Evidence that aetiological risk factors for psychiatric disorders cause distinct patterns of cognitive deficits

Poly (I:C)-induced maternal immune activation generates impairment of reversal learning performance in offspring

Maternal immune activation (MIA) induces a variety of behavioral and brain abnormalities in offspring of rodent models, compatible with neurodevelopmental disorders, such as schizophrenia or autism. However, it remains controversial whether MIA impairs reversal learning, a basic expression of cognitive flexibility that seems to be altered in schizophrenia. In the present study, MIA was induced by administration of a single dose of polyriboinosinic-polyribocytidylic acid (Poly (I:C) (5 mg/kg i.p.)) or saline to mouse pregnant dams in gestational day (GD) 9.5. Immune activation was monitored through changes in weight and temperature. The offspring were evaluated when they reached adulthood (8 weeks) using a touchscreen-based system to investigate the effects of Poly (I:C) on discrimination and reversal learning performance. After an initial pre-training, mice were trained to discriminate between two different stimuli, of which only one was rewarded (acquisition phase). When the correct response reached above 80% values for two consecutive days, the images were reversed (reversal phase) to assess the adaptation capacity to a changing environment. Maternal Poly (I:C) treatment did not interfere with the learning process but induced deficits in reversal learning compared to control saline animals. Thus, the accuracy in the reversal phase was lower, and Poly (I:C) animals required more sessions to complete it, suggesting impairments in cognitive flexibility. This study advances the knowledge of how MIA affects behavior, especially cognitive domains that are impaired in schizophrenia. The findings support the validity of the Poly (I:C)-based MIA model as a tool to develop pharmacological treatments targeting cognitive deficits associated with neurodevelopmental disorders.

Maternal choline supplementation modulates cognition and induces anti-inflammatory signaling in the prefrontal cortices of adolescent rats exposed to maternal immune activation

Maternal infection has long been described as a risk factor for neurodevelopmental disorders, especially autism spectrum disorders (ASD) and schizophrenia. Although many pathogens do not cross the placenta and infect the developing fetus directly, the maternal immune response to them is sufficient to alter fetal neurodevelopment, a phenomenon termed maternal immune activation (MIA). Low maternal choline is also a risk factor for neurodevelopmental disorders, and most pregnant people do not receive enough of it. In addition to its role in neurodevelopment, choline is capable of inducing anti-inflammatory signaling through a nicotinic pathway. Therefore, it was hypothesized that maternal choline supplementation would blunt the neurodevelopmental impact of MIA in offspring through long-term instigation of cholinergic anti-inflammatory signaling. To model MIA in rats, the viral mimetic polyinosinic:polycytidylic acid (poly(I:C)) was used to elicit a maternal antiviral innate immune response in dams both with and without choline supplementation. Offspring were reared to both early and late adolescent stages (postnatal days 28 and 50, respectively), where anxiety-related behaviors and cognition were examined. After behavioral testing, animals were euthanized, and their prefrontal cortices (PFCs) were collected for analysis. MIA offspring demonstrated sex-specific patterns of altered cognition and repetitive behaviors, which were modulated by maternal choline supplementation. Choline supplementation also bolstered anti-inflammatory signaling in the PFCs of MIA animals at both early and late adolescent stages. These findings suggest that maternal choline supplementation may be sufficient to blunt some of the behavioral and neurobiological impacts of inflammatory exposures in utero, indicating that it may be a cheap, safe, and effective intervention for neurodevelopmental disorders.

Automation at the service of the study of executive functions in preclinical models

