A neuropeptide making memories.

Neuropeptides are the most diverse class of signaling molecules in the brain. Despite evidence for their involvement in several behavioral functions, the precise circuit elements and neuronal computations they control remain elusive. In this issue, Melzer et al. (2021) reveal how the neuropeptide GRP facilitates memory in the neocortex.

Understanding the role of the NMDA receptor subunit, GluN2D, in mediating NMDA receptor antagonist-induced behavioral disruptions in male and female mice.

Noncompetitive NMDA receptor (NMDAR) antagonists like phencyclidine (PCP) and ketamine cause psychosis-like symptoms in healthy humans, exacerbate schizophrenia symptoms in people with the disorder, and disrupt a range of schizophrenia-relevant behaviors in rodents, including hyperlocomotion. This is negated in mice lacking the GluN2D subunit of the NMDAR, suggesting the GluN2D subunit mediates the hyperlocomotor effects of these drugs. However, the role of GluN2D in mediating other schizophrenia-relevant NMDAR antagonist-induced behavioral disturbances, and in both sexes, is unclear. This study aimed to investigate the role of the GluN2D subunit in mediating schizophrenia-relevant behaviors induced by a range of NMDA receptor antagonists. Using both male and female GluN2D knockout (KO) mice, we examined the effects of the NMDAR antagonist's PCP, the S-ketamine enantiomer (S-ket), and the ketamine metabolite R-norketamine (R-norket) on locomotor activity, anxiety-related behavior, and recognition and short-term spatial memory. GluN2D-KO mice showed a blunted locomotor response to R-norket, S-ket, and PCP, a phenotype present in both sexes. GluN2D-KO mice of both sexes showed an anxious phenotype and S-ket, R-norket, and PCP showed anxiolytic effects that were dependent on sex and genotype. S-ket disrupted spatial recognition memory in females and novel object recognition memory in both sexes, independent of genotype. This datum identifies a role for the GluN2D subunit in sex-specific effects of NMDAR antagonists and on the differential effects of the R- and S-ket enantiomers.

Maternal selenium dietary supplementation alters sociability and reinforcement learning deficits induced by in utero exposure to maternal immune activation in mice.

Maternal immune activation (MIA) during pregnancy increases the risk for the unborn foetus to develop neurodevelopmental conditions such as autism spectrum disorder and schizophrenia later in life. MIA mouse models recapitulate behavioural and biological phenotypes relevant to both conditions, and are valuable models to test novel treatment approaches. Selenium (Se) has potent anti-inflammatory properties suggesting it may be an effective prophylactic treatment against MIA. The aim of this study was to determine if Se supplementation during pregnancy can prevent adverse effects of MIA on offspring brain and behaviour in a mouse model. Selenium was administered via drinking water (1.5 ppm) to pregnant dams from gestational day (GD) 9 to birth, and MIA was induced at GD17 using polyinosinic:polycytidylic acid (poly-I:C, 20 mg/kg via intraperitoneal injection). Foetal placenta and brain cytokine levels were assessed using a Luminex assay and brain elemental nutrients assessed using inductively coupled plasma- mass spectrometry. Adult offspring were behaviourally assessed using a reinforcement learning paradigm, the three-chamber sociability test and the open field test. MIA elevated placental IL-1ß and IL-17, and Se supplementation successfully prevented this elevation. MIA caused an increase in foetal brain calcium, which was prevented by Se supplement. MIA caused in offspring a female-specific reduction in sociability, which was recovered by Se, and a male-specific reduction in social memory, which was not recovered by Se. Exposure to poly-I:C or selenium, but not both, reduced performance in the reinforcement learning task. Computational modelling indicated that this was predominantly due to increased exploratory behaviour, rather than reduced rate of learning the location of the food reward. This study demonstrates that while Se may be beneficial in ameliorating sociability deficits caused by MIA, it may have negative effects in other behavioural domains. Caution in the use of Se supplementation during pregnancy is therefore warranted.

