Cortical grey matter reductions associated with treatment-resistant chronic unipolar depression. Controlled magnetic resonance imaging study

History of depression as a risk factor for dementia: an updated review

OBJECTIVE

This review updates an earlier meta-analysis of the data on history of depression as a risk factor for dementia. It also considers the available evidence on the hypotheses proposed to explain the association between history of depression and dementia.

METHOD

A meta-analysis was carried out on results from seven case-control and six prospective studies. A qualitative review was carried out on the evidence related to the hypotheses to explain the association.

RESULTS

The meta-analysis found evidence to support an association from both case-control studies (estimated relative risk 2.01; 95% CI 1.16-3.50) and prospective studies (estimated relative risk 1.87; 95% CI 1.09-3.20). However, the evidence did not clearly support any one hypothesis explaining the association. The most likely contenders are: (i) depression can be an early prodrome of dementia, (ii) depression brings forward the clinical manifestation of dementing diseases, and (iii) depression leads to damage to the hippocampus through a glucocorticoid cascade.

CONCLUSIONS

The possibility that history of depression is a risk factor for dementia needs to be taken seriously and explanations of the association need to be further researched.

Pathophysiologische und neuropsychologische Aspekte depressiver Störungen

Zusammenfassung: Bei depressiven Störungen sind zahlreiche neurobiologische Auffälligkeiten dokumentiert. Aufschluß darüber geben Untersuchungen bei primärer Depression sowie Untersuchungen bei depressiven Störungen, die sich im Zusammenhang mit Hirnschädigungen, wie etwa Schlaganfällen, manifestieren. Ebenfalls lassen neuropsychologische Befunde Rückschlüsse auf pathophysiologische Mechanismen zu. Vieles deutet darauf hin, daß es bei depressiven Störungen zu einer Störung eines komplexen neuronalen Netzwerkes kommt, insbesondere unter Beteiligung präfrontaler cortikaler Strukturen, der Amygdala und der Basalganglien sowie ihrer monoaminergen Afferenzen aus Hirnstamm und pontinem Tegmentum. Der Befund eines reduzierten Hippokampusvolumens bei Subtypen der Depression geht möglicherweise auf einen Hypercortisolismus zurück. Neurobiologische Auffälligkeiten stellen einen wichtigen Anknüpfungspunkt für antidepressive Therapien dar. Insgesamt ist die Depression als eine psychobiologische Störung konzeptualisierbar, bei der biologische und psychologische Faktoren eng miteinander verzahnt sind.

Cerebral asymmetry and the effects of sex and handedness on brain structure: a voxel-based morphometric analysis of 465 normal adult human brains

We used voxel-based morphometry (VBM) to examine human brain asymmetry and the effects of sex and handedness on brain structure in 465 normal adults. We observed significant asymmetry of cerebral grey and white matter in the occipital, frontal, and temporal lobes (petalia), including Heschl's gyrus, planum temporale (PT) and the hippocampal formation. Males demonstrated increased leftward asymmetry within Heschl's gyrus and PT compared to females. There was no significant interaction between asymmetry and handedness and no main effect of handedness. There was a significant main effect of sex on brain morphology, even after accounting for the larger global volumes of grey and white matter in males. Females had increased grey matter volume adjacent to the depths of both central sulci and the left superior temporal sulcus, in right Heschl's gyrus and PT, in right inferior frontal and frontomarginal gyri and in the cingulate gyrus. Females had significantly increased grey matter concentration extensively and relatively symmetrically in the cortical mantle, parahippocampal gyri, and in the banks of the cingulate and calcarine sulci. Males had increased grey matter volume bilaterally in the mesial temporal lobes, entorhinal and perirhinal cortex, and in the anterior lobes of the cerebellum, but no regions of increased grey matter concentration.

