Reduction in hippocampal formation volume is caused mainly by its shortening in chronic schizophrenia: assessment by MRI

Effect of high-endurance exercise intervention on sleep-dependent procedural memory consolidation in individuals with schizophrenia: a randomized controlled trial

BACKGROUND

Little is known about the effects of physical exercise on sleep-dependent consolidation of procedural memory in individuals with schizophrenia. We conducted a randomized controlled trial (RCT) to assess the effectiveness of physical exercise in improving this cognitive function in schizophrenia.

METHODS

A three-arm parallel open-labeled RCT took place in a university hospital. Participants were randomized and allocated into either the high-intensity-interval-training group (HIIT), aerobic-endurance exercise group (AE), or psychoeducation group for 12 weeks, with three sessions per week. Seventy-nine individuals with schizophrenia spectrum disorder were contacted and screened for their eligibility. A total of 51 were successfully recruited in the study. The primary outcome was sleep-dependent procedural memory consolidation performance as measured by the finger-tapping motor sequence task (MST). Assessments were conducted during baseline and follow-up on week 12.

RESULTS

The MST performance scored significantly higher in the HIIT (n = 17) compared to the psychoeducation group (n = 18) after the week 12 intervention (p < 0.001). The performance differences between the AE (n = 16) and the psychoeducation (p = 0.057), and between the AE and the HIIT (p = 0.999) were not significant. Yet, both HIIT (p < 0.0001) and AE (p < 0.05) showed significant within-group post-intervention improvement.

CONCLUSIONS

Our results show that HIIT and AE were effective at reverting the defective sleep-dependent procedural memory consolidation in individuals with schizophrenia. Moreover, HIIT had a more distinctive effect compared to the control group. These findings suggest that HIIT may be a more effective treatment to improve sleep-dependent memory functions in individuals with schizophrenia than AE alone.

Polygenic effects of schizophrenia on hippocampal grey matter volume and hippocampus-medial prefrontal cortex functional connectivity

BACKGROUND

Schizophrenia is a complex mental disorder with high heritability and polygenic inheritance. Multimodal neuroimaging studies have also indicated that abnormalities of brain structure and function are a plausible neurobiological characterisation of schizophrenia. However, the polygenic effects of schizophrenia on these imaging endophenotypes have not yet been fully elucidated.

AIMS

To investigate the effects of polygenic risk for schizophrenia on the brain grey matter volume and functional connectivity, which are disrupted in schizophrenia.

METHOD

Genomic and neuroimaging data from a large sample of Han Chinese patients with schizophrenia (N = 509) and healthy controls (N = 502) were included in this study. We examined grey matter volume and functional connectivity via structural and functional magnetic resonance imaging, respectively. Using the data from a recent meta-analysis of a genome-wide association study that comprised a large number of Chinese people, we calculated a polygenic risk score (PGRS) for each participant.

RESULTS

The imaging genetic analysis revealed that the individual PGRS showed a significantly negative correlation with the hippocampal grey matter volume and hippocampus-medial prefrontal cortex functional connectivity, both of which were lower in the people with schizophrenia than in the controls. We also found that the observed neuroimaging measures showed weak but similar changes in unaffected first-degree relatives of patients with schizophrenia.

CONCLUSIONS

These findings suggested that genetically influenced brain grey matter volume and functional connectivity may provide important clues for understanding the pathological mechanisms of schizophrenia and for the early diagnosis of schizophrenia.

Is formal thought disorder in schizophrenia related to structural and functional aberrations in the language network? A systematic review of neuroimaging findings

Formal thought disorder (FTD) is a core feature of schizophrenia, a marker of illness severity and a predictor of outcome. The underlying neural mechanisms are still a matter of debate. This study aimed at 1) reviewing the literature on the neural correlates of FTD in schizophrenia, and 2) testing the hypothesis that FTD correlates with structural and functional aberrations in the language network. Medline, PsychInfo, and Embase were searched for neuroimaging studies, which applied a clinical measure to assess FTD in adults with schizophrenia and were published in English or German in peer-reviewed journals until December 2016. Of 412 articles identified, 61 studies were included in the review. Volumetric studies reported bilateral grey matter deficits (L > R) to be associated with FTD in the inferior frontal gyrus, the superior temporal gyrus and the inferior parietal lobe. The same regions showed hyperactivity in resting state functional magnetic resonance imaging (fMRI) studies and both hyper- and hypoactivity in fMRI studies that employed semantic processing or free speech production tasks. Diffusion tensor imaging studies demonstrated white matter aberrations in fibre tracts that connect the frontal and temporo-parietal regions. FTD in schizophrenia was found to be associated with structural and functional aberrations in the language network. However, there are studies that did not find an association between FTD and neural aberrations of the language network and regions not included in the language network have been associated with FTD. Thus, future research is needed to clarify the specificity of the language network for FTD in schizophrenia.

Formal thought disorders: from phenomenology to neurobiology

Formal thought disorder (FTD) is present in most psychiatric disorders and in some healthy individuals. In this Review, we present a comprehensive, integrative, and multilevel account of what is known about FTD, covering genetic, cellular, and neurotransmitter effects, environmental influences, experimental psychology and neuropsychology, brain imaging, phenomenology, linguistics, and treatment. FTD is a dimensional, phenomenologically defined construct, which can be clinically subdivided into positive versus negative and objective versus subjective symptom clusters. Because FTDs have been traditionally linked to schizophrenia, studies in other diagnoses are scarce. Aetiologically, FTD is the only symptom under genetic influence in schizophrenia as shown in linkage studies, but familial communication patterns (allusive thinking) have also been associated with the condition. Positive FTDs are related to synaptic rarefication in the glutamate system of the superior and middle lateral temporal cortices. Cortical volume of the left superior temporal gyrus is decreased in patients with schizophrenia who have positive FTD in structural MRI studies and shows reversed hemispheric (right more than left) activation in functional MRI experiments during speech production. Semantic network dysfunction in positive FTD has been demonstrated in experiments of indirect semantic hyperpriming (reaction time). In acute positive FTD, antipsychotics are effective, but a subgroup of patients have treatment-resistant, chronic, positive or negative FTD. Specific psychotherapy as treatment for FTD has not yet been developed. With this solid data on the pathogenesis of FTD, we can now implement clinical studies to treat this condition.

Atrophy of pyramidal neurons and increased stress-induced glutamate levels in CA3 following chronic suppression of adult neurogenesis

Following their birth in the adult hippocampal dentate gyrus, newborn progenitor cells migrate into the granule cell layer where they differentiate, mature, and functionally integrate into existing circuitry. The hypothesis that adult hippocampal neurogenesis is physiologically important has gained traction, but the precise role of newborn neurons in hippocampal function remains unclear. We investigated whether loss of new neurons impacts dendrite morphology and glutamate levels in area CA3 of the hippocampus by utilizing a human GFAP promoter-driven thymidine kinase genetic mouse model to conditionally suppress adult neurogenesis. We found that chronic ablation of new neurons induces remodeling in CA3 pyramidal cells and increases stress-induced release of the neurotransmitter glutamate. The ability of persistent impairment of adult neurogenesis to influence hippocampal dendrite morphology and excitatory amino acid neurotransmission has important implications for elucidating newborn neuron function, and in particular, understanding the role of these cells in stress-related excitoxicity.

