Synaptic estrogen receptor-alpha levels in prefrontal cortex in female rhesus monkeys and their correlation with cognitive performance

Sex differences in age-associated neurological diseases-A roadmap for reliable and high-yield research

Once taken into consideration, sex differences in neurological diseases emerge in abundance: (i) Stroke severity is significantly higher in females than in males, (ii) Alzheimer's disease (AD) pathology is more pronounced in females, and (iii) conspicuous links with hormonal cycles led to female-specific diagnoses, such as catamenial migraines and epilepsy. While these differences receive increasing attention in isolation, they likely link to similar processes in the brain. Hence, this review aims to present an overview of the influences of sex chromosomes, hormones, and aging on male and female brains across health and disease, with a particular focus on AD and stroke. The focus here on advancements across several fields holds promise to fuel future research and to lead to an enriched understanding of the brain and more effective personalized neurologic care for all.

Oral administration of ethinyl estradiol and the brain-selective estrogen prodrug DHED in a female common marmoset model of menopause: Effects on cognition, thermoregulation, and sleep

Menopausal symptoms of sleep disturbances, cognitive deficits, and hot flashes are understudied, in part due to the lack of animal models in which they co-occur. Common marmosets (Callithrix jacchus) are valuable nonhuman primates for studying these symptoms, and we examined changes in cognition (reversal learning), sleep (48 h/wk of sleep recorded by telemetry), and thermoregulation (nose temperature in response to mild external warming) in middle-aged, surgically-induced menopausal marmosets studied at baseline, during 3-week phases of ethinyl estradiol (EE2, 4 μg/kg/day, p.o.) treatment and after EE2 withdrawal. We also assessed a brain-selective hormonal therapy devoid of estrogenic effects in peripheral tissues on the same measures (cognition, sleep, thermoregulation) after treatment with the estrogen prodrug 10β,17β-dihydroxyestra-1,4-dien-3-one (DHED, 100 μg/kg/day, p.o) and DHED withdrawal. Reversal learning performance was improved with EE2 or DHED treatment relative to phases without hormone administration, as indicated by a faster reversal of the stimulus/reward contingencies. Both EE2 and DHED increased non-REM sleep and reduced nighttime awakenings relative to baseline, but to the detriment of REM sleep which was highest at baseline. Nasal temperature in response to mild external warming was highest, and overnight core body temperature lowest, in the DHED treatment phase compared to both the EE2 and baseline phases. These results suggest that low dose estradiol, delivered either peripherally or centrally via DHED, benefits selective aspects of cognition and sleep in a marmoset menopause model. DHED appears a promising therapeutic candidate for alleviating the cognitive and sleep disruptions associated with estrogen deficiency in primates.

The aged female rhesus macaque as a translational model for human menopause and hormone therapy

Progress in understanding the causes of physiological and behavioral changes in post-menopausal women is hampered by the paucity of animal models that accurately recapitulate these age-associated changes. Here we evaluate the translational potential of female rhesus macaques (Macaca mulatta). Like women, these long-lived diurnal primates show marked neuroendocrine changes during aging, as well as perturbed sleep-wake cycles and cognitive decline. Furthermore, the brains of old rhesus macaques show some of the same pathological hallmarks of Alzheimer's disease as do humans, including amyloidosis and tauopathology. Importantly, unlike humans, rhesus macaques can be maintained under tightly controlled environmental conditions, such as photoperiod, temperature and diet, and tissues can be collected with zero postmortem interval; this makes them especially suitable for studies aimed at elucidating underlying molecular mechanisms. Recent findings from female macaques are helping to elucidate how sex-steroids influence gene expression within the brain and contribute to the maintenance of cognitive function and amelioration of age-associated pathologies. Taken together, these findings emphasize the translational value of female rhesus macaques as a model for elucidating causal mechanisms that underlie normative and pathological changes in post-menopausal women. They also provide a pragmatic platform upon which to develop safe and effective therapies.

Sex-dependent alterations in hippocampal connectivity are linked to cerebrovascular and amyloid pathologies in normal aging

INTRODUCTION

Compared to males, females have an accelerated trajectory of cognitive decline in Alzheimer's disease (AD). The neurobiological factors underlying the more rapid cognitive decline in AD in females remain unclear. This study explored how sex-dependent alterations in hippocampal connectivity over 2 years are associated with cerebrovascular and amyloid pathologies in normal aging.

METHODS

Thirty-three females and 21 males 65 to 93 years of age with no cognitive impairment performed a face-name associative memory functional magnetic resonance imaging (fMRI) task with a 2-year follow-up. We acquired baseline carbon 11-labeled Pittsburgh compound B ([11 C]PiB) positron emission tomography (PET) and T2-weighted fluid-attenuated inversion recovery (T2-FLAIR) MRI to quantify amyloid β (Aβ) burden and white matter hyperintensity (WMH) volume, respectively.

RESULTS

Males had increased hippocampal-prefrontal connectivity over 2 years, associated with greater Aβ burden. Females had increased bilateral hippocampal functional connectivity, associated with greater WMH volume.

DISCUSSION

These findings suggest sex-dependent compensatory mechanisms in the memory network in the presence of cerebrovascular and AD pathologies and may explain the accelerated trajectory of cognitive decline in females.

The Pathological Effects of Circulating Hydrophobic Bile Acids in Alzheimer's Disease

Recent clinical studies have revealed that the serum levels of toxic hydrophobic bile acids (deoxy cholic acid, lithocholic acid [LCA], and glycoursodeoxycholic acid) are significantly higher in patients with Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) when compared to control subjects. The elevated serum bile acids may be the result of hepatic peroxisomal dysfunction. Circulating hydrophobic bile acids are able to disrupt the blood-brain barrier and promote the formation of amyloid-β plaques through enhancing the oxidation of docosahexaenoic acid. Hydrophobic bile acid may find their ways into the neurons via the apical sodium-dependent bile acid transporter. It has been shown that hydrophobic bile acids impose their pathological effects by activating farnesoid X receptor and suppressing bile acid synthesis in the brain, blocking NMDA receptors, lowering brain oxysterol levels, and interfering with 17β-estradiol actions such as LCA by binding to E2 receptors (molecular modelling data exclusive to this paper). Hydrophobic bile acids may interfere with the sonic hedgehog signaling through alteration of cell membrane rafts and reducing brain 24(S)-hydroxycholesterol. This article will 1) analyze the pathological roles of circulating hydrophobic bile acids in the brain, 2) propose therapeutic approaches, and 3) conclude that consideration be given to reducing/monitoring toxic bile acid levels in patients with AD or aMCI, prior/in combination with other treatments.

Effects of social rank and pubertal delay on brain structure in female rhesus macaques

Adverse social experience during childhood and adolescence leads to developmental alterations in emotional and stress regulation and underlying neurocircuits. We examined the consequences of social subordination (low social rank) in juvenile female rhesus monkeys, as an ethologically valid model of chronic social stressor exposure, on brain structural and behavioral development through the pubertal transition. Adolescence is a developmental period of extensive brain remodeling and increased emotional and stress reactivity. Puberty-induced increases in gonadal hormones, particularly estradiol (E2), are likely involved due to its organizational effects on the brain and behavior. Thus, we also examined how experimentally delaying pubertal onset with Lupron (gonadotropin releasing hormone -GnRH- agonist used clinically to delay early puberty) interacted with social rank (dominant vs. subordinate) to affect brain and behavioral outcomes. Using a longitudinal experimental design, structural MRI (sMRI) scans were collected on socially housed juvenile female rhesus monkeys living in indoor-outdoor enclosures prior to the onset of puberty (18-25 months), defined as menarche or the initial occurrence of perineal swelling and coloration, and again at 29-36 months, when all control animals had reached puberty but none of the Lupron-treated had. We examined the effects of both social rank and pubertal delay on overall structural brain volume (i.e. intracranial, grey matter (GM) and white matter (WM) volumes), as well as on cortico-limbic regions involved in emotion and stress regulation: amygdala (AMYG), hippocampus (HC), and prefrontal cortex (PFC). Measures of stress physiology, social behavior, and emotional reactivity were collected to examine functional correlates of the brain structural effects. Apart from expected developmental effects, subordinates had bigger AMYG volumes than dominant animals, most notably in the right hemisphere, but pubertal delay with Lupron-treatment abolished those differences, suggesting a role of gonadal hormones potentiating the brain structural impact of social stress. Subordinates also had elevated baseline cortisol, indicating activation of stress systems. In general, Lupron-treated subjects had smaller AMYG and HC volume than controls, but larger total PFC (driven by bigger GM volumes), and different, region-specific, developmental patterns dependent on age and social rank. These findings highlight a region-specific effect of E2 on structural development during female adolescence, independent of those due to chronological age. Pubertal delay and AMYG volume, in turn, predicted differences in emotional reactivity and social behavior. These findings suggest that exposure to developmental increases in E2 modifies the consequences of adverse social experience on the volume of cortico-limbic regions involved in emotional and stress regulation during maturation. But, even more importantly, they indicate different brain structural effects of chronological age and pubertal developmental stage in females, which are very difficult to disentangle in human studies. These findings have additional relevance for young girls who experience prolonged pubertal delays or for those whose puberty is clinically arrested by pharmacological administration of Lupron.

