Physiological variation in estradiol and brain function: a functional magnetic resonance imaging study of verbal memory across the follicular phase of the menstrual cycle

Neuroprotective effects of novel compound FMDB on cognition, neurogenesis and apoptosis in APP/PS1 transgenic mouse model of Alzheimer's disease

Clinical and experimental studies have shown that the sharp reduction of estrogen is one of the important reasons for the high incidence of Alzheimer's disease (AD) in elderly women, but there is currently no such drug for treatment of AD. Our group first designed and synthesized a novel compound R-9-(4fluorophenyl)-3-methyl-10,10,-Hydrogen-6-hydrogen-benzopyran named FMDB. In this study, our aim is to investigate the neuroprotective effects and mechanism of FMDB in APP/PS1 transgenic mice. 6 months old APP/PS1 transgenic mice were intragastrical administered with FMDB (1.25, 2.5 and 5 mg/kg) every other day for 8 weeks. LV-ERβ-shRNA was injected bilaterally into the hippocampus of APP/PS1 mice to knockdown estrogen receptor β (ERβ). We found that FMDB ameliorated cognitive impairment in the Morris water maze and novel object recognition tests, increased hippocampal neurogenesis and prevented hippocampal apoptotic responses in APP/PS1 mice. Importantly, FMDB activated nuclear ERβ mediated CBP/p300, CREB and brain-derived neurotrophic factor (BDNF) signaling, and membrane ERβ mediated PI3K/Akt, CREB and BDNF signaling in the hippocampus. Our study demonstrated the contributions and mechanism of FMDB to cognition, neurogenesis and apoptosis in APP/PS1 mice. These lay the experimental foundation for the development of new anti-AD drugs.

Analytic Background in the Neuroscience of the Potential Project "Hippocrates"

This paper reviews the principles identified in analytic neuroscience that could be used in the setup of an international project, "Hippocrates" (H-project), named after the author of the endocrine theory of temperaments. The H-project can aim to summarize the findings in functional neurochemistry of consistent behavioural patterns (CBPs) in health (such as temperament traits) and psychopathology (symptoms of psychiatric disorders); to have systematically structured neurochemical investigations; to have an analysis of CBPs that include all ranges of behavioural histories and to have these modules complemented by regional contrasts related to climate, diets and other bio-environmental factors. The review highlights the benefits of constructivism and illustrates the contrast between constructivism and current approaches in terms of analytic and methodological aspects. (1) "Where" the neurochemical biomarkers should be measured: the review expands the range of needed measurements to out-of-brain systems, including environmental factors, and explores the concept of Specialized Extended Phenotype. (2) "What" should be measured but is missing: the review points to the need for measurement of the "Throw & Catch" neurochemical relays; behavioural and neuronal events contributing to the consistency of the CBPs but not documented in measurements. (3) Structuring the H-project's setup: the paper briefly describes a proposed earlier neurochemical framework, Functional Ensemble of Temperament that that accommodates the neurochemical continuum between temperament and symptoms of psychiatric disorders. This framework is in line with documented "Throw & Catch" neurochemical relays and can also be used to organize data about the personal and professional history of an individual.

Sex Hormones, Sleep, and Memory: Interrelationships Across the Adult Female Lifespan

As the population of older adults grows, so will the prevalence of aging-related conditions, including memory impairments and sleep disturbances, both of which are more common among women. Compared to older men, older women are up to twice as likely to experience sleep disturbances and are at a higher risk of cognitive decline and Alzheimer's disease and related dementias (ADRD). These sex differences may be attributed in part to fluctuations in levels of female sex hormones (i.e., estrogen and progesterone) that occur across the adult female lifespan. Though women tend to experience the most significant sleep and memory problems during the peri-menopausal period, changes in memory and sleep have also been observed across the menstrual cycle and during pregnancy. Here, we review current knowledge on the interrelationships among female sex hormones, sleep, and memory across the female lifespan, propose possible mediating and moderating mechanisms linking these variables and describe implications for ADRD risk in later life.

The influence of hormonal contraception on depression and female sexuality: a narrative review of the literature

OBJECTIVE

Over the past decades, an increasing number of women have been using hormonal contraception. The potential role of sex hormones in regulating vegetative, psychophysiological, and cognitive functions has been highlighted in several studies, and there is a need to further understand the impact of hormonal contraception on women's quality of life, especially as regards psychological health and sexuality.

METHODS

We conducted a narrative review aimed at clarifying the mechanisms involved in the interaction between sex hormones and the brain, also focusing on the association between hormonal contraception and mood and sexual function.

RESULTS

Our findings clarified that hormonal contraception may be associated with depressive symptoms, especially among adolescents, and with sexual dysfunction. However, the evidence included in this review was conflicting and did not support the hypothesis that hormonal contraception directly causes depressive symptoms, major depressive disorder, or sexual dysfunction.

CONCLUSIONS

The optimal hormonal contraception should be identified in the context of shared decision making, considering the preferences and needs of each woman, as well as her physical and psychosexual conditions.