Classical and quantum trial wave functions in auxiliary-field quantum Monte Carlo applied to oxygen allotropes and a CuBr2 model system.

In this work, we test a recently developed method to enhance classical auxiliary-field quantum Monte Carlo (AFQMC) calculations with quantum computers against examples from chemistry and material science, representative of classes of industry-relevant systems. As molecular test cases, we calculate the energy curve of H4 and the relative energies of ozone and singlet molecular oxygen with respect to triplet molecular oxygen, which is industrially relevant in organic oxidation reactions. We find that trial wave functions beyond single Slater determinants improve the performance of AFQMC and allow it to generate energies close to chemical accuracy compared to full configuration interaction or experimental results. In the field of material science, we study the electronic structure properties of cuprates through the quasi-1D Fermi-Hubbard model derived from CuBr2, where we find that trial wave functions with both significantly larger fidelities and lower energies over a mean-field solution do not necessarily lead to AFQMC results closer to the exact ground state energy.

BDNF Val66Met genotype and adolescent glucocorticoid treatment induce sex-specific disruptions to fear extinction and amygdala GABAergic interneuron expression in mice.

BACKGROUND: The BDNF Val66Met single nucleotide polymorphism has been implicated in stress sensitivity and Post-Traumatic Stress Disorder (PTSD) risk. We previously reported that chronic young-adult stress hormone treatment enhanced fear memory in adult BDNFVal66Met mice with the Met/Met genotype. This study aimed to extend this work to fear extinction learning, spontaneous recovery of fear, and neurobiological correlates in the amygdala. METHODS: Male and female Val/Val and Met/Met mice received corticosterone in their drinking water during late adolescence to model chronic stress. Following a 2-week recovery period, the mice underwent fear conditioning and extinction training. Immunofluorescent labelling was used to assess density of three interneuron subtypes; somatostatin, parvalbumin and calretinin, within distinct amygdala nuclei. RESULTS: No significant effects of genotype, treatment or sex were found for fear learning. However, adolescent CORT treatment selectively abolished fear extinction of female Met/Met mice. No effect of genotype, sex, or treatment was observed for spontaneous recovery of fear. Significant main effects of genotype and CORT emerged for somatostatin and calretinin cell density, again in females only, further supporting sex-specific effects of the Met/Met genotype and chronic CORT exposure. CONCLUSION: BDNF Val66Met genotype interacts with chronic adolescent stress hormone exposure to abolish fear extinction in female Met/Met mice in adulthood. This effect was associated with female-specific interneuron dysfunction induced by either genotype or stress hormone exposure, depending on the interneuron subtype. These data provide biological insight into the role of BDNF in sex differences in sensitivity to stress and vulnerability to stress-related disorders in adulthood.

Maternal immune activation targeted to a window of parvalbumin interneuron development improves spatial working memory: Implications for autism.

Maternal immune activation (MIA) increases risk for neuropsychiatric disorders such as autism spectrum disorder (ASD) in offspring later in life through unknown causal mechanisms. Growing evidence implicates parvalbumin-containing GABAergic interneurons as a key target in rodent MIA models. We targeted a specific neurodevelopmental window of parvalbumin interneurons in a mouse MIA model to examine effects on spatial working memory, a key domain in ASD that can manifest as either impairments or improvements both clinically and in animal models. Pregnant dams received three consecutive intraperitoneal injections of Polyinosinic:polycytidylic acid (poly(I:C), 5 mg/kg) at gestational days 13, 14 and 15. Spatial working memory was assessed in young adult offspring using touchscreen operant chambers and the Trial-Unique Non-matching to Location (TUNL) task. Anxiety, novelty seeking and short-term memory were assessed using Elevated Plus Maze (EPM) and Y-maze novelty preference tasks. Fluorescent immunohistochemistry was used to assess hippocampal parvalbumin cell density, intensity and co-expression with perineuronal nets. qPCR was used to assess the expression of putatively implicated gene pathways. MIA targeting a window of parvalbumin interneuron development increased spatial working memory performance on the TUNL touchscreen task which was not influenced by anxiety or novelty seeking behaviour. The model reduced fetal mRNA levels of Gad1 and adult hippocampal mRNA levels of Pvalb and the distribution of low intensity parvalbumin interneurons was altered. We speculate a specific timing window for parvalbumin interneuron development underpins the apparently paradoxical improved spatial working memory phenotype found both across several rodent models of autism and clinically in ASD.