Amygdala-hippocampal volume and verbal memory in first-degree relatives of schizophrenic patients

Verbal memory deficits have been related to reduced volume of medial temporal structures in several neurological and psychiatric populations, including schizophrenic patients. Impairments in verbal memory have been proposed to be a marker of risk for schizophrenia. Recently, relatives of schizophrenic patients have been reported to have reduced volume of the amygdala-hippocampal complex. In this study, we evaluate the possibility that amygdala-hippocampal volume reductions may constitute one neural substrate of verbal memory deficits in first-degree relatives. Subjects were 20 healthy first-degree relatives of schizophrenic patients and 14 demographically similar controls. Verbal memory was assessed with the Logical Memory Test. Subjects were scanned with high-resolution MRI and the images were transformed into Talairach space. Volumes of interest were amygdala-anterior hippocampus and posterior hippocampus. Relatives of schizophrenic patients had intact immediate verbal memory but significantly poorer delayed verbal memory than controls. Relatives also had significantly reduced amygdala-anterior hippocampus volumes. Across all subjects, delayed verbal memory was significantly correlated with amygdala-anterior hippocampus volume. The magnitude of the correlation did not differ between the groups. These data provide an empirical link between memory performance and volumetric abnormalities in the amygdala-hippocampal complex in the relatives of schizophrenic patients.

The Hypothalamic-Pituitary-Adrenal Axis in Major Depressive Disorder: A Brief Primer for Primary Care Physicians

BACKGROUND: One of the most enduring and replicated findings in biological psychiatry is activation of the hypothalamic-pituitary-adrenal (HPA) axis in a subset of patients with major depressive disorder. This review will discuss some of these findings and their pertinence to the assessment and treatment of depressed patients. METHOD: MEDLINE, PsychINFO, and Current Contents databases were searched for pertinent articles on the HPA axis in patients with depression. In addition, hand searches were conducted of references from these sources and abstracts from meetings and books on this topic. Articles that would provide an overview of major or interesting studies in the field were selected for inclusion. RESULTS: The data support that HPA axis activation is common in depressed patients. Frequently reported findings include elevated cortisol and corticotropin-releasing hormone (CRH), nonsuppression on the dexamethasone suppression test, a blunted adrenocorticotropic hormone (ACTH) response to CRH, and hippocampal volume reduction. Evidence of HPA axis activation appears to have prognostic value and is associated with increased risk of depression relapse and even suicide. CONCLUSION: Future research in this area will focus on a better understanding of the etiology and long-term consequences of HPA axis activation in depressed patients. In addition, medications that act on the HPA axis are currently in development and may be part of the psychiatrist's and primary care physician's pharmacopoeia in the near future.

Cerebral metabolism in major depression and obsessive-compulsive disorder occurring separately and concurrently

BACKGROUND

The frequent comorbidity of major depressive disorder (MDD) and obsessive-compulsive disorder (OCD) suggests a fundamental relationship between them. We sought to determine whether MDD and OCD have unique cerebral metabolic patterns that remain the same when they coexist as when they occur independently.

METHODS

[18F]-fluorodeoxyglucose positron emission tomography (PET) brain scans were obtained on 27 subjects with OCD alone, 27 with MDD alone, 17 with concurrent OCD+MDD, and 17 normal control subjects, all in the untreated state. Regional cerebral glucose metabolism was compared between groups.

RESULTS

Left hippocampal metabolism was significantly lower in subjects with MDD alone and in subjects with concurrent OCD+MDD than in control subjects or subjects with OCD alone. Hippocampal metabolism was negatively correlated with depression severity across all subjects. Thalamic metabolism was significantly elevated in OCD alone and in MDD alone. Subjects with concurrent OCD+MDD had significantly lower metabolism in thalamus, caudate, and hippocampus than subjects with OCD alone.

CONCLUSIONS

Left hippocampal dysfunction was associated with major depressive episodes, regardless of primary diagnosis. Other cerebral metabolic abnormalities found in OCD and MDD occurring separately were not seen when the disorders coexisted. Depressive episodes occurring in OCD patients may be mediated by different basal ganglia-thalamic abnormalities than in primary MDD patients.

Stress hormone-related psychopathology: pathophysiological and treatment implications

Stress is commonly associated with a variety of psychiatric conditions, including major depression, and with chronic medical conditions, including diabetes and insulin resistance. Whether stress causes these conditions is uncertain, but plausible mechanisms exist by which such effects might occur. To the extent stress-induced hormonal alterations (e.g., chronically elevated cortisol levels and lowered dehydroepiandrosterone [DHEA] levels) contribute to psychiatric and medical disease states, manipulations that normalize these hormonal aberrations should prove therapeutic. In this review, we discuss mechanisms by which hormonal imbalance (discussed in the frameworks of "allostatic load" and "anabolic balance") might contribute to illness. We then review certain clinical manifestations of such hormonal imbalances and discuss pharmacological and behavioural treatment strategies aimed at normalizing hormonal output and lessening psychiatric and physical pathology.