Oral contraceptives in the central nervous system: Basic pharmacology, methodological considerations, and current state of the field

Millions of women around the world use combined oral contraceptives (OCs), yet surprisingly little is known about their central nervous system (CNS) effects. This article provides a short overview of the basic pharmacology of OCs, emphasizing features that may be relevant to understanding their effects in the CNS. Historical and recent findings from studies of cognitive function, mood, and negative affect (depressive changes under OC use) are then reviewed. We also present data from an archival dataset from our own laboratory in which we explore dysphoric changes in women using four generations of contraceptive progestins. Current data in the field are consistent with a modest effect of OC use on CNS variables, but conclusions based on current findings must be made very cautiously because of multiple methodological issues in many published studies to date, and inconsistencies in the findings. Directions for future research over the next 10 years are suggested. (150 words).

Associations Between Midlife Menopausal Hormone Therapy Use, Incident Diabetes, and Late Life Memory in the Wisconsin Longitudinal Study

BACKGROUND

Prior research suggests a link between menopausal hormone therapy (MHT) use, memory function, and diabetes risk. The menopausal transition is a modifiable period to enhance long-term health and cognitive outcomes, although studies have been limited by short follow-up periods precluding a solid understanding of the lasting effects of MHT use on cognition.

OBJECTIVE

We examined the effects of midlife MHT use on subsequent diabetes incidence and late life memory performance in a large, same-aged, population-based cohort. We hypothesized that the beneficial effects of MHT use on late life cognition would be partially mediated by reduced diabetes risk.

METHODS

1,792 women from the Wisconsin Longitudinal Study (WLS) were included in analysis. We employed hierarchical linear regression, Cox regression, and causal mediation models to test the associations between MHT history, diabetes incidence, and late life cognitive performance.

RESULTS

1,088/1,792 women (60.7%) reported a history of midlife MHT use and 220/1,792 (12.3%) reported a history of diabetes. MHT use history was associated with better late life immediate recall (but not delayed recall), as well as a reduced risk of diabetes with protracted time to onset. Causal mediation models suggest that the beneficial effect of midlife MHT use on late life immediate recall were at least partially mediated by diabetes risk.

CONCLUSION

Our data support a beneficial effect of MHT use on late life immediate recall (learning) that was partially mediated by protection against diabetes risk, supporting MHT use in midlife as protective against late life cognitive decline and adverse health outcomes.

Estradiol and progesterone in female reward-learning, addiction, and therapeutic interventions

Sex steroid hormones like estradiol (E2) and progesterone (P4) guide the sexual organization and activation of the developing brain and control female reproductive behavior throughout the lifecycle; importantly, these hormones modulate functional activity of not just the endocrine system, but most of the nervous system including the brain reward system. The effects of E2 and P4 can be seen in the processing of and memory for rewarding stimuli and in the development of compulsive reward-seeking behaviors like those seen in substance use disorders. Women are at increased risk of developing substance use disorders; however, the origins of this sex difference are not well understood and therapeutic interventions targeting ovarian hormones have produced conflicting results. This article reviews the contribution of the E2 and P4 in females to functional modulation of the brain reward system, their possible roles in origins of addiction vulnerability, and the development and treatment of compulsive reward-seeking behaviors.

Effects of neural-derived estradiol on actin polymerization and synaptic plasticity-related proteins in prefrontal and hippocampal cells of mice

Neural-derived 17β-estradiol (E2) plays an important role in the synaptic plasticity of the hippocampus and prefrontal cortex, but the mechanism is not well defined. This study was designed to explore the effect and mechanism of neural-derived E2 on synaptic plasticity of the hippocampus and prefrontal cortex. Primary cultured hippocampal and prefrontal cells in mice were randomly divided into the DMSO (D), aromatase (Rate-limiting enzymes for E2 synthesizes) inhibitor letrozole (L), and ERs antagonist (MPG) treated groups. After intervention for 48 h, the cell was collected, and then, the expressions of AMPA-receptor subunit GluR1 (GluR1), synaptophysin (SYN), p-21-Activated kinase (PAK) phosphorylation, Rho kinase (ROCK), p-Cofilin, F-actin, and G-actin proteins were detected. Letrozole or ER antagonists inhibited the expression of GluR1, F-actin/G-actin, p-PAK and p-Cofilin proteins in prefrontal cells significantly. And the expressions of GluR1 and F-actin/G-actin proteins were declined in hippocampal cells markedly after adding letrozole or ERs antagonists. In conclusion, neural-derived E2 and ERs regulated the synaptic plasticity, possibly due to promoting actin polymerization in prefrontal and hippocampal cells. The regional specificity in the effect of neural-derived E2 and ERs on the actin polymerization-related pathway may provide a theoretical basis for the functional differences between the hippocampus and prefrontal cortex.

Psychobiological risk factors for suicidal thoughts and behaviors in adolescence: a consideration of the role of puberty

Suicide is the second leading cause of death among adolescents. While clinicians and researchers have begun to recognize the importance of considering multidimensional factors in understanding risk for suicidal thoughts and behaviors (STBs) during this developmental period, the role of puberty has been largely ignored. In this review, we contend that the hormonal events that occur during puberty have significant effects on the organization and development of brain systems implicated in the regulation of social stressors, including amygdala, hippocampus, striatum, medial prefrontal cortex, orbitofrontal cortex, and anterior cingulate cortex. Guided by previous experimental work in adults, we also propose that the influence of pubertal hormones and social stressors on neural systems related to risk for STBs is especially critical to consider in adolescents with a neurobiological sensitivity to hormonal changes. Furthermore, facets of the pubertal transition, such as pubertal timing, warrant deeper investigation and may help us gain a more comprehensive understanding of sex differences in the neurobiological and psychosocial mechanisms underlying adolescent STBs. Ultimately, advancing our understanding of the pubertal processes that contribute to suicide risk will improve early detection and facilitate the development of more effective, sex-specific, psychiatric interventions for adolescents.

Endolysosome Localization of ERα Is Involved in the Protective Effect of 17α-Estradiol against HIV-1 gp120-Induced Neuronal Injury

Neurotoxic HIV-1 viral proteins contribute to the development of HIV-associated neurocognitive disorder (HAND), the prevalence of which remains high (30-50%) with no effective treatment available. Estrogen is a known neuroprotective agent; however, the diverse mechanisms of estrogen action on the different types of estrogen receptors is not completely understood. In this study, we determined the extent to which and mechanisms by which 17α-estradiol (17αE2), a natural less-feminizing estrogen, offers neuroprotection against HIV-1 gp120-induced neuronal injury. Endolysosomes are important for neuronal function, and endolysosomal dysfunction contributes to HAND and other neurodegenerative disorders. In hippocampal neurons, estrogen receptor α (ERα) is localized to endolysosomes and 17αE2 acidifies endolysosomes. ERα knockdown or overexpressing an ERα mutant that is deficient in endolysosome localization prevents 17αE2-induced endolysosome acidification. Furthermore, 17αE2-induced increases in dendritic spine density depend on endolysosome localization of ERα. Pretreatment with 17αE2 protected against HIV-1 gp120-induced endolysosome deacidification and reductions in dendritic spines; such protective effects depended on endolysosome localization of ERα. In male HIV-1 transgenic rats, we show that 17αE2 treatment prevents the development of enlarged endolysosomes and reduction in dendritic spines. Our findings demonstrate a novel endolysosome-dependent pathway that governs the ERα-mediated neuroprotective actions of 17αE2, findings that might lead to the development of novel therapeutic strategies against HAND.SIGNIFICANCE STATEMENT Extranuclear presence of membrane-bound estrogen receptors (ERs) underlie the enhancing effect of estrogen on cognition and synaptic function. The estrogen receptor subtype ERα is present on endolysosomes and plays a critical role in the enhancing effects of 17αE2 on endolysosomes and dendritic spines. These findings provide novel insight into the neuroprotective actions of estrogen. Furthermore, 17αE2 protected against HIV-1 gp120-induced endolysosome dysfunction and reductions in dendritic spines, and these protective effects of 17αE2 were mediated via endolysosome localization of ERα. Such findings provide a rationale for developing 17αE2 as a therapeutic strategy against HIV-associated neurocognitive disorders.

