The parahippocampal region in the rodent brain includes the perirhinal, postrhinal, and entorhinal cortices, the presubiculum, and the parasubiculum. In recent years, the perirhinal and postrhinal cortices have been a focus in memory research because they supply highly processed, polymodal sensory information to the hippocampus, both directly and via the entorhinal cortex. Available evidence indicates that these cortices receive different complements of cortical information, which are then forwarded to the hippocampus via parallel pathways. Here we have summarized the cortical, subcortical, and hippocampal connections of the perirhinal and postrhinal cortices in order to provide further insight into the nature of the information that is processed by these regions prior to arriving in the hippocampus. As has been previously described, the cortical afferents of the rodent postrhinal cortex are dominated by structures known to be involved in the processing of visual and spatial information, whereas the cortical afferents of the perirhinal cortex result in remarkable convergence of polymodal sensory information. The two regions are also differentiated by their cortical efferents. The perirhinal cortex projects more strongly to piriform, frontal, and insular regions, whereas the postrhinal cortex projects preferentially to visual and visuospatial regions. The subcortical connections of the two regions provide further evidence that they have different functions. For example, the perirhinal cortex has strong reciprocal connections with the amygdala, which suggest involvement in processing affective stimuli. Subcortical input to the postrhinal cortex is dominated by projections from dorsal thalamic structures, particularly the lateral posterior nucleus. Although the perirhinal and postrhinal cortices are considered to contribute to the episodic memory system, many questions remain about their particular roles. A detailed description of the anatomical connections of the perirhinal and postrhinal cortices will permit the generation of new, anatomically guided, hypotheses about their role in episodic memory and other cognitive processes.

Objective: We examined the short-term efficacies of three estrogen-like compounds under placebo-controlled conditions in women with perimenopause-related depression (PMD). Methods: Women with PMD were randomized in a double-blind parallel design to one of four treatments: transdermal 17-beta estradiol (TE) (100 mcg/d); oral raloxifene (60 mg/d); a proprietary phytoestrogen compound, Rimostil (1,000 mg twice/d); or placebo for 8 weeks. The main outcome measures were the Center for Epidemiology Studies Depression Scale, 17-item Hamilton Rating Scale for Depression (HRSD), and the Beck Depression Inventory completed at each clinic visit. Secondary outcomes included a visual analogue self-rating completed at each clinic visit, and daily self-ratings of hot flush severity. Cognitive tests were performed at pretreatment baseline and at the end of the trial. In the primary analysis, we obtained four repeated measures in each woman in the four treatment arms. Analyses were done with SAS Version 9.4 software (SAS Institute, Inc, Cary, NC), using PROC MIXED (for mixed models). All models included the following four explanatory variables, regardless of whether they were statistically significant: 1) treatment group (TE, raloxifene, Rimostil, placebo); 2) week (W2, W4, W6, W8); 3) treatment group-by-week interaction; and 4) baseline value of the measure being analyzed. The inclusion of additional variables was evaluated individually for each outcome measure. Results: Sixty-six women were randomized into the trial, four women dropped out of the trial, and 62 women were included in the final data analysis. No effect of treatment group was observed in either the Center for Epidemiology Studies Depression Scale (P = 0.34) or Beck Depression Inventory (P = 0.27) scores; however, there was a difference in HRSD scores between treatment groups (P = 0.0037) that pair-wise comparisons of the combined weekly scores in each treatment demonstrated TE's beneficial effects on HRSD scores compared with Rimostil (P = 0.0005), and less consistently with placebo (P = 0.099). The average (SD) of the baseline scores for each treatment group on the HRSD was as follows: TE—15.3 (4.5), raloxifene—16.0 (3.7), Rimostil—14.0 (2.7), and placebo—15.2 (3.0). Whereas the HRSD scores after 8 weeks of treatment (least-square means) were TE—5.2(1.1), raloxifene—5.8(1.2), Rimostil—11.2(1.4), and placebo—7.8(1.1). No differences were observed between raloxifene and either TE or placebo in any scale score. HRSD scores in women assigned to TE were improved compared with those on Rimostil during weeks 6 and 8 (P values = 0.0008, 0.0011, respectively). Cognitive testing at week 8 showed that none of the three active treatment groups performed better than placebo. Conclusions: This study did not identify significant therapeutic benefits of TE, Rimostil, or raloxifene compared with placebo in PMD. However, improvements in depression ratings were observed between TE compared with Rimostil. Thus, our findings do not support the role of ERbeta compounds in the treatment of PMD (and indeed could suggest a more important role of ERalpha).