Are child-, adolescent-, and adult-onset depression one and the same disorder?

This paper reviews prior research studies examining neurobiological correlates and treatment response of depression in children, adolescents, and adults. Although there are some similarities in research findings observed across the life cycle, both children and adolescents have been found to differ from depressed adults on measures of basal cortisol secretion, corticotropin stimulation post-corticotropin releasing hormone (CRH) infusion, response to several serotonergic probes, immunity indices, and efficacy of tricyclic medications. These differences are proposed to be due to 1) developmental factors, 2) stage of illness factors (e.g., number of episodes, total duration of illness), or 3) heterogeneity in clinical outcome (e.g., recurrent unipolar course vs. new-onset bipolar disorder). Relevant clinical and preclinical studies that provide support for these alternate explanations of the discrepant findings are reviewed, and directions for future research are discussed. To determine whether child-, adolescent-, and adult-onset depression represent the same condition, it is recommended that researchers 1) use the same neuroimaging paradigms in child, adolescent, and adult depressed cohorts; 2) carefully characterize subjects' stage of illness; and 3) conduct longitudinal clinical and repeat neurobiological assessments of patients of different ages at various stages of illness. In addition, careful attention to familial subtypes (e.g., depressive spectrum disorders vs. familial pure depressive disorders) and environmental factors (e.g., trauma history) are suggested for future investigations.

Regional cerebral volume measurements in late-life depression: relationship to clinical correlates, neuropsychological impairment and response to treatment

BACKGROUND

Elderly people who develop depression have demonstrable changes in cerebral structure but little is known of the relationship between regional cerebral volumes, treatment response and cognitive impairment.

METHOD

Forty-four patients with major depression diagnosed according to DSM-IIIR criteria underwent magnetic resonance imaging and regional cerebral volumes were quantified using multispectral analysis. Response to antidepressant treatment was assessed prospectively and a neuropsychological test battery was administered.

RESULTS

There was a trend for smaller fronto-temporal volumes in the treatment-resistant patients. Impaired immediate working memory was linked with reduced frontal and parietal lobe volume and impaired short-term memory functioning was associated with reduced temporal lobe volume. Ventricular enlargement was associated with prior administration of electro-convulsive therapy, poor physical health and later age at onset of first episode of depression.

CONCLUSION

In late-life depression, brain changes should not preclude vigorous antidepressant treatment. Regional cerebral volume changes may be a complication of poor physical health and are associated with memory dysfunction even upon recovery from depression.

Physical activity-antidepressant treatment combination: impact on brain-derived neurotrophic factor and behavior in an animal model

The mechanism of antidepressant action, at the cellular level, is not clearly understood. It has been reported that chronic antidepressant treatment leads to an up-regulation of brain-derived neurotrophic factor (BDNF) mRNA levels in the hippocampus, and that physical activity (voluntary running) enhances this effect. We wished to investigate whether BDNF expression brought about by these interventions may overcome deficits caused by acute stress, and might impact behavior in an animal model. In this report, we have tested the hypothesis that the combination of the antidepressant, tranylcypromine, and physical exercise could lead to decreased neurotrophin deficits and enhanced swimming time in animals that have been forced to swim in an inescapable water tank. Rats were either treated with tranylcypromine, engaged in voluntary running, or both for one week. After these treatments, the animals underwent a two-day forced swimming procedure. BDNF mRNA levels were significantly depressed in untreated animals subjected to forced swimming. Animals that either underwent prior activity or received antidepressant showed BDNF mRNA levels restored to baseline. Animals receiving the combined intervention showed an increase in hippocampal BDNF mRNA well above baseline. Swimming time during a five-minute test was significantly enhanced in animals receiving the combined intervention over untreated animals. Swimming time was not significantly enhanced over that of animals receiving antidepressant alone, however. Enhanced swimming time correlated with increased levels of BDNF mRNA in one hippocampal sub-region (CA4-hilus). These results suggest that the combination of exercise and antidepressant treatment may have significant neurochemical, and possibly behavioral, effects. In addition, these results support the possibility that the enhancement of BDNF expression may be an important element in the clinical response to antidepressant treatment. The induction of BDNF expression by activity/pharmacological treatment combinations could represent an important intervention for further study, to potentially improve depression treatment and management.