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

Several magnetic resonance imaging studies have reported hippocampal volume reduction in patients with schizophrenia, but other studies have reported contrasting results. In this review and meta-analysis, the authors aim to clarify whether a reduction in hippocampal volume characterizes patients with schizophrenia by considering illness phase (chronic and first episode) and hippocampus side separately. They made a detailed literature search for studies reporting physical volumetric hippocampal measures of patients with schizophrenia and healthy control (HC) participants and found 44 studies that were eligible for meta-analysis. Individual meta-analyses were also performed on 13 studies of first-episode patients and on 22 studies of chronic patients. The authors also detected any different findings when only males or both males and females were considered. Finally, additional meta-analyses and analyses of variance investigated the role of the factors "illness phase" and "side" on hippocampal volume reduction. Overall, the patient group showed significant bilateral hippocampal volume reduction compared with HC. Interestingly, first-episode and chronic patients showed same-size hippocampal volume reduction. Moreover, the left hippocampus was smaller than the right hippocampus in patients and HC. This review and meta-analysis raises the question about whether hippocampal volume reduction in schizophrenia is of neurodevelopmental origin. Future studies should specifically investigate this issue.

Reinforcement ambiguity and novelty do not account for transitive inference deficits in schizophrenia

The capacity for transitive inference (TI), a form of relational memory organization, is impaired in schizophrenia patients. In order to disambiguate deficits in TI from the effects of ambiguous reinforcement history and novelty, 28 schizophrenia and 20 nonpsychiatric control subjects were tested on newly developed TI and non-TI tasks that were matched on these 2 variables. Schizophrenia patients performed significantly worse than controls on the TI task but were able to make equivalently difficult nontransitive judgments as well as controls. Neither novelty nor reinforcement ambiguity accounted for the selective deficit of the patients on the TI task. These findings implicate a disturbance in relational memory organization, likely subserved by hippocampal dysfunction, in the pathophysiology of schizophrenia.

Stress and HPA-axis functioning in young people at ultra high risk for psychosis

It is thought that hypothalamic-pituitary-adrenal (HPA) axis functioning mediates between the experience of stress and development of psychotic symptoms. This study aimed to evaluate this model in a cohort of young people at ultra high risk (UHR) of psychosis. Information about the experience of psychological symptoms and recent stressful experiences was obtained from 23 young people who met UHR criteria. Plasma samples were taken to assess cortisol and glucocorticoid receptor numbers, and an MRI scan was also performed. Plasma cortisol levels were significantly and positively correlated with the experience of 'hassles' but not with the experience of stressful life events. Significant positive associations were also found between plasma cortisol levels and level of depression and anxiety. No significant relationships were found between plasma cortisol level and global psychopathology, psychotic symptomatology, functioning or pituitary and hippocampal volumes. These results suggest that the number of hassles experienced by young people at UHR of psychosis could be an important factor in raising their cortisol levels, which might, in turn, affect the severity of depressive and anxiety symptoms. No other relationships were found between plasma cortisol levels and the experience of psychotic symptoms, functioning or hippocampal and pituitary volumes. These results indicate possible impairment in HPA-axis functioning in the early stages of psychotic illness, but further investigation of the relationships between these parameters is required.

MRI abnormalities of the hippocampus and cavum septi pellucidi in females with schizotypal personality disorder

OBJECTIVE

This study examined MRI hippocampal volume and cavum septi pellucidi (CSP) in female subjects with schizotypal personality disorder (SPD) and comparison subjects.

METHOD

MRI was performed on 20 SPD and 29 comparison subjects with delineation of left and right hippocampi. Number of slices containing the CSP was counted. Subjects were given a working memory task, the Delayed Alternation task and other measures of working memory including the Wechsler Memory Test-Revised and the California Verbal Learning Test. Clinical measures were derived from the SCID-II.

RESULTS

SPD females evinced bilaterally smaller hippocampal volumes compared with non-psychiatric female subjects (15.1% on left, 15.7% on right). Additionally, SPD subjects showed statistically significantly more slices containing CSP, and a trend level difference when large CSP was defined as four or more slices (20% vs. 6.9%). SPD subjects demonstrated more errors, more perseverations, and a trend toward more failure to maintain set on the Delayed Alternating task, which were associated with smaller left hippocampal volumes. There was no difference between groups in logical memory, verbal learning or semantic clustering nor a significant correlation between these measures and hippocampal volumes. Clinically, in SPD subjects, right hippocampal volumes correlated negatively with odd appearance/behavior and positively with suspiciousness/paranoia, and odd speech was positively correlated with the number of slices containing a CSP in exploratory analyses.

CONCLUSIONS

Female SPD subjects showed bilaterally smaller hippocampal volumes and larger CSP than comparison subjects, similar to what has been shown in schizophrenia. Moreover, these abnormalities have clinically significant associations which may help to explain some of the manifestations of the disorder.

Tolloid-like 1 is negatively regulated by stress and glucocorticoids

Glucocorticoids affect a variety of tissues to enable the organism to adapt to the stress. Hippocampal neurons contain glucocorticoid receptors and respond to elevated glucocorticoid levels by down-regulating the HPA axis. Chronically, however, stress is deleterious to hippocampal neurons. Chronically elevated levels of glucocorticoids result in a decrease in the number of dendritic spines, reduced axonal growth and synaptogenesis, and decreased neurogenesis in the hippocampus. Tolloid-like 1 (Tll-1) is a metalloprotease that potentiates the activity of the bone morphogenetic proteins (BMPs). Neurogenesis in the hippocampus of both developing and adult mammals requires BMPs. In this study, we demonstrate that Tll-1 expression is increased in mice that have increased neurogenesis. The Tll-1 promoter contains glucocorticoid response elements which are capable of binding to purified glucocorticoid receptor. Glucocorticoids decrease Tll-1 expression in vitro. Finally, prenatal stress leads to a decrease in Tll-1 mRNA expression in the hippocampus of adult female mice that is not observed in adult male mice indicating that Tll-1 expression is differentially regulated in males and females. The results of this study indicate that Tll-1 is responsive to glucocorticoids and this mechanism might influence neurogenesis in the hippocampus.

MR-based in vivo hippocampal volumetrics: 2. Findings in neuropsychiatric disorders

Magnetic resonance imaging (MRI) has opened a new window to the brain. Measuring hippocampal volume with MRI has provided important information about several neuropsychiatric disorders. We reviewed the literature and selected all English-language, human subject, data-driven papers on hippocampal volumetry, yielding a database of 423 records. Smaller hippocampal volumes have been reported in epilepsy, Alzheimer's disease, dementia, mild cognitive impairment, the aged, traumatic brain injury, cardiac arrest, Parkinson's disease, Huntington's disease, Cushing's disease, herpes simplex encephalitis, Turner's syndrome, Down's syndrome, survivors of low birth weight, schizophrenia, major depression, posttraumatic stress disorder, chronic alcoholism, borderline personality disorder, obsessive-compulsive disorder, and antisocial personality disorder. Significantly larger hippocampal volumes have been correlated with autism and children with fragile X syndrome. Preservation of hippocampal volume has been reported in congenital hyperplasia, children with fetal alcohol syndrome, anorexia nervosa, attention-deficit and hyperactivity disorder, bipolar disorder, and panic disorder. Possible mechanisms of hippocampal volume loss in neuropsychiatric disorders are discussed.