Impact of exogenous estradiol on task-based and resting-state neural signature during and after fear extinction in healthy women

Fluctuations of endogenous estrogen modulates fear extinction, but the influence of exogenous estradiol is less studied. Moreover, little focus has been placed on the impact of estradiol on broad network connectivity beyond the fear extinction circuit. Here, we examined the effect of acute exogenous estradiol administration on fear extinction-induced brain activation, whole-brain functional connectivity (FC) during the fear extinction task and post-extinction resting-state. Ninety healthy women (57 using oral contraceptives [OC], 33 naturally cycling [NC]) were fear conditioned on day 1. They ingested an estradiol or placebo pill prior to extinction learning on day 2 (double-blind design). Extinction memory was assessed on day 3. Task-based functional MRI data were ascertained on days 2 and 3 and resting-state data were collected post-extinction on day 2 and pre-recall on day 3. Estradiol administration significantly modulated the neural signature associated with fear extinction learning and memory, consistent with prior studies. Importantly, estradiol administration induced significant changes in FC within multiple networks, including the default mode and somatomotor networks during extinction learning, post-extinction, and during extinction memory recall. Exploratory analyses revealed that estradiol impacted ventromedial prefrontal cortex (vmPFC) activation and FC differently in the NC and OC women. The data implicate a more diffused and significant effect of acute estradiol administration on multiple networks. Such an effect might be beneficial to modulating attention and conscious processes in addition to engaging neural processes associated with emotional learning and memory consolidation.

Comparative neuropathology in aging primates: A perspective

While humans exhibit a significant degree of neuropathological changes associated with deficits in cognitive and memory functions during aging, non-human primates (NHP) present with more variable expressions of pathological alterations among individuals and species. As such, NHP with long life expectancy in captivity offer an opportunity to study brain senescence in the absence of the typical cellular pathology caused by age-related neurodegenerative illnesses commonly seen in humans. Age-related changes at neuronal population, single cell, and synaptic levels have been well documented in macaques and marmosets, while age-related and Alzheimer's disease-like neuropathology has been characterized in additional species including lemurs as well as great apes. We present a comparative overview of existing neuropathologic observations across the primate order, including classic age-related changes such as cell loss, amyloid deposition, amyloid angiopathy, and tau accumulation. We also review existing cellular and ultrastructural data on neuronal changes, such as dendritic attrition and spine alterations, synaptic loss and pathology, and axonal and myelin pathology, and discuss their repercussions on cellular and systems function and cognition.

Sex differences in recovery of motor function in a rhesus monkey model of cortical injury

BACKGROUND

Stroke disproportionately affects men and women, with women over 65 years experiencing increased severity of impairment and higher mortality rates than men. Human studies have explored risk factors that contribute to these differences, but additional research is needed to investigate how sex differences affect functional recovery and hence the severity of impairment. In the present study, we used our rhesus monkey model of cortical injury and fine motor impairment to compare sex differences in the rate and degree of motor recovery following this injury.

METHODS

Aged male and female rhesus monkeys were trained on a task of fine motor function of the hand before undergoing surgery to produce a cortical lesion limited to the hand area representation of the primary motor cortex. Post-operative testing began two weeks after the surgery and continued for 12 weeks. All trials were video recorded and latency to retrieve a reward was quantitatively measured to assess the trajectory of post-operative response latency and grasp pattern compared to pre-operative levels.

RESULTS

Postmortem analysis showed no differences in lesion volume between male and female monkeys. However, female monkeys returned to their pre-operative latency and grasp patterns significantly faster than males.

CONCLUSIONS

These findings demonstrate the need for additional studies to further investigate the role of estrogens and other sex hormones that may differentially affect recovery outcomes in the primate brain.

Cognitive aging is associated with redistribution of synaptic weights in the hippocampus

Behaviors that rely on the hippocampus are particularly susceptible to chronological aging, with many aged animals (including humans) maintaining cognition at a young adult-like level, but many others the same age showing marked impairments. It is unclear whether the ability to maintain cognition over time is attributable to brain maintenance, sufficient cognitive reserve, compensatory changes in network function, or some combination thereof. While network dysfunction within the hippocampal circuit of aged, learning-impaired animals is well-documented, its neurobiological substrates remain elusive. Here we show that the synaptic architecture of hippocampal regions CA1 and CA3 is maintained in a young adult-like state in aged rats that performed comparably to their young adult counterparts in both trace eyeblink conditioning and Morris water maze learning. In contrast, among learning-impaired, but equally aged rats, we found that a redistribution of synaptic weights amplifies the influence of autoassociational connections among CA3 pyramidal neurons, yet reduces the synaptic input onto these same neurons from the dentate gyrus. Notably, synapses within hippocampal region CA1 showed no group differences regardless of cognitive ability. Taking the data together, we find the imbalanced synaptic weights within hippocampal CA3 provide a substrate that can explain the abnormal firing characteristics of both CA3 and CA1 pyramidal neurons in aged, learning-impaired rats. Furthermore, our work provides some clarity with regard to how some animals cognitively age successfully, while others' lifespans outlast their "mindspans."

Dynamic community detection reveals transient reorganization of functional brain networks across a female menstrual cycle

Sex steroid hormones have been shown to alter regional brain activity, but the extent to which they modulate connectivity within and between large-scale functional brain networks over time has yet to be characterized. Here, we applied dynamic community detection techniques to data from a highly sampled female with 30 consecutive days of brain imaging and venipuncture measurements to characterize changes in resting-state community structure across the menstrual cycle. Four stable functional communities were identified, consisting of nodes from visual, default mode, frontal control, and somatomotor networks. Limbic, subcortical, and attention networks exhibited higher than expected levels of nodal flexibility, a hallmark of between-network integration and transient functional reorganization. The most striking reorganization occurred in a default mode subnetwork localized to regions of the prefrontal cortex, coincident with peaks in serum levels of estradiol, luteinizing hormone, and follicle stimulating hormone. Nodes from these regions exhibited strong intranetwork increases in functional connectivity, leading to a split in the stable default mode core community and the transient formation of a new functional community. Probing the spatiotemporal basis of human brain–hormone interactions with dynamic community detection suggests that hormonal changes during the menstrual cycle result in temporary, localized patterns of brain network reorganization.

Sex steroid hormones influence the central nervous system across multiple spatiotemporal scales. Estrogen and progesterone concentrations rise and fall throughout the menstrual cycle, but it remains poorly understood whether day-to-day fluctuations in hormones shape human brain dynamics. Here, we assessed the structure and stability of resting-state brain network connectivity in concordance with serum hormone levels from a female who underwent fMRI and venipuncture for 30 consecutive days. Our results reveal that while network structure is largely stable over the course of a menstrual cycle, temporary reorganization of several large-scale functional brain networks occurs during the ovulatory window. In particular, a default mode subnetwork exhibits increased connectivity with itself and with nodes belonging to the temporoparietal and limbic networks, providing novel perspective into brain-hormone interactions.

The scientific body of knowledge - Whose body does it serve? A spotlight on oral contraceptives and women's health factors in neuroimaging

Women constitute half of the world's population, yet neuroscience research does not serve the sexes equally. Fifty years of preclinical animal evidence documents the tightly-coupled relationship between our endocrine and nervous systems, yet human neuroimaging studies rarely consider how endocrine factors shape the structural and functional architecture of the human brain. Here, we quantify several blind spots in neuroimaging research, which overlooks aspects of the human condition that impact women's health (e.g. the menstrual cycle, hormonal contraceptives, pregnancy, menopause). Next, we illuminate potential consequences of this oversight: today over 100 million women use oral hormonal contraceptives, yet relatively few investigations have systematically examined whether disrupting endogenous hormone production impacts the brain. We close by presenting a roadmap for progress, highlighting the University of California Women's Brain Initiative which is addressing unmet needs in women's health research.

