Hippocampal volume reduction in first-episode and chronic schizophrenia: a review and meta-analysis

Heterozygosity for nuclear factor one x affects hippocampal-dependent behaviour in mice

Identification of the genes that regulate the development and subsequent functioning of the hippocampus is pivotal to understanding the role of this cortical structure in learning and memory. One group of genes that has been shown to be critical for the early development of the hippocampus is the Nuclear factor one (Nfi) family, which encodes four site-specific transcription factors, NFIA, NFIB, NFIC and NFIX. In mice lacking Nfia, Nfib or Nfix, aspects of early hippocampal development, including neurogenesis within the dentate gyrus, are delayed. However, due to the perinatal lethality of these mice, it is not clear whether this hippocampal phenotype persists to adulthood and affects hippocampal-dependent behaviour. To address this we examined the hippocampal phenotype of mice heterozygous for Nfix (Nfix (+/-)), which survive to adulthood. We found that Nfix (+/-) mice had reduced expression of NFIX throughout the brain, including the hippocampus, and that early hippocampal development in these mice was disrupted, producing a phenotype intermediate to that of wild-type mice and Nfix(-/-) mice. The abnormal hippocampal morphology of Nfix (+/-) mice persisted to adulthood, and these mice displayed a specific performance deficit in the Morris water maze learning and memory task. These findings demonstrate that the level of Nfix expression during development and within the adult is essential for the function of the hippocampus during learning and memory.

Multiple risk pathways for schizophrenia converge in serine racemase knockout mice, a mouse model of NMDA receptor hypofunction

Schizophrenia is characterized by reduced hippocampal volume, decreased dendritic spine density, altered neuroplasticity signaling pathways, and cognitive deficits associated with impaired hippocampal function. We sought to determine whether this diverse pathology could be linked to NMDA receptor (NMDAR) hypofunction, and thus used the serine racemase-null mutant mouse (SR(-/-)), which has less than 10% of normal brain D-serine, an NMDAR coagonist. We found that D-serine was necessary for the maintenance of long-term potentiation in the adult hippocampal dentate gyrus and for full NMDAR activity on granule cells. SR(-/-) mice had reduced dendritic spines and hippocampal volume. These morphological changes were paralleled by diminished BDNF/Akt/mammalian target of rapamycin (mTOR) signaling and impaired performance on a trace-conditioning memory task. Chronic D-serine treatment normalized the electrophysiological, neurochemical, and cognitive deficits in SR(-/-) mice. These results demonstrate that NMDAR hypofunction can reproduce the numerous hippocampal deficits associated with schizophrenia, which can be reversed by chronic peripheral D-serine treatment.

Personalized medicine in psychiatry: problems and promises

The central theme of personalized medicine is the premise that an individual's unique physiologic characteristics play a significant role in both disease vulnerability and in response to specific therapies. The major goals of personalized medicine are therefore to predict an individual's susceptibility to developing an illness, achieve accurate diagnosis, and optimize the most efficient and favorable response to treatment. The goal of achieving personalized medicine in psychiatry is a laudable one, because its attainment should be associated with a marked reduction in morbidity and mortality. In this review, we summarize an illustrative selection of studies that are laying the foundation towards personalizing medicine in major depressive disorder, bipolar disorder, and schizophrenia. In addition, we present emerging applications that are likely to advance personalized medicine in psychiatry, with an emphasis on novel biomarkers and neuroimaging.

Hippocampal shape abnormalities of patients with childhood-onset schizophrenia and their unaffected siblings

OBJECTIVE

The hippocampus has been implicated in the pathogenesis of schizophrenia, and hippocampal volume deficits have been a consistently reported abnormality, but the subregional specificity of the deficits remains unknown. The authors explored the nature and developmental trajectory of subregional shape abnormalities of the hippocampus in patients with childhood-onset schizophrenia (COS), their healthy siblings, and healthy volunteers.

METHOD

Two hundred twenty-five anatomic brain magnetic resonance images were obtained from 103 patients with COS, 169 from their 79 healthy siblings, and 255 from 101 age- and sex-matched healthy volunteers (age range = 9-29 years). The hippocampus was segmented using FreeSurfer automated image analysis software, and hippocampal shape was evaluated by comparing subjects at more than 6,000 vertices on the left and right hippocampal surfaces. Longitudinal data were examined using mixed model regression analysis.

RESULTS

Patients with COS showed significant bilateral inward deformation in the anterior hippocampus. Healthy siblings also showed a trend for anterior inward deformation. However, the trajectory of shape change did not differ significantly between the groups. Inward deformations in the anterior hippocampus were positively related to positive symptom severity, whereas outward surface displacement was positively related to overall functioning.

CONCLUSION

This is the first and largest longitudinal three-way analysis of subregional hippocampal shape abnormalities in patients with COS and their healthy siblings compared with healthy controls. The anterior hippocampal abnormalities in COS suggest the pathophysiologic importance of this subregion in schizophrenia. The trend level and overlapping shape abnormalities in the healthy siblings suggest a more subtle, subregionally specific neuroanatomic endophenotype.

Hippocampal volume in subjects at high risk of psychosis: a longitudinal MRI study

INTRODUCTION

The hippocampal formation has been studied extensively in schizophrenic psychoses and alterations in hippocampal anatomy have been consistently reported. Chronic schizophrenia seems to be associated with bilateral hippocampal volume (HV) reduction, while in patients with an at-risk mental state (ARMS) there are contradictory results. This is the first region of interest (ROI) based follow-up MRI study of hippocampal volume comparing ARMS individuals with and without transition to psychosis. The aim was to investigate the timing of HV changes in ARMS in the early phase of psychosis.

