Age-related deficits in spatial memory and hippocampal spines in virgin, female Fischer 344 rats

Steroid Hormone Interaction with Dendritic Spines: Implications for Neuropsychiatric Disease

Dendritic spines, key sites for neural plasticity, are influenced by gonadal steroids. In this chapter, we review the effects of gonadal steroids on dendritic spine density in areas important to cognitive function, the hippocampus, and prefrontal cortex. Most of these animal model studies investigated the effects of estrogen in females, but we also include more recent data on androgen effects in both males and females. The underlying genomic and non-genomic mechanisms related to gonadal steroid-induced spinogenesis are also reviewed. Subsequently, we discuss possible reasons for the observed sex differences in many neuropsychiatric diseases, which appear to be caused, in part, by aberrant synaptic connections that may involve dendritic spine pathology. Overall, knowledge concerning the regulation of dendritic spines by gonadal hormones has grown since the initial discoveries in the 1990s, and current research points to a potential role for aberrant spine functioning in many neuropsychiatric disorders.

Sex differences in cognition following variations in endocrine status

Spatial memory, mediated primarily by the hippocampus, is responsible for orientation in space and retrieval of information regarding location of objects and places in an animal's environment. Since the hippocampus is dense with steroid hormone receptors and is capable of robust neuroplasticity, it is not surprising that changes in spatial memory performance occur following a variety of endocrine alterations. Here, we review cognitive changes in both spatial and nonspatial memory tasks following manipulations of the hypothalamic-pituitary-adrenal and gonadal axes and after exposure to endocrine disruptors in rodents. Chronic stress impairs male performance on numerous behavioral cognitive tasks and enhances or does not impact female cognitive function. Sex-dependent changes in cognition following stress are influenced by both organizational and activational effects of estrogen and vary depending on the developmental age of the stress exposure, but responses to gonadal hormones in adulthood are more similar than different in the sexes. Also discussed are possible underlying neural mechanisms for these steroid hormone-dependent, cognitive effects. Bisphenol A (BPA), an endocrine disruptor, given at low levels during adolescent development, impairs spatial memory in adolescent male and female rats and object recognition memory in adulthood. BPA's negative effects on memory may be mediated through alterations in dendritic spine density in areas that mediate these cognitive tasks. In summary, this review discusses the evidence that endocrine status of an animal (presence or absence of stress hormones, gonadal hormones, or endocrine disruptors) impacts cognitive function and, at times, in a sex-specific manner.

Noise as a cause of neurodegenerative disorders: molecular and cellular mechanisms

Noise as an environmental stressor becomes of increasing importance in our industrialized world, and especially traffic noise from the environment represents a potential novel neurodegenerative risk factor, as well as for hearing loss. A significant number of studies have been suggested that the overproduction of reactive oxygen species (ROS) has a complex role in stimulation of pathologic events. Experimental studies upon molecular pathways of traffic noise exposure proposed that it increased the level of stress hormones and mediated the inflammatory and oxidative stress (OS) pathways resulting in endothelial and neuronal dysfunction. Studies have shown that neurons are especially sensitive to OS due to high polyunsaturated fatty acids content in membranes, high oxygen uptake, and weak antioxidant defense. However, OS induces the necrotic and apoptotic cell deaths in the cochlea. Chronic noise is one of the many overall reasons of obtained sensorineural hearing loss which destroys cognitive functions in human and animals, as well as suppresses neurogenesis in the hippocampus. Nevertheless, behavioral disorders caused by noise are mainly accompanied with oxidative stress, but the clear molecular mechanism of neurodegeneration due to disruption of the pro- and antioxidant systems is still not fully understood. This paper aims to highlight the down-stream pathophysiology of noise-induced mental disorders, including hearing loss, annoyance, anxiety, depression, memory loss, and Alzheimer's disease, describing the underlying mechanisms of induction of inflammation and oxidative stress.