Post-stress changes in BDNF and Bcl-2 immunoreactivities in hippocampal neurons: effect of chronic administration of olanzapine

In the present study, we used a repeated restraint stress animal model to observe the changes in the expression of brain-derived neurotrophic factor (BDNF) and B cell lymphoma protein-2 (Bcl-2) in hippocampal neurons of rats, monitored the time course of the expression over 3 weeks post-stress period, and examined the effects of the chronic administration of olanzapine on the time course. Olanzapine is an atypical antipsychotic drug that has been shown to be neuroprotective in previous in vitro studies. We found: (1) the repeated restraint stress decreases the levels of expression of BDNF and Bcl-2 in hippocampal neurons; (2) the stress-induced decreases spontaneously recover to their pre-stress levels in 3 weeks after the last stress exposure; (3) administration of olanzapine for 1 week returns the expression of Bcl-2 to its pre-stress level, and the administration for 3 weeks causes an excessive expression of BDNF in hippocampal neurons. In the context of the lower levels of BDNF and Bcl-2, and structural brain abnormalities observed in patients with schizophrenia, our findings suggest that BDNF and Bcl-2 may be involved in the pathophysiology of schizophrenia and in the therapeutic action of atypical antipsychotic drugs.

Structural plasticity and tianeptine: cellular and molecular targets

The hippocampal formation, a structure involved in declarative, spatial and contextual memory, undergoes atrophy in depressive illness along with impairment in cognitive function. Animal model studies have shown that the hippocampus is a particularly sensitive and vulnerable brain region that responds to stress and stress hormones. Studies on models of stress and glucocorticoid actions reveal that the hippocampus shows a considerable degree of structural plasticity in the adult brain. Stress suppresses neurogenesis of dentate gyrus granule neurons, and repeated stress causes remodeling of dendrites in the CA3 region, a region that is particularly important in memory processing. Both forms of structural remodeling of the hippocampus are mediated by adrenal steroids working in concert with excitatory amino acids (EAA) and N-methyl-D-aspartate (NMDA) receptors. EAA and NMDA receptors are also involved in neuronal death that is caused in pyramidal neurons by seizures, head trauma, and ischemia, and alterations of calcium homeostasis that accompany age-related cognitive impairment. Tianeptine (tianeptine) is an effective antidepressant that prevents and even reverses the actions of stress and glucocorticoids on dendritic remodeling in an animal model of chronic stress. Multiple neurotransmitter systems contribute to dendritic remodeling, including EAA, serotonin, and gamma-aminobutyric acid (GABA), working synergistically with glucocorticoids. This review summarizes findings on neurochemical targets of adrenal steroid actions that may explain their role in the remodeling process. In studying these actions, we hope to better understand the molecular and cellular targets of action of tianeptine in relation to its role in influencing structural plasticity of the hippocampus.

Rightward cerebral asymmetry in subtypes of schizophrenia according to Leonhard's classification and to DSM-IV: a structural MRI study

Although well documented, brain structural abnormalities in schizophrenia are non-specific, and morphometric parameters show significant overlap between patients and healthy controls. Such inconsistencies in neuroimaging findings could represent different levels of severity along a single pathogenic process or distinct clinical and etiopathological psychoses within a schizophrenic spectrum. The aim of the present study was the investigation of distinct brain abnormalities in different subtypes of schizophrenia. Forty patients were classified according to DSM-IV and Leonhard's classifications. Psychopathology was assessed by the Positive and Negative Syndrome Scale (PANSS) and the Negative Symptom Rating Scale (NSRS). Patients were compared to 20 healthy volunteers on volumetric measures of cerebral structures (hemisphere, hippocampus and planum temporale) and ventricular-brain ratio (VBR) obtained by magnetic resonance imaging. Patients showed rightward asymmetry of cerebral hemispheres and increased VBR. Rightward asymmetry correlated with severity of negative symptoms and prevailed in the systematic forms of Leonhard, suggesting a distinct pattern of left hemisphere abnormality in this subgroup of psychoses. Increased VBR values showed a single normal distribution in the subgroups, indicating that ventricular enlargement is not restricted to a subgroup but is present to a certain degree in all cases.

Anterior hippocampal volume reduction in male patients with schizophrenia

Quantitative high resolution magnetic resonance imaging (MRI) was utilized to measure anterior, posterior, and total hippocampal volumes in 27 male patients with chronic schizophrenia and 24 male controls. To optimize measurement techniques, hippocampal volumes were: (1) acquired with 1.4-mm slices; (2) excluded with the amygdala; (3) normalized for position; and (4) corrected for total intracranial volume (ICV). The results of a linear mixed effects regression analysis, which made it possible to analyze total anterior and total posterior hippocampal volumes separately, indicated that the anterior hippocampus was significantly smaller in the schizophrenic group relative to the control group. There were no significant group differences with respect to posterior hippocampal volumes, and no significant correlations between hippocampal volumes and illness duration. A significant lateralized asymmetry was also noted in both groups with the right hippocampal volume being larger than the left. These preliminary findings support a significant anterior hippocampal volume reduction in men with schizophrenia as well as a similar hippocampal volume asymmetry in both male controls and schizophrenics.

Quantification of frontal and temporal lobe brain-imaging findings in schizophrenia: a meta-analysis

Magnetic resonance imaging (MRI) and positron emission tomography (PET) studies of the frontal and temporal lobes in schizophrenia patients and healthy controls have proliferated over the past 2 decades, but there have been relatively few attempts to quantify the evidence. In this meta-analytic review, 155 studies on frontal and temporal lobe neurobiology were synthesized, reflecting results from 4043 schizophrenia patients and 3977 normal controls. Cohen's d was used to quantify case-control differences, and moderator variable analysis indexed the relation of sample and imaging characteristics to the magnitude of these differences. Frontal metabolic and blood flow deficiencies in conjunction with cognitive activation tasks ("hypofrontality") emerged as the strongest body of evidence, demonstrating abnormalities that distinguish approximately half of schizophrenia patients from healthy people. Most case-control comparisons with structural and functional imaging yield small and in many cases unstable findings. Technical scanning parameters like slice thickness and magnet strength did not vary with case-control differences consistently across the meta-analyses. However, patient sample characteristics including sample size, handedness and gender composition emerged frequently as moderators of brain-imaging effect sizes.

Pathogenesis of schizophrenia: Part I. Symptomatology, cognitive characteristics and brain morphology

The objective of the present study was to provide a pathophysiological model of the development of schizophrenia. The method used was a selective review of recent findings, including those in our own department, concerning the clinical symptoms, cognitive characteristics and morphological brain changes in schizophrenia. A four-syndrome classification was proposed in which 'alienation syndrome' is separated from delusion syndrome. Memory organization deficit in schizophrenia patients was correlated with reduced activation of the left inferior frontal regions. Magnetic resonance imaging and statistical parametric mapping analysis revealed that volume reduction in the temporal lobe was seen in both schizotypal disorder and schizophrenia patients, but schizophrenia patients had additional changes in the medial and dorsolateral frontal regions. In conclusion, a temporo-frontal dual pathology of schizophrenia was suggested.