Cognitive flexibility involves the capability to switch between different perspectives and implement novel strategies upon changed circumstances. The Wisconsin Card Sorting Test (in humans) and the Attentional Set-Shifting Task (ASST, in rodents) evaluate individual capability to acquire a reward-associated rule and subsequently disregard it in favour of a new one. Both tasks entail consecutive stages wherein subjects discriminate between: two stimuli of a given category (simple discrimination, SD); the stimuli of SD confounded by an irrelevant stimulus of a different category (compound discrimination, CD); different stimuli belonging to the SD category (intradimensional shift, IDS); and two stimuli of the confounding category (extradimensional shift, EDS). The ASST is labour intensive, not sufficiently standardised, and prone to experimental error. Here, we tested the validity of a new, commercially available, automated version of ASST (OPERON) in two independent experiments conducted in: different mouse strains (C57BL/6 and CD1 mice) to confirm their differential cognitive capabilities (Experiment 1); and an experimental model of chronic stress (administration of corticosterone in the drinking water; Experiment 2). In both experiments, OPERON confirmed the findings obtained through the manual version. Just as in Experiment 1 both versions captured the deficit of C57BL/6 mice on the reversal of the CD (CDR), so also in Experiment 2 they provided analogous evidence that corticosterone treated mice have a remarkable impairment in the IDS. Thus, OPERON capitalises upon automated phenotyping to overcome the limitation of the manual version of the ASST while providing comparable results.

Lipopolysaccharide-induced maternal immune activation modulates microglial CX3CR1 protein expression and morphological phenotype in the hippocampus and dentate gyrus, resulting in cognitive inflexibility during late adolescence

Inflammation during pregnancy can disturb brain development and lead to disorders in the progeny, including autism spectrum disorder and schizophrenia. However, the mechanism by which a prenatal, short-lived increase of cytokines results in adverse neurodevelopmental outcomes remains largely unknown. Microglia-the brain's resident immune-cells-stand as fundamental cellular mediators, being highly sensitive and responsive to immune signals, which also play key roles during normal development. The fractalkine signaling axis is a neuron-microglia communication mechanism used to regulate neurogenesis and network formation. Previously, we showed hippocampal reduction of fractalkine receptor (Cx3cr1) mRNA at postnatal day (P) 15 in male offspring exposed to maternal immune activation induced with lipopolysaccharide (LPS) during late gestation, which was concomitant to an increased dendritic spine density in the dentate gyrus, a neurogenic niche. The current study sought to evaluate the origin and impact of this reduced hippocampal Cx3cr1 mRNA expression on microglia and cognition. We found that microglial total cell number and density are not affected in the dorsal hippocampus and dentate gyrus, respectively, but that the microglial CX3CR1 protein is decreased in the hippocampus of LPS-male offspring at P15. Further characterization of microglial morphology in the dentate gyrus identified a more ameboid phenotype in LPS-exposed offspring, predominantly in males, at P15. We thus explored maternal plasma and fetal brain cytokines to understand the mechanism behind microglial priming, showing a robust immune activation in the mother at 2 and 4 hrs after LPS administration, while only IL-10 tended towards upregulation at 2 hrs after LPS in fetal brains. To evaluate the functional long-term consequences, we assessed learning and cognitive flexibility behavior during late adolescence, finding that LPS affects only the latter with a male predominance on perseveration. A CX3CR1 gene variant in humans that results in disrupted fractalkine signaling has been recently associated with an increased risk for neurodevelopmental disorders. We show that an acute immune insult during late gestation can alter fractalkine signaling by reducing the microglial CX3CR1 protein expression, highlighting neuron-microglial fractalkine signaling as a relevant target underlying the outcomes of environmental risk factors on neurodevelopmental disorders.

Hidden talents: Poly (I:C)-induced maternal immune activation improves mouse visual discrimination performance and reversal learning in a sex-dependent manner

While there is a strong focus on the negative consequences of maternal immune activation (MIA) on developing brains, very little attention is directed towards potential advantages of early life challenges. In this study, we utilized a polyinosine-polycytidylic acid (poly(I:C)) MIA model to test visual pairwise discrimination (PD) and reversal learning (RL) in mice using touchscreen technology. Significant sex differences emerged in that MIA reduced the latency for males to make a correct choice in the PD task while females reached criterion sooner, made fewer errors, and utilized fewer correction trials in RL compared to saline controls. These surprising improvements were accompanied by the sex-specific upregulation of several genes critical to cognitive functioning, indicative of compensatory plasticity in response to MIA. In contrast, when exposed to a 'two-hit' stress model (MIA + loss of the social component of environmental enrichment [EE]), mice did not display anhedonia but required an increased number of PD and RL correction trials. These animals also had significant reductions of CamK2a mRNA in the prefrontal cortex. Appropriate functioning of synaptic plasticity, via mediators such as this protein kinase and others, are critical for behavioral flexibility. Although EE has been implicated in, delaying the appearance of symptoms associated with certain brain disorders, these findings are in line with evidence that it also makes individuals more vulnerable to its loss. Overall, with the right 'dose', early life stress exposure can confer at least some functional advantages, which are lost when the number or magnitude of these exposures become too great.