A potential role for dendritic spines in bisphenol-A induced memory impairments during adolescence and adulthood

Developmental exposure to Bisphenol A (BPA), an endocrine disrupting chemical, alters many behaviors and neural parameters in rodents and non-human-primates. The effects of BPA are mediated via gonadal hormone, primarily, estrogen receptors, and are not limited to the perinatal period since recent studies show impairments further into development. The studies described in this chapter address the effects of BPA administration during early adolescence on memory and dendritic spine density in intact male and female rats as well as ovariectomized (OVX) rats in late adolescence and show that some of these adolescent induced changes endure into adulthood. In general, BPA impairs spatial memory and induces decreases in dendritic spine density in the hippocampus and the medial prefrontal cortex, two areas important for memory. The effects of adolescent BPA in intact females are compared to OVX females in an attempt to address the importance of estrogens in the mechanism(s) underlying the profound neuronal alterations occurring during adolescent development. In addition, potential mechanisms by which acute and chronic BPA induce structural alterations are discussed. These studies suggest a complex interaction between low doses of BPA, gonadal state and neural development.

Estrogenic regulation of memory: The first 50 years

This review highlights fifty years of progress in research on estradiol's role in regulating behavior(s). It was initially thought that estradiol was only involved in regulating estrus/menstrual cycles and concomitant sexual behavior, but it is now clear that estradiol also influences the higher order neural function of cognition. We provide a brief overview of estradiol's regulation of memory and some mechanisms which underlie its effects. Given systemically or directly into the hippocampus, to ovariectomized female rodents, estradiol or specific agonists, enhance learning and/or memory in a variety of rodent cognitive tasks. Acute (within minutes) or chronic (days) treatments enhance cognitive functions. Under the same treatment conditions, dendritic spine density on pyramidal neurons in the CA1 area of the hippocampus and medial prefrontal cortex increase which suggests that these changes are an important component of estrogen's ability to impact memory processes. Noradrenergic, dopaminergic and serotoninergic activity are also altered in these areas following estrogen treatments. Memory enhancements and increased spine density by estrogens are not limited to females but are also present in castrate males. In the next fifty years, neuroscientists need to determine how currently described neural changes mediate improved memory, how interactions among areas important for memory promote memory and the potential significance of neurally derived estrogens in normal cognitive processing. Answering these questions may provide significant advances for treatment of dementias as well as age and neuro-degenerative disease related memory loss.

Impact of Repetitive Mild Traumatic Brain Injury on Behavioral and Hippocampal Deficits in a Mouse Model of Chronic Stress

Clinical studies examining the interaction between traumatic brain injury (TBI) and stress-related disorders (e.g., post-traumatic stress disorder) are often complicated by methodological constraints, such as heterogeneity in injury type and severity, time post-trauma, and predisposing risk factors. Developing relevant animal models whereby many variables can be efficiently controlled is thus essential to understanding this elusive relationship. Here, we use our repeated unpredictable stress (RUS) paradigm, in combination with our established mouse model of repetitive mild TBI (r-mTBI), to assess the impact of repeated exposures to these paradigms on behavioral and neurobiological measures. C57BL/6J male mice were exposed to RUS and r-mTBI at 3 and 6 months of age followed by batteries of behavioral testing. Mice were euthanized 10 days and 3 months post-exposure, with brain and plasma samples collected for molecular profiling. The RUS paradigm involved exposure to a predator odor (trimethylthiazoline; TMT) while under restraint, daily unstable social housing, five inescapable footshocks on separate days, and chronic social isolation. Animals receiving r-mTBI ( × 5) and stress were exposed to a single closed-head injury 1 h after each footshock. Stress-alone mice showed significant weight loss, recall of traumatic memories, and anxiety-like and passive stress-coping behavior when compared with control mice. However, in stress+r-mTBI animals, the changes in cued fear memory, anxiety, and stress-coping tests were diminished, possibly due to TBI-induced hyperactivity. We also report complex brain molecular and neuropathological findings. Stress and r-mTBI, either individually or comorbidly, were associated with a chronic reduction in dendritic spine GluN2A/GluN2B ratio in the hippocampus. While stress augmented the r-mTBI-dependent astrogliosis in the corpus callosum, it mitigated r-mTBI-induced increases in hippocampal pro-brain-derived neurotrophic factor. We anticipate that our model will be a good platform to untangle the complex comorbid pathophysiology in stress disorders and r-mTBI.

The analysis of hippocampus neuronal density (CA1 and CA3) after Ocimum sanctum ethanolic extract treatment on the young adulthood and middle age rat model

Aim:

This study aimed to assess the changes in neuronal density in CA1 and CA3 regions in the hippocampus of young adulthood and middle age rat model after feeding by Ocimum sanctum ethanolic extract.