Menstrual Cycle Variations in Gray Matter Volume, White Matter Volume and Functional Connectivity: Critical Impact on Parietal Lobe

The role of gonadal hormones in neural plasticity remains unclear. This study aimed to examine the effects of naturally fluctuating hormone levels over the menstrual cycle in healthy females. Gray matter, functional connectivity (FC) and white matter changes over the cycle were assessed by using functional magnetic resonance imaging (fMRI), resting state fMRI, and structural MRIs, respectively, and associated with serum gonadal hormone levels. Moreover, electrocutaneous sensitivity was evaluated in 14 women in four phases of their menstrual cycle (menstrual, follicular, ovulatory, and luteal). Electrocutaneous sensitivity was greater during follicular compared to menstrual phase. Additionally, pain unpleasantness was lower in follicular phase than other phases while pain intensity ratings did not change over the cycle. Significant variations in cycle phase effects on gray matter volume were found in the left inferior parietal lobule (IPL) using voxel-based morphometry. Subsequent Freesurfer analysis revealed greater thickness of left IPL during the menstrual phase when compared to other phases. Also, white matter volume fluctuated across phases in left IPL. Blood estradiol was positively correlated with white matter volume both in left parietal cortex and whole cortex. Seed-driven FC between left IPL and right secondary visual cortex was enhanced during ovulatory phase. A seed placed in right IPL revealed enhanced FC between left and right IPL during the ovulatory phase. Additionally, we found that somatosensory cortical gray matter was thinner during follicular compared to menstrual phase. We discuss these results in the context of likely evolutionary pressures selecting for enhanced perceptual sensitivity across modalities specifically during ovulation.

Slow electroencephalographic oscillations and behavioral measures as predictors of high executive processing in early postmenopausal females: A discriminant analysis approach

Decline in cognitive function is frequent in early postmenopause. There are postmenopausal females who show high performance while others display low performance in executive function, modulated by the prefrontal cortex. These differences have led to confusing and inconclusive results, which have not been explained entirely by the decline in estrogens, which affect the prefrontal cortex functions. An analysis of brain function and the application of a discriminant analysis can help to clarify the deficits in executive function shown by some postmenopausal females. The objective was to examine electroencephalographic recording during the performance of an executive function test in early postmenopausal females, ten with a high level of performance and ten with a low level of performance. Absolute power of delta, theta, alpha1, alpha2, beta1 and beta2 and the numbers of completed categories, trials, perseverative errors and overall errors were submitted to stepwise discriminant analysis to identify predictor variables. Four predictors emerged as significant of group membership based on cognitive performance, with the high-performance group characterized by more completed categories, more delta power, less theta power and more alpha1 power. These findings suggest that postmenopausal females classified in the high-performance group displayed appropriate temporary activation in slow oscillations during executive processing.

Sexual dimorphism of physical activity on cognitive aging: Role of immune functioning

OBJECTIVE

Exercise is one of the most potent strategies available to support cognitive health with age, yet substantial variability exists. Sexual dimorphism is evident for brain and immune functioning, the latter being implicated as important pathway for exercise. We examined the moderating role of sex on the relationship between physical activity and systemic inflammatory and brain health outcomes in support of more personalized approaches to behavioral interventions.

METHODS

Our discovery cohort included 45 typically aging women matched on age (±5y) and education (±2y) to 45 men (mean age = 72.5; Clinical Dementia Rating = 0) who completed self-reported current physical activity (Physical Activity Scale for Elderly), blood draw, neuropsychological evaluation, and brain MRI. An independent sample of 45 typically aging women and 36 men who completed the same measures comprised a replication cohort. Plasma was analyzed for 11 proinflammatory cytokine and chemokine markers via MesoScale Discovery.

RESULTS

Discovery cohort: Reported physical activity did not differ between sexes (150 vs. 157, p = 0.72). There was a significant interaction between sex and physical activity on chemokine markers MDC, MIP-1b, MCP-4, and eotaxin-3 (ps < 0.03), with a similar trend for MCP-1 and INFγ (ps < 0.09). Men who reported greater activity demonstrated lower inflammatory markers, an effect attenuated-to-absent in women. An interaction between sex and physical activity was also observed for parahippocampal volumes (p = 0.02) and cognition (processing speed and visual memory; ps < 0.04). Again, the beneficial effect of physical activity on outcomes was present in men, but not women. Replication cohort analyses conferred a consistent effect of sex on the relationship between physical activity and immune markers; models examining neurobehavioral outcomes did not strongly replicate. Across cohorts, post-hoc models demonstrated an interaction between sex and activity-related inflammatory markers on total gray matter volume and visual memory. Men with higher inflammatory markers demonstrated poorer brain structure and function, whereas inflammatory markers did not strongly relate to neurobehavioral outcomes in women.

CONCLUSIONS

Greater physical activity was associated with lower markers of inflammation in clinically normal older men, but not women - an effect consistently replicated across cohorts. Additionally, men appeared disproportionately vulnerable to the adverse effects of peripheral inflammatory markers on brain structure and function compared to women. Immune activation may be a male-specific pathway through which exercise confers neurobehavioral benefit.

Synaptic effects of estrogen

The concept that estradiol may act as a local neuromodulator in the brain, rapidly affecting connectivity and synaptic function, has been firmly established by research over the last 30 years. De novo synthesis of estradiol within the brain as well as signaling mechanisms mediating responses to the hormone have been demonstrated, along with morphological evidence indicating rapid changes in synaptic input following increases in local estradiol levels. These rapid synaptic effects may play important roles in both physiological and pathophysiological responses to changes in circulating hormone levels, as well as in neurodegenerative disease. How local effects of estradiol on synaptic plasticity are integrated into changes in the overall activity of neural networks in the brain, however, remains a subject that is only incompletely understood.

Functional reorganization of brain networks across the human menstrual cycle

The brain is an endocrine organ, sensitive to the rhythmic changes in sex hormone production that occurs in most mammalian species. In rodents and nonhuman primates, estrogen and progesterone's impact on the brain is evident across a range of spatiotemporal scales. Yet, the influence of sex hormones on the functional architecture of the human brain is largely unknown. In this dense-sampling, deep phenotyping study, we examine the extent to which endogenous fluctuations in sex hormones alter intrinsic brain networks at rest in a woman who underwent brain imaging and venipuncture for 30 consecutive days. Standardized regression analyses illustrate estrogen and progesterone's widespread associations with functional connectivity. Time-lagged analyses examined the temporal directionality of these relationships and suggest that cortical network dynamics (particularly in the Default Mode and Dorsal Attention Networks, whose hubs are densely populated with estrogen receptors) are preceded-and perhaps driven-by hormonal fluctuations. A similar pattern of associations was observed in a follow-up study one year later. Together, these results reveal the rhythmic nature in which brain networks reorganize across the human menstrual cycle. Neuroimaging studies that densely sample the individual connectome have begun to transform our understanding of the brain's functional organization. As these results indicate, taking endocrine factors into account is critical for fully understanding the intrinsic dynamics of the human brain.

Sex-Specific Relationship Between Long-Term Maintenance of Physical Activity and Cognition in the Health ABC Study: Potential Role of Hippocampal and Dorsolateral Prefrontal Cortex Volume

BACKGROUND

Physical activity (PA) is a promising strategy for the promotion of brain health, although substantial variation exists in the effects of PA at the individual level. Given the greater prevalence and faster progression of Alzheimer's disease in women compared to men, and known sex differences in brain architecture, analysis of sex differences in the relationship between PA, cognition, and brain region volumes is warranted.

METHODS

To address this, we conducted secondary analyses of data from the Health, Aging, and Body Composition study. To determine whether longitudinal changes in PA over 10 years predicted declines in global cognitive functioning and executive functions and processing speed differently in males and females, latent growth curve modeling was utilized. Magnetic resonance imaging was performed at year 10, and the hippocampus and dorsolateral prefrontal cortex were identified as regions of interest.