Effects of iTBS-rTMS on the Behavioral Phenotype of a Rat Model of Maternal Immune Activation

Repetitive transcranial magnetic stimulation (rTMS) is considered a promising therapeutic tool for treating neuropsychiatric diseases. Previously, we found intermittent theta-burst stimulation (iTBS) rTMS to be most effective in modulating cortical excitation-inhibition balance in rats, accompanied by improved cortical sensory processing and sensory learning performance. Using an animal schizophrenia model based on maternal immune activation (MIA) we tested if iTBS applied to either adult or juvenile rats can affect the behavioral phenotype in a therapeutic or preventive manner, respectively. In a sham-controlled fashion, iTBS effects in MIA rats were compared with rats receiving vehicle NaCl injection instead of the synthetic viral strand. Prior to iTBS, adult MIA rats showed deficits in sensory gating, as tested with prepulse inhibition (PPI) of the acoustic startle reflex, and deficits in novel object recognition (NOR). No differences between MIA and control rats were evident with regard to signs of anxiety, anhedonia and depression but MIA rats were somewhat superior to controls during the training phase of Morris Water Maze (MWM) test. MIA but not control rats significantly improved in PPI following iTBS at adulthood but without significant differences between verum and sham application. If applied during adolescence, verum but not sham-iTBS improved NOR at adulthood but no difference in PPI was evident in rats treated either with sham or verum-iTBS. MIA and control rat responses to sham-iTBS applied at adulthood differed remarkably, indicating a different physiological reaction to the experimental experiences. Although verum-iTBS was not superior to sham-iTBS, MIA rats seemed to benefit from the treatment procedure in general, since differences-in relation to control rats declined or disappeared. Even if classical placebo effects can be excluded, motor or cognitive challenges or the entire handling procedure during the experiments appear to alleviate the behavioral impairments of MIA rats.

Gestational poly(I:C) attenuates, not exacerbates, the behavioral, cytokine and mTOR changes caused by isolation rearing in a rat 'dual-hit' model for neurodevelopmental disorders

Many psychiatric illnesses have a multifactorial etiology involving genetic and environmental risk factors that trigger persistent neurodevelopmental impairments. Several risk factors have been individually replicated in rodents, to understand disease mechanisms and evaluate novel treatments, particularly for poorly-managed negative and cognitive symptoms. However, the complex interplay between various factors remains unclear. Rodent dual-hit neurodevelopmental models offer vital opportunities to examine this and explore new strategies for early therapeutic intervention. This study combined gestational administration of polyinosinic:polycytidylic acid (poly(I:C); PIC, to mimic viral infection during pregnancy) with post-weaning isolation of resulting offspring (to mirror adolescent social adversity). After in vitro and in vivo studies required for laboratory-specific PIC characterization and optimization, we administered 10 mg/kg i.p. PIC potassium salt to time-mated Lister hooded dams on gestational day 15. This induced transient hypothermia, sickness behavior and weight loss in the dams, and led to locomotor hyperactivity, elevated striatal cytokine levels, and increased frontal cortical JNK phosphorylation in the offspring at adulthood. Remarkably, instead of exacerbating the well-characterized isolation syndrome, gestational PIC exposure actually protected against a spectrum of isolation-induced behavioral and brain regional changes. Thus isolation reared rats exhibited locomotor hyperactivity, impaired associative memory and reversal learning, elevated hippocampal and frontal cortical cytokine levels, and increased mammalian target of rapamycin (mTOR) activation in the frontal cortex - which were not evident in isolates previously exposed to gestational PIC. Brains from adolescent littermates suggest little contribution of cytokines, mTOR or JNK to early development of the isolation syndrome, or resilience conferred by PIC. But notably hippocampal oxytocin, which can protect against stress, was higher in adolescent PIC-exposed isolates so might contribute to a more favorable outcome. These findings have implications for identifying individuals at risk for disorders like schizophrenia who may benefit from early therapeutic intervention, and justify preclinical assessment of whether adolescent oxytocin manipulations can modulate disease onset or progression.