Materials and Methods:

In this research, 30 male Wistar rats consist of young to middle-aged rats were divided into three groups (3, 6, and 9 months old) and treated with a different dosage of O. sanctum ethanolic extract (0, 50, and 100 mg/kg b.w.) for 45 days. Furthermore, cresyl violet staining was performed to analyze hippocampus formation mainly in CA1 and CA3 area. The concentrations of acetylcholine (Ach) in brain tissues were analyzed by enzyme-linked immunosorbent assay.

Results:

In our in vivo models using rat model, we found that the administration of O. sanctum ethanolic extract with a dosage of 100 mg/kg b.w. for 45 days induced the density of pyramidal cells significantly in CA1 and CA3 of the hippocampus. These results were supported by an increase of Ach concentrations on the brain tissue.

Conclusions:

The administration of O. sanctum ethanolic extract may promote the density of the pyramidal cells in the CA1 and CA3 mediated by the up-regulated concentration of Ach.

The aminoestrogen prolame increases recognition memory and hippocampal neuronal spine density in aged mice

The aging brain shows biochemical and morphological changes in the dendrites of pyramidal neurons from the limbic system associated with memory loss. Prolame (N-(3-hydroxy-1,3,5 (10)-estratrien-17β-yl)-3-hydroxypropylamine) is a non-feminizing aminoestrogen with antithrombotic activity that prevents neuronal deterioration, oxidative stress, and neuroinflammation. Our aim was to evaluate the effect of prolame on motor and cognitive processes, as well as its influence on the dendritic morphology of neurons at the CA1, CA3, and granule cells of the dentate gyrus (DG) regions of hippocampus (HP), and medium spiny neurons of the nucleus accumbens (NAcc) of aged mice. Dendritic morphology was assessed with the Golgi-Cox stain procedure followed by Sholl analysis. Prolame (60 µg/kg) was subcutaneously injected daily for 60 days in 18-month-old mice. Immediately after treatment, locomotor activity in a new environment and recognition memory using the Novel Object Recognition Task (NORT) were evaluated. Prolame-treated mice showed a significant increase in the long-term exploration quotient, but locomotor activity was not modified in comparison to control animals. Prolame-treated mice showed a significant increase in dendritic spines density and dendritic length in neurons of the CA1, CA3, and DG regions of the HP, whereas dendrites of neurons in the NAcc remained unmodified. In conclusion, prolame administration promotes hippocampal plasticity processes but not in the NAcc neurons of aged mice, thus improving long-term recognition memory. Prolame could become a pharmacological alternative to prevent or delay the brain aging process, and thus the emergence of neurodegenerative diseases that affect memory.

The endocrine-brain-aging triad where many paths meet: female reproductive hormone changes at midlife and their influence on circuits important for learning and memory

Female mammals undergo natural fluctuations in sex steroid hormone levels throughout life. These fluctuations span from early development, to cyclic changes associated with the menstrual or estrous cycle and pregnancy, to marked hormone flux during perimenopause, and a final decline at reproductive senescence. While the transition to reproductive senescence is not yet fully understood, the vast majority of mammals experience this spontaneous, natural phenomenon with age, which has broad implications for long-lived species. Indeed, this post-reproductive life stage, and its transition, involves significant and enduring physiological changes, including considerably altered sex steroid hormone and gonadotropin profiles that impact multiple body systems, including the brain. The endocrine-brain-aging triad is especially noteworthy, as many paths meet and interact. Many of the brain regions affected by aging are also sensitive to changes in ovarian hormone levels, and aging and reproductive senescence are both associated with changes in memory performance. This review explores how menopause is related to cognitive aging, and discusses some of the key neural systems and molecular factors altered with age and reproductive hormone level changes, with an emphasis on brain regions important for learning and memory.

Effect of behavioral testing on spine density of basal dendrites in the CA1 region of the hippocampus modulated by (56)Fe irradiation

A unique feature of the space radiation environment is the presence of high-energy charged particles, including (56)Fe ions, which can present a significant hazard to space flight crews during and following a mission. (56)Fe irradiation-induced cognitive changes often involve alterations in hippocampal function. These alterations might involve changes in spine morphology and density. In addition to irradiation, performing a cognitive task can also affect spine morphology. Therefore, it is often hard to determine whether changes in spine morphology and density are due to an environmental challenge or group differences in performance on cognitive tests. In this study, we tested the hypothesis that the ability of exploratory behavior to increase specific measures of hippocampal spine morphology and density is affected by (56)Fe irradiation. In sham-irradiated mice, exploratory behavior increased basal spine density in the CA1 region of the hippocampus and the enclosed blade of the dentate gyrus. These effects were not seen in irradiated mice. In addition, following exploratory behavior, there was a trend toward a decrease in the percent stubby spines on apical dendrites in the CA3 region of the hippocampus in (56)Fe-irradiated, but not sham-irradiated, mice. Other hippocampal regions and spine measures affected by (56)Fe irradiation showed comparable radiation effects in behaviorally naïve and cognitively tested mice. Thus, the ability of exploratory behavior to alter spine density and morphology in specific hippocampal regions is affected by (56)Fe irradiation.