Spectral dynamic causal modelling in healthy women reveals brain connectivity changes along the menstrual cycle

Longitudinal menstrual cycle studies allow to investigate the effects of ovarian hormones on brain organization. Here, we use spectral dynamic causal modelling (spDCM) in a triple network model to assess effective connectivity changes along the menstrual cycle within and between the default mode, salience and executive control networks (DMN, SN, and ECN). Sixty healthy young women were scanned three times along their menstrual cycle, during early follicular, pre-ovulatory and mid-luteal phase. Related to estradiol, right before ovulation the left insula recruits the ECN, while the right middle frontal gyrus decreases its connectivity to the precuneus and the DMN decouples into anterior/posterior parts. Related to progesterone during the mid-luteal phase, the insulae (SN) engage to each other, while decreasing their connectivity to parietal ECN, which in turn engages the posterior DMN. When including the most confident connections in a leave-one out cross-validation, we find an above-chance prediction of the left-out subjects' cycle phase. These findings corroborate the plasticity of the female brain in response to acute hormone fluctuations and may help to further understand the neuroendocrine interactions underlying cognitive changes along the menstrual cycle.

Preliminary Report: Localized Cerebral Blood Flow Mediates the Relationship between Progesterone and Perceived Stress Symptoms among Female Collegiate Club Athletes after Mild Traumatic Brain Injury

Female athletes are under-studied in the field of concussion research, despite evidence of higher injury prevalence and longer recovery time. Hormonal fluctuations caused by the natural menstrual cycle (MC) or hormonal contraceptive (HC) use impact both post-injury symptoms and neuroimaging findings, but the relationships among hormone, symptoms, and brain-based measures have not been jointly considered in concussion studies. In this preliminary study, we compared cerebral blood flow (CBF) measured with arterial spin labeling between concussed female club athletes 3-10 days after mild traumatic brain injury (mTBI) and demographic, HC/MC matched controls (CON). We tested whether CBF statistically mediates the relationship between progesterone serum levels and post-injury symptoms, which may support a hypothesis for progesterone's role in neuroprotection. We found a significant three-way relationship among progesterone, CBF, and perceived stress score (PSS) in the left middle temporal gyrus for the mTBI group. Higher progesterone was associated with lower (more normative) PSS, as well as higher (more normative) CBF. CBF mediates 100% of the relationship between progesterone and PSS (Sobel p value = 0.017). These findings support a hypothesis for progesterone having a neuroprotective role after concussion and highlight the importance of controlling for the effects of sex hormones in future concussion studies.

Neuroimaging the menstrual cycle: A multimodal systematic review

Increasing evidence indicates that ovarian hormones affect brain structure, chemistry and function of women in their reproductive age, potentially shaping their behavior and mental health. Throughout the reproductive years, estrogens and progesterone levels fluctuate across the menstrual cycle and can modulate neural circuits involved in affective and cognitive processes. Here, we review seventy-seven neuroimaging studies and provide a comprehensive and data-driven evaluation of the accumulating evidence on brain plasticity associated with endogenous ovarian hormone fluctuations in naturally cycling women (n = 1304). The results particularly suggest modulatory effects of ovarian hormones fluctuations on the reactivity and structure of cortico-limbic brain regions. These findings highlight the importance of performing multimodal neuroimaging studies on neural correlates of systematic ovarian hormone fluctuations in naturally cycling women based on careful menstrual cycle staging.

Eye-movements during number comparison: Associations to sex and sex hormones

Multi-digit numbers are of a hierarchical nature with whole number magnitudes depending on digit magnitudes. Processing of multi-digit numbers can occur in a holistic or decomposed fashion. The unit-decade compatibility effect during number comparison is often used as a measure of decomposed processing. It refers to the fact that performance is reduced when the larger number contains the smaller unit digit (e.g. 73 vs. 26). It has been demonstrated that women show a larger compatibility effect than men, which is in accordance with their general tendency towards focusing on stimulus details during processing of visual hierarchical stimuli (local processing style). Such a local processing style has been related to higher progesterone and lower testosterone levels. One method to study individual processing styles is eye-tracking. The aim of the present study was to examine whether sex and sex hormones (estradiol, progesterone, testosterone) relate to eye movement behavior in the number comparison task. Unlike previous studies we found no evidence for sex differences in the behavioral compatibility effect. Nevertheless, women look more often and longer at individual digits and show a stronger compatibility effect in fixation durations compared to men, while men show more saccades between numbers than women. Estradiol and progesterone were related to fewer fixations and shorter fixation durations and more saccades between numbers in men, but not in women. Furthermore, the compatibility effect in the number of fixations and fixation durations was negatively related to testosterone in women. In summary, this is the first study to demonstrate sex differences and sex hormone influences on eye gaze behavior during number comparison.

Sex hormones and human brain function

Sex hormones have organizational and activational effects on the human brain and can interact with the neurotransmitter systems. These biologic mechanisms may have a far-reaching impact, with both behavioral consequences and structural as well as functional brain modulation. The impact of cycling hormone levels throughout the menstrual cycle on cognitive and emotion processing has especially received some attention recently. Therefore, the aim of this chapter is to give an overview of findings regarding the effects of estradiol and progesterone, but also testosterone, on functional brain domains comprising cognition, emotion, and reward processing.