Mathematical processing is affected by daily but not cumulative glucocorticoid dose in patients with systemic lupus erythematosus

OBJECTIVES

The impact of glucocorticoids on neurocognitive performance in patients with SLE is not fully addressed. We aimed to study the effect of daily and cumulative glucocorticoid dose on neurocognitive performance in SLE patients.

METHODS

Consecutive SLE patients and gender- and age-matched healthy controls (HCs) underwent the computer-based Automated Neuropsychological Assessment Matric (ANAM), which evaluates eight neurocognitive domains including learning, recall, visual perception, mental rotation, short-term memory, attention, sustained attention and working memory. The total and individual-domain throughput scores (TPSs) and the presence of cognitive dysfunction (total TPS <1.5 s.d. below the mean TPS of HCs) were compared between SLE patients and HCs. Within the SLE group, univariate and independent associations between prednisolone dose (daily and cumulative) and individual-domain TPS were studied by univariate and multivariable linear regression, respectively.

RESULTS

A total of 96 SLE patients and 96 HCs were studied. SLE patients scored significantly worse across all the neurocognitive domains and had a significantly lower mean total TPS (P < 0.001) and a higher prevalence of cognitive dysfunction compared with HCs (25.0 vs 7.3%, P = 0.001). In SLE patients, daily prednisolone dose was significantly and negatively correlated with mathematical-processing TPS, which probes working memory (P = 0.018). No significant correlation between cumulative prednisolone dose and any of the individual-domain TPSs was found. In multivariable regression, higher daily prednisolone dose and doses >9 mg daily remained independently associated with lower mathematical-processing TPSs (P = 0.031).

CONCLUSION

Daily prednisolone dose ≥9 mg, but not cumulative glucocorticoid dose, had an independent negative impact on mathematical processing in SLE patients.

Maternal Immune Activation by Poly I:C as a preclinical Model for Neurodevelopmental Disorders: A focus on Autism and Schizophrenia

Maternal immune activation (MIA) in response to a viral infection during early and mid-gestation has been linked through various epidemiological studies to a higher risk for the child to develop autism or schizophrenia-related symptoms.. This has led to the establishment of the pathogen-free poly I:C-induced MIA animal model for neurodevelopmental disorders, which shows relatively high construct and face validity. Depending on the experimental variables, particularly the timing of poly I:C administration, different behavioural and molecular phenotypes have been described that relate to specific symptoms of neurodevelopmental disorders such as autism spectrum disorder and/or schizophrenia. We here review and summarize epidemiological evidence for the effects of maternal infection and immune activation, as well as major findings in different poly I:C MIA models with a focus on poly I:C exposure timing, behavioural and molecular changes in the offspring, and characteristics of the model that relate it to autism spectrum disorder and schizophrenia.

Reward and punishment learning in schizophrenia and bipolar disorder

Prior studies on reward learning deficits in psychiatric disorders have used probabilistic learning tasks, making it unclear whether impairment is due to the probabilistic nature of the task rather than reward processing. In this study, we tested probabilistic vs. deterministic reward and punishment learning in healthy controls and three patient groups: schizophrenia (SZ), psychotic bipolar disorder (BD), and nonpsychotic BD. Experimental results show that reward learning was impaired in patients with SZ and patients with psychotic BD in the probabilistic learning task compared to patients with nonpsychotic BD and healthy controls. In contrast, punishment learning in the probabilistic task was impaired in patients with nonpsychotic BD compared to the other patient groups and healthy controls. There were no significant differences among all groups in the deterministic learning task scores. We also found that Hamilton Depression Scale scores negatively correlated with probabilistic learning performance. Our data may suggest that reward learning impairment may be due to the nature of the task as well as subtype of BD.