Iron chelation by deferiprone does not rescue the Niemann-Pick Disease Type C1 mouse model.

Niemann-Pick Disease Type C (NP-C) is a fatal lysosomal storage disorder with progressive neurodegeneration. In addition to the characteristic cholesterol and lipid overload phenotype, we previously found that altered metal homeostasis is also a pathological feature. Increased brain iron in the Npc1-/- mouse model of NP-C may potentially contribute to neurodegeneration, similar to neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Deferiprone (DFP) is a brain penetrating iron chelator that has demonstrated effectiveness in preventing neurological deterioration in Parkinson's disease clinical trials. Therefore, we hypothesized that DFP treatment, targeting brain iron overload, may have therapeutic benefits for NP-C. Npc1-/- mice were assigned to four experimental groups: (1) pre-symptomatic (P15) + 75 mg/kg DFP; (2) pre-symptomatic (P15) + 150 mg/kg DFP; (3) symptomatic (P49) + 75 mg/kg DFP; (4) symptomatic (P49) + 150 mg/kg DFP. Our study found that in Npc1-/- mice, DFP treatment did not offer any improvement over the expected disease trajectory and median lifespan. Moreover, earlier treatment and higher dose of DFP resulted in adverse effects on body weight and onset of ataxia. The outcome of our study indicated that, despite increased brain iron, Npc1-/- mice were vulnerable to pharmacological iron depletion, especially in early life. Therefore, based on the current model, iron chelation therapy is not a suitable treatment option for NP-C.

The maternal immune activation model uncovers a role for the Arx gene in GABAergic dysfunction in schizophrenia.

A hallmark feature of schizophrenia is altered high frequency neural oscillations, including reduced auditory-evoked gamma oscillatory power, which is underpinned by parvalbumin (PV) interneuron dysfunction. Maternal immune activation (MIA) in rodents models an environmental risk factor for schizophrenia and recapitulates these PV interneuron changes. This study sought to link reduced PV expression in the MIA model with alterations to auditory-evoked gamma oscillations and transcript expression. We further aligned transcriptional findings from the animal model with human genome sequencing data. We show that MIA, induced by the viral mimetic, poly-I:C in C57Bl/6 mice, caused in adult offspring reduced auditory-evoked gamma and theta oscillatory power paralleled by reduced PV protein levels. We then showed the Arx gene, critical to healthy neurodevelopment of PV interneurons, is reduced in the forebrain of MIA exposed mice. Finally, in a whole-genome sequenced patient cohort, we identified a novel missense mutation of ARX in a patient with schizophrenia and in the Psychiatric Genomics Consortium 2 cohort, a nominal association of proximal ARX SNPs with the disorder. This suggests MIA, as a risk factor for schizophrenia, may be influencing Arx expression to induce the GABAergic dysfunction seen in schizophrenia and that the ARX gene may play a role in the prenatal origins of schizophrenia pathophysiology.

Layer 1 NDNF interneurons are specialized top-down master regulators of cortical circuits.

Diverse types of inhibitory interneurons (INs) impart computational power and flexibility to neocortical circuits. Whereas markers for different IN types in cortical layers 2-6 (L2-L6) have been instrumental for generating a wealth of functional insights, only the recent identification of a selective marker (neuron-derived neurotrophic factor [NDNF]) has opened comparable opportunities for INs in L1 (L1INs). However, at present we know very little about the connectivity of NDNF L1INs with other IN types, their input-output conversion, and the existence of potential NDNF L1IN subtypes. Here, we report pervasive inhibition of L2/3 INs (including parvalbumin INs and vasoactive intestinal peptide INs) by NDNF L1INs. Intersectional genetics revealed similar physiology and connectivity in the NDNF L1IN subpopulation co-expressing neuropeptide Y. Finally, NDNF L1INs prominently and selectively engage in persistent firing, a physiological hallmark disconnecting their output from the current input. Collectively, our work therefore identifies NDNF L1INs as specialized master regulators of superficial neocortex according to their pervasive top-down afferents.

