Background Major Depressive Disorder (MDD) has been associated reliably with ruminative responding; this kind of responding is composed of both maladaptive and adaptive components. Levels of activity in the default-mode network (DMN) relative to the task-positive network (TPN), as well as activity in structures that influence DMN and TPN functioning, may represent important neural substrates of maladaptive and adaptive rumination in MDD. Methods We used a unique metric to estimate DMN dominance over TPN from blood-oxygen-level dependent data collected during eyes-closed rest in 17 currently depressed and 17 never-disordered adults. We calculated correlations between this metric of DMN dominance over TPN and the depressive, brooding, and reflective subscales of the Ruminative Responses Scale, correcting for associations between these measures both with one another and with severity of depression. Finally, we estimated and compared across groups right fronto-insular cortex (RFIC) response during initiations of ascent in DMN and in TPN activity. Results In the MDD participants, increasing levels of DMN dominance were associated with higher levels of maladaptive, depressive rumination and lower levels of adaptive, reflective rumination. Moreover, our RFIC state-change analysis showed increased RFIC activation in the MDD participants at the onset of increases in TPN activity; conversely, healthy control participants exhibited increased RFIC response at the onset of increases in DMN activity. Conclusions These findings support a formulation in which the DMN undergirds representation of negative, self-referential information in depression, and the RFIC, when prompted by increased levels of DMN activity, initiates an adaptive engagement of the TPN.

The meta-analytic results support an elegant and neuroanatomically viable model of the salience of negative information in major depressive disorder. In this proposed model, high baseline pulvinar activity in depression first potentiates responding of the brain's salience network to negative information; next, and owing potentially to low striatal dopamine levels in depression, this viscerally charged information fails to propagate up the cortical-striatal-pallidalthalamic circuit to the dorsolateral prefrontal cortex for contextual processing and reappraisal.

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. B ehavioral, biochemical, and physiological data in animals demonstrate that the gonadal steroid hormones estrogen and progesterone affect behavior and modulate neuronal activity (1-4). These hormones not only influence ovulation and reproductive behavior but also affect cognitive functions, affective state, vulnerability to drugs of abuse, and pain sensitivity. Although ovarian steroids have widespread neurophysiological effects, including on the dopaminergic system, and although estrogen and progesterone receptors are densely present along midbrain dopaminergic neurons and other components of the reward system (such as the amygdala and striatum), little is known about the influences of estrogen and progesterone on the dopamine-dependent reward system in women.Substantial preclinical data, including behavioral and neurochemical differences between sexes, across the estrous cycle, and in postovariectomy hormone replacement (5, 6), attest to neuroregulatory effects of both estrogen and progesterone on the dopaminergic system (7, 8), not only on the tuberoinfundibular dopaminergic system involved in control of the anterior pituitary and important for ovulation and reproductive behavior, but also on the mesolimbic and mesocortical dopa...

BackgroundAbnormalities of the striatum and frontal cortex have been reported consistently in studies of neural structure and function in major depressive disorder (MDD). Despite speculation that compromised connectivity between these regions may underlie symptoms of MDD, little work has investigated the integrity of frontostriatal circuits in this disorder.MethodsFunctional magnetic resonance images were acquired from 21 currently depressed and 19 never-disordered women during wakeful rest. Using four predefined striatal regions-of-interest, seed-to-whole brain correlations were computed and compared between groups.ResultsCompared to controls, depressed participants exhibited attenuated functional connectivity between the ventral striatum and both ventromedial prefrontal cortex and subgenual anterior cingulate cortex. Depressed participants also exhibited stronger connectivity between the dorsal caudate and dorsal prefrontal cortex, which was positively correlated with severity of the disorder.ConclusionsDepressed individuals are characterized by aberrant connectivity in frontostriatal circuits that are posited to support affective and cognitive processing. Further research is required to examine more explicitly the link between patterns of disrupted connectivity and specific symptoms of depression, and the extent to which these patterns precede the onset of depression and normalize with recovery from depressive illness.