RESULTS

Maintaining PA over 10 years predicted less declines in executive functions and processing speed in females but not males. Maintaining PA over 10 years was significantly associated with greater volume of the left dorsolateral prefrontal cortex, a brain region involved in executive functions, in year 10 in females only. Maintaining physical activity was associated with better global cognitive function in both males and females, and also predicted volume of the left hippocampus, albeit in different directions with females showing a negative relationship and males showing a positive relationship.

CONCLUSIONS

These findings suggest that the relationship of PA with cognition and its neurobiological correlates differ by sex, with females apparently benefiting from PA to a greater extent than males. Development of personalized, tailored exercise recommendations to promote healthy brain aging should account for sex differences.

Applying a Women's Health Lens to the Study of the Aging Brain

A major challenge in neuroscience is to understand what happens to a brain as it ages. Such insights could make it possible to distinguish between individuals who will undergo typical aging and those at risk for neurodegenerative disease. Over the last quarter century, thousands of human brain imaging studies have probed the neural basis of age-related cognitive decline. "Aging" studies generally enroll adults over the age of 65, a historical precedent rooted in the average age of retirement. A consequence of this research tradition is that it overlooks one of the most significant neuroendocrine changes in a woman's life: the transition to menopause. The menopausal transition is marked by an overall decline in ovarian sex steroid production-up to 90% in the case of estradiol-a dramatic endocrine change that impacts multiple biological systems, including the brain. Despite sex differences in the risk for dementia, the influence that biological sex and sex hormones have on the aging brain is historically understudied, leaving a critical gap in our understanding of the aging process. In this Perspective article, we highlight the influence that endocrine factors have on the aging brain. We devote particular attention to the neural and cognitive changes that unfold in the middle decade of life, as a function of reproductive aging. We then consider emerging evidence from animal and human studies that other endocrine factors occurring earlier in life (e.g., pregnancy, hormonal birth control use) also shape the aging process. Applying a women's health lens to the study of the aging brain will advance knowledge of the neuroendocrine basis of cognitive aging and ensure that men and women get the full benefit of our research efforts.

Estrogen-Dependent Functional Spine Dynamics in Neocortical Pyramidal Neurons of the Mouse

Surgical ovariectomy has been shown to reduce spine density in hippocampal CA1 pyramidal cells of rodents, and this reduction is reversed by 17β-estradiol (E2) treatment in a model of human estrogen replacement therapy. Here, we report reduction of spine density in apical dendrites of layer 5 pyramidal neurons of several neocortical regions that is reversed by subsequent E2 treatment in ovariectomized (OVX) female Thy1M-EGFP mice. We also found that OVX-associated reduction of spine density in somatosensory cortex was accompanied by a reduction in miniature EPSC (mEPSC) frequency (but not mIPSC frequency), indicating a change in functional synapses. OVX-associated spine loss in somatosensory cortex was also rescued by an agonist of the G-protein-linked estrogen receptor (GPER) but not by agonists of the classic estrogen receptors ERα/ERβ, whereas the opposite selectivity was found in area CA1. Acute treatment of neocortical slices with E2 also rescued the OVX-associated reduction in mEPSC frequency, which could be mimicked by a GPER agonist and abolished by a GPER antagonist. Time-lapse in vivo two-photon imaging showed that OVX-associated reduction in spine density is achieved by both an increase in spine loss rate and a decrease in spine gain rate and that subsequent rescue by E2 reversed both of these processes. Crucially, the spines added after E2 rescue were no more likely to reappear at or nearby the sites of pre-OVX spines than those in control mice treated with vehicle. Thus, a model of estrogen replacement therapy, although restoring spine density and dynamics, does not entirely restore functional connectivity.SIGNIFICANCE STATEMENT Estrogen replacement therapy following menopause or surgical removal of the ovaries is a widespread medical practice, yet little is known about the consequences of such treatment for cells in the brain. Here, we show that estrogen replacement reverses some of the effects of surgical removal of the ovaries on the structure and function of brain cells in the mouse. Yet, importantly, the fine wiring of the brain is not returned to the presurgery state by estrogen treatment, suggesting lasting functional consequences.

Amyloid deposition is associated with different patterns of hippocampal connectivity in men versus women

Compared to men, women are disproportionally affected by Alzheimer's disease (AD) and have an accelerated trajectory of cognitive decline and disease progression. Neurobiological factors underlying gender differences in AD remain unclear. This study investigated brain beta-amyloid (Aβ)-related neural system differences in cognitively normal older men and women (N = 61; 41 females, 65-93 years old). We found that men and women showed different associations between Aβ load and hippocampal functional connectivity. During associative memory encoding, in men greater Aβ burden was accompanied by greater hippocampus-prefrontal connectivity (i.e., more synchronized activities), whereas in women hippocampal connectivity did not vary by Aβ burden. For resting-state data, the interaction of gender × Aβ on hippocampal connectivity did not survive multiple comparison in the whole-brain analyses. In the region of interest-based analyses, resting-state hippocampal-prefrontal connectivity was positively correlated with Aβ load in men and was negatively correlated with Aβ load in women. The observed Aβ-related neural differences may explain the accelerated trajectory of cognitive decline and AD progression in women.

Estrogen Alters the Synaptic Distribution of Phospho-GluN2B in the Dorsolateral Prefrontal Cortex While Promoting Working Memory in Aged Rhesus Monkeys

Age- and menopause-related deficits in working memory can be partially restored with estradiol replacement in women and female nonhuman primates. Working memory is a cognitive function reliant on persistent firing of dorsolateral prefrontal cortex (dlPFC) neurons that requires the activation of GluN2B-containing glutamate NMDA receptors. We tested the hypothesis that the distribution of phospho-Tyr1472-GluN2B (pGluN2B), a predominant form of GluN2B seen at the synapse, is sensitive to aging or estradiol treatment and coupled to working memory performance. First, ovariectomized young and aged rhesus monkeys (Macaca mulatta) received long-term cyclic vehicle (V) or estradiol (E) treatment and were tested on the delayed response (DR) test of working memory. Then, serial section electron microscopic immunocytochemistry was performed to quantitatively assess the subcellular distribution of pGluN2B. While the densities of pGluN2B immunogold particles in dlPFC dendritic spines were not different across age or treatment groups, the percentage of gold particles located within the synaptic compartment was significantly lower in aged-E monkeys compared to young-E and aged-V monkeys. On the other hand, the percentage of pGluN2B gold particles in the spine cytoplasm was decreased with E treatment in young, but increased with E in aged monkeys. In aged monkeys, DR average accuracy inversely correlated with the percentage of synaptic pGluN2B, while it positively correlated with the percentage of cytoplasmic pGluN2B. Together, E replacement may promote cognitive health in aged monkeys, in part, by decreasing the relative representation of synaptic pGluN2B and potentially protecting the dlPFC from calcium toxicity.

Synaptic distributions of pS214-tau in rhesus monkey prefrontal cortex are associated with spine density, but not with cognitive decline

Female rhesus monkeys and women are subject to age- and menopause-related deficits in working memory, an executive function mediated by the dorsolateral prefrontal cortex (dlPFC). Long-term cyclic administration of 17β-estradiol improves working memory, and restores highly plastic axospinous synapses within layer III dlPFC of aged ovariectomized monkeys. In this study, we tested the hypothesis that synaptic distributions of tau protein phosphorylated at serine 214 (pS214-tau) are altered with age or estradiol treatment, and couple to working memory performance. First, ovariectormized young and aged monkeys received vehicle or estradiol treatment, and were tested on the delayed response (DR) test of working memory. Serial section electron microscopic immunocytochemistry was then performed to quantitatively assess the subcellular synaptic distributions of pS214-tau. Overall, the majority of synapses contained pS214-tau immunogold particles, which were predominantly localized to the cytoplasm of axon terminals. pS214-tau was also abundant within synaptic and cytoplasmic domains of dendritic spines. The density of pS214-tau immunogold within the active zone, cytoplasmic, and plasmalemmal domains of axon terminals, and subjacent to the postsynaptic density within the subsynaptic domains of dendritic spines, were each reduced with age. None of the variables examined were directly linked to cognitive status, but a high density of pS214-tau immunogold particles within presynaptic cytoplasmic and plasmalemmal domains, and within postsynaptic subsynaptic and plasmalemmal domains, accompanied high synapse density. Together, these data support a possible physiological, rather than pathological, role for pS214-tau in the modulation of synaptic morphology in monkey dlPFC.