Probing top-down information in neocortical layer 1.

Accurate perception of the environment is a constructive process that requires integration of external bottom-up sensory signals with internally generated top-down information. Decades of work have elucidated how sensory neocortex processes physical stimulus features. By contrast, examining how top-down information is encoded and integrated with bottom-up signals has been challenging using traditional neuroscience methods. Recent technological advances in functional imaging of brain-wide afferents in behaving mice have enabled the direct measurement of top-down information. Here, we review the emerging literature on encoding of these internally generated signals by different projection systems enriched in neocortical layer 1 during defined brain functions, including memory, attention, and predictive coding. Moreover, we identify gaps in current knowledge and highlight future directions for this rapidly advancing field.

Inhibitory top-down projections from zona incerta mediate neocortical memory.

Top-down projections convey a family of signals encoding previous experiences and current aims to the sensory neocortex, where they converge with external bottom-up information to enable perception and memory. Whereas top-down control has been attributed to excitatory pathways, the existence, connectivity, and information content of inhibitory top-down projections remain elusive. Here, we combine synaptic two-photon calcium imaging, circuit mapping, cortex-dependent learning, and chemogenetics in mice to identify GABAergic afferents from the subthalamic zona incerta as a major source of top-down input to the neocortex. Incertocortical transmission undergoes robust plasticity during learning that improves information transfer and mediates behavioral memory. Unlike excitatory pathways, incertocortical afferents form a disinhibitory circuit that encodes learned top-down relevance in a bidirectional manner where the rapid appearance of negative responses serves as the main driver of changes in stimulus representation. Our results therefore reveal the distinctive contribution of long-range (dis)inhibitory afferents to the computational flexibility of neocortical circuits.

Income Disparities in Outcomes of Horizontal Strabismus Surgery in a Pediatric Population.

PURPOSE: To examine postoperative outcomes in pediatric patients undergoing strabismus surgery to determine the potential impact of socioeconomic disparities on ophthalmic outcomes. METHODS: This study included 284 children undergoing strabismus surgery at a tertiary institution with at least 11 months of follow-up and no prior strabismus surgery or other neurologic or ophthalmologic conditions. Demographics, insurance, operative parameters, and appointments scheduled/attended were collected via chart review. Ocular alignment was recorded preoperatively and postoperatively at 3, 12, and 24 months. Two-sided t tests and chi-squared analyses were used to compare demographic and operative parameters. Logistic regression was employed to determine predictive factors for ophthalmic outcomes. RESULTS: There was no difference in failure rates between patients with Medicaid and patients with private insurance 24 months postoperatively (45.9% vs 50.5%, respectively, P = .46). Patients with Medicaid were more likely to not follow up postoperatively (28.2% vs 9.6%, respectively, P < .01), whereas patients with private insurance were more likely to complete more than three follow-up appointments in 24 months (21.5% vs 39.0%, respectively, P < .01). Postoperative attendance was linked to Medicaid status (P < .01) but not travel time, neighborhood income levels, or social deprivation index factors. CONCLUSIONS: There was no difference in failure rates between patients with Medicaid and patients with private insurance. Medicaid status was significantly predictive of loss to follow-up. [J Pediatr Ophthalmol Strabismus. 2022;59(3):156-163.].

The non-indigenous Oithona davisae in a Mediterranean transitional environment: coexistence patterns with competing species.