Maternal Immune Activation and Neuropsychiatric Illness: A Translational Research Perspective

Epidemiologic studies, including prospective birth cohort investigations, have implicated maternal immune activation in the etiology of neuropsychiatric disorders. Maternal infectious pathogens and inflammation are plausible risk factors for these outcomes and have been associated with schizophrenia, autism spectrum disorder, and bipolar disorder. Concurrent with epidemiologic research are animal models of prenatal immune activation, which have documented behavioral, neurochemical, neuroanatomic, and neurophysiologic disruptions that mirror phenotypes observed in these neuropsychiatric disorders. Epidemiologic studies of maternal immune activation offer the advantage of directly evaluating human populations but are limited in their ability to uncover pathogenic mechanisms. Animal models, on the other hand, are limited in their generalizability to psychiatric disorders but have made significant strides toward discovering causal relationships and biological pathways between maternal immune activation and neuropsychiatric phenotypes. Incorporating these risk factors in reverse translational animal models of maternal immune activation has yielded a wealth of data supporting the predictive potential of epidemiologic studies. To further enhance the translatability between epidemiology and basic science, the authors propose a complementary approach that includes deconstructing neuropsychiatric outcomes of maternal immune activation into key pathophysiologically defined phenotypes that are identifiable in humans and animals and that evaluate the interspecies concordance regarding interactions between maternal immune activation and genetic and epigenetic factors, including processes involving intergenerational disease transmission. [AJP AT 175: Remembering Our Past As We Envision Our Future October 1857: The Pathology of Insanity J.C. Bucknill: "In the brain the state of inflammation itself either very quickly ceases or very soon causes death; but when it does cease it leaves behind it consequences which are frequently the causes of insanity, and the conditions of cerebral atrophy." (Am J Psychiatry 1857; 14:172-193 )].

Increased cortical neuronal responses to NMDA and improved attentional set-shifting performance in rats following prebiotic (B-GOS®) ingestion

We have previously shown that prebiotics (dietary fibres that augment the growth of indigenous beneficial gut bacteria) such as Bimuno™ galacto-oligosaccharides (B-GOS®), increased N-methyl-D-aspartate (NMDA) receptor levels in the rat brain. The current investigation examined the functional correlates of these changes in B-GOS®-fed rats by measuring cortical neuronal responses to NMDA using in vivo NMDA micro-iontophoresis electrophysiology, and performance in the attentional set-shifting task. Adult male rats were supplemented with B-GOS® in the drinking water 3 weeks prior to in vivo iontophoresis or behavioural testing. Cortical neuronal responses to NMDA iontophoresis, were greater (+30%) in B-GOS® administered rats compared to non-supplemented controls. The intake of B-GOS® also partially hindered the reduction of NMDA responses by the glycine site antagonist, HA-966. In the attentional set-shifting task, B-GOS® -fed rats shifted from an intra-dimensional to an extra-dimensional set in fewer trials than controls, thereby indicating greater cognitive flexibility. An initial exploration into the mechanisms revealed that rats ingesting B-GOS® had increased levels of plasma acetate, and cortical GluN2B subunits and Acetyl Co-A Carboxylase mRNA. These changes were also observed in rats fed daily for 3 weeks with glyceryl triacetate, though unlike B-GOS®, cortical histone deacetylase (HDAC1, HDAC2) mRNAs were also increased which suggested an additional epigenetic action of direct acetate supplementation. Our data demonstrate that a pro-cognitive effect of B-GOS® intake in rats is associated with an increase in cortical NMDA receptor function, but the role of circulating acetate derived from gut bacterial fermentation of this prebiotic requires further investigation.