Cutting to the Pathophysiology Chase: Translating Cutting-Edge Neuroscience to Rehabilitation Practice in Sports-Related Concussion Management

Mild traumatic brain injury, or concussion, is a common sports injury. Concussion involves physical injury to brain tissue and vascular and axonal damage that manifests as transient and often nonspecific clinical symptoms. Concussion diagnosis is challenging, and the relationship between brain injury and clinical symptoms is unclear. The purpose of this commentary was to translate cutting-edge neuroscience to rehabilitation practice. We (1) highlight potential biomarkers that may improve our understanding of concussion and its recovery, (2) explain why researchers must address the paucity of concussion research in female athletes, and (3) present female-specific factors that should be accounted for in future studies. Integrating objective, quantitative measures of concussion pathophysiology with concussion history, genetics, and genomics will help caregivers identify concussed athletes, tailor recovery protocols, and protect athletes from potential long-term effects of cumulative head impact. J Orthop Sports Phys Ther 2019;49(11):811-818. Epub 1 Jun 2019. doi:10.2519/jospt.2019.8884.

The cycling brain: menstrual cycle related fluctuations in hippocampal and fronto-striatal activation and connectivity during cognitive tasks

Estradiol and progesterone vary along the menstrual cycle and exert opposite effects on a variety of neurotransmitter systems. However, few studies have addressed menstrual cycle-dependent changes in the brain. In the present study we investigate menstrual cycle changes in brain activation and connectivity patterns underlying cognition. Thirty-six naturally cycling women underwent functional MRI during two cognitive tasks: spatial navigation and verbal fluency. While no significant performance differences were observed along the menstrual cycle, the changes in brain activation patterns are strikingly similar during both tasks. Irrespective of the task, estradiol boosts hippocampal activation during the pre-ovulatory cycle phase and progesterone boosts fronto-striatal activation during the luteal cycle phase. Connectivity analyses suggest that the increase in right-hemispheric frontal activation is the result of inter-hemispheric decoupling and is involved in the down-regulation of hippocampal activation.

The Impact of Estradiol on Neurogenesis and Cognitive Functions in Alzheimer's Disease

Alzheimer's disease (AD) is described as cognitive and memory impairments with a sex-related epidemiological profile, affecting two times more women than men. There is emerging evidence that alternations in the hippocampal neurogenesis occur at the early stage of AD. Therapies that may effectively slow, stop, or regenerate the dying neurons in AD are being extensively investigated in the last few decades, but none has yet been found to be effective. The regulation of endogenous neurogenesis is one of the main therapeutic targets for AD. Mounting evidence indicates that the neurosteroid estradiol (17β-estradiol) plays a supporting role in neurogenesis, neuronal activity, and synaptic plasticity of AD. This effect may provide preventive and/or therapeutic approaches for AD. In this article, we discuss the molecular mechanism of potential estradiol modulatory action on endogenous neurogenesis, synaptic plasticity, and cognitive function in AD.

ERα and/or ERβ activation ameliorates cognitive impairment, neurogenesis and apoptosis in type 2 diabetes mellitus mice

Estrogen receptors (ERs) are thought to be associated with the onset and progression of neurodegenerative injuries and diseases, but the relationship and mechanisms underlying between ERs and cognition in type 2 diabetes remain elusive. In the current study, we investigated the effects of ERα and ERβ on the cognition, neurogenesis and apoptosis in high-fat diet and streptozocin-induced diabetic mice. We found that ERα and/or ERβ activation using their agonists (0.5 mg/kg E2, PPT or DPN) ameliorate memory impairment in the Morris water maze and Y-maze tests, increase hippocampal neurogenesis and prevent hippocampal apoptotic responses. Importantly, treatment with the pharmacologic ERs agonists caused significant increases in the membrane ERα and ERβ expression and subsequent PI3K/Akt, CREB and BDNF activation in the hippocampus of type 2 diabetes mellitus mice. Our data indicate that ERα and ERβ are involved in the cognitive impairment in type 2 diabetes, and that activated ERs, such as application of ERs agonists, could be a novel and promising strategy for the treatment of diabetic cognitive impairment.

Sex, age, and sex hormones affect recall of words in a directed forgetting paradigm

During the course of serious discussion, an unexpected interruption may induce forgetting of the original topic of a conversation. Sex, age, and sex hormone levels may affect frequency and extension of forgetting. In a list-method directed forgetting paradigm, subjects have to learn two word lists. After learning list 1, subjects receive either a forget or a remember list 1 cue. When the participants had learned list 2 and completed a distraction task, they were asked to write down as many recalled items as possible, starting either with list 1 or list 2 items. In the present study, 96 naturally cycling women, 60 oral contraceptive users, 56 postmenopausal women, and 41 young men were assigned to one of these different experimental conditions. Forget-cued young subjects recall fewer list 1 items (list 1 forgetting) but more list 2 items (list 2 enhancement) compared with remember-cued subjects. However, forget-cued postmenopausal women showed reduced list 1 forgetting but enhanced list 2 retention. Remember-cued naturally cycling women recalled more list 1 items than oral contraceptive users, young men, and postmenopausal women. In forget-cued follicular women, salivary progesterone correlated positively with recalled list 2 items. Salivary 17β-estradiol did not correlate with recalled list 1 or list 2 items in either remember- or forget-cued young women. However, salivary 17β-estradiol correlated with item recall in remember-cued postmenopausal women. Our findings suggest that sex hormones do not globally modulate verbal memory or forgetting, but selectively affect cue-specific processing. © 2016 Wiley Periodicals, Inc.