A twin study of genetic contributions to hippocampal morphology in schizophrenia

Our goal was to establish whether altered hippocampal morphology represents a trait marker for genetic vulnerability in schizophrenia. We outlined the hippocampi on high-resolution MR images obtained from matched samples of control and discordant monozygotic and dizygotic co-twins (N = 40 pairs). Hippocampal measures were used in statistical tests specifically designed to identify disease-associated genetic and nongenetic influences on morphology. 3D surface average maps of the hippocampus were additionally compared in biological risk groups. Smaller hippocampal volumes were confirmed in schizophrenia. Dizygotic affected co-twins showed smaller left hippocampi compared to their healthy siblings. Disease-associated effects were not present between monozygotic discordant co-twins. Monozygotic, but not dizygotic, unaffected co-twins exhibited smaller left hippocampi compared to control twins, supporting genetic influences. Surface areas and posterior volumes similarly revealed schizophrenia and genetic liability effects. Results suggest that hippocampal volume reduction may be a trait marker for identifying individuals possessing a genetic predisposition for schizophrenia.

The neurobiology and neuroendocrinology of stress. Implications for post-traumatic stress disorder from a basic science perspective

Stress is a condition of the mind and a factor in the expression of disease that differs among individuals. In post-traumatic stress disorder (PTSD), traumatic events can create a long-lasting state of physiologic reactivity that amplifies and exacerbates the effects of daily life events. The elevated activities of physiologic systems lead to wear and tear, called "allostatic load." It reflects not only the impact of life experiences but also of genes, individual life-style habits (e.g., diet, exercise, and substance abuse), and developmental experiences that set life-long patterns of behavior and physiologic reactivity. Hormones associated with stress and allostatic load protect the body in the short run and promote adaptation, but in the long run allostatic load causes changes in the body that lead to disease.

Regional changes in brain gray and white matter in patients with schizophrenia demonstrated with voxel-based analysis of MRI

This study examined regional structural changes in the whole brain in 45 medicated patients with schizophrenia (23 males and 22 females), comparing with 42 age- and sex-matched healthy volunteers (22 males and 20 females). Automated voxel-based analysis on three-dimensional magnetic resonance imaging (MRI) was conducted using statistical parametric mapping (SPM). Compared with the controls, relative gray matter in the patients was significantly reduced in the left superior temporal, left middle and inferior frontal, right inferior frontal, and bilateral anterior cingulate and medial temporal areas. Gray matter reductions in the left superior temporal and prefrontal areas were found predominantly in the male patients, while the anterior cingulate gray mater reduction was more striking in the female patients. On the contrary, significant gray matter increases in the patients were found in the parietal areas and the cerebellum. In the white matter, significant reduction was found in the bilateral anterior limbs of the internal capsule and the superior occipitofrontal fasciculus, whereas the bilateral parietal white matter showed significant increases. These results suggest that a pathological process in schizophrenia predominantly affects the fronto-temporolimbic-paralimbic regions. Reduced white matter in the connecting bundles, which was first found in this study, may imply morphological substrates for abnormalities in the fronto-thalamic and fronto-temporolimbic connectivity in schizophrenia.

Metyrapone reveals that previous chronic stress differentially impairs hippocampal-dependent memory

Chronic stress facilitates fear conditioning in rats with hippocampal neuronal atrophy and in rats in which the atrophy is prevented with tianeptine, a serotonin re-uptake enhancer. The purpose of this study was to determine whether the lack of dissociation between fear conditioning performance and hippocampal integrity was masked by the presence of endogenous corticosteroids during training. As in previous studies, rats were stressed by daily restraint (6 h/day for 21 days), trained in the conditioning chamber (day 23), and then assessed for conditioned fear (day 25) at a time when hippocampal dendritic atrophy persists. On the training day, half of the control and stressed rats were. injected with metyrapone to reduce corticosterone release. Two hours later, two paired or unpaired presentations of tone and footshock were delivered. Although metyrapone reduced conditioned fear in all rats, only stressed rats showed dissociated fear conditioning (i.e. tone conditioning was reduced while contextual conditioning was eliminated). Chronically stressed rats, regardless of metyrapone treatment displayed more rearing in the open field when tested immediately after the completion of fear conditioning. These data support the hypothesis that increased emotionality and enhanced fear conditioning exhibited by chronically stressed rats maybe due to endogenous corticosterone secretion at the time of fear conditioned training. Moreover,these data suggest that chronic stress impairs hippocampal-dependent processes more robustly than hippocampal-independent processes after metyrapone to reduce corticosterone secretion during aversive training.

Selective bilateral hippocampal volume loss in chronic schizophrenia

BACKGROUND

The hippocampus is implicated in the pathophysiology of schizophrenia; however, volumetric changes are subtle and have limited diagnostic specificity. It is possible that the shape of the hippocampus may be more characteristic of schizophrenia.

METHODS

Forty-five patients with chronic schizophrenia and 139 healthy control subjects were scanned using magnetic resonance imaging. Hippocampi were traced manually, and two-dimensional shape information was analyzed.

RESULTS

Two shape factors were found to be adequate to represent variance in the shape of the hippocampus. One of these factors, representing volume loss behind the head of the hippocampus, provided a degree of discrimination between patients with chronic schizophrenia and healthy control subjects; however, overall hippocampal volume following appropriate adjustment for brain volume showed a similar level of discrimination. Patients with chronic schizophrenia were best characterized using these two measures together, but diagnostic specificity was only moderate.

CONCLUSIONS

This study identified that less of the hippocampus was distributed in its posterior two-thirds in patients with chronic schizophrenia, and specifically in the region just posterior to the hippocampal head. Group discrimination on the basis of hippocampal volume and shape measures was moderately good. A full three-dimensional analysis of hippocampal shape, based on large samples, would be a useful extension of the study.

Three-dimensional mapping of temporo-limbic regions and the lateral ventricles in schizophrenia: gender effects

BACKGROUND

Local alterations in morphological parameters are poorly characterized in several brain regions widely implicated in schizophrenia neuropathology.

METHODS

Surface-based anatomical modeling was applied to magnetic resonance data to obtain three-dimensional (3D) average anatomical maps and measures of location, shape, asymmetry, and volume for the lateral ventricles, hippocampus, amygdala, and superior temporal gyrus in schizophrenic (n = 25; 15 male) and normal subjects (n = 28; 15 male) matched for demographic variables. For all regions, intra-group variability was visualized and group differences assessed statistically to discriminate local alterations in anatomy across sex and diagnosis.

RESULTS

Posterior hippocampal volumes, lengths, and widths were reduced in patients. The right amygdala showed volume increases in schizophrenia patients versus controls. Ventricular enlargements, pronounced in the left hemisphere, occurred in the superior and lateral dimensions in patients, and these effects interacted with gender. Superior horn anterior extremes, inferior horn volumes, and hippocampal asymmetries exhibited gender effects. Significant group differences were absent in superior temporal gyrus parameters. Finally, regional variability profiles differed across groups.

CONCLUSIONS

Clear morphometric differences of the lateral ventricles, hippocampus, and amygdala indicate regional displacements and shape distortions in several functional systems in schizophrenia. Alterations in these structures as mapped in 3D may provide the foundation for establishing brain abnormalities not previously defined at such a local level.