Facial Sadness Recognition is Modulated by Estrogen Receptor Gene Polymorphisms in Healthy Females

Polymorphisms of the estrogen receptor ESR1 and ESR2 genes have been linked with cognitive deficits and affective disorders. The effects of these genetic variants on emotional processing in females with low estrogen levels are not well known. The aim was to explore the impact of the ESR1 and ESR2 genes on the responses to the facial emotion recognition task in females. Postmenopausal healthy female volunteers were genotyped for the polymorphisms Xbal and PvuII of ESR1 and the polymorphism rs1256030 of ESR2. The effect of these polymorphisms on the response to the facial emotion recognition of the emotions happiness, sadness, disgust, anger, surprise, and fear was analyzed. Females carrying the P allele of the PvuII polymorphism or the X allele of the Xbal polymorphism of ESR1 easily recognized facial expressions of sadness that were more difficult for the women carrying the p allele or the x allele. They displayed higher accuracy, fast response time, more correct responses, and fewer omissions to complete the task, with a large effect size. Women carrying the ESR2 C allele of ESR2 showed a faster response time for recognizing facial expressions of anger. These findings link ESR1 and ESR2 polymorphisms in facial emotion recognition of negative emotions.

Estrogens, Aging, and Working Memory

PURPOSE OF REVIEW

Working memory (WM) is a key process that is integral to many complex cognitive tasks, and it declines significantly with advancing age. This review will survey recent evidence supporting the idea that the functioning of the WM system in women is modulated by circulating estrogens.

RECENT FINDINGS

In postmenopausal women, increased estrogen concentrations may be associated with improved WM function, which is evident on WM tasks that have a high cognitive load or significant manipulation demands. Experimental studies in rhesus monkeys and human neuroimaging studies support a prefrontal locus for these effects. Defining the basic neurochemical or cellular mechanisms that underlie the ability of estrogens to regulate WM is a topic of current research in both human and animal investigations. An emerging body of work suggests that frontal executive elements of the WM system are influenced by the circulating estrogen concentrations currently available to the CNS and that the effects are region-specific within the frontal cortex. These findings have implications for women's brain health and cognitive aging.

Neurosteroid Metabolites of Gonadal Steroid Hormones in Neuroprotection: Implications for Sex Differences in Neurodegenerative Disease

Gonadal steroid hormones are neurotrophic and neuroprotective. These effects are modulated by local metabolism of the hormones within the brain. Such control is necessary to maintain normal function, as several signaling pathways that are activated by gonadal steroid hormones in the brain can also become dysregulated in disease. Metabolites of the gonadal steroid hormones—particularly 3α-hydroxy, 5α-reduced neurosteroids—are synthesized in the brain and can act through different mechanisms from their parent steroids. These metabolites may provide a mechanism for modulating the responses to their precursor hormones, thereby providing a regulatory influence on cellular responses. In addition, there is evidence that the 3α-hydroxy, 5α-reduced neurosteroids are neuroprotective in their own right, and therefore may contribute to the overall protection conferred by their precursors. In this review article, the rapidly growing body of evidence supporting a neuroprotective role for this class of neurosteroids will be considered, including a discussion of potential mechanisms that may be involved. In addition, we explore the hypothesis that differences between males and females in local neurosteroid production may contribute to sex differences in the development of neurodegenerative disease.

The Neuromodulatory Effects of Sex Hormones on Functional Cerebral Asymmetries and Cognitive Control

Abstract. Nearly 20 years ago, Hausmann and Güntürkün (2000a, 2000b) published a review article in the Journal of Neuropsychology/Zeitschrift für Neuropsychologie on the influences of sex hormones on functional cerebral asymmetries (FCAs). They further presented a neuroendocrinological model (Hausmann & Güntürkün, 2000c) that could potentially explain how sex hormones modulate FCAs. Their model proposed that high levels of progesterone reduce the synaptic efficiency of cortico-cortical transmission, leading to a reduction of FCAs. However, empirical data testing their hypothesis directly were missing. Using various approaches, we have now gathered behavioral, electrophysiological, and neuroimaging data that partly support the original idea, while also pointing toward estradiol-modulating FCAs. The current review provides an update on this fascinating topic and briefly explores clinical applications.

Diet matters: Glucocorticoid-related neuroadaptations associated with calorie intake in female rhesus monkeys

Exposure to psychosocial stressors increases consumption of palatable, calorically dense diets (CDD) and the risk for obesity, especially in females. While consumption of an obesogenic diet and chronic stress have both been shown to decrease dopamine 2 receptor (D2R) binding and alter functional connectivity (FC) within the prefrontal cortex (PFC) and the nucleus accumbens (NAcc), it remains uncertain how social experience and dietary environment interact to affect reward pathways critical for the regulation of motivated behavior. Using positron emission tomography (PET) and resting state functional connectivity magnetic resonance neuroimaging (rs-fMRI), in female rhesus monkeys maintained in a low calorie chow (n = 18) or a dietary choice condition (chow and a CDD; n = 16) for 12 months, the current study tested the overarching hypothesis that the adverse social experience resulting from subordinate social status would interact with consumption of an obesogenic diet to increase caloric intake that would be predicted by greater cortisol, lower prefrontal D2R binding potential (D2R-BP) and lower PFC-NAcc FC. Results showed that the consequences of adverse social experience imposed by chronic social subordination vary significantly depending on the dietary environment and are associated with alterations in prefrontal D2R-BP and FC in NAcc-PFC sub-regions that predict differences in caloric intake, body weight gain, and fat accumulation. Higher levels of cortisol in the chow-only condition were associated with mild inappetence, as well as increased orbitofrontal (OFC) D2R-BP and greater FC between the NAcc and the dorsolateral PFC (dlPFC) and ventromedial PFC (vmPFC). However, increased cortisol release in females in the dietary choice condition was associated with reduced prefrontal D2R-BP, and opposite FC between the NAcc and the vmPFC and dlPFC observed in the chow-only females. Importantly, the degree of these glucocorticoid-related neuroadaptations predicted significantly more total calorie intake as well as more consumption of the CDD for females having a dietary choice, but had no relation to calorie intake in the chow-only condition. Overall, the current findings suggest that dietary environment modifies the consequences of adverse social experience on reward pathways and appetite regulation and, in an obesogenic dietary environment, may reflect impaired cognitive control of food intake.

Reorganization of Functional Networks in Verbal Working Memory Circuitry in Early Midlife: The Impact of Sex and Menopausal Status

Converging preclinical and human evidence indicates that the decline in ovarian estradiol production during the menopausal transition may play a mechanistic role in the neuronal changes that occur early in the aging process. Here, we present findings from a population-based fMRI study characterizing regional and network-level differences in working memory (WM) circuitry in midlife men and women (N = 142; age range 46-53), as a function of sex and reproductive stage. Reproductive histories and hormonal evaluations were used to determine menopausal status. Participants performed a verbal WM task during fMRI scanning. Results revealed robust differences in task-evoked responses in dorsolateral prefrontal cortex and hippocampus as a function of women's reproductive stage, despite minimal variance in chronological age. Sex differences in regional activity and functional connectivity that were pronounced between men and premenopausal women were diminished for postmenopausal women. Critically, analyzing data without regard to sex or reproductive status obscured group differences in the circuit-level neural strategies associated with successful working memory performance. These findings underscore the importance of reproductive age and hormonal status, over and above chronological age, for understanding sex differences in the aging of memory circuitry. Further, these findings suggest that early changes in working memory circuitry are evident decades before the age range typically targeted in cognitive aging studies.

The treatment of premenstrual syndrome with preparations of Vitex agnus castus: a systematic review and meta-analysis

BACKGROUND

Premenstrual syndrome is characterized by the cyclic occurrence of physical, behavioral and psychological symptoms during the luteal phase of the menstrual cycle disappearing within a few days of the onset of menstruation. Generally symptoms are mild, but 5-8% of women suffer from severe PMS. Apart from conventional drugs, like serotonin reuptake inhibitors and oral contraceptives, complementary and alternative medicines such as Vitex agnus castus are used by many women experiencing PMS.

OBJECTIVE

Our objective was to determine the efficacy, tolerability, and acceptability of Vitex agnus castus preparations for treatment of premenstrual syndrome.