How antidepressants work: new perspectives on the pathophysiology of depressive disorder

BACKGROUND

New research in animals is beginning to change radically our understanding of the biology of stress and the effects of antidepressant agents.

AIMS

To relate recent findings from the basic neurosciences to the pathophysiology of depressive disorder.

METHOD

Drawing together findings from molecular and physiological studies in rats, social studies in primates and neuropsychological studies in humans, we review the neurotrophic and neuroplastic effects of antidepressants and stress.

RESULTS

Stress and antidepressants have reciprocal actions on neuronal growth and vulnerability (mediated by the expression of neurotrophins) and synaptic plasticity (mediated by excitatory amino acid neurotransmission) in the hippocampus and other brain structures. Stressors have the capacity to progressively disrupt both the activities of individual cells and the operating characteristics of networks of neurons throughout the life cycle, while antidepressant treatments act to reverse such injurious effects.

CONCLUSIONS

We propose a central role for the regulation of synaptic connectivity in the pathophysiology of depressive disorder.

Repeated electroconvulsive stimulation, but not antidepressant drugs, induces mossy fibre sprouting in the rat hippocampus

Electroconvulsive stimulation (ECS) has been shown recently to induce axonal sprouting of granule cells in the rodent hippocampus. This may relate to the clinical efficacy of electroconvulsive therapy (ECT) in humans. We compared the effects of three different clinically effective antidepressant treatments on mossy fibre sprouting in the rat dentate gyrus using Timm's histochemistry: (1) repeated spaced ECS; (2) daily administration for 4 weeks of the serotonin re-uptake inhibitor fluoxetine (1 mg/kg); and (3) daily administration for 4 weeks of the noradrenaline re-uptake inhibitor desipramine (5 mg/kg). The effect of subconvulsive electrical stimulation was also examined. Repeated ECS-induced sprouting while subconvulsive stimulation (which is ineffective clinically) did not. The two well-established chemical antidepressant therapies were also ineffective, indicating that induction of mossy fibre sprouting is not a common property of effective antidepressant agents. It is possible that the ability to induce sprouting might relate to the superior efficacy of ECT when compared to chemical antidepressants in clinical practice. Alternatively, it may contribute to the transient cognitive impairment that accompanies ECS in humans and other species.

Aging affects transcranial magnetic modulation of hippocampal evoked potentials

Transcranial magnetic stimulation (TMS) is being proposed as a method of choice for the treatment of clinical depression, yet its action in the brain is still not well understood. In previous studies we found that TMS has a long-term effect on reactivity of the hippocampus to perforant path stimulation. Since the efficacy of antidepressants is highly age-dependent, we studied possible age-related effects of TMS on hippocampal evoked responses. Young adult (3 months), aging (10 months) and aged (24-26 months) awake rats were subjected to daily TMS for one week, followed by measurements of several parameters of reactivity to perforant path stimulation in the anesthetized rat. TMS did not affect responses of the hippocampus to single perforant path stimulation, but reduced drastically paired-pulse and frequency dependent depression in the young and aging but not the old rats. Likewise, TMS increased LTP expression in the young but not the old rats, and reduced the efficacy of serotonin modulation of reactivity of the hippocampus, in the young but not the old rats. Thus, long term effects of chronic TMS on local GABAergic inhibition are highly age dependent.

Differential lesion patterns in CADASIL and sporadic subcortical arteriosclerotic encephalopathy: MR imaging study with statistical parametric group comparison

PURPOSE

To differentiate lesion patterns in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) from those in patients with sporadic subcortical arteriosclerotic encephalopathy (sSAE).

MATERIALS AND METHODS

Magnetic resonance (MR; T2-weighted and fluid-attenuated inversion-recovery) images obtained in 28 patients with CADASIL were compared with images obtained in 24 patients with sSAE by using an automated pixel-based group comparison with statistical parametric mapping and regional semiquantitative rating.

