Effects of blood estrogen level on cortical activation patterns during cognitive activation as measured by functional MRI

Sex differences in brain activation pattern during a visuospatial cognitive task: a functional magnetic resonance imaging study in healthy volunteers

Sex differences in mental rotation tasks, favoring men, have been noted in behavioral studies and functional imaging studies. In the present study ten female and ten male volunteers underwent functional magnetic resonance imaging in a conventional block design. Regions of activation were detected after performance of a mental rotation task inside the scanner. In contrast to previous studies, confounding factors such as performance differences between genders or high error rates were excluded. Men showed significantly stronger parietal activation, while women showed significantly greater right frontal activation. Our results point to gender specific differences in the neuropsychological processes involved in mental rotation tasks.

Menstrual cycle-dependent neural plasticity in the adult human brain is hormone, task, and region specific

In rodents, cyclically fluctuating levels of gonadal steroid hormones modulate neural plasticity by altering synaptic transmission and synaptogenesis. Alterations of mood and cognition observed during the menstrual cycle suggest that steroid-related plasticity also occurs in humans. Cycle phase-dependent differences in cognitive performance have almost exclusively been found in tasks probing lateralized neuronal domains, i.e., cognitive domains such as language, which are predominantly executed by one hemisphere. To search for neural correlates of hormonally mediated neural plasticity in humans, we thus conducted a functional magnetic resonance imaging study measuring brain activity related to a semantic decision task in the language domain. This was contrasted with a letter-matching task in the perceptual domain, in which we expected no steroid hormone-mediated effect. We investigated 12 young healthy women in a counterbalanced repeated-measure design during low-steroid menstruation and high-steroid midluteal phase. Steroid serum levels correlated with the volume and lateralization of particular brain activations related to the semantic task but not with brain activity related to the perceptual task. More specifically, bilateral superior temporal recruitment correlated positively with progesterone and medial superior frontal recruitment with both progesterone and estradiol serum levels, whereas activations in inferior and middle frontal cortex were unaffected by steroid levels. In contrast to these specific interactions, testosterone levels correlated nonselectively with overall activation levels by neural and/or vascular factor(s). In conclusion, our data demonstrate steroid hormone responsivity in the adult human brain by revealing neural plasticity in the language domain, which appears hormone, task, and region specific.

Changes in saccadic latencies over the human menstrual cycle

The study assessed differences in sensorimotor processing as reflected in measurements of saccadic latencies at 3 different stages in the menstrual cycle (menstruation, early luteal, and premenstruation) in naturally cycling women (n = 13), and at the same time intervals in women taking an oral contraceptive (n = 6), and male controls (n = 8). Subjects (M age = 22.0 yr., SD = 2.2 yr.) were recruited by questionnaire from the student population of the University of Cambridge. Latencies were measured using a portable infrared scleral oculometer. Changes in latency across the menstrual cycle occurred only in the naturally cycling women (F(2.11) = 5.95, p < .05). Premenstrual latencies were greater (199.3 +/- 12.7 msec., M +/- SD) compared to those during menstruation (191.9 +/- 11.1 msec.) or midcycle (196.9 +/- 12.7 msec.). These findings could account for the loss of musculoskeletal coordination reported by some women prior to menstruation and suggests that administration of an oral contraceptive may alleviate this effect.

Estrogen and cognitive functioning in women

Research in basic neuroscience has provided biological plausibility for the hypothesis that estrogen replacement therapy (ERT) would protect against cognitive aging in healthy women. The weight of the evidence from randomized controlled trials of estrogen and cognition in women shows that this hormone preferentially protects verbal memory in postmenopausal women, whereas findings from observational studies are less consistent and show a more diffuse effect of estrogen on a range of cognitive functions. There is fairly consistent evidence from epidemiological studies that ERT significantly reduces the risk of Alzheimer's disease (AD) in women. On the other hand, findings from controlled treatment trials of women diagnosed with probable AD failed to show that physiological doses of ERT ameliorate existing deficits in cognitive functioning and/or prevent further deterioration in memory that inevitably occurs in these women over time. Finally, an accumulating body of evidence is beginning to suggest that the immediate postmenopausal period may constitute a critical window for treatment with ERT that maximizes its potential to protect against cognitive decline with aging and/or to reduce the risk of AD.