Reproductive Steroid Regulation of Mood and Behavior

In this article, we examine evidence supporting the role of reproductive steroids in the regulation of mood and behavior in women and the nature of that role. In the first half of the article, we review evidence for the following: (i) the reproductive system is designed to regulate behavior; (ii) from the subcellular to cellular to circuit to behavior, reproductive steroids are powerful neuroregulators; (iii) affective disorders are disorders of behavioral state; and (iv) reproductive steroids affect virtually every system implicated in the pathophysiology of depression. In the second half of the article, we discuss the diagnosis of the three reproductive endocrine-related mood disorders (premenstrual dysphoric disorder, postpartum depression, and perimenopausal depression) and present evidence supporting the relevance of reproductive steroids to these conditions. Existing evidence suggests that changes in reproductive steroid levels during specific reproductive states (i.e., the premenstrual phase of the menstrual cycle, pregnancy, parturition, and the menopause transition) trigger affective dysregulation in susceptible women, thus suggesting the etiopathogenic relevance of these hormonal changes in reproductive mood disorders. Understanding the source of individual susceptibility is critical to both preventing the onset of illness and developing novel, individualized treatments for reproductive-related affective dysregulation. © 2016 American Physiological Society. Compr Physiol 6:1135-1160, 2016e.

Use of Galvanic Skin Responses, Salivary Biomarkers, and Self-reports to Assess Undergraduate Student Performance During a Laboratory Exam Activity

Typically, self-reports are used in educational research to assess student response and performance to a classroom activity. Yet, addition of biological and physiological measures such as salivary biomarkers and galvanic skin responses are rarely included, limiting the wealth of information that can be obtained to better understand student performance. A laboratory protocol to study undergraduate students' responses to classroom events (e.g., exams) is presented. Participants were asked to complete a representative exam for their degree. Before and after the laboratory exam session, students completed an academic achievement emotions self-report and an interview that paralleled these questions when participants wore a galvanic skin sensor and salivary biomarkers were collected. Data collected from the three methods resulted in greater depth of information about students' performance when compared to the self-report. The work can expand educational research capabilities through more comprehensive methods for obtaining nearer to real-time student responses to an examination activity.

Neurocognitive effects of estrogens across the adult lifespan in nonhuman primates: State of knowledge and new perspectives

This article is part of a Special Issue "Estradiol and cognition". This review discusses the unique contribution of nonhuman primate research to our understanding of the neurocognitive effects of estrogens throughout the adult lifespan in females. Mounting evidence indicates that estrogens affect many aspects of hippocampal, prefrontal and cholinergic function in the primate brain and the underlying mechanisms are beginning to be elucidated. In addition, estrogens may also influence cognitive function indirectly, via the modulation of other systems that impact cognition. We will focus on the effects of estrogens on sleep and emphasize the need for primate models to better understand these complex interactions. Continued research with nonhuman primates is essential for the development of therapies that are optimal for the maintenance of women's cognitive health throughout the lifespan.

Emotional and cognitive functional imaging of estrogen and progesterone effects in the female human brain: a systematic review

Ovarian hormones are pivotal for the physiological maintenance of the brain function as well as its response to environmental stimuli. There is mounting evidence attesting the relevance of endogenous ovarian hormones as well as exogenous estradiol and progesterone for emotional and cognitive processing. The present review systematically summarized current knowledge on sex steroid hormonal modulation of neural substrates of emotion and cognition revealed by functional magnetic resonance imaging (fMRI). Twenty-four studies of healthy naturally cycling and combined oral contraceptives (COC) user women, or women undergoing experimental manipulations, during their reproductive age, were included. Furthermore, six studies of premenstrual dysphoric disorder (PMDD), a hormonally based mood disorder, and three of gender dysphoria (GD), which provides an intriguing opportunity to examine the effect of high-dose cross-sex hormone therapy (CSHT) on brain functioning, were included. Globally, low (early follicular and the entire follicular phase for estrogen and progesterone, respectively) and high (COC, CSHT, late follicular and luteal phase for estrogen; COC, mid- and late-luteal phase for progesterone) hormonal milieu diversely affected the response of several brain regions including the amygdala, anterior cingulate cortex, and inferior frontal gyrus, but their functional recruitment across groups and domains was scattered. The constellation of findings provides initial evidence of the influence of sex steroid hormones on cortical and subcortical regions implicated in emotional and cognitive processing. Further well-powered and multimodal neuroimaging studies will be needed to identify the neural mechanism of functional brain alterations induced by sex steroid hormones.

