Sex differences in episodic memory: minimal influence of estradiol

Gender-specificities in Alzheimer's disease and mild cognitive impairment

BACKGROUND

Amnestic Mild Cognitive Impairment (MCI) is a condition with an increased risk for developing Alzheimer's disease (AD). Presently, gender differences are neglected in the assessment of MCI and AD.

METHODS

We examined verbal and visuospatial episodic memory in 143 subjects diagnosed as healthy controls (HC; N = 48, Mini-Mental State Examination (MMSE) 29.2 +/- 1.0 (mean +/- standard deviation)), MCI (N = 43,MMSE 28.5 +/- 1.4), and AD (N = 49, MMSE 25.1 +/- 2.2).

FINDINGS

Female HC and MCI subjects performed better on verbal episodic memory tasks than males. In contrast, visuospatial episodic memory was better in male than female AD patients.

CONCLUSIONS

We interpret the results in light of a gender-specific cognitive reserve and conclude that the gender-specificity of neuropsychological performance needs to be accounted for in clinical diagnosis of Alzheimer's disease.

Sex differences in two event-related potentials components related to semantic priming

Although sex differences in language processing are well documented in behavioral studies, only a few electrophysiological studies have explored this topic. We analyzed sex differences in two language-related components of event-related potentials (ERPs): the N400 and the Late Positive Complex (LPC). Ten men and 10 women, matched by age and handedness, participated in the study. Two semantic priming paradigms were presented: word pairs (60 congruent and 60 incongruent) and sentences (50 with congruent and 50 with incongruent ending words). In addition, the effect of context was investigated by a comparison between ERP effects obtained in single word priming and sentential priming. The N400 effect was earlier and larger in women, and the LPC effect was larger in men. Furthermore, the LPC effect in men, but not in women, was much larger with sentence priming than with word priming, suggesting that the LPC effect may be more dependent on context in men than in women. The opposite sex difference on the two ERP components indicates different underlying mechanisms. While the LPC effect is thought to be generated by purely explicit mechanisms, such as postlexical integrative processes, the N400 effect may be also governed by prelexical implicit and explicit mechanisms. Our results were consistent with the notion of more automated processing of language in women than in men.

Endogenous estrogen is not associated with cognitive performance before, during, or after menopause

OBJECTIVE

In a population-based sample of women (45, 50, or 55 years old), behavioral data and blood serum were collected concurrently, enabling us (1) to investigate cognitive differences among premenopausal, perimenopausal, and postmenopausal groups of women and (2) to evaluate the relationship between blood estrogen levels and cognitive performance.

DESIGN

Groups of premenopausal (n = 129), perimenopausal (n = 58), and postmenopausal (n = 55) women were tested on tasks assessing episodic and semantic memory, verbal fluency, visuospatial performance, and face recognition. Blood serum was collected concurrently for analyses of estrogen levels.

RESULTS

With inclusion of controls for age and education, results showed that there were no differences in cognitive performance among premenopausal, perimenopausal, and postmenopausal groups of women. In addition, there were no associations between blood estrogen levels and cognitive performance.

CONCLUSIONS

These results do not support the hypothesis that estrogen or menopausal status affects cognitive performance in middle-aged women.

Sex differences in face recognition memory in patients with temporal lobe epilepsy, patients with generalized epilepsy, and healthy controls

The influence of sex on face recognition memory was studied in 49 patients with temporal lobe epilepsy, 20 patients with generalized epilepsy, and 32 healthy controls. After learning 20 faces, serially presented for 5 seconds each, subjects had to recognize the 20 among 40 faces (including 20 new faces) immediately and 24 hours later. Women had better face recognition than men, with no significant differences between groups. Women's advantage was due mainly to superior delayed recognition. Taken together, the results suggest that sex has a similar impact on face recognition in patients with epilepsy and healthy controls, and that testing delayed face recognition raises sensitivity for sex differences. The influence of sex on face recognition in patients with epilepsy should be acknowledged when evaluating individuals or comparing groups.