The Venice lagoon (VL) has been recognized as a hot spot of introduction of non-indigenous species (NIS), due to several anthropogenic factors and environmental stressors that combined may facilitate NIS invasions. In the last decades an increasing number of zooplankton NIS have been observed in the VL. This work aims to provide a picture of the annual cycle and distribution of the recently recorded non-indigenous copepod Oithona davisae, considering the coexistence patterns with the congeneric resident Oithona nana. Therefore, zooplankton samplings were carried out monthly from August 2016 to July 2017 at five Long-Term Ecological Research LTER stations in the VL. Oithona davisae showed a persistent occurrence throughout the year with the highest abundances in the warm season and in the inner areas, while the congeneric O. nana, showing a different distribution pattern, resulted more abundant near the inlets of the Lagoon, where O. davisae reached the minimum density. Oithona davisae seems to find local conditions that promote its settlement and distribution, especially in the inner and more trophic lagoon sites. In other European coastal embayments or transitional waters, O. davisae occupied the niche left by the indigenous O. nana or can replace this congeneric species through competitive exclusion mechanisms. Our data indicate that, for now, such species replacement has not occurred in the VL. One of the causes is the extreme variety of habitats and niches offered by this environment allowing a balanced coexistence with O. nana and in general with the resident copepod community.

Suitability of a dual COI marker for marine zooplankton DNA metabarcoding.

As DNA metabarcoding has become an emerging tool for surveying biodiversity, including its application in legally binding assessments, reliable and efficient barcodes are requested, especially for the highly diverse group of zooplankton. This study focuses on comparing the efficiency of two mitochondrial COI barcodes based on the internal primers mlCOIintF and mlCOIintR utilizing mesozooplankton samples collected in a Mediterranean lagoon. Our results indicate that after a slight adjustment, the mlCOIintR primer performs in combination with jdgLCO1490 (herein) very comparably to the much more widely used primer system mlCOIintF/jgHCO2198+dgHCO2198, in terms of level of taxonomic resolution, species detection and their relative abundance in terms of numbers of reads. As for some groups, like Ctenophora, this barcode is not suitable; a combination of them may be the best option to rely on the Folmer region in its entirety without the risk of losing information for a limited primer match.

Synaptogenic activity of the axon guidance molecule Robo2 underlies hippocampal circuit function.

Synaptic connectivity within adult circuits exhibits a remarkable degree of cellular and subcellular specificity. We report that the axon guidance receptor Robo2 plays a role in establishing synaptic specificity in hippocampal CA1. In vivo, Robo2 is present and required postsynaptically in CA1 pyramidal neurons (PNs) for the formation of excitatory (E) but not inhibitory (I) synapses, specifically in proximal but not distal dendritic compartments. In vitro approaches show that the synaptogenic activity of Robo2 involves a trans-synaptic interaction with presynaptic Neurexins, as well as binding to its canonical extracellular ligand Slit. In vivo 2-photon Ca2+ imaging of CA1 PNs during spatial navigation in awake behaving mice shows that preventing Robo2-dependent excitatory synapse formation cell autonomously during development alters place cell properties of adult CA1 PNs. Our results identify a trans-synaptic complex linking the establishment of synaptic specificity to circuit function.

DNA metabarcoding and morphological analysis - Assessment of zooplankton biodiversity in transitional waters.

Zooplankton biodiversity assessment is a crucial element in monitoring marine ecosystem processes and community responses to environmental alterations. In order to evaluate the suitability of metabarcoding for zooplankton biodiversity assessment and biomonitoring as a fast and more cost-effective method, seasonal zooplankton sampling was carried out in the Venice Lagoon and the nearby coastal area (Northern Adriatic Sea). The molecular analysis showed higher taxa richness compared to the classical morphological method (224 vs. 88 taxa), discriminating better the meroplanktonic component, morphologically identified only up to order level. Both methods revealed a similar spatio-temporal distribution pattern and the sequence abundances and individual counts were significantly correlated for various taxonomic groups. These results indicate that DNA metabarcoding is an efficient tool for biodiversity assessments in ecosystems with high spatial and temporal variability, where high sampling effort is required as well as fast alert systems for non-native species (NIS).