METHODS

Magnetic resonance imaging data from 18 antipsychotic-naïve individuals with an ARMS were collected within the FePsy-clinic for early detection of psychoses. During follow-up 8 subjects transitioned to psychosis (ARMS-T) and 10 did not (ARMS-NT). Subjects were re-scanned after the onset of psychosis or at the end of the follow-up if they did not develop psychosis.

RESULTS

Across both groups there was a significant decrease in HV over time (p<0.05). There was no significant difference in progression between ARMS-T and ARMS-NT. Antipsychotic medication at follow up was associated with increased HV (p<0.05).

CONCLUSIONS

We found a decrease of HV over time in subjects with an ARMS, independently of clinical outcome. We may speculate that the decrease of HV over time might reflect brain degeneration processes.

Developmental trajectories of amygdala and hippocampus from infancy to early adulthood in healthy individuals

Knowledge of amygdalar and hippocampal development as they pertain to sex differences and laterality would help to understand not only brain development but also the relationship between brain volume and brain functions. However, few studies investigated development of these two regions, especially during infancy. The purpose of this study was to examine typical volumetric trajectories of amygdala and hippocampus from infancy to early adulthood by predicting sexual dimorphism and laterality. We performed a cross-sectional morphometric MRI study of amygdalar and hippocampal growth from 1 month to 25 years old, using 109 healthy individuals. The findings indicated significant non-linear age-related volume changes, especially during the first few years of life, in both the amygdala and hippocampus regardless of sex. The peak ages of amygdalar and hippocampal volumes came at the timing of preadolescence (9–11 years old). The female amygdala reached its peak age about one year and a half earlier than the male amygdala did. In addition, its rate of growth change decreased earlier in the females. Furthermore, both females and males displayed rightward laterality in the hippocampus, but only the males in the amygdala. The robust growth of the amygdala and hippocampus during infancy highlight the importance of this period for neural and functional development. The sex differences and laterality during development of these two regions suggest that sex-related factors such as sex hormones and functional laterality might affect brain development.

Hippocampal volume and the AKT signaling system in first-episode schizophrenia

OBJECTIVE

The phosphoinositide 3'-kinase (PI3K)--protein kinase B (AKT1)--glycogen synthase kinase (GSK)-3β system is modulated by several factors implicated in the pathophysiology of schizophrenia. Evidence suggests that neuregulin 1 (NRG1) induces decreased AKT phosphorylation in schizophrenia relative to healthy controls, which may be related to dysfunctional neurodevelopment and neuroplasticity. The aim of this study was to investigate the relationship between NRG1--induced AKT phosphorylation and hippocampal volume in schizophrenia.

METHODS

Participants were 20 first-episode patients with schizophrenia who did not receive psychotropic medications and 20 matched healthy controls. We measured the phosphorylated AKT--total AKT and phosphorylated ERK (extracellular signal-regulated kinase)--total ERK ratios in peripheral lymphoblasts before and after NRG1 administration. Whole-brain, left, and right hippocampal volumes were quantified using FreeSurfer software.

RESULTS

Patients with schizophrenia displayed decreased AKT but normal ERK ratio compared with controls. Patients also had a reduction in left hippocampal volume. There was no significant difference between patients and controls in whole-brain and right hippocampal volume. Decreased AKT ratio was associated with reduced hippocampal volume. There was no significant relationship between ERK ratio and brain structure.

CONCLUSION

Activation of the AKT system is specifically associated with hippocampal volume in first-episode schizophrenia, which provides further evidence for the pivotal role of this messenger system in the pathophysiology of psychotic disorders.

Do Apparent Overlaps between Schizophrenia and Autistic Spectrum Disorders Reflect Superficial Similarities or Etiological Commonalities?

STUDY BACKGROUND: Schizophrenia and autism are both neurodevelopmental disorders that were once considered to be the same disorder expressed in different developmental periods. Although they were separated diagnostically about 40 years ago, they share several clinical and possibly, etiological features. This paper reviews overlaps in four domains of function to consider the issue of whether these similarities are sporadic and likely to represent superficial similarities, or whether the disorders are more likely to share some features in common. METHODS: Representative areas of function were reviewed and compared for aspects of cognition (nonverbal reasoning, memory and language), social function (orienting/joint attention, eye contact and theory of mind), brain function (structural differences) and genetics. To facilitate comparisons with schizophrenia, a focus on high functioning autism/Asperger's disorder was utilized, particularly in the sections on cognition and social function. RESULTS: Significant similarities (and differences) characterized comparisons in each domain. CONCLUSIONS: Disturbed function in similar clinical (in cognition and social function), neurobiological (brain volumes) and genetic (e.g., involvement of the same genes or chromosomal locations) domains in autism and schizophrenia supports the hypothesis that while they are distinct disorders, they are not entirely unique. Additional studies of similarities and differences between them may thus shed light on common etiological mechanisms and hopefully, facilitate the development of novel treatment targets.

Schizophrenia as a disorder of disconnectivity

Schizophrenia is considered as a neurodevelopmental disorder with genetic and environmental factors playing a role. Animal models show that developmental hippocampal lesions are causing disconnectivity of the prefrontal cortex. Magnetic resonance imaging and postmortem investigations revealed deficits in the temporoprefrontal neuronal circuit. Decreased oligodendrocyte numbers and expression of oligodendrocyte genes and synaptic proteins may contribute to disturbances of micro- and macro-circuitry in the pathophysiology of the disease. Functional connectivity between cortical areas can be investigated with high temporal resolution using transcranial magnetic stimulation (TMS), electroencephalography (EEG), and magnetoencephalography (MEG). In this review, disconnectivity between different cortical areas in schizophrenia patients is described. The specificity and the neurobiological origin of these connectivity deficits and the relation to the symptom complex of schizophrenia and the glutamatergic and GABAergic system are discussed.