Effects of testosterone on synaptic plasticity mediated by androgen receptors in male SAMP8 mice

Synaptic changes are closely associated with cognitive deficits. In addition, testosterone (T) is known to exert regulative effects on synaptic plasticity. T may improve cognitive deficits in Alzheimer's disease (AD) patients, but the underlying mechanisms of androgenic action on cognitive performance remain unclear. The aim of this study was thus to examine the protective mechanism attributed to T on cognitive performance in an AD senescence, accelerated mouse prone 8 (SAMP8) animal model. Using Golgi staining to quantify the dendritic spine density in hippocampal CA1 region, molecular biomarkers of synapse function were analyzed using immunohistochemistry and western blot. T significantly increased the dendritic spine density in hippocampal CA1 region, while flutamide (F) inhibited these T-mediated effects. Immunohistochemistry and western blot analysis showed that the expression levels of brain derived neurotrophic factor (BDNF), postsynaptic density 95 (PSD-95), and p-cyclic-AMP response element binding protein (CREB)/CREB levels were significantly elevated in the T group, but F reduced the T-induced effects in these biomarkers to control levels. There were no significant differences in the expression levels of PSD-95, BDNF, and p-CREB/CREB between C and F. These findings indicate that the effects of T on improvement in synaptic plasticity were mediated via androgen receptor (AR). It is conceivable that new treatments targeted toward preventing synaptic pathology in AD may involve the use of androgen-acting drugs.

Effect of soy milk on circulating 17- β estradiol, number of neurons in cerebral cortex and hippocampus and determination of their ratio in neonatal ovariectomized rats

This study was conducted to evaluate the effect of soy milk on serum 17- β estradiol level and number of neurons in cerebral cortex and hippocampus as well as determination of the ratio of neurons in cortical and hippocampal regions in neonatal ovariectomized rats. Thirty female rats (one day old) were divided into six groups of five. At day 7, ovariectomy surgery was performed in four groups and two other groups were assumed as sham and control groups. Three groups of ovareictomaized rats were fed with soy milk at the doses of 0.75, 1.50 and 3.00 mL kg^-1 per day since they were 14. At day 60, the blood samples were collected to measure the17- β estradiol concentration, and then the brain of rats were prepared for histological studies. The serum 17- β estradiol level significantly increased in ovariectomized rats fed with soy milk compared to ovariectomized rats with no soy milk supplementation. In addition, the results showed that soy milk significantly increased the number of neurons in CA1, CA2 and dentate gyrus regions of hippocampus and granular layer of cerebral cortex in ovariectomized rats, whereas there was no significant change in number of neurons in CA3 zone of hippocampus and molecular, pyramidal and multiform layers of cerebral cortex in ovariectomized rats fed with soy milk. The ratio of cerebral cortex neurons to hippocampal neurons had no significant changes among the experimental groups.

The evolving role of dendritic spines and memory: Interaction(s) with estradiol

This article is part of a Special Issue "Estradiol and Cognition". Memory processing is presumed to depend on synaptic plasticity, which appears to have a role in mediating the acquisition, consolidation, and retention of memory. We have studied the relationship between estrogen, recognition memory, and dendritic spine density in the hippocampus and medial prefrontal cortex, areas critical for memory, across the lifespan in female rodents. The present paper reviews the literature on dendritic spine plasticity in mediating both short and long term memory, as well as the decreased memory that occurs with aging and Alzheimer's disease. It also addresses the role of acute and chronic estrogen treatments in these processes.