Effects of sex chromosome dosage on corpus callosum morphology in supernumerary sex chromosome aneuploidies

Background

Supernumerary sex chromosome aneuploidies (sSCA) are characterized by the presence of one or more additional sex chromosomes in an individual’s karyotype; they affect around 1 in 400 individuals. Although there is high variability, each sSCA subtype has a characteristic set of cognitive and physical phenotypes. Here, we investigated the differences in the morphometry of the human corpus callosum (CC) between sex-matched controls 46,XY (N =99), 46,XX (N =93), and six unique sSCA karyotypes: 47,XYY (N =29), 47,XXY (N =58), 48,XXYY (N =20), 47,XXX (N =30), 48,XXXY (N =5), and 49,XXXXY (N =6).

Methods

We investigated CC morphometry using local and global area, local curvature of the CC boundary, and between-landmark distance analysis (BLDA). We hypothesized that CC morphometry would vary differentially along a proposed spectrum of Y:X chromosome ratio with supernumerary Y karyotypes having the largest CC areas and supernumerary X karyotypes having significantly smaller CC areas. To investigate this, we defined an sSCA spectrum based on a descending Y:X karyotype ratio: 47,XYY, 46,XY, 48,XXYY, 47,XXY, 48,XXXY, 49,XXXXY, 46,XX, 47,XXX. We similarly explored the effects of both X and Y chromosome numbers within sex. Results of shape-based metrics were analyzed using permutation tests consisting of 5,000 iterations.

Results

Several subregional areas, local curvature, and BLDs differed between groups.

Moderate associations were found between area and curvature in relation to the spectrum and X and Y chromosome counts. BLD was strongly associated with X chromosome count in both male and female groups.

Conclusions

Our results suggest that X- and Y-linked genes have differential effects on CC morphometry. To our knowledge, this is the first study to compare CC morphometry across these extremely rare groups.

Longitudinal assessment of chemotherapy-induced alterations in brain activation during multitasking and its relation with cognitive complaints

PURPOSE

To examine whether cognitive complaints after treatment for breast cancer are associated with detectable changes in brain activity during multitasking.

PATIENTS AND METHODS

Eighteen patients who were scheduled to receive chemotherapy performed a functional magnetic resonance imaging multitasking task in the scanner before the start of treatment (t1) and 4 to 6 months after finishing treatment (t2). Sixteen patients who were not scheduled to receive chemotherapy and 17 matched healthy controls performed the same task at matched intervals. Task difficulty level was adjusted individually to match performance across participants. Statistical Parametric Mapping 8 (SPM8) software was used for within-group, between-group, and group-by-time interaction image analyses.

RESULTS

Voxel-based paired t tests revealed significantly decreased activation (P < .05) from t1 to t2 at matched performance in the multitasking network of chemotherapy-treated patients, whereas no changes were noted in either of the control groups. At baseline, there were no differences between the groups. Furthermore, in contrast to controls, the chemotherapy-treated patients reported a significant increase in cognitive complaints (P < .05) at t2. Significant (P < .05) correlations were found between these increases and decreases in multitasking-related brain activation. Moreover, a significant group-by-time interaction (P < .05) was found whereby chemotherapy-treated patients showed decreased activation and healthy controls did not.

CONCLUSION

These results suggest that changes in brain activity may underlie chemotherapy-induced cognitive complaints. The observed changes might be related to chemotherapy-induced damage to the brain or reduced connectivity between brain regions rather than to changes in effort or changes in functional strategy. To the best of our knowledge, this is the first longitudinal study providing evidence for a relationship between longitudinal changes in cognitive complaints and changes in brain activation after chemotherapy.

Brain sex matters: estrogen in cognition and Alzheimer's disease

Estrogens are the primary female sex hormones and play important roles in both reproductive and non-reproductive systems. Estrogens can be synthesized in non-reproductive tissues such as liver, heart, muscle, bone and the brain. During the past decade, increasing evidence suggests that brain estrogen can not only be synthesized by neurons, but also by astrocytes. Brain estrogen also works locally at the site of synthesis in paracrine and/or intracrine fashion to maintain important tissue-specific functions. Here, we will focus on the biology of brain estrogen and its impact on cognitive function and Alzheimer's disease. This comprehensive review provides new insights into brain estrogens by presenting a better understanding of the tissue-specific estrogen effects and their roles in healthy ageing and cognitive function.

Estrogen and the prefrontal cortex: towards a new understanding of estrogen's effects on executive functions in the menopause transition

Midlife decline in cognition, specifically in areas of executive functioning, is a frequent concern for which menopausal women seek clinical intervention. The dependence of executive processes on prefrontal cortex function suggests estrogen effects on this brain region may be key in identifying the sources of this decline. Recent evidence from rodent, nonhuman primate, and human subject studies indicates the importance of considering interactions of estrogen with neurotransmitter systems, stress, genotype, and individual life events when determining the cognitive effects of menopause and estrogen therapy.