A review of MRI findings in schizophrenia

After more than 100 years of research, the neuropathology of schizophrenia remains unknown and this is despite the fact that both Kraepelin (1919/1971: Kraepelin, E., 1919/1971. Dementia praecox. Churchill Livingston Inc., New York) and Bleuler (1911/1950: Bleuler, E., 1911/1950. Dementia praecox or the group of schizophrenias. International Universities Press, New York), who first described 'dementia praecox' and the 'schizophrenias', were convinced that schizophrenia would ultimately be linked to an organic brain disorder. Alzheimer (1897: Alzheimer, A., 1897. Beitrage zur pathologischen anatomie der hirnrinde und zur anatomischen grundlage einiger psychosen. Monatsschrift fur Psychiarie und Neurologie. 2, 82-120) was the first to investigate the neuropathology of schizophrenia, though he went on to study more tractable brain diseases. The results of subsequent neuropathological studies were disappointing because of conflicting findings. Research interest thus waned and did not flourish again until 1976, following the pivotal computer assisted tomography (CT) finding of lateral ventricular enlargement in schizophrenia by Johnstone and colleagues. Since that time significant progress has been made in brain imaging, particularly with the advent of magnetic resonance imaging (MRI), beginning with the first MRI study of schizophrenia by Smith and coworkers in 1984 (Smith, R.C., Calderon, M., Ravichandran, G.K., et al. (1984). Nuclear magnetic resonance in schizophrenia: A preliminary study. Psychiatry Res. 12, 137-147). MR in vivo imaging of the brain now confirms brain abnormalities in schizophrenia. The 193 peer reviewed MRI studies reported in the current review span the period from 1988 to August, 2000. This 12 year period has witnessed a burgeoning of MRI studies and has led to more definitive findings of brain abnormalities in schizophrenia than any other time period in the history of schizophrenia research. Such progress in defining the neuropathology of schizophrenia is largely due to advances in in vivo MRI techniques. These advances have now led to the identification of a number of brain abnormalities in schizophrenia. Some of these abnormalities confirm earlier post-mortem findings, and most are small and subtle, rather than large, thus necessitating more advanced and accurate measurement tools. These findings include ventricular enlargement (80% of studies reviewed) and third ventricle enlargement (73% of studies reviewed). There is also preferential involvement of medial temporal lobe structures (74% of studies reviewed), which include the amygdala, hippocampus, and parahippocampal gyrus, and neocortical temporal lobe regions (superior temporal gyrus) (100% of studies reviewed). When gray and white matter of superior temporal gyrus was combined, 67% of studies reported abnormalities. There was also moderate evidence for frontal lobe abnormalities (59% of studies reviewed), particularly prefrontal gray matter and orbitofrontal regions. Similarly, there was moderate evidence for parietal lobe abnormalities (60% of studies reviewed), particularly of the inferior parietal lobule which includes both supramarginal and angular gyri. Additionally, there was strong to moderate evidence for subcortical abnormalities (i.e. cavum septi pellucidi-92% of studies reviewed, basal ganglia-68% of studies reviewed, corpus callosum-63% of studies reviewed, and thalamus-42% of studies reviewed), but more equivocal evidence for cerebellar abnormalities (31% of studies reviewed). The timing of such abnormalities has not yet been determined, although many are evident when a patient first becomes symptomatic. There is, however, also evidence that a subset of brain abnormalities may change over the course of the illness. The most parsimonious explanation is that some brain abnormalities are neurodevelopmental in origin but unfold later in development, thus setting the stage for the development of the symptoms of schizophrenia. Or there may be additional factors, such as stress or neurotoxicity, that occur during adolescence or early adulthood and are necessary for the development of schizophrenia, and may be associated with neurodegenerative changes. Importantly, as several different brain regions are involved in the neuropathology of schizophrenia, new models need to be developed and tested that explain neural circuitry abnormalities effecting brain regions not necessarily structurally proximal to each other but nonetheless functionally interrelated. (ABSTRACT TRUNCATED)

Enlargement of the fornix in early-onset schizophrenia: a quantitative MRI study

Abnormalities of temporal lobe structure and frontal lobe function occur in schizophrenia. There have been few studies of young people with schizophrenia and little is known about temporo-frontal connectivity in the disease. Therefore, the cross-sectional area of the body of the fornix was measured on MR images from 17 young people with schizophrenia, nine with other serious psychiatric illnesses and eight without illness. The mean age of each group was 16-17 years. The mean cross-sectional fornix area in subjects with schizophrenia was significantly larger than that in subjects without illness ( approximately 40%) and psychiatric controls ( approximately 26%). There was no such significant difference between subjects without illness and psychiatric controls. The nature of the larger fornix in early-onset schizophrenia, whether it persists and whether it occurs in schizophrenia presenting in adulthood, remain to be elucidated.

Plasticity of the hippocampus: adaptation to chronic stress and allostatic load

The hippocampus is an important structure for declarative, spatial, and contextual memory and is implicated in the perception of chronic pain. The hippocampal formation is vulnerable to damage from seizures, ischemia, and head trauma and is particularly sensitive to the effects of adrenal glucocorticoids secreted during the diurnal rhythm and chronic stress. Adrenal steroids typically have adaptive effects in the short run, but promote pathophysiology when there is either repeated stress or dysregulation of the HPA axis. The damaging actions of glucocorticoids under such conditions have been termed "allostatic load", referring to the cost to the body of adaptation to adverse conditions. Adrenal steroids display both protective and damaging effects in the hippocampus. They biphasically modulate excitability of hippocampal neurons, and high glucocorticoid levels and severe acute stress impair declarative memory in a reversible manner. The hippocampus also displays structural plasticity, involving ongoing neurogenesis of the dentate gyrus, synaptogenesis under control of estrogens in the CA1 region, and dendritic remodeling caused by repeated stress or elevated levels of exogenous glucocorticoids in the CA3 region. In all three forms of structural plasticity, excitatory amino acids participate along with circulating steroid hormones. Glucocorticoids and stressors suppress neurogenesis in the dentate gyrus. They also potentiate the damage produced by ischemia and seizures. Moreover, the aging rat hippocampus displays elevated and prolonged levels of excitatory amino acids released during acute stress. Our working hypothesis is that structural plasticity in response to repeated stress starts out as an adaptive and protective response, but ends up as damage if the imbalance in the regulation of the key mediators is not resolved. It is likely that morphological rearrangements in the hippocampus brought on by various types of allostatic load alter the manner in which the hippocampus participates in memory functions and it is conceivable that these may also have a role in chronic pain perception.

Sylvian fissure and medial temporal lobe structures in patients with schizophrenia: a magnetic resonance imaging study

Volumes of the medial temporal lobe structures (i.e. the amygdala, hippocampus, and parahippocampal gyrus), Sylvian fissure, and inferior horn of the lateral ventricle relative to the cerebral hemisphere were measured in 24 patients with schizophrenia and 23 normal controls using magnetic resonance imaging. The patients had significantly larger Sylvian fissures and inferior horns bilaterally than the controls. In the patients the right Sylvian fissure size showed a significant positive correlation with the duration of illness. Moreover, earlier onset of illness was significantly correlated with decreased volume of the left medial temporal lobe structures. These results replicate previous finding of inferior horn enlargement and suggest the significance of the Sylvian fissure and the medial temporal lobe structures in pathophysiology of schizophrenia.