Estradiol and cognitive function: past, present and future

A historical perspective on estradiol's enhancement of cognitive function is presented, and research, primarily in animals, but also in humans, is reviewed. Data regarding the mechanisms underlying the enhancements are discussed. Newer studies showing rapid effects of estradiol on consolidation of memory through membrane interactions and activation of inter-cellular signaling pathways are reviewed as well as studies focused on traditional genomic mechanisms. Recent demonstrations of intra-neuronal estradiol synthesis and possible actions as a neurosteroid to promote memory are discussed. This information is applied to the critical issue of the current lack of effective hormonal (or other) treatments for cognitive decline associated with menopause and aging. Finally, the critical period hypothesis for estradiol effects is discussed along with novel strategies for hormone/drug development. Overall, the historical record documents that estradiol positively impacts some aspects of cognitive function, but effective therapeutic interventions using this hormone have yet to be realized.

Exogenous dehydroisoandrosterone sulfate reverses the dendritic changes of the central neurons in aging male rats

Sex hormones are known to help maintaining the cognitive ability in male and female rats. Hypogonadism results in the reduction of the dendritic spines of central neurons which is believed to undermine memory and cognition and cause fatigue and poor concentration. In our previous studies, we have reported age-related regression in dendrite arbors along with loss of dendritic spines in the primary somatosensory cortical neurons in female rats. Furthermore, castration caused a reduction of dendritic spines in adult male rats. In light of this, it was surmised that dendritic structures might change in normal aging male rats with advancing age. Recently, dehydroepiandrosterone sulfate (DHEAS) has been reported to have memory-enhancing properties in aged rodents. In this study, normal aging male rats, with a reduced plasma testosterone level of 75-80%, were used to explore the changes in behavioral performance of neuronal dendritic arbor and spine density. Aging rats performed poorer in spatial learning memory (Morris water maze). Concomitantly, these rats showed regressed dendritic arbors and spine loss on the primary somatosensory cortical and hippocampal CA1 pyramidal neurons. Exogenous DHEAS and testosterone treatment reversed the behavioral deficits and partially restored the spine loss of cortical neurons in aging male rats but had no effects on the dendritic arbor shrinkage of the affected neurons. It is concluded therefore that DHEAS, has the efficacy as testosterone, and that it can exert its effects on the central neuron level to effectively ameliorate aging symptoms.

Effects of hormone therapy on cognition and mood

OBJECTIVE

Results of the Women's Health Initiative (WHI) and Women's Health Initiative Memory Study (WHIMS) suggested that hormone therapy (HT) may be detrimental to cognitive health. This article reviews clinical studies that address issues relevant to those results.

DESIGN

Literature review.

INTERVENTION(S)

A search of Pubmed and Web of Science was conducted using the search terms HT and cognition, HT and mood. Clinical and observational studies were selected if they were published after the year 2000. Theories of HT mechanisms of action, pharmacology, biology, and observational and clinical trials are discussed.

RESULT(S)

Although observational and clinical trials show conflicting findings, methodologic considerations must be acknowledged. HT formulation and dose, route of administration, timing of initiation, length of treatment, and health of participants all contribute to inconsistencies in results. Transdermal estradiol and micronized progesterone administered at time of menopause are generally associated with cognitive and affective benefit.

CONCLUSION(S)

At the present time, results from existing studies are equivocal regarding the benefits of HT on cognition and affect. Future studies, such as the Kronos Early Estrogen Prevention Study (KEEPS), should address methodologic inconsistencies to provide clearer answers to this important question.

Genistein partly eases aging and estropause-induced primary cortical neuronal changes in rats

Gonadal hormones can modulate brain morphology and behavior. Recent studies have shown that hypogonadism could result in cortical function deficits. To this end, hormone therapy has been used to ease associated symptoms but the risk may outweigh the benefits. Here we explored whether genistein, a phytoestrogen, is effective in restoring the cognitive and central neuronal changes in late middle age and surgically estropause female rats. Both animal groups showed poorer spatial learning than young adults. The dendritic arbors and spines of the somatosensory cortical and CA1 hippocampal pyramidal neurons were revealed with intracellular dye injection and analyzed. The results showed that dendritic spines on these neurons were significantly decreased. Remarkably, genistein treatment rescued spatial learning deficits and restored the spine density on all neurons in the surgically estropause young females. In late middle age females, genistein was as effective as estradiol in restoring spines; however, the recovery was less thorough than on young OHE rats. Neither genistein nor estradiol rectified the shortened dendritic arbors of the aging cortical pyramidal neurons suggesting that dendritic arbors and spines are differently modulated. Thus, genistein could work at central level to restore excitatory connectivity and appears to be potent alternative to estradiol for easing aging and menopausal syndromes.