Estrogens and memory in physiological and neuropathological conditions

Ovarian hormones can influence brain regions crucial to higher cognitive functions, such as learning and memory, acting at structural, cellular and functional levels, and modulating neurotransmitter systems. Among the main effects of estrogens, the protective role that they may play against the deterioration of cognitive functions occurring with normal aging is of essential importance. In fact, during the last century, there has been a 30 years increase in female life expectancy, from 50 to 83 years; however, the mean age of spontaneous menopause remains stable, 50-51 years, with variability related to race and ethnicity. Therefore, women are now spending a greater fraction of their lives in a hypoestrogenic state. Although many cognitive functions seem to be unaffected by normal aging, age-related impairments are particularly evident in tasks involving working memory (WM), whose deficits are a recognized feature of Alzheimer's disease (AD). Many studies conducted over the past two decades showed that the female gonadal hormone estradiol can influence performance of learning and memory tasks, both in animal and humans. There is a great deal of evidence, mostly from animal models, that estrogens can facilitate or enhance performance on WM tasks; therefore, it is very important to clarify their role on this type of memory. To this aim, in this review we briefly describe the most relevant neurobiological bases of estrogens, that can explain their effects on cognitive functioning, and then we summarize the results of works conducted in our laboratory, both on animals and humans, utilizing the menstrual/estrous cycle as a useful noninvasive model. Finally, we review the possible role of estrogens in neuropathological conditions, such as AD and schizophrenia.

Alterations in brain activation during working memory processing associated with breast cancer and treatment: a prospective functional magnetic resonance imaging study

PURPOSE

To prospectively examine alterations in working memory (WM) -associated brain activation related to breast cancer and treatment by using functional magnetic resonance imaging.

PATIENTS AND METHODS

Patients treated with chemotherapy (CTx+; n = 16) or without chemotherapy (CTx-; n = 12) and healthy controls (n = 15) were scanned during an n-back task at baseline (after surgery but before radiation, chemotherapy, and/or antiestrogen treatment), 1 month after completion of chemotherapy (M1), and 1 year later (Y1), or at yoked intervals for CTx- and controls. SPM5 was used for all image analyses, which included cross-sectional between-group and group-by-time interaction and longitudinal within-group analyses, all using a statistical threshold of 0.001.

RESULTS

At baseline, patients with cancer showed increased bifrontal and decreased left parietal activation compared with controls. At M1, both cancer groups showed decreased frontal hyperactivation compared with controls, with increased hyperactivation at Y1. These cross-sectional findings were confirmed by group-by-time interaction analyses, which showed frontal activation decreases from baseline to M1 in patients compared with controls. Within-group analyses showed different patterns of longitudinal activation change by treatment group (CTx+ or CTx-), with prominent alterations in the frontal lobes bilaterally.

CONCLUSION

Significant frontal lobe hyperactivation to support WM was found in patients with breast cancer. Superimposed on this background, patients showed decreased frontal activation at M1, with partial return to the previously abnormal baseline at Y1. These functional changes correspond to frontal lobe regions where we previously reported structural changes in this cohort and provide prospective, longitudinal data that further elucidate mechanisms underlying cognitive effects related to breast cancer and its treatment.

Influence of estradiol on functional brain organization for working memory

Working memory is a cognitive function that is affected by aging and disease. To better understand the neural substrates for working memory, the present study examined the influence of estradiol on working memory using functional magnetic resonance imaging. Pre-menopausal women were tested on a verbal n-back task during the early (EF) and late follicular (LF) phases of the menstrual cycle. Although brain activation patterns were similar across the two phases, the most striking pattern that emerged was that estradiol had different associations with the two hemispheres. Increased activation in left frontal circuitry in the LF phase was associated with increased estradiol levels and decrements in working memory performance. In contrast, increased activation in right hemisphere regions in the LF phase was associated with improved task performance. The present study showed that better performance in the LF than the EF phase was associated with a pattern of reduced recruitment of the left-hemisphere and increased recruitment of the right-hemisphere in the LF compared to EF phase. We speculate that estradiol interferes with left-hemisphere working-memory processing in the LF phase, but that recruitment of the right hemisphere can compensate for left-hemisphere interference. This may be related to the proposal that estradiol can reduce cerebral asymmetries by modulating transcallosal communication (Hausmann, 2005).

Menstrual cycle variations in the BOLD-response to a number bisection task: implications for research on sex differences

Numerical processing involves either number magnitude processing, which has been related to spatial abilities and relies on superior parietal regions, or arithmetic fact retrieval, which has been related to verbal abilities and involves the inferior parietal lobule. Since men score better in spatial and women in verbal tasks, we assume that women have advantages in fact retrieval, while men have benefits in number magnitude processing. According to findings on menstrual cycle variations in spatial and verbal abilities, fact retrieval should improve during the luteal phase and magnitude processing during the follicular phase. To dissociate sex- and menstrual cycle-dependent effects on fact retrieval and number magnitude processing, we applied a number bisection task in 15 men and 15 naturally cycling women. Multiplicative items (e.g. 12_15_18) are part of a multiplication series and can be solved by fact retrieval, while non-multiplicative items (e.g. 11_14_17) are not part of a multiplication series and require number magnitude processing. In men and women in their luteal phase, error rates were higher and deactivation of the medial prefrontal cortex and the bilateral inferior parietal lobules was stronger for non-multiplicative compared to multiplicative items (positive multiplicativity effect), while in the follicular phase women showed higher error rates and stronger deactivation in multiplicative compared to non-multiplicative items (negative multiplicativity effect). Thus, number magnitude processing improves, while arithmetic fact retrieval impairs during the follicular phase. While a female superiority in arithmetic fact retrieval could not be confirmed, we observed that sex differences are significantly modulated by menstrual cycle phase.