Stress and hippocampal plasticity: implications for the pathophysiology of affective disorders

The hippocampal formation, a structure involved in declarative, spatial and contextual memory, is a particularly sensitive and vulnerable brain region to stress and stress hormones. The hippocampus shows a considerable degree of structural plasticity in the adult brain. Stress suppresses neurogenesis of dentate gyrus granule neurons, and repeated stress causes atrophy of dendrites in the CA3 region. In addition, ovarian steroids regulate synapse formation during the estrous cycle of female rats. All three forms of structural remodeling of the hippocampus are mediated by hormones working in concert with excitatory amino acids (EAA) and N-methyl-D-aspartate (NMDA) receptors. EAA and NMDA receptors are also involved in neuronal death that is caused in pyramidal neurons by seizures and by ischemia and prolonged psychosocial stress. In the human hippocampus, magnetic resonance imaging studies have shown that there is a selective atrophy in recurrent depressive illness, accompanied by deficits in memory performance. Hippocampal atrophy may be a feature of affective disorders that is not treated by all medications. From a therapeutic standpoint, it is essential to distinguish between permanent damage and reversible atrophy in order to develop treatment strategies to either prevent or reverse deficits. In addition, remodeling of brain cells may occur in other brain regions. Possible treatments are discussed. Copyright 2001 John Wiley & Sons, Ltd.

The neurobiology of stress: from serendipity to clinical relevance

The hormones and other physiological agents that mediate the effects of stress on the body have protective and adaptive effects in the short run and yet can accelerate pathophysiology when they are over-produced or mismanaged. Here we consider the protective and damaging effects of these mediators as they relate to the immune system and brain. 'Stress' is a principle focus, but this term is rather imprecise. Therefore, the article begins by noting two new terms, allostasis and allostatic load that are intended to supplement and clarify the meanings of 'stress' and 'homeostasis'. For the immune system, acute stress enhances immune function whereas chronic stress suppresses it. These effects can be beneficial for some types of immune responses and deleterious for others. A key mechanism involves the stress-hormone dependent translocation of immune cells in the blood to tissues and organs where an immune defense is needed. For the brain, acute stress enhances the memory of events that are potentially threatening to the organism. Chronic stress, on the other hand, causes adaptive plasticity in the brain, in which local neurotransmitters as well as systemic hormones interact to produce structural as well as functional changes, involving the suppression of ongoing neurogenesis in the dentate gyrus and remodelling of dendrites in the Ammon's horn. Under extreme conditions only does permanent damage ensue. Adrenal steroids tell only part of the story as far as how the brain adapts, or shows damage, and local tissue modulators - cytokines for the immune response and excitatory amino acid neurotransmitters for the hippocampus. Moreover, comparison of the effects of experimenter-applied stressors and psychosocial stressors show that what animals do to each other is often more potent than what experimenters do to them. And yet, even then, the brain is resilient and capable of adaptive plasticity. Stress-induced structural changes in brain regions such as the hippocampus have clinical ramifications for disorders such as depression, post-traumatic stress disorder and individual differences in the aging process.

Effects of adverse experiences for brain structure and function

Studies of the hippocampus as a target of stress and stress hormones have revealed a considerable degree of structural plasticity in the adult brain. Repeated stress causes shortening and debranching of dendrites in the CA3 region of the hippocampus and suppresses neurogenesis of dentate gyrus granule neurons. Both forms of structural remodeling of the hippocampus appear to be reversible and are mediated by glucocorticoid hormones working in concert with excitatory amino acids (EAA) and N-methyl-D-aspartate (NMDA) receptors, along with transmitters such as serotonin and the GABA-benzodiazepine system. Glucocorticoids, EAA, and NMDA receptors are also involved in neuronal damage and death that is caused in pyramidal neurons by seizures and by ischemia. A similar mechanism may be involved in hippocampal damage caused by severe and prolonged psychosocial stress. Studies using magnetic resonance imaging have shown that there is a selective atrophy of the human hippocampus in a number of psychiatric disorders, as well as during aging in some individuals, accompanied by deficits in declarative, spatial, and contextual memory performance. It is therefore important to appreciate how hippocampal dysfunction may play a role in the symptoms of the psychiatric illness and, from a therapeutic standpoint, to distinguish between a permanent loss of cells and a reversible remodeling to develop treatment strategies to prevent or reverse deficits. Remodeling of the hippocampus may be only the tip of the iceberg; other brain regions may also be affected.

An MRI study of temporal lobe structures in men with bipolar disorder or schizophrenia

BACKGROUND

Hippocampal atrophy has been described in postmortem and magnetic resonance imaging studies of schizophrenia. The specificity of this finding to schizophrenia remains to be determined. The neuropathology of bipolar disorder is understudied, and temporal lobe structures have only recently been evaluated.

METHODS

Twenty-four bipolar, 20 schizophrenic, and 18 normal comparison subjects were evaluated using magnetic resonance brain imaging. Image data were acquired using a three-dimensional spoiled GRASS sequence, and brain images were reformatted in three planes. Temporal lobe structures including the amygdala, hippocampus, parahippocampus, and total temporal lobe were measured to obtain volumes for each structure in the three subject groups. Severity of symptoms in both patient groups was assessed at the time the magnetic resonance images were obtained.

RESULTS

Hippocampal volumes were significantly smaller in the schizophrenic group than in both bipolar and normal comparison subjects. Further, amygdala volumes were significantly larger in the bipolar group than in both schizophrenic and normal comparison subjects.

CONCLUSIONS

The results suggest differences in affected limbic structures in patients with schizophrenia and bipolar disorder. These specific neuroanatomic abnormalities may shed light on the underlying pathophysiology and presentation of the two disorders.

Neuroanatomy of comorbid schizophrenia and learning disability: a controlled study

BACKGROUND

Reasons for the higher frequency of schizophrenia in learning-disabled populations are uncertain. We investigated the neuroanatomical basis for this phenomenon by structural magnetic resonance imaging (MRI) in patients with learning disability and schizophrenia, learning-disabled patients, and patients with schizophrenia.

METHODS

Age-matched and sex-matched patients with learning disability (20 cases), schizophrenia (25), and both disorders (23) underwent MRI scans of the brain. Whole brain areas and specific regions of interest were examined. 29 normal controls were also scanned.

FINDINGS

The scans of the group with both disorders were closely similar to those of the schizophrenic group, in terms of both general structures and the structure of the amygdala-hippocampus. However, the amygdala-hippocampus was significantly smaller on both sides than that of normal controls (left 4.1 vs 4.5 cm3, p=0.011; right 4.2 vs 4.99 cm3, p<0.0001). The brains of learning-disabled patients were generally smaller than those of the other three groups, but the amygdalohippocampal complexes were larger.

INTERPRETATION

In terms of brain structure, patients with comorbid learning disability and schizophrenia resemble patients with schizophrenia and not those with learning disability. We suggest that the higher frequency of schizophrenia in learning-disabled patients is due to a greater tendency of schizophrenic patients to develop cognitive deficits, and that within the learning-disabled population there may be individuals whose deficits result from undiagnosed schizophrenia.

