ERPs responses to dominance features from human faces.

Social dominance is an important feature of social life. Dominance has been proposed to be one of two trait dimensions underpinning social judgments of human faces. Yet, the neural bases of the ability to identify different dominance levels in others based on intrinsically facial cues remains poorly understood. Here, we used event-related potentials to determine the temporal dynamics of facial dominance evaluation based on facial features signaling physical strength/weakness in humans. Twenty-seven participants performed a dominance perception task where they passively viewed faces with different dominance levels. Dominance levels did not modulate an early component of face processing, known as the N170 component, but did modulate the late positive potential (LPP) component. These findings indicate that participants inferred dominance levels at a late stage of face evaluation. Furthermore, the highest level of dominant faces and the lowest level of submissive faces both elicited higher LPP amplitudes than faces with a neutral dominance level. Taken together, the present study provides new insights regarding the dynamics of the neurocognitive processes underlying facial dominance evaluation.

Hormone therapy at early post-menopause increases cognitive control-related prefrontal activity.

Clinical data have been equivocal and controversial as to the benefits to the brain and cognition of hormone therapy (HT) in postmenopausal women. Recent reevaluation of the role of estrogens proposed that HT may effectively prevent the deleterious effects of aging on cognition, and reduces the risks of dementia, including Alzheimer's disease, if initiated early at the beginning of menopause. Yet, little is known about the effects of HT on brain activation related to cognitive control, the ability to make flexible decisions in relation to internal goals. Here, we used fMRI to directly test for a modulation of sequential 17ß estradiol (2 mg/day) plus oral progesterone (100 mg/day) on task switching-related brain activity in women at early postmenopause. The results showed that HT enhanced dorsolateral prefrontal cortex recruitment during task switching. Between-subjects correlation analyses revealed that women who engaged more the dorsolateral prefrontal cortex showed higher task switching performance after HT administration. These results suggest that HT, when taken early at the beginning of postmenopause, may have beneficial effect on cognitive control prefrontal mechanisms. Together, these findings demonstrate that HT can prevent the appearance of reduced prefrontal cortex activity, a neurophysiological measure observed both in healthy aging and early dementia.

Hormonal treatment increases the response of the reward system at the menopause transition: a counterbalanced randomized placebo-controlled fMRI study.

Preclinical research using rodent models demonstrated that estrogens play neuroprotective effects if they are administered during a critical period near the time of cessation of ovarian function. In women, a number of controversial epidemiological studies reported that a neuroprotective effect of estradiol may be obtained on cognition and mood-related disorders if hormone therapy (HT) begins early at the beginning of menopause. Yet, little is known about the modulatory effects of early HT administration on brain activation near menopause. Here, we investigated whether HT, initiated early during the menopause transition, increases the response of the reward system, a key brain circuit involved in motivation and hedonic behavior. We used fMRI and a counterbalanced, double-blind, randomized and crossover placebo-controlled design to investigate whether sequential 17ß-estradiol plus oral progesterone modulate reward-related brain activity. Each woman was scanned twice while presented with images of slot machines, once after receiving HT and once under placebo. The fMRI results demonstrate that HT, relative to placebo, increased the response of the striatum and ventromedial prefrontal cortex, two areas that have been shown to be respectively involved during reward anticipation and at the time of reward delivery. Our neuroimaging results bridge the gap between animal studies and human epidemiological studies of HT on cognition. These findings establish a neurobiological foundation for understanding the neurofunctional impact of early HT initiation on reward processing at the menopause transition.

Menstrual cycle phase modulates reward-related neural function in women.

There is considerable evidence from animal studies that the mesolimbic and mesocortical dopamine systems are sensitive to circulating gonadal steroid hormones. Less is known about the influence of estrogen and progesterone on the human reward system. To investigate this directly, we used functional MRI and an event-related monetary reward paradigm to study women with a repeated-measures, counterbalanced design across the menstrual cycle. Here we show that during the midfollicular phase (days 4-8 after onset of menses) women anticipating uncertain rewards activated the orbitofrontal cortex and amygdala more than during the luteal phase (6-10 days after luteinizing hormone surge). At the time of reward delivery, women in the follicular phase activated the midbrain, striatum, and left fronto-polar cortex more than during the luteal phase. These data demonstrate augmented reactivity of the reward system in women during the midfollicular phase when estrogen is unopposed by progesterone. Moreover, investigation of between-sex differences revealed that men activated ventral putamen more than women during anticipation of uncertain rewards, whereas women more strongly activated the anterior medial prefrontal cortex at the time of reward delivery. Correlation between brain activity and gonadal steroid levels also revealed that the amygdalo-hippocampal complex was positively correlated with estradiol level, regardless of menstrual cycle phase. Together, our findings provide evidence of neurofunctional modulation of the reward system by gonadal steroid hormones in humans and establish a neurobiological foundation for understanding their impact on vulnerability to drug abuse, neuropsychiatric diseases with differential expression across males and females, and hormonally mediated mood disorders.