Interactions between estradiol, BDNF and dendritic spines in promoting memory

Several lines of evidence have converged to indicate that memory formation involves plasticity of dendritic spines in the medial prefrontal cortex (PFC) and the hippocampus. Memory varies with estrogen levels throughout the lifespan of the female. Generally, increased levels of estrogen are related to greater dendritic spine density on pyramidal cells in the PFC and the hippocampus and to improved memory function. Brain-derived neurotrophic factor (BDNF) is a growth factor which increases dendritic spines and enhances memory function. Estrogens increase BDNF levels in the PFC and the hippocampus. In the present review we provide evidence that estradiol and BDNF may work in concert to enhance cognition. In adult females, fluctuations in recognition memory following ovariectomy and estradiol replacement, during the estrous cycle, in pregnancy and with aging are accompanied by similar changes in circulating estradiol, BDNF levels and spine density alterations in the PFC and the hippocampus. In addition, both estradiol and BDNF induce spine plasticity via rapid membrane effects and slower transcriptional regulation via the CREB pathway. Moreover, estradiol increases BDNF levels through action on nuclear receptors. While the exact mechanism(s) for the influence of estrogens and BDNF on memory remain unclear, this combination may provide the basis for new and more effective strategies for treating age-related and neurodegenerative memory loss.

Remodeling of axo-spinous synapses in the pathophysiology and treatment of depression

Dendritic spines provide a compartment for assembly and functional organization of synaptic machinery that plays a fundamental role in neuronal communication and neuroplasticity. Studies in humans as well as in animal models have demonstrated abnormal spine architecture in several psychiatric disorders, including depression and other stress-related illnesses. The negative impact of stress on the density and organization of spines is thought to contribute to the behavioral deficits caused by stress exposure. Moreover, there is now evidence that medication-induced recovery involves changes in synaptic plasticity and dendrite morphology, including increased expression of pre- and postsynaptic plasticity-related proteins, as well as the density and function of axo-spinous synapses. Here we review the evidence from brain imaging and postmortem studies demonstrating that depression is accompanied by structural and functional alterations of cortical and limbic brain regions, including the prefrontal cortex, hippocampus and amygdala. In addition, we present more direct evidence from basic research studies that exposure to stress alters spine morphology, function and plasticity and that antidepressants, particularly new rapid acting agents, reverse these effects. Elucidation of the signaling pathways and molecular mechanisms that control spine synapse assembly and plasticity will contribute to a better understanding of the pathophysiology of depression and development of novel, more effective therapeutic agents.

Estrogens facilitate memory processing through membrane mediated mechanisms and alterations in spine density

Estrogens exert sustained, genomically mediated effects on memory throughout the female life cycle, but here we review new studies documenting rapid effects of estradiol on memory, which are exerted through membrane-mediated mechanisms. Use of recognition memory tasks in rats shows that estrogens enhance memory consolidation within 1h. 17α-Estradiol is more potent than 17β-estradiol, and the dose response relationship between estrogens and memory is an inverted U shape. Use of specific estrogen receptor (ER) agonists suggests mediation by an ERβ-like membrane receptor. Enhanced memory is associated with increased spine density and altered noradrenergic activity in the medial prefrontal cortex and hippocampus within 30 min of administration. The environmental chemical, bisphenol-A, rapidly antagonizes enhancements in memory in both sexes possibly through actions on spines. Thus, estradiol and related compounds exert rapid alterations in cognition through non-genomic mechanisms, a finding which may provide a basis for better understanding and treating memory impairments.

What do we know about aging and spatial cognition? Reviews and perspectives

In order to cope with normal cognitive aging we must understand the patterns and neurofunctional underpinnings of cognitive and behavioral changes throughout adulthood. In this review, we summarize recent advances in our understanding of age-related behavioral differences and changes in brain structure throughout the spatial domain. Although spatial cognition is critically important to everyday life, few studies have examined the relationship between this cognitive function and neural changes in the aged brain. Thus, spatial cognition is considered a key area in which the cognitive neuroscience of aging may expand in the near future. The first section of this review examines the methodologies and studies used to assess differences in spatial cognition during normal cognitive aging in animals and humans. We then relate how each domain of spatial cognition (e.g., visuospatial perception, mental imagery, memory and navigation) is affected by the aging process, and discuss possible links with changes in neural mechanisms. Lastly, we address putative links among the age-related deterioration patterns of the various spatial domains and make suggestions for future research.