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A Val66Met single nucleotide polymorphism (SNP) in the brain-derived neurotrophic factor (BDNF) gene impairs activity-dependent BDNF release in cultured hippocampal neurons and predicts impaired memory and exaggerated basal hippocampal activity in healthy humans. Several clinical genetic association studies, along with multi-modal evidence for hippocampal dysfunction in schizophrenia indirectly suggest a relationship between schizophrenia and genetically-determined BDNF function in the hippocampus. To directly test this hypothesized relationship, we studied 47 medication-free patients with schizophrenia or schizoaffective disorder and 74 healthy comparison individuals with genotyping for the Val66Met SNP and [15O]H2O positron emission tomography (PET) to measure resting and working memory-related hippocampal regional cerebral blood flow (rCBF). In patients, harboring a Met allele was associated with significantly less hippocampal rCBF. This finding was opposite to the genotype effect seen in healthy participants, resulting in a significant diagnosis-by-genotype interaction. Exploratory analyses of interregional resting rCBF covariation revealed a specific and significant diagnosis-by-genotype interaction effect on hippocampal-prefrontal coupling. A diagnosis-by-genotype interaction was also found for working-memory related hippocampal rCBF change, which was uniquely attenuated in Met allele-carrying patients. Thus, both task-independent and task-dependent hippocampal neurophysiology accommodates a Met allelic background differently in patients with schizophrenia than in control subjects. Potentially consistent with the hypothesis that cellular sequelae of the BDNF Val66Met SNP interface with aspects of schizophrenic hippocampal and frontotemporal dysfunction, these results warrant future investigation to understand the contributions of unique patient trait or state variables to these robust interactions.

Brain-derived neurotrophic factor (BDNF) is an important modulator of constitutive stress responses mediated by limbic frontotemporal circuits, and its gene contains a functional polymorphism (Val66Met) that may influence trait stress sensitivity. Reports of an association of this polymorphism with anxiety-related personality traits have been controversial and without clear neurophysiological support. We, therefore, determined the relationship between resting regional cerebral blood flow (rCBF) and a well-validated measure of anxiety-related personality, the TPQ Harm Avoidance (HA) scale, as a function of BDNF Val66Met genotype. Sixty-four healthy participants of European ancestry underwent resting H215O positron emission tomography scans. For each genotype group separately, we first determined the relationship between participants' HA scores and their resting rCBF values in each voxel across the entire brain, and then directly compared these HA-rCBF relationships between Val66Met genotype groups. HA-rCBF relationships differed between Val homozygotes and Met carriers in several regions relevant to stress regulation: subgenual cingulate, orbital frontal cortex, and the hippocampal/parahippocampal region. In each of these areas, the relationship was positive in Val homozygotes and negative in Met carriers. These data demonstrate a coupling between trait anxiety and basal resting blood flow in frontolimbic neurocircuitry that may be determined in part by genetically mediated BDNF signaling.

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Substantial evidence suggests that circulating ovarian steroids modulate behavior differently in women with PMDD than in those without this condition. However, hormonal state-related abnormalities of neural functioning in PMDD remain to be better characterized. In addition, while altered neural function in PMDD likely co-exists with alterations in intrinsic cellular function, such a relationship has not been explored. Here, we investigated the effects of ovarian steroids on basal, resting regional cerebral blood flow (rCBF) in PMDD, and, in an exploratory analysis, we tested whether the rCBF findings were linked to the expression of ESC/E(Z) genes, which form an essential ovarian steroid-regulated gene-silencing complex. Resting rCBF was measured with oxygen-15 water PET (189 PET sessions in 43 healthy women and 20 women with PMDD) during three self-as-own-control conditions: GnRH agonist (Lupron)-induced ovarian suppression, estradiol add-back, and progesterone add-back. ESC/E(Z) gene expression data were obtained from RNA-sequencing of lymphoblastoid cell lines performed in a previous study and were examined in relation to hormone-induced changes in rCBF. In the rCBF PET data, there was a significant diagnosis-by-hormone interaction in the subgenual cingulate (PFDR = 0.05), an important neuroanatomical hub for regulating affective state. Whereas control women showed no hormonally-related changes in resting rCBF, those with PMDD showed decreased resting rCBF during both estradiol (P = 0.02) and progesterone (P = 0.0002) add-back conditions. In addition, in PMDD, ESC/E(Z) gene expression correlated with the change in resting rCBF between Lupron-alone and progesterone conditions (Pearson r = −0.807, P = 0.016). This work offers a formulation of PMDD that integrates behavioral, neural circuit, and cellular mechanisms, and may provide new targets for future therapeutic interventions.

Background Abnormalities in the hypothalamic pituitary-adrenal (HPA) axis are frequent accompaniments of depression, and studies have documented the role of stress and stressful life events in the ontogeny of perimenopausal depressions (PMD). Since HPA axis function in women is further modulated by both aging and ovarian steroids, it is possible that a dysregulated HPA axis contributes to the increased risk of PMD. Objective We examined HPA axis function in perimenopausal women with and without depression using the combined dexamethasone-CRH (Dex/CRH) test. Methods Dex/CRH tests were performed on 20 women with PMD and 20 women who were also perimenopausal but without current or past depression (control women). Main outcome measures were plasma levels of cortisol and ACTH and 24-hour urinary free cortisol. Five women took chronic stable medications, otherwise all women were medically healthy, and both groups were comparable with respect to reproductive stage and age. Standardized symptom rating scales were administered to each woman prior to Dex/CRH testing. Results No group differences were present in either baseline or stimulated ACTH and cortisol secretion. Baseline plasma measures of estradiol, progesterone and 24-hour UFC levels similarly did not differ in PMD and control women. Discussion Despite reports of increased stress responsiveness in PMD, we observed no abnormalities of HPA axis activity associated with PMD compared with women without depression. These findings suggest that PMD is not uniformly associated with HPA dysregulation and could reflect underlying pathophysiologic processes that are distinct from women with non-reproductive-related depressions.