RESULTS

Visual rating showed higher lesion scores for CADASIL in the temporal and temporopolar white matter (WM). Statistical parametric mapping group analysis independently revealed more extensive bilateral involvement of the anterior temporal and superior frontal WM in CADASIL. There were bilateral signal intensity reductions within the dentate nucleus, deep cerebellar WM, crus cerebri, and thalamus. Lesions extended remarkably more often into arcuate fibers in the temporopolar and paramedian superior frontal lobes in CADASIL. Linear discriminant analysis was used to classify 96% (50 of 52) of the cases correctly, with temporopolar WM and arcuate fiber involvement contributing most to the discrimination function.

CONCLUSION

The presented MR imaging criteria are useful in the diagnostic work-up in patients with leukoencephalopathy and help to differentiate CADASIL from sSAE. The observed pattern of vulnerability in CADASIL suggests future directions for research in the pathophysiology of this disorder. In addition, the study demonstrates the potential of automated image analysis to explore MR imaging lesion patterns.

The neurobiology of the stress cascade and its potential relevance for schizophrenia

This review explores the neurobiology of stress and its possible role in the etiology of schizophrenia. Major life events may play a role in onset and relapse in schizophrenia. Other data suggest that early stress exposure increases schizophrenia risk, especially in individuals with latent vulnerability. Animal research has led to an elucidation of the mechanisms by which stress and cortisol are toxic to the hippocampus and impair cognition. Associations among these factors have been found in a variety of human conditions, including psychiatric illness and normal aging. These mechanisms are plausible in schizophrenia, which is characterized by a degree of cortisol dysregulation, hippocampal abnormality, and cognitive impairment. Characterization of the role of the stress cascade in schizophrenia has implications for novel pharmacologic and other treatment, especially for cognitive symptoms, which are debilitating and largely refractory to treatment.

Neuroplasticity and cellular resilience in mood disorders

Although mood disorders have traditionally been regarded as good prognosis diseases, a growing body of data suggests that the long-term outcome for many patients is often much less favorable than previously thought. Recent morphometric studies have been investigating potential structural brain changes in mood disorders, and there is now evidence from a variety of sources demonstrating significant reductions in regional CNS volume, as well as regional reductions in the numbers and/or sizes of glia and neurons. Furthermore, results from recent clinical and preclinical studies investigating the molecular and cellular targets of mood stabilizers and antidepressants suggest that a reconceptualization about the pathophysiology and optimal long-term treatment of recurrent mood disorders may be warranted. It is proposed that impairments of neuroplasticity and cellular resilience may underlie the pathophysiology of mood disorders, and further that optimal long-term treatment for these severe illnesses may only be achieved by the early and aggressive use of agents with neurotrophic/neuroprotective effects. It is noteworthy that lithium, valproate and antidepressants indirectly regulate a number of factors involved in cell survival pathways including CREB, BDNF, bcl-2 and MAP kinases, and may thus bring about some of their delayed long-term beneficial effects via underappreciated neurotrophic effects. The development of novel treatments which more directly target molecules involved in critical CNS cell survival and cell death pathways have the potential to enhance neuroplasticity and cellular resilience, and thereby modulate the long-term course and trajectory of these devastating illnesses.

Postmortem studies in mood disorders indicate altered numbers of neurons and glial cells

The influence of stress and glucocorticoids on neuronal pathology has been demonstrated in animal and clinical studies. It has been proposed that stress-induced changes in the hippocampus may be central to the development of depression in genetically vulnerable individuals. New evidence implicates the prefrontal cortex (PFC) in addition to the hippocampus as a site of neuropathology in depression. The PFC may be involved in stress-mediated neurotoxicity because stress alters PFC functions and glucocorticoid receptors, the PFC is directly interconnected with the hippocampus, and metabolic alterations are present in the PFC in depressed patients. Postmortem studies in major depression and bipolar disorder provide the first evidence for specific neuronal and glial histopathology in mood disorders. Three patterns of morphometric cellular changes are noted: cell loss (subgenual PFC), cell atrophy (dorsolateral PFC and orbitofrontal cortex), and increased numbers of cells (hypothalamus, dorsal raphe nucleus). The relevance of cellular changes in mood disorders to stress and prolonged PFC development and a role of neurotrophic/neuroprotective factors are suggested, and a link between cellular changes and the action of therapeutic drugs is discussed. The precise anatomic localization of dysfunctional neurons and glia in mood disorders may reveal cortical targets for novel antidepressants and mood stabilizers.