Subtype-associated metabolite differences in the temporal lobe in schizophrenia detected by proton magnetic resonance spectroscopy

Brain imaging studies have indicated that the medial temporal lobe functions aberrantly in schizophrenic patients. Both diagnostic subtype and gender may affect functional and morphologic abnormalities in this region. We investigated subtype- and gender-associated differences in metabolites in the left medial temporal lobe in 40 medicated schizophrenic patients by proton magnetic resonance spectroscopy and compared findings with those in 40 healthy control subjects. Peaks corresponding to N-acetylaspartate (NAA), choline-containing compounds (Cho), creatine-phosphocreatine (Cr), and inositol were measured. Schizophrenic patients showed a decrease in the NAA/Cr ratio in the left medial temporal lobe, and patients with the disorganized subtype of illness showed significantly lower NAA/Cr and Cho/Cr ratios than those with paranoid schizophrenia. The NAA/Cr ratio in patients with the undifferentiated subtype also was significantly lower than in the paranoid subtype. No significant associations were observed between metabolite ratios and clinical symptom scores, age at onset of illness, or gender. These findings suggest that patients with the disorganized and undifferentiated subtypes have greater impairments in neuronal integrity or function in the left medial temporal lobe than patients with other subtypes of schizophrenia.

Reduced hippocampal N-acetylaspartate without volume loss in schizophrenia

Quantitative magnetic resonance imaging (MRI) can measure total gray matter volume but cannot discriminate between neurons and glia. Proton magnetic resonance spectroscopic imaging (1H MRSI) measures N-acetylaspartate (NAA) which is a selective marker of neuronal loss or neuronal dysfunction. The objective of this study was to obtain quantitative measures of hippocampal volume and hippocampal NAA to determine if there was evidence for hippocampal neuronal dysfunction or neuronal loss in schizophrenia. Quantitative MRI and 1H MRSI was performed on the right and left hippocampal regions in 23 chronic schizophrenic patients and 18 control subjects. Relative to the control group, the patients with schizophrenia demonstrated no change in hippocampal volumes bilaterally, but significantly decreased NAA in the hippocampal regions bilaterally. There was also no correlation between hippocampal volumes and NAA in either the schizophrenics or controls. These findings suggest that: (1) hippocampal NAA may be a more sensitive measure of neuronal loss than volumetric measurements; and (2) reduced hippocampal NAA may be measuring neuronal dysfunction or damage rather than neuronal loss in this sample of schizophrenics.

Reduction of the parahippocampal gyrus and the hippocampus in patients with chronic schizophrenia

BACKGROUND

There have been many studies reporting reduced volume of the hippocampus or other limbic structures in patients with schizophrenia, but the literature is inconsistent.

AIMS

To compare patients with either first-episode or chronic schizophrenia with controls using high-resolution volumetric magnetic resonance imaging (MRI) scans.

METHOD

Thirteen patients with first-episode schizophrenia, 27 with chronic schizophrenia and 31 controls had 1.5 mm coronal slices taken through the whole brain using a spoiled-grass MRI acquisition protocol.

RESULTS

The parahippocampal gyrus was reduced significantly on the left side in patients with chronic schizophrenia compared with controls for both male and female patients, whereas the hippocampus was reduced significantly on both sides only in female patients. There were no significant reductions in any structure between patients with first-episode schizophrenia and controls.

CONCLUSIONS

Volumetric reduction seen in patients with chronic schizophrenia may be due to an active degenerative process occurring after the onset of illness.

Volumetric MRI measurements of the tree shrew hippocampus

Protocols suitable for repeated magnetic resonance imaging (MRI) studies of the tree shrew's brain were established. This included the development of (i) a technique for prolonged inhalation anesthesia by endotracheal intubation; (ii) a reproducible fixation of the animal's head in a stereotaxic frame and finally (iii) the set-up of the hardware (rf coil) and software (MRI sequences) of the MRI system. The endotracheal intubation as well as the repeated and prolonged anesthesia showed no complications. The in vivo measurements of the tree shrew's hippocampal formation revealed a high reproducibility. Right and left hippocampal volume was determined as 85.2 mm3 +/- 8% and 87.4 mm3 +/- 10%, respectively. The utility of MRI in delineating alterations in brain anatomy was demonstrated in three animals receiving cortisol via the drinking water (5 mg/animal/day). After a 4-week treatment, in two of the three tree shrews a reduction in hippocampal volume was observed. Thus, the MRI protocols used here allow for repeated and non-invasive measurements of changes in hippocampal anatomy within the same animal and to monitor the temporal dynamics of structural alterations within this brain structure.

MRI anatomy of schizophrenia

Structural magnetic resonance imaging (MRI) data have provided much evidence in support of our current view that schizophrenia is a brain disorder with altered brain structure, and consequently involving more than a simple disturbance in neurotransmission. This review surveys 118 peer-reviewed studies with control group from 1987 to May 1998. Most studies (81%) do not find abnormalities of whole brain/intracranial contents, while lateral ventricle enlargement is reported in 77%, and third ventricle enlargement in 67%. The temporal lobe was the brain parenchymal region with the most consistently documented abnormalities. Volume decreases were found in 62% of 37 studies of whole temporal lobe, and in 81% of 16 studies of the superior temporal gyrus (and in 100% with gray matter separately evaluated). Fully 77% of the 30 studies of the medial temporal lobe reported volume reduction in one or more of its constituent structures (hippocampus, amygdala, parahippocampal gyrus). Despite evidence for frontal lobe functional abnormalities, structural MRI investigations less consistently found abnormalities, with 55% describing volume reduction. It may be that frontal lobe volume changes are small, and near the threshold for MRI detection. The parietal and occipital lobes were much less studied; about half of the studies showed positive findings. Most studies of cortical gray matter (86%) found volume reductions were not diffuse, but more pronounced in certain areas. About two thirds of the studies of subcortical structures of thalamus, corpus callosum and basal ganglia (which tend to increase volume with typical neuroleptics), show positive findings, as do almost all (91%) studies of cavum septi pellucidi (CSP). Most data were consistent with a developmental model, but growing evidence was compatible also with progressive, neurodegenerative features, suggesting a "two-hit" model of schizophrenia, for which a cellular hypothesis is discussed. The relationship of clinical symptoms to MRI findings is reviewed, as is the growing evidence suggesting structural abnormalities differ in affective (bipolar) psychosis and schizophrenia.

Stress and hippocampal plasticity

The hippocampus is a target of stress hormones, and it is an especially plastic and vulnerable region of the brain. It also responds to gonadal, thyroid, and adrenal hormones, which modulate changes in synapse formation and dendritic structure and regulate dentate gyrus volume during development and in adult life. Two forms of structural plasticity are affected by stress: Repeated stress causes atrophy of dendrites in the CA3 region, and both acute and chronic stress suppresses neurogenesis of dentate gyrus granule neurons. Besides glucocorticoids, excitatory amino acids and N-methyl-D-aspartate (NMDA) receptors are involved in these two forms of plasticity as well as in neuronal death that is caused in pyramidal neurons by seizures and by ischemia. The two forms of hippocampal structural plasticity are relevant to the human hippocampus, which undergoes a selective atrophy in a number of disorders, accompanied by deficits in declarative episodic, spatial, and contextual memory performance. It is important, from a therapeutic standpoint, to distinguish between a permanent loss of cells and a reversible atrophy.

