyanins as well as naringenin (Nar), which metabolic analysis revealed as an important flavonoid in R. meyeri anthocyanins. RNA-sequencing (RNA-seq) and enzyme-linked immuno sorbent assay (ELISA) methods were also used to investigate Nar-specific mechanisms of anti-aging. After R. meyeri anthocyanin treatment, NSC proliferation accelerated, and NSCs had decreased senescence markers, and reduced P16ink4a expression. R. meyeri anthocyanin treatment also reversed age-dependent neuronal loss in vivo and in vitro. Nar blocked mNSC aging in vitro and improved spatial memory and cognitive abilities in aging mice through downregulation of plasma TNF-α protein. These findings suggest that R. meyeri anthocyanins increase NSC proliferation and improve neurogenesis with aging via Nar-induced reductions in TNF-α protein levels in vivo.