STUDY DESIGN

All journals in the Ovid software from inception through January 2016 were searched, including the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, and PsycINFO. Gray literature was searched by Google Scholar and manufacturers of Vitex agnus castus preparations were contacted for information about unpublished trials. We included randomized controlled trials with Vitex agnus castus in women with premenstrual syndrome and/or premenstrual dysphoric disorder with a minimal duration of 2 menstrual cycles. The eligibility of the manuscripts was assessed by 2 reviewers independently. The data abstracted included characteristics of the study design, characteristics of the patient population, intervention details, type of comparator, method of diagnosis, and outcome measures. We adhered to the PRISMA guidelines.

RESULTS

We found 17 randomized controlled trials of Vitex agnus castus in the treatment of premenstrual syndrome. Fourteen of these could be included in the quantitative analysis. Thirteen of 14 studies with placebo, dietary supplements, or herbal preparations as controls reported positive effects of Vitex agnus castus on total premenstrual syndrome symptoms. Unfortunately most of the trials are associated with a high risk of bias. The pooled effect of Vitex agnus castus in placebo-controlled trials was large (Hedges g, -1.21; 95% confidence interval, -1.53 to -0.88), but heterogeneity was extremely high (I², 91%). We were unable to single out factors that could explain this heterogeneity satisfactorily. The funnel plot and Egger tests suggest the presence of publication bias.

CONCLUSION

Although meta-analysis shows a large pooled effect of Vitex agnus castus in placebo-controlled trials, the high risk of bias, high heterogeneity, and risk of publication bias of the included studies preclude a definitive conclusion. The pooled treatment effects should be viewed as merely explorative and, at best, overestimating the real treatment effect of Vitex agnus castus for premenstrual syndrome symptoms. There is a clear need for high-quality trials of appropriate size examining the effect of standardized extracts of Vitex agnus castus in comparison to placebo, selective serotonin reuptake inhibitors, and oral contraceptives to establish relative efficacy.

The influence of pubertal maturation on antisaccade performance

Adolescence is a period characterized by continued improvements in inhibitory control, and this persisting immaturity is believed to interact with affective/motivational behavior to generate the impulsive and risk-taking behavior evidenced at this time. Puberty is a central event of adolescence that has been shown to influence affective/motivational behavior. However, despite plausible mechanisms by which puberty might influence inhibitory control, researchers have yet to test this possibility rigorously. Thus, we designed a study to examine the unique role of pubertal maturation, independent of age, in the development of inhibitory control. In order to minimize age-related variability while maximizing pubertal status variability, we recruited 78 participants (34 F) whose ages narrowly spanned the mean age of gonadarche for each sex (F: ages 11-13, M: ages 12-14). Two complementary measures were used to assess pubertal status: (1) circulating blood serum testosterone and estradiol levels reflecting internal manifestations of pubertal maturation, and (2) Tanner staging by a trained nurse reflecting pubertal maturation's external manifestations. Inhibitory control was assessed using the antisaccade task, and findings were adjusted for the potential effect of age. Results revealed no association between testosterone levels and error rates or response latencies in either sex. In girls, estradiol levels were not associated with error rates, but were associated with faster response latencies. There was similarly no association between Tanner status and error rates, although girls in more advanced pubertal stages showed faster response latencies. Power analyses indicate that findings of a lack of association did not reflect limited statistical power. Thus, in a study designed to isolate the effects of pubertal maturation independent of age, both external and internal indices of pubertal maturation converged to indicate that age-related improvements in cold antisaccade performance are independent of pubertal maturation.

Diverse Synaptic Distributions of G Protein-coupled Estrogen Receptor 1 in Monkey Prefrontal Cortex with Aging and Menopause

Age- and menopause-related impairment in working memory mediated by the dorsolateral prefrontal cortex (dlPFC) occurs in humans and nonhuman primates. Long-term cyclic 17β-estradiol treatment rescues cognitive deficits in aged ovariectomized rhesus monkeys while restoring highly plastic synapses. Here we tested whether distributions of G protein-coupled estrogen receptor 1 (GPER1) within monkey layer III dlPFC synapses are sensitive to age and estradiol, and coupled to cognitive function. Ovariectomized young and aged monkeys administered vehicle or estradiol were first tested on a delayed response test of working memory. Then, quantitative serial section immunoelectron microscopy was used to determine the distributions of synaptic GPER1. GPER1-containing nonperforated axospinous synapse density was reduced with age, and partially restored with estrogen treatment. The majority of synapses expressed GPER1, which was predominately localized to presynaptic cytoplasm and mitochondria. GPER1 was also abundant at plasmalemmas, and within cytoplasmic and postsynaptic density (PSD) domains of dendritic spines. GPER1 levels did not differ with age or treatment, and none of the variables examined were tightly associated with cognitive function. However, greater representation of GPER1 subjacent to the PSD accompanied higher synapse density. These data suggest that GPER1 is positioned to support diverse functions key to synaptic plasticity in monkey dlPFC.

Does puberty mark a transition in sensitive periods for plasticity in the associative neocortex?

Postnatal brain development is studded with sensitive periods during which experience dependent plasticity is enhanced. This enables rapid learning from environmental inputs and reorganization of cortical circuits that matches behavior with environmental contingencies. Significant headway has been achieved in characterizing and understanding sensitive period biology in primary sensory cortices, but relatively little is known about sensitive period biology in associative neocortex. One possible mediator is the onset of puberty, which marks the transition to adolescence, when animals shift their behavior toward gaining independence and exploring their social world. Puberty onset correlates with reduced behavioral plasticity in some domains and enhanced plasticity in others, and therefore may drive the transition from juvenile to adolescent brain function. Pubertal onset is also occurring earlier in developed nations, particularly in unserved populations, and earlier puberty is associated with vulnerability for substance use, depression and anxiety. In the present article we review the evidence that supports a causal role for puberty in developmental changes in the function and neurobiology of the associative neocortex. We also propose a model for how pubertal hormones may regulate sensitive period plasticity in associative neocortex. We conclude that the evidence suggests puberty onset may play a causal role in some aspects of associative neocortical development, but that further research that manipulates puberty and measures gonadal hormones is required. We argue that further work of this kind is urgently needed to determine how earlier puberty may negatively impact human health and learning potential. This article is part of a Special Issue entitled SI: Adolescent plasticity.

Impact of Sex and Menopausal Status on Episodic Memory Circuitry in Early Midlife

Cognitive neuroscience of aging studies traditionally target participants age 65 and older. However, epidemiological surveys show that many women report increased forgetfulness earlier in the aging process, as they transition to menopause. In this population-based fMRI study, we stepped back by over a decade to characterize the changes in memory circuitry that occur in early midlife, as a function of sex and women's reproductive stage. Participants (N = 200; age range, 45-55) performed a verbal encoding task during fMRI scanning. Reproductive histories and serologic evaluations were used to determine menopausal status. Results revealed a pronounced impact of reproductive stage on task-evoked hippocampal responses, despite minimal difference in chronological age. Next, we examined the impact of sex and reproductive stage on functional connectivity across task-related brain regions. Postmenopausal women showed enhanced bilateral hippocampal connectivity relative to premenopausal and perimenopausal women. Across women, lower 17β-estradiol concentrations were related to more pronounced alterations in hippocampal connectivity and poorer performance on a subsequent memory retrieval task, strongly implicating sex steroids in the regulation of this circuitry. Finally, subgroup analyses revealed that high-performing postmenopausal women (relative to low and middle performers) exhibited a pattern of brain activity akin to premenopausal women. Together, these findings underscore the importance of considering reproductive stage, not simply chronological age, to identify neuronal and cognitive changes that unfold in the middle decades of life. In keeping with preclinical studies, these human findings suggest that the decline in ovarian estradiol production during menopause plays a significant role in shaping memory circuitry.

SIGNIFICANCE STATEMENT

Maintaining intact memory function with age is one of the greatest public health challenges of our time, and women have an increased risk for memory disorders relative to men later in life. We studied adults early in the aging process, as women transition into menopause, to identify neuronal and cognitive changes that unfold in the middle decades of life. Results demonstrate regional and network-level differences in memory encoding-related activity as a function of women's reproductive stage, independent of chronological age. Analyzing data without regard to sex or menopausal status obscured group differences in circuit-level neural strategies associated with successful memory retrieval. These findings suggest that early changes in memory circuitry are evident decades before the age range traditionally targeted by cognitive neuroscience of aging studies.