3D MRI studies of neuroanatomic changes in unipolar major depression: the role of stress and medical comorbidity

Increasing evidence has accumulated for structural brain changes associated with unipolar recurrent major depression. Studies of neuroanatomic structure in early-onset recurrent depression have only recently found evidence for depression-associated structural change. Studies using high-resolution three-dimensional magnetic resonance imaging (MRI) are now available to examine smaller brain structures with precision. Brain changes associated with early-onset major depression have been reported in the hippocampus, amygdala, caudate nucleus, putamen, and frontal cortex, structures that are extensively interconnected. They comprise a neuroanatomic circuit that has been termed the limbic-cortical-striatal-pallidal-thalamic tract. Of these structures, volume loss in the hippocampus is the only consistently observed change to persist past the resolution of the depression. Possible mechanisms for tissue loss include neuronal loss through exposure to repeated episodes of hypercortisolemia; glial cell loss, resulting in increased vulnerability to glutamate neurotoxicity; stress-induced reduction in neurotrophic factors; and stress-induced reduction in neurogenesis. Many depressed patients, particularly those with late-onset depression, have comorbid physical illnesses producing a high rate of hyperintensities in deep white matter and subcortical gray matter and brain damage to key structures involved in the modulation of emotion. Combining MRI studies with functional studies has the potential to localize abnormalities in blood flow, metabolism, and neurotransmitter receptors and provide a better integrated model of depression.

Effects of early adverse experiences on brain structure and function: clinical implications

Child abuse is associated with markedly elevated rates of major depression and other psychiatric disorders in adulthood. This article reviews preclinical studies examining the effects of early stress, factors that modify the impact of these experiences, and neurobiological changes associated with major depression. Preclinical studies demonstrate that early stress can alter the development of the hypothalamic-pituitary-adrenal axis, hypothalamic and extrahypothalamic corticotropin releasing hormone, monoaminergic, and gamma-aminobutyric acid/benzodiazepine systems. Stress has also been shown to promote structural and functional alterations in brain regions similar to those seen in adults with depression. Emerging data suggest, however, that the long-term effects of early stress can be moderated by genetic factors and the quality of the subsequent caregiving environment. These effects also can be prevented or reversed with various pharmacologic interventions. Preclinical studies of early stress can provide valuable insights in understanding the pathophysiology and treatment of major depression. They also can provide an important tool to use to investigate interactions between genes and environments in determining an individual's sensitivity to stress. More research is needed to understand how inherent factors interact with experiences of abuse and other psychosocial factors to confer vulnerability to develop depression.

Imaging serotonergic neurotransmission in depression: hippocampal pathophysiology may mirror global brain alterations

The recent development of [carbonyl-(11)C]WAY-100635 for serotonin (5-HT)(1A) and [(18)F]setoperone and [(18)F]altanserin for 5-HT(2A) positron emission tomography receptor imaging has allowed studies of 5-HT neurotransmission in depressive disorders. The hippocampus is likely to be an important brain structure in the pathophysiology of depression because it may mediate both cognitive deficits and hypercortisolemia found in this disorder. Decreased 5-HT(1A) binding was reported in the medial temporal cortex, which receives dense 5-HT innervation, and also throughout neocortical regions. Because the 5-HT(1A) antagonist pindolol may hasten antidepressant effects of selective serotonin reuptake inhibitor medications, its receptor occupancy has been measured in both presynaptic and postsynaptic sites. The results are controversial but suggest that pindolol has preferential occupancy of somatodendritic autoreceptors in the raphe. The results of 5-HT(2A) receptors are mixed, with one showing a significant decrease in the right orbitoinsular cortex and three not detecting a significant change. The disparate findings in patients with depression almost certainly reflect the heterogeneity of the disorder, and we highlight the utility of the hippocampus as a useful target region not only to compare depressed subjects with healthy subjects but also to correlate findings with cognitive function and activity of the limbic-hypothalamic-pituitary axis system.

The madness of Nietzsche: a misdiagnosis of the millennium?

This article represents a personal discussion about Nietzsche's mental illness, which formed part of a larger paper 'The masks of Nietzsche and eternal return of the repressed'. This was presented at the 6th Annual Conference of The Friedrich Nietzsche Society, September 1996, Manchester UK, as reported by Nussbaumer-Benz (1998).