Verified hormone therapy improves episodic memory performance in healthy postmenopausal women

Studies of hormone therapy (HT) and cognition have yielded conflicting results. The aim of this observational study was to examine the effect of estradiol, via serum verified HT (estradiol, estriol, progesterone) and endogenous estradiol, on 108 healthy postmenopausal women's cognitive performance. The results demonstrated that the 43 HT-users performed at a significantly higher level than non-users on episodic memory tasks and on a verbal fluency task, whereas HT-users and non-users did not differ on tasks assessing semantic memory and spatial visualization. In addition, there was a positive relationship between serum estradiol level and episodic memory performance, indicating that postmenopausal HT is associated with enhanced episodic memory and verbal fluency, independent of age and education. These observational results suggest that HT use may be sufficient to exert small, yet positive effects on female sensitive cognitive tasks. Hormone therapy compliance and formulation is discussed as confounding factors in previous research.

Surprising lack of sex differences in normal cognitive aging in twins

Sex differences in the etiology of normal cognitive functioning in aging remain largely unexplored. We conducted an investigation of genetic and environmental contributions to sex differences in level of cognitive performance and rate of decline in the Swedish Adoption/Twin Study of Aging (SATSA) (Finkel & Pedersen, 2004) data set. Behavioral genetic parameterizations of a latent growth curve model were fit to longitudinal data on 11 cognitive measures. Seven hundred and ninety-eight non-demented individuals had cognitive data across four waves of measurement covering 13 years. Participants ranged in age from 44 to 88 at first testing wave; 60% were female. Results indicated sex differences in mean performance for five cognitive measures and in rates of decline for Information and Card Rotations. Only Synonyms demonstrated sex differences in genetic and environmental contributions to mean performance: heritability was higher in men than women. Despite differential longevity and susceptibility to disease, there are no consistent indications that men and women show different patterns of cognitive aging.

Negative Association of Testosterone on Spatial Visualization in 35 to 80 Year Old Men

Androgens have been linked to visuospatial ability. We examined the relationship between serum free testosterone (T) levels and spatial visualization ability in a population-based sample of 450 healthy men between the ages of 35 and 80 years. They were tested on block design and Mini Mental State Examination (MMSE) draw-a-figure, as well as tasks assessing episodic memory, semantic memory, procedural memory, and verbal fluency. Blood was analyzed for free T and estradiol. Participants were grouped into high or low free T based on age-specific median values. Participants with low free T performed at a superior level on both the block design task and draw-a-figure task as compared to participants with high free T. The results are discussed within the scant body of research on androgens and cognition in men.

Sex differences in eye gaze and symbolic cueing of attention

Observing a face with averted eyes results in a reflexive shift of attention to the gazed-at location. Here we present results that show that this effect is weaker in males than in females (Experiment 1). This result is predicted by the 'extreme male brain' theory of autism (Baron-Cohen, 2003), which suggests that males in the normal population should display more autism-like traits than females (e.g., poor joint attention). Indeed, participants' scores on the Autism-Spectrum Quotient (Baron-Cohen, Wheelwright, Stott, Bolton, & Goodyear, 2001) negatively correlated with cueing magnitude. Furthermore, exogenous orienting did not differ between the sexes in two peripheral cueing experiments (Experiments 2a and 2b). However, a final experiment showed that using nonpredictive arrows instead of eyes as a central cue also revealed a large gender difference. This demonstrates that reduced orienting from central cues in males generalizes beyond gaze cues. These results show that while peripheral cueing is equivalent in the male and female brains, the attention systems of the two sexes treat noninformative symbolic cues very differently.

Rey's verbal learning test: normative data for 1855 healthy participants aged 24-81 years and the influence of age, sex, education, and mode of presentation

The Verbal Learning Test (VLT; Rey, 1958) evaluates the declarative memory. Despite its extensive use, it has been difficult to establish normative data because test administration has not been uniform. The purpose of the present study was to gather normative data for the VLT for a large number (N = 1855) of healthy participants aged 24-81 years, using a procedure in which the words to be learned were presented either verbally or visually. The results showed that VLT performance decreased in an age-dependent manner from an early age. The learning capacity of younger versus older adults differed quantitatively rather than qualitatively. Females and higher educated participants outperformed males and lower educated participants over the entire age range tested. Presentation mode affected VLT performance differently: auditory presentation resulted in a better recall on Trial 1 (a short-term or working memory measure), whereas visual presentation yielded a better performance on Trial 3, Trial 4, and Delta (a learning measure).