Aerobic Exercise as a Tool to Improve Hippocampal Plasticity and Function in Humans: Practical Implications for Mental Health Treatment

Aerobic exercise (AE) has been widely praised for its potential benefits to cognition and overall brain and mental health. In particular, AE has a potent impact on promoting the function of the hippocampus and stimulating neuroplasticity. As the evidence-base rapidly builds, and given most of the supporting work can be readily translated from animal models to humans, the potential for AE to be applied as a therapeutic or adjunctive intervention for a range of human conditions appears ever more promising. Notably, many psychiatric and neurological disorders have been associated with hippocampal dysfunction, which may underlie the expression of certain symptoms common to these disorders, including (aspects of) cognitive dysfunction. Augmenting existing treatment approaches using AE based interventions may promote hippocampal function and alleviate cognitive deficits in various psychiatric disorders that currently remain untreated. Incorporating non-pharmacological interventions into clinical treatment may also have a number of other benefits to patient well being, such as limiting the risk of adverse side effects. This review incorporates both animal and human literature to comprehensively detail how AE is associated with cognitive enhancements and stimulates a cascade of neuroplastic mechanisms that support improvements in hippocampal functioning. Using the examples of schizophrenia and major depressive disorder, the utility and implementation of an AE intervention to the clinical domain will be proposed, aimed to reduce cognitive deficits in these, and related disorders.

Cognitive Dysfunction in Major Depressive Disorder. A Translational Review in Animal Models of the Disease

Major Depressive Disorder (MDD) is the most common psychiatric disease, affecting millions of people worldwide. In addition to the well-defined depressive symptoms, patients suffering from MDD consistently complain about cognitive disturbances, significantly exacerbating the burden of this illness. Among cognitive symptoms, impairments in attention, working memory, learning and memory or executive functions are often reported. However, available data about the heterogeneity of MDD patients and magnitude of cognitive symptoms through the different phases of MDD remain difficult to summarize. Thus, the first part of this review briefly overviewed clinical studies, focusing on the cognitive dysfunctions depending on the MDD type. As animal models are essential translational tools for underpinning the mechanisms of cognitive deficits in MDD, the second part of this review synthetized preclinical studies observing cognitive deficits in different rodent models of anxiety/depression. For each cognitive domain, we determined whether deficits could be shared across models. Particularly, we established whether specific stress-related procedures or unspecific criteria (such as species, sex or age) could segregate common cognitive alteration across models. Finally, the role of adult hippocampal neurogenesis in rodents in cognitive dysfunctions during MDD state was also discussed.

Inflammation in schizophrenia: A question of balance

In the past decade, there has been renewed interest in immune/inflammatory changes and their associated oxidative/nitrosative consequences as key pathophysiological mechanisms in schizophrenia and related disorders. Both brain cell components (microglia, astrocytes, and neurons) and peripheral immune cells have been implicated in inflammation and the resulting oxidative/nitrosative stress (O&NS) in schizophrenia. Furthermore, down-regulation of endogenous antioxidant and anti-inflammatory mechanisms has been identified in biological samples from patients, although the degree and progression of the inflammatory process and the nature of its self-regulatory mechanisms vary from early onset to full-blown disease. This review focuses on the interactions between inflammation and O&NS, their damaging consequences for brain cells in schizophrenia, the possible origins of inflammation and increased O&NS in the disorder, and current pharmacological strategies to deal with these processes (mainly treatments with anti-inflammatory or antioxidant drugs as add-ons to antipsychotics).

Evidence that the attentional set shifting test in rats can be applied in repeated testing paradigms

The attentional set shifting task (ASST) can be used to assess aspects of executive function, including reversal learning and set shifting. It has frequently been employed in between-subjects experimental designs: however, the clear advantages of within-subjects designs (reduction in variance, animal numbers, and cost) mean that investigation of the suitability of the ASST for within subjects designs is warranted. Rats were tested three times: test 1 (24 h after training), test 2 (24 h later), and test 3 (seven days later). On all three test days, animals showed the expected pattern of performance across the seven task stages with evidence of normal reversal learning (significant increase in trials to criterion when the rule was reversed) and intact set formation (significantly more trials to criterion for an extradimensional shift than for an intradimensional shift). There was a small decrease in total trials required to complete the task between test 1 and test 3 but this was not specific to any stage of the task. Latency to dig decreased on repeated testing suggesting some facilitation of associative learning. In conclusion, the rodent ASST is suitable for within-subject design longitudinal studies, increasing the utility and the translational value of this test and reducing numbers of animals needed in studies.