Are action and perception in near and far space additive or interactive factors?

Functional imaging has revealed differential neural mechanisms underlying action directed toward near or far space. Because some neuropsychological studies of patients with visuospatial neglect failed to show near/far dissociations with perceptual tasks, we investigated whether action and perception elicit distinct cerebral representations in near and far space. We measured regional cerebral blood flow with positron emission tomography in normal volunteers who performed manual line bisection (action) and made line bisection judgments (perception). Stimuli were presented in near space or far space. Far space presentation enhanced activations in occipital cortex extending into the medial occipitotemporal cortex bilaterally, while near space presentation enhanced left occipital-parietal, parietal, and premotor cortex activity. Manual bisection activated the extrastriate, superior parietal, and premotor cortex bilaterally, while bisection judgments activated the right inferior parietal cortex, anterior cingulate, right dorsolateral prefrontal cortex, and extrastriate and superior temporal cortex bilaterally. The neural mechanisms responsible for the two tasks (perceptual/motor) were not differentially modulated by space of presentation.

Coordinate and categorical judgements in spatial imagery. An fMRI study

We aimed at verifying whether the hemispheric specialisation for categorical/coordinate spatial judgements also applies to the spatial imagery domain by the use of whole-brain fMRI. In a block-design experiment we used the "coordinate" mental clock test, contrasting it with a "categorical" task applied to the same clock stimuli; as a control task we used a syllable counting task requiring a verbal-phonological judgement on the same material of the two imagery tasks. Our results showed that categorical and coordinate spatial judgements on imagined stimuli rely on the activation of a set of cortical areas, centred upon the superior parietal lobule (SPL) bilaterally. These regions, together with other parietal and prefrontal areas, showed a pattern of relative lateralization, with the left hemisphere being mainly activated during the categorical task and the right in the coordinate task. These data confirm the strong involvement of the SPL in spatial processing. Moreover, our findings suggest that different interconnected neural networks are activated to comply with specific test requirements, giving rise to functional imaging patterns compatible with psychological theories on hemispheric specialization.

Cerebral correlates of selective attention in schizophrenic patients with formal thought disorder: a controlled H2 15O-PET study

There is a widespread belief that formal thought disorders may be associated with disturbed selective attention in schizophrenia. Two hypotheses are derived: (1) patients with slightly pronounced formal thought disorders should differ from those with severely expressed formal thought disorders in terms of selective attention; and (2) the cerebral correlates of selective attention should be organised differently in mildly versus severely thought-disordered patients. We compared 20 female schizophrenic patients, one-half with mild, one-half with obvious formal thought disorders, and 10 control subjects on a neuropsychological battery and a cognitive activation task for selective attention (Go/NoGo) for the assessment of rCBF using H2 15O-PET. While the first hypothesis has not been confirmed, we found that the cerebral regions activated by selective attention in the two patient groups showed completely differing organisations. Low degrees of formal thought disorders were associated with significant activations in frontal superior gyrus and ventral anterior thalamic nucleus whereas high degrees of formal thought disorders were accompanied by significant activations in fusiform gyrus and precuneus. We suggest that differing task-solving strategies are applied by both clinical subgroups to achieve comparable results on the selective attention paradigm.

Estrogen induces a rapid increase of calcium-calmodulin-dependent protein kinase II activity in the hippocampus

Molecular genetics experiments using gene targeting and transgenic technology demonstrated the importance of alpha-calcium-calmodulin-dependent protein kinase II (alphaCaMKII) in long-term potentiation (LTP) and memory. Little information is available though on how CaMKII activity may be regulated in vivo. We show that estradiol benzoate activates CaMKII in a dose and time-dependent manner in mouse hippocampus after 30 min stimulation. The effect of estrogen is via a very rapid nongenomic mechanism that is blocked in vitro in hippocampal primary neurons by the pure estrogen receptor antagonist, ICI 182,780. These results suggest that estrogen action in the hippocampus is linked to CaMKII activation.