Mapping of grey matter changes in schizophrenia

Studies of brain changes in schizophrenia have suggested that the disorder is associated with reductions in both global and regional grey matter. In this study, we used structural neuroimaging to differentiate between these two types of change and to examine regional grey matter throughout the whole brain. Grey matter from magnetic resonance images was segmented and transformed into stereotactic space, and patients with schizophrenia and controls were compared with respect to regional grey matter (after compensating for global grey matter differences). In two preliminary analyses to test our methodology, we demonstrated that: (1) in the transformed grey matter maps, voxel values at the location of the caudate nuclei were correlated with region-of-interest measurements of caudate area in native image space, and (2) the technique detected regional grey matter changes resulting from artificial lesions created in the native images. We then used a factorial design to examine data from two studies, comprising a total of 42 schizophrenics and 52 controls. Analysis of the main effect of schizophrenia on regional grey matter revealed significant reductions in (a) the right temporal pole, insula and amygdala, (b) the left temporal pole, insula and dorsolateral prefrontal cortex.

Hippocampal volume reduction in male schizophrenic patients

Using magnetic resonance imaging of the brain, we examined volumetric measurements of total brain, hemispheres, lateral ventricles and the hippocampus/amygdala complex in male subjects (41 first-episode schizophrenics, 30 chronic schizophrenic patients and 32 healthy controls). We found significantly smaller total brain size in the chronic schizophrenic group, significantly larger lateral ventricles in both patient groups and hippocampal volume reduction bilaterally in first-episode patients (-13.2% left, -12.05% right) and chronic patients (-10.6% left, -10.5% right) compared to controls--irrespective of diagnostic subtype, family history for psychiatric diseases, psychopathology, duration of illness or age at onset.

Neurodevelopmental and neuroprogressive processes in schizophrenia. Antithetical or complementary, over a lifetime trajectory of disease?

The neurodevelopmental model of schizophrenia maintains ascendancy among current etiopathologic perspectives on schizophrenia. However, inconsistencies across studies and the absence thus far of pathognomic brain changes suggest the need for complex conceptualization of neurodevelopmental arrest, including some reconciliation with the competing neurodegenerative model of schizophrenia. This article critically reviews the preponderance of evidence for each model and provides an account of how these may interact or synergize to produce the characteristic clinical expression of schizophrenia.

Brain abnormality in schizophrenia. A systematic and quantitative review of volumetric magnetic resonance imaging studies

BACKGROUND

Numerous in vivo brain imaging studies suggest that cerebral structure is abnormal in schizophrenia, but implicate different regions to varying extents.

METHOD

We identified published MRI studies in schizophrenia with searches of the computerised literature and key journals. Reports giving the volumes of cortical structures in people with schizophrenia and controls were included. The percentage differences in volumes were calculated and the median taken as a summary measure for each brain region.

RESULTS

Forty relevant studies were identified. The median percentage volume differences revealed overall reductions in the whole brain (3%), temporal lobe (6% left, 9.5% right), and the amygdala/ hippocampal complex (6.5%, 5.5%); and increases in the lateral ventricles (44%, 36%), that were greatest in the body and occipital horns. Segmentation studies suggest that grey matter is reduced but that white matter volumes may actually be increased. In men, substantial reductions were also evident in the amygdala and hippocampus, as well as the largest reductions of all in the parahippocampus (14%, 9%). Few studies gave figures for women alone.

CONCLUSIONS

Several brain structures in schizophrenia are affected to a greater extent than expected from overall reductions in brain volume. Further studies are required in affected women, and to try to identify clinical and aetiological associations of these findings.

Reliability and validity of MRI measurement of the amygdala and hippocampus in children with fragile X syndrome

Evidence from numerous structural magnetic resonance imaging (MRI) studies has converged to implicate mesial temporal lobe structures in the pathophysiology of several developmental and psychiatric disorders. Efforts to integrate the results of these studies are challenged, however, by the lack of consistency, detail and precision in published protocols for the manual measurement of the amygdala and hippocampus. In this study, we describe a highly detailed, standardized protocol for measuring the amygdala and the hippocampus. Within the context of this protocol, we tested the inter- and intra-rater reliability of two frequently cited methods for normalizing the anatomical position of the amygdala and hippocampus prior to measurement. One method consisted of creating a coronal data set in which images are rotated in a plane perpendicular to the long axis of the hippocampus. The second method consisted of creating a coronal data set in which images are rotated in a plane perpendicular to the axis connecting the anterior and posterior commissures. Inter- and intra-rater reliability coefficients (using the intraclass correlation) ranged from 0.80 to 0.98, indicating that both methods for positional normalization are highly reliable. In addition, we tested the validity of each method by comparing the temporal lobe anatomy of children with fragile X syndrome to a group of unaffected children matched by age and gender. We found that hippocampal volumes in children with fragile X were significantly increased when either rotational method was used. These results replicated previous findings, suggesting that either method can be validly applied to neuronanatomic studies of pediatric populations.

Controversies surrounding glucocorticoid-mediated cell death in the hippocampus

The adrenal gland releases mineralocorticoids (MCs) and glucocorticoids (GCs) in response to a variety of stimuli, including stress. Once released, these adrenal steroids mediate a plethora of physiological responses in both the periphery and the central nervous system. The collective actions of GCs in the brain are paradoxical, however, in that basal levels of GCs are essential for neuronal development, plasticity and survival, while stress levels of GCs produce neuronal loss. Aging represents another contradictory function of GCs in the brain, since lifelong exposure to GCs has been implicated as a causative factor in senescent neuronal loss. In addition, glucocorticoids have also been shown to intensify neuronal damage in the hippocampus during ischemia and excitotoxicity through mechanisms that modulate synaptic glutamate concentrations. Conversely, the absence of adrenal steroids has been shown to regulate both neurogenesis and neuronal loss in the dentate gyrus of the hippocampus. Evidence continues to accumulate which suggests that GC-induced neuronal death in all these physiological and pathophysiological settings occurs by apoptosis. Accordingly, this review will examine the pharmacological, cellular and molecular mechanisms through which glucocorticoids mediate or contribute to neuronal remodeling and, ultimately, neuronal death.

Stress effects on morphology and function of the hippocampus

The hippocampal formation, which contains high levels of adrenal steroid receptors, is vulnerable to insults such as stroke, seizures, and head trauma, and it is also sensitive and vulnerable to the effects of stress. We have discovered that the hippocampus of rodents and tree shrews shows atrophy of pyramidal neurons in the CA3 region. Psychosocial stress and restraint stress produce atrophy over approximately 3-4 weeks. Atrophy is blocked by inhibiting adrenal steroid formation and by blocking the actions of excitatory amino acids using Dilantin or NMDA receptor inhibitors. Glucocorticoid administration also blocks CA3 atrophy, but Dilantin administration blocks this as well, indicating that excitatory amino acid release mediates the atrophy, which likely involves disassembly of the dendritic cytoskeleton. Studies with in vivo microdialysis in several laboratories have shown that glutamate release in the hippocampus increases in stress and that stress-induced glutamate release is reduced by adrenalectomy. Recent electron microscopy of mossy fiber terminals on CA3 neurons has revealed a depletion of synaptic vesicles as a result of repeated stress. The mossy fiber terminals appear to be responsible for driving atrophy of CA3 neurons, which involves principally atrophy of the apical dendrites. These results are discussed in relation to data from MRI showing atrophy of the whole human hippocampus in Cushing's disease, recurrent depressive illness, PTSD, and normal aging as well as dementia.