Raloxifene recovers effects of prenatal immune activation on cognitive task-induced gamma power.

There is currently no treatment available for the cognitive symptoms of schizophrenia, but evidence suggests that selective estrogen receptor modulators (SERMs) may provide relief. Our recent animal model data showed that a lack of female sex hormones in mice impairs the ability of hippocampal neurons to synchronise and generate oscillations within the frequency range of 30-80 Hz (gamma power) leading to cognitive impairment, while both estradiol and the SERM, raloxifene, recovered this. Given that cognitive impairment is accompanied by abnormal gamma power in schizophrenia, this study aimed to determine the effects of raloxifene on gamma power during spatial memory tasks in the prenatal immune challenged (poly-I:C) mouse model with relevance to schizophrenia. Pregnant dams received the viral mimetic poly-I:C (20 mg/kg, i.p.) at gestational day 17. Male and female offspring were treated with placebo or raloxifene implants at adulthood. Local field potentials from the CA1 hippocampus were simultaneously recorded during the Y-maze test of short term spatial memory and the cheeseboard maze test of long-term spatial learning and memory and cognitive flexibility. In female but not male mice, poly I:C exposure reduced gamma power during decision making and prolonged the time spent in the centre (decision making phase) during the Y-maze task. Female poly-I:C exposed mice also showed increased gamma power during acquisition of the cheeseboard long term memory task and perseverative behaviour. Treatment with raloxifene recovered gamma power and decision making deficits in the Y-maze and restored gamma power changes during the cheeseboard maze task as well as perseverative behaviour. Male mice showed no electrophysiological or behavioural effects of poly-I:C or raloxifene treatment. In summary, poly-I:C exposure induced female specific cognitive impairments accompanied by altered neural oscillations in the gamma frequency and raloxifene recovered these abnormalities.

Leucine-rich repeat-containing synaptic adhesion molecules as organizers of synaptic specificity and diversity.

The brain harbors billions of neurons that form distinct neural circuits with exquisite specificity. Specific patterns of connectivity between distinct neuronal cell types permit the transfer and computation of information. The molecular correlates that give rise to synaptic specificity are incompletely understood. Recent studies indicate that cell-surface molecules are important determinants of cell type identity and suggest that these are essential players in the specification of synaptic connectivity. Leucine-rich repeat (LRR)-containing adhesion molecules in particular have emerged as key organizers of excitatory and inhibitory synapses. Here, we discuss emerging evidence that LRR proteins regulate the assembly of specific connectivity patterns across neural circuits, and contribute to the diverse structural and functional properties of synapses, two key features that are critical for the proper formation and function of neural circuits.

On the Developmental Timing of Stress: Delineating Sex-Specific Effects of Stress across Development on Adult Behavior.

Stress, and the chronic overactivation of major stress hormones, is associated with several neuropsychiatric disorders. However, clinical literature on the exact role of stress either as a causative, triggering, or modulatory factor to mental illness remains unclear. We suggest that the impact of stress on the brain and behavior is heavily dependent on the developmental timing at which the stress has occurred, and as such, this may contribute to the overall variability reported on the association of stress and mental illness. Here, animal models provide a way to comprehensively assess the temporal impact of stress on behavior in a controlled manner. This review particularly focuses on the long-term impact of stress on behavior in various rodent stress models at three major developmental time points: early life, adolescence, and adulthood. We characterize the various stressor paradigms into physical, social, and pharmacological, and discuss commonalities and differences observed across these various stress-inducing methods. In addition, we discuss here how sex can influence the impact of stress at various developmental time points. We conclude here that early postnatal life and adolescence represent particular periods of vulnerability, but that stress exposure during early life can sometimes lead to resilience, particularly to fear-potentiated memories. In the adult brain, while shorter periods of stress tended to enhance spatial memory, longer periods caused impairments. Overall, males tended to be more vulnerable to the long-term effects of early life and adolescent stress, albeit very few studies incorporate both sexes, and further well-powered sex comparisons are needed.