The interactive effect of acute ovarian suppression and the cholinergic system on visuospatial working memory in young women

Women have an increased risk of developing Alzheimer's Dementia (AD) compared to men. It has been postulated that this risk may be modulated by a reduction in the neuroprotective effects of estrogen on the brain in the early postmenopausal period. This view is supported by, for example, findings that ovariectomy in younger women (i.e. prior to menopause) significantly increases the risk for the development of memory problems and AD in later life. However, the biological basis underlying these cognitive changes is still poorly understood. Our aim in the current study was to understand the interactive effects of acute, pharmacological-induced menopause (after Gonadotropin Hormone Releasing Hormone agonist (GnRHa) treatment) and scopolamine (a cholinergic antagonist used to model the memory decline associated with aging and AD) on brain functioning. To this end we used fMRI to study encoding during a Delayed Match to Sample (DMTS) (visual working memory) task. We report a relative attenuation in BOLD response brought about by scopolamine in regions that included bilateral prefrontal cortex and the left parahippocampal gyrus. Further, this was greater in women post-GnRHa than in women whose ovaries were functional. Our results also indicate that following pharmacological-induced menopause, cholinergic depletion produces a more significant behavioural deficit in overall memory performance, as manifest by increased response time. These findings suggest that acute loss of ovarian hormones exacerbate the effects of cholinergic depletion on a memory-related, behavioural measure, which is dependent on fronto-temporal brain regions. Overall, our findings point to a neural network by which acute loss of ovarian function may interact to negatively impact encoding.

Menstrual cycle modulation of medial temporal activity evoked by negative emotion

Previous studies have indicated phase-related differences in HPA activity and amygdala responsiveness in women, such that the response to negative emotional images is reduced during high-estrogen phases of the menstrual cycle. Other research has indicated an opposite effect of exogenous progesterone, increasing amygdala activity at some doses. However, no study to date has assessed the response of the brain's arousal circuitry to negative images during the luteal phase, when both progesterone and estrogen levels are elevated. To address this question, 17 naturally cycling women were each scanned during the early follicular and mid-luteal phases of the cycle, and response to IAPS images was assessed by fMRI. The results indicated significantly increased activity in hippocampus and amygdala during mid-luteal scans when compared to scans in the early follicular phase. These findings suggest that progesterone-mediated effects dominate during the luteal phase, and further suggest that estrogen and progesterone may play opposing roles in modulating the brain's arousal circuitry.

Estrogen actions in the brain and the basis for differential action in men and women: a case for sex-specific medicines

The classic view of estrogen actions in the brain was confined to regulation of ovulation and reproductive behavior in the female of all mammalian species studied, including humans. Burgeoning evidence now documents profound effects of estrogens on learning, memory, and mood as well as neurodevelopmental and neurodegenerative processes. Most data derive from studies in females, but there is mounting recognition that estrogens play important roles in the male brain, where they can be generated from circulating testosterone by local aromatase enzymes or synthesized de novo by neurons and glia. Estrogen-based therapy therefore holds considerable promise for brain disorders that affect both men and women. However, as investigations are beginning to consider the role of estrogens in the male brain more carefully, it emerges that they have different, even opposite, effects as well as similar effects in male and female brains. This review focuses on these differences, including sex dimorphisms in the ability of estradiol to influence synaptic plasticity, neurotransmission, neurodegeneration, and cognition, which, we argue, are due in a large part to sex differences in the organization of the underlying circuitry. There are notable sex differences in the incidence and manifestations of virtually all central nervous system disorders, including neurodegenerative disease (Parkinson's and Alzheimer's), drug abuse, anxiety, and depression. Understanding the cellular and molecular basis of sex differences in brain physiology and responses to estrogen and estrogen mimics is, therefore, vitally important for understanding the nature and origins of sex-specific pathological conditions and for designing novel hormone-based therapeutic agents that will have optimal effectiveness in men or women.

Aging, estrogens, and episodic memory in women

OBJECTIVE

To review the relation in midlife and beyond between estrogen exposures and episodic memory in women.

BACKGROUND

Episodic memory performance declines with usual aging, and impairments in episodic memory often portend the development of Alzheimer disease. In the laboratory, estradiol influences hippocampal function and animal learning. However, it is controversial whether estrogens affect memory after a woman's reproductive years.

METHOD

Focused literature review, including a summary of a systematic search of clinical trials of estrogens in which outcomes included an objective measure of episodic memory.