The role of reproductive hormones in maintaining cognition

This article briefly reviews the impact of hormones on cognition. Estrogen has the most profound impact on brain functioning. Testosterone also seems to have significant brain-related benefits, whereas progesterone seems to have minor or possibly even adverse effects. As the field of neuroscience progresses, more definitive conclusions will follow. As the focus is shifted, however, from extending life to improving the quality of life, the existing data are very compelling. The brain is a target for the sex steroid hormones. Clearly, this is an exciting and dynamic area for further study. Although skeptics may believe that more definitive proof is necessary before recommending hormone replacement for their patients to preserve their cognitive health, it seems prudent to discuss the evidence available to empower the patient further to guide their own treatment options and validate their symptoms. For those who still subscribe to the menopause-is-natural philosophy this question is posed, "why does the brain naturally have sex hormone receptors if they are not necessary?"

Effects of ovarian hormones on human cortical excitability

Ovarian steroids appear to alter neuronal function in women, but direct physiological evidence is lacking. In animals, estradiol enhances excitatory neurotransmission. Progesterone-derived neurosteroids increase GABAergic inhibition. The effect of weak transcranial magnetic stimulation of the motor cortex on the motor evoked potential (MEP) from transcranial magnetic stimulation given milliseconds later is changed by GABAergic and glutamatergic agents. Using this technique previously, we showed more inhibition in the luteal phase relative to the midfollicular menstrual phase, which is consistent with a progesterone effect. To detect the effects of estradiol, we have now divided the follicular phase. We tested 14 healthy women during the early follicular (low estradiol, low progesterone), late follicular (high estradiol, low progesterone), and luteal (high estradiol, high progesterone) phases, with interstimulus intervals from 2 to 10msec (10 trials at each interval and 40 unconditioned trials). We calculated the ratio of the conditioned MEP at each interval to the mean unconditioned MEP: the higher the ratio, the less inhibition and the more facilitation caused by the first stimulus. The combined ratios increased significantly from the early follicular phase to the late follicular phase and then decreased again in the luteal phase. These findings demonstrate an excitatory neuronal effect associated with estradiol and confirm our earlier finding of inhibition associated with progesterone.

Effects of estrogen on patterns of brain activity at rest and during cognitive activity: a review of neuroimaging studies

Animal and human studies provide evidence of systematic effects of estrogen on cerebral activity and cognitive function. In this article, we review studies of the activational effects of estrogen on cerebral activity during rest and during the performance of cognitive tasks in pre- and postmenopausal women. The goal is twofold--to better understand evidence suggesting that estrogen influences brain functioning and argue for the importance of considering hormone effects when designing neuroimaging studies. Hormone-related increases in blood flow during the resting state have been documented in healthy elderly women, elderly women with cerebrovascular disease, and middle-aged postmenopausal women with early menopause. There is no reliable influence of estrogen on blood flow during the resting state in women with Alzheimer's disease. Hormone therapy has been associated with changes in brain activation patterns in middle-aged and elderly postmenopausal women during performance of verbal and figural memory tasks, providing critical biological support for the view that estrogen might protect against age-associated changes in cognition and lower the risk of Alzheimer's disease. There is a paucity of studies examining changes in brain activation patterns across the menstrual cycle and a need for randomized studies of hormone therapy in postmenopausal women to confirm findings from observational studies. General procedural guidelines for controlling and investigating hormone effects in neuroimaging studies are discussed.

Evidence of abnormal amygdala functioning in borderline personality disorder: a functional MRI study

BACKGROUND

Intense and rapidly changing mood states are a major feature of borderline personality disorder (BPD); however, there have only been a few studies investigating affective processing in BPD, and in particular no neurofunctional correlates of abnormal emotional processing have been identified so far.

METHODS

Six female BPD patients without additional major psychiatric disorder and six age-matched female control subjects underwent functional magnetic resonance imaging (fMRI) to measure regional cerebral hemodynamic changes following brain activity when viewing 12 standardized emotionally aversive slides compared to 12 neutral slides, which were presented in random order.

RESULTS

Our main finding was that BPD subjects but not control subjects were characterized by an elevated blood oxygenation level dependent fMRI signal in the amygdala on both sides. In addition, activation of the medial and inferolateral prefrontal cortex was seen in BPD patients. Both groups showed activation in the temporo-occipital cortex including the fusiform gyrus in BPD subjects but not in control subjects.

CONCLUSIONS

Enhanced amygdala activation in BPD is suggested to reflect the intense and slowly subsiding emotions commonly observed in response to even low-level stressors. Borderline subjects' perceptual cortex may be modulated through the amygdala leading to increased attention to emotionally relevant environmental stimuli.