Sex differences in spatial visualization and episodic memory as a function of alcohol consumption

AIMS

Sex differences in visuospatial ability as well as episodic memory have been reliably demonstrated, irrespective of alcoholism. Studies in alcoholics have consistently documented cognitive deficits in visuospatial ability, problem solving and memory function. This cross-sectional, population-based study examined if sex differences in cognitive performance could be impacted by alcohol consumption.

METHODS

Drinking data were collected from 2224 randomly sampled adults, aged between 35 and 85 years, who participated in the Betula study on memory, health and aging. Participants were classified into non-, light, moderate and heavy drinking subgroups based on sex-adjusted normative values. Cognitive tasks demonstrating clear sex differences, such as episodic memory tasks (favouring women) and spatial visualization tasks (favouring men), were conducted and performance was assessed by sex and the drinking group.

RESULTS

After controlling for age and education, overall analyses found expected sex differences in episodic memory and spatial visualization that were apparent across the entire population. When these sex differences were examined by drinking group, visuospatial performance favouring men disappeared for the moderate to heavy drinking groups, but higher performance by women on episodic memory tasks was consistent across all levels of alcohol consumption. Traditional biomarkers of increased alcohol consumption (GGT and MCV) correlated with the reported drinks/day.

CONCLUSIONS

These results lend support to the theory that moderate alcohol intake may be beneficial to cognitive function in women, but not necessarily in men.

Raloxifene exposure enhances brain activation during memory performance in healthy elderly males; its possible relevance to behavior

Raloxifene is a selective estrogen receptor modulator (SERM) that is prescribed in females only, but its use in male subjects is increasingly considered. With a growing number of patients having potential benefit from raloxifene, the need for an assessment of its effects on brain function is growing. Effects of estrogens on brain function are very subtle and difficult to detect by neuropsychological assessment. Functional imaging techniques, however, have been relatively successful in detecting such changes. This study used functional magnetic resonance imaging (fMRI) to examine effects of raloxifene treatment on memory function. Healthy elderly males (n = 28; mean age 63.6 years, SD 2.4) were scanned during performance on a face encoding paradigm. Scans were made at baseline and after 3 months of treatment with either raloxifene (n = 14) or placebo (n = 14). Treatment effects were analyzed using mixed-effects statistical analysis (FSL). Activation during task performance involved bilateral parietal and prefrontal areas, anterior cingulate gyrus, and inferior prefrontal, occipital, and mediotemporal areas bilaterally. When compared to placebo, raloxifene treatment significantly enhanced activation in these structures (Z > 3.1), except for mediotemporal areas. Task performance accuracy diminished in the placebo group (P = 0.02), but remained constant in the raloxifene group (P = 0.60). In conclusion, raloxifene treatment enhanced brain activation in areas spanning a number of different cognitive domains, suggesting an effect on cortical arousal. Such effects may translate into small effects on behavior, including effects on attention and working memory performance, executive functions, verbal skills, and episodic memory. Further neuropsychological assessment is necessary to test the validity of these predictions.

Mood changes after cognitive testing in late middle-age: impacts of sex and habitual alcohol consumption

Men and women (50-67 years) completed drinking diaries and, on the basis of this, were divided into low (<2 units/day, 1 UK unit=8 g alcohol) and moderate (2-5 units/day) alcohol groups. They completed analogue rating scales of mood and bodily symptoms before and after two extended computerised cognitive tests. After the tests, the women showed significantly greater increases in self-ratings on the factors of anxiety and discontentment and felt significantly less alert than did the men. They also showed significantly greater increases in bodily symptoms of somatic anxiety and ratings of aggressive mood than did the men. There were no significant effects of alcohol or Sex x Alcohol interactions on the self-ratings, but the men showed significant positive correlations of alcohol and negative mood. On both the cognitive tests, there were significant Sex x Alcohol interactions because the moderate-drinking men performed worse than the low-drinking men, whereas the moderate-drinking women performed better than the low-drinking women. Thus, the middle-aged women responded much more than did the men with negative mood changes to the psychological stress of cognitive testing, although their cognitive performance was not worse.