RESULTS

The natural menopause transition is not associated with the objective changes in episodic memory. Strong clinical trial evidence indicates that initiating estrogen-containing hormone therapy after the age of about 60 years does not benefit episodic memory. Clinical trial findings in middle-aged women before the age of 60 years are limited by smaller sample sizes and shorter treatment durations, but these also do not indicate substantial memory effects. Limited short-term evidence, however, suggests that estrogens may improve verbal memory after surgical menopause. Although hormone therapy initiation in old age increases dementia risk, observational studies raise the question of an early critical window during which midlife estrogen therapy reduces late-life Alzheimer disease. However, almost no data address whether midlife estrogen therapy affects episodic memory in old age.

CONCLUSIONS

Episodic memory is not substantially impacted by the natural menopause transition or improved by the use of estrogen-containing hormone therapy after the age of 60 years. Further research is needed to determine whether outcomes differ after surgical menopause or whether episodic memory later in life is modified by midlife estrogenic exposures.

Female fear: influence of estrus cycle on behavioral response and neuronal activation

Our observation that male rat's innate fear response differed with hormonal status, as well as the higher prevalence of fear and anxiety disorders in human females led to the current investigation of the impact of phases of the estrus cycle on innate fear responding. Female rats in different phases of the cycle were exposed to an innate fear-inducing stimulus (2,5-dihydro-2,4,5-trimethylthiazoline, TMT odor) and monitored for changes in behavior and brain activation. Behavioral data showed freezing responses to TMT were significantly enhanced during estrus as compared to other phases of the cycle. This data was supported by significant increases in pixel intensity in cortical and sub-cortical regions in estrus compared to proestrus and diestrus. Imaging results demonstrated significant increases in brain activation in the somatosensory and insular cortices when comparing estrus to diestrus. There were significant increases in neural activity in the bed nucleus of the stria terminals (BNST) and septum in estrus as compared to proestrus. Additionally, the hippocampus, hypothalamus, olfactory system, and cingulate cortex show significant increases in the estrus phase when compared to both diestrus and proestrus. Taken together, these results suggest that the female's hormonal status may be correlated with alterations in both neuronal and behavioral indices of fear.

Blood oxygenation level dependent functional magnetic resonance imaging: current and potential uses in obstetrics and gynaecology

Blood-oxygenation-level-dependent functional magnetic resonance imaging is a noninvasive technique that has become increasingly popular in the neurosciences. It measures the proportion of oxygenated haemoglobin in specific areas of the brain, mirroring blood flow and therefore function. Here we review how the findings from functional studies impact on areas of gynaecological practice as diverse as chronic pain, continence, and premenstrual dysphoric disorder. Finally we review some of the more novel applications of the technique, such as imaging of pelvic floor function and the effects of hypoxia on the fetus.

The interactive effect of the cholinergic system and acute ovarian suppression on the brain: an fMRI study

Recent evidence suggests that loss of ovarian function following ovariectomy is a risk factor for Alzheimer's disease (AD); however, the biological basis of this risk remains poorly understood. We carried out an fMRI study into the interaction between loss of ovarian function (after Gonadotropin Hormone Releasing Hormone agonist (GnRHa) treatment) and scopolamine (a cholinergic antagonist used to model the memory decline associated with aging and AD). Behaviorally, cholinergic depletion produced a deficit in verbal recognition performance in both GnRHa-treated women and wait list controls, but only GnRHa-treated women made more false positive errors with cholinergic depletion. Similarly, cholinergic depletion produced a decrease in activation in the left inferior frontal gyrus (LIFG; Brodmann area 45)--a brain region implicated in retrieving word meaning--in both groups, and activation in this area was further reduced following GnRHa treatment. These findings suggest biological mechanisms through which ovarian hormone suppression may interact with the cholinergic system and the LIFG. Furthermore, this interaction may provide a useful model to help explain reports of increased risk for cognitive decline and AD in women following ovariectomy.

Reversibility of the effects of acute ovarian hormone suppression on verbal memory and prefrontal function in pre-menopausal women

BACKGROUND

Whilst acute loss of ovarian function is associated with memory deficits, the biological basis of this is poorly understood. We have previously reported that acute loss of function during Gonadotropin Hormone Releasing Hormone agonists (GnRHa) treatment is associated with impaired verbal memory and a disruption of corresponding left inferior frontal gyrus (LIFG) during the encoding stage. In the current study, we provide a critical extension to this work by determining whether this memory deficit is reversible following normalization of ovarian function. To do this we carried out a further imaging study using the same verbal memory recognition task after cessation of GnRHa-induced ovarian suppression.

METHOD

We used event-related fMRI to study verbal episodic memory performance and brain activation at the LIFG in 13 healthy pre-menopausal women pre-, during, and post-acute ovarian hormone suppression using GnRHa.

RESULTS

Following resolution of acute GnRHa-induced ovarian suppression, verbal recognition scores returned to their initial levels and this restoration was associated with a restored level of left frontal activation during successful encoding of words.

CONCLUSIONS

Our findings suggest that the memory deficits associated with acute ovarian suppression are reversed following resolution of normal ovarian function and are associated with reversible attenuation of LIFG activation during encoding. These findings lend further support to the hypothesis that memory difficulties reported by some women following acute ovarian hormone withdrawal are reversible and may have a clear neurobiological basis.