Sex biology contributions to vulnerability to Alzheimer's disease: A think tank convened by the Women's Alzheimer's Research Initiative

More than 5 million Americans are living with Alzheimer's disease (AD) today, and nearly two-thirds of Americans with AD are women. This sex difference may be due to the higher longevity women generally experience; however, increasing evidence suggests that longevity alone is not a sufficient explanation and there may be other factors at play. The Alzheimer's Association convened an expert think tank to focus on the state of the science and level of evidence around gender and biological sex differences for AD, including the knowledge gaps and areas of science that need to be more fully addressed. This article summarizes the think tank discussion, moving forward a research agenda and funding program to better understand the biological underpinnings of sex- and gender-related disparities of risk for AD.

Estrogen in prefrontal cortex blocks stress-induced cognitive impairments in female rats

Animal and human studies have found that males and females show distinct stress responses. Recent studies suggest the contribution of estrogen in the brain to this sexual dimorphism. Repeated stress has been found to impair cognitive behaviors via suppressing glutamatergic transmission and glutamate receptor surface expression in pyramidal neurons of prefrontal cortex (PFC) in male rats. On the contrary, female rats exposed to the same stress paradigms show normal synaptic function and PFC-mediated cognition. The level of aromatase, the enzyme for the biosynthesis of estrogen, is significantly higher in the PFC of females than males. The stress-induced glutamatergic deficits and memory impairment are unmasked by blocking estrogen receptors or aromatase in females, suggesting a protective role of estrogen against the detrimental effects of repeated stress.

Age and Long-Term Hormone Treatment Effects on the Ultrastructural Morphology of the Median Eminence of Female Rhesus Macaques

The median eminence (ME) of the hypothalamus comprises the hypothalamic nerve terminals, glia (especially tanycytes) and the portal capillary vasculature that transports hypothalamic neurohormones to the anterior pituitary gland. The ultrastructure of the ME is dynamically regulated by hormones and undergoes organizational changes during development and reproductive cycles in adult females, but relatively little is known about the ME during aging, especially in nonhuman primates. Therefore, we used a novel transmission scanning electron microscopy technique to examine the cytoarchitecture of the ME of young and aged female rhesus macaques in a preclinical monkey model of menopausal hormone treatments. Rhesus macaques were ovariectomized and treated for 2 years with vehicle, estradiol (E2), or estradiol + progesterone (E2 + P4). While the overall cytoarchitecture of the ME underwent relatively few changes with age and hormones, changes to some features of neural and glial components near the portal capillaries were observed. Specifically, large neuroterminal size was greater in aged compared to young adult animals, an effect that was mitigated or reversed by E2 alone but not by E2 + P4 treatment. Overall glial size and the density and tissue fraction of the largest subset of glia were greater in aged monkeys, and in some cases reversed by E2 treatment. Mitochondrial size was decreased by E2, but not E2 + P4, only in aged macaques. These results contrast substantially with work in rodents, suggesting that the ME of aging macaques is less vulnerable to age-related disorganization, and that the effects of E2 on monkeys' ME are age specific.

Cognitive Effects of Hormone Therapy Continuation or Discontinuation in a Sample of Women at Risk for Alzheimer Disease

OBJECTIVE

Use of estrogen-based hormone therapy (HT) as a protection from cognitive decline and Alzheimer disease (AD) is controversial, although cumulative data support HT use when initiated close to menopause onset with estrogen formulations containing 17β-estradiol preferable to conjugated equine estrogen formulations. Little is known regarding specific populations of women who may derive benefit from HT.

METHODS

Women with heightened risk for AD (aged 49-69), all of whom were taking HT for at least 1 year and most of whom initiated HT close to menopause onset, underwent cognitive assessment followed by randomization to continue or discontinue HT. Assessments were repeated at 2 years after randomization.

RESULTS

Women who continued HT performed better on cognitive domains composed of measures of verbal memory and combined attention, working memory, and processing speed measures. Women who used 17β-estradiol versus conjugated equine estrogen, whether randomized to continue or discontinue HT, showed better verbal memory performance at the 2-year follow-up assessment. An interaction was also found with HT randomization and family history of AD in a first-degree relative. All female offspring of patients with AD declined in verbal memory; however, women who continued HT declined less than women who discontinued HT. Women without a first-degree relative with AD showed verbal memory improvement (likely because of practice effects) with continuance and declined with discontinuance of HT.

CONCLUSION

Continuation of HT use appears to protect cognition in women with heightened risk for AD when initiated close to menopause onset.

Working memory in pregnant women: Relation to estrogen and antepartum depression

This article is part of a Special Issue "Estradiol and cognition". Subjective changes in concentration and memory are commonly reported by women during the second or third trimesters of pregnancy, but the nature of the problem is poorly understood. We hypothesized that these self-reports might reflect difficulties in working memory (WM). It was further hypothesized that antepartum depression (depression arising during pregnancy) may play an etiological role, either on its own or due to secondary changes in endocrine function or sleep. Using WM tasks that emphasized executive control processes mediated by the prefrontal cortex (PFC) we compared pregnant women tested at 34-36 weeks of gestation (n = 28) with age- and education-matched non-pregnant controls (n = 26). All pregnant women were screened for depression. Evidence of a WM disturbance was found, and was evident only among pregnant women showing depressive symptoms. In contrast, pregnant women who were not depressed showed WM performance that equalled, or even significantly exceeded, non-pregnant controls. No significant differences were observed on control tests of other cognitive functions. Multiple regression revealed that serum estradiol concentrations, along with severity of depressive affect but not sleep disruption, significantly predicted variation in the WM scores. In agreement with studies of estradiol and WM in other contexts, higher estradiol was associated with better WM, while higher levels of depressive symptoms predicted poorer WM. We conclude that memory disturbance during gestation might not be as widespread as commonly believed, but can be seen among women experiencing antepartum depression. The high level of WM performance found in healthy, non-depressed, pregnant women is discussed from an adaptationist perspective.

Sex hormones affect language lateralisation but not cognitive control in normally cycling women

This article is part of a Special Issue "Estradiol and Cognition". Natural fluctuations of sex hormones during the menstrual cycle have been shown to modulate language lateralisation. Using the dichotic listening (DL) paradigm, a well-established measurement of language lateralisation, several studies revealed that the left hemispheric language dominance was stronger when levels of estradiol were high. A recent study (Hjelmervik et al., 2012) showed, however, that high levels of follicular estradiol increased lateralisation only in a condition that required participants to cognitively control (top-down) the stimulus-driven (bottom-up) response. This finding suggested that sex hormones modulate lateralisation only if cognitive control demands are high. The present study investigated language lateralisation in 73 normally cycling women under three attention conditions that differed in cognitive control demands. Saliva estradiol and progesterone levels were determined by luminescence immunoassays. Women were allocated to a high or low estradiol group. The results showed a reduced language lateralisation when estradiol and progesterone levels were high. The effect was independent of the attention condition indicating that estradiol marginally affected cognitive control. The findings might suggest that high levels of estradiol especially reduce the stimulus-driven (bottom-up) aspect of lateralisation rather than top-down cognitive control.

Estrogen Effects on Cognitive and Synaptic Health Over the Lifecourse

Estrogen facilitates higher cognitive functions by exerting effects on brain regions such as the prefrontal cortex and hippocampus. Estrogen induces spinogenesis and synaptogenesis in these two brain regions and also initiates a complex set of signal transduction pathways via estrogen receptors (ERs). Along with the classical genomic effects mediated by activation of ER α and ER β, there are membrane-bound ER α, ER β, and G protein-coupled estrogen receptor 1 (GPER1) that can mediate rapid nongenomic effects. All key ERs present throughout the body are also present in synapses of the hippocampus and prefrontal cortex. This review summarizes estrogen actions in the brain from the standpoint of their effects on synapse structure and function, noting also the synergistic role of progesterone. We first begin with a review of ER subtypes in the brain and how their abundance and distributions are altered with aging and estrogen loss (e.g., ovariectomy or menopause) in the rodent, monkey, and human brain. As there is much evidence that estrogen loss induced by menopause can exacerbate the effects of aging on cognitive functions, we then review the clinical trials of hormone replacement therapies and their effectiveness on cognitive symptoms experienced by women. Finally, we summarize studies carried out in nonhuman primate models of age- and menopause-related cognitive decline that are highly relevant for developing effective interventions for menopausal women. Together, we highlight a new understanding of how estrogen affects higher cognitive functions and synaptic health that go well beyond its effects on reproduction.