The N-methyl-D-aspartate receptor, synaptic plasticity, and depressive disorder. A critical review

The roles of the N-methyl-D-aspartate (NMDA) receptor and NMDA receptor-mediated synaptic plasticity are reviewed in the context of depressive disorder and its treatment. The mode of action of antidepressant treatment is poorly understood. Animal studies have suggested that many antidepressant drugs show activity at the NMDA receptor and that NMDA antagonists have antidepressant profiles in preclinical models of depression. A post-mortem study in humans has suggested that certain binding characteristics of the NMDA receptor may be down-regulated in the brains of suicide victims. "Depressogenic" stressors in animals and chronic administration of antidepressant agents perturb NMDA-dependent synaptic plasticity in the hippocampus.

Memory impairment in out-of-hospital cardiac arrest survivors is associated with global reduction in brain volume, not focal hippocampal injury

BACKGROUND AND PURPOSE

More than 30% of out-of-hospital cardiac arrest (OHCA) survivors suffer significant memory impairment. The hippocampus may be vulnerable to hypoxic injury during cardiac arrest. The purpose of this study was to determine whether selective hippocampal injury is the substrate for this memory impairment.

METHODS

Seventeen OHCA survivors and 12 patients with uncomplicated myocardial infarction were studied. OHCA survivors were divided into those with impaired and intact memory. Memory was assessed by use of the Rivermead Behavioural Memory Test and Doors and People Test. MRI was used to determine intracranial, whole-brain, amygdala-hippocampal complex, and temporal lobe volumes. Brain structure was also examined by statistical parametric mapping.

RESULTS

Left amygdala-hippocampal volume was reduced in memory-impaired OHCA victims compared with control subjects (mean 3. 93 cm(3) and 95% CI 3.50 to 4.36 cm(3) versus mean 4.65 cm(3) and 95% CI 4.37 to 4.93 cm(3); P=0.002). Left temporal lobe and whole-brain volumes were also reduced. There were no differences in amygdala-hippocampal volume indexed against ipsilateral temporal lobe volume. Significant correlations were observed between total brain volume and Rivermead Behavioural Memory Test (r=0.56, P<0.05) and Doors and People Test (r=0.67, P<0.01) scores in OHCA survivors. Both recall and recognition were compromised in memory-impaired subjects. Statistical parametric mapping did not detect focal brain abnormalities in these subjects. Global cerebral atrophy was confirmed by qualitative assessment.

CONCLUSIONS

Memory impairment in OHCA survivors is associated with global cerebral atrophy, not selective hippocampal damage. Rehabilitation protocols need to account for the global nature of the brain injury.

Increased neurogenesis in a model of electroconvulsive therapy

BACKGROUND

Electroconvulsive therapy (ECT) is a widely used and efficient treatment modality in psychiatry, although the basis for its therapeutic effect is still unknown. Past research has shown seizure activity to be a regulator of neurogenesis in the adult brain. This study examines the effect of a single and multiple electroconvulsive seizures on neurogenesis in the rat dentate gyrus.

METHODS

Rats were given either a single or a series of 10 electroconvulsive seizures. At different times after the seizures, a marker of proliferating cells, Bromodeoxyuridine (BrdU), was administered to the animals. Subsequently, newborn cells positive for BrdU were counted in the dentate gyrus. Double staining with a neuron-specific marker indicated that the newborn cells displayed a neuronal phenotype.

RESULTS

A single electroconvulsive seizure significantly increased the number of new born cells in the dentate gyrus. These cells survived for at least 3 months. A series of seizures further increased neurogenesis, indicating a dose-dependent mechanism.

CONCLUSIONS

We propose that generation of new neurons in the hippocampus may be an important neurobiologic element underlying the clinical effects of electroconvulsive seizures.

Voxel-based morphometry--the methods

At its simplest, voxel-based morphometry (VBM) involves a voxel-wise comparison of the local concentration of gray matter between two groups of subjects. The procedure is relatively straightforward and involves spatially normalizing high-resolution images from all the subjects in the study into the same stereotactic space. This is followed by segmenting the gray matter from the spatially normalized images and smoothing the gray-matter segments. Voxel-wise parametric statistical tests which compare the smoothed gray-matter images from the two groups are performed. Corrections for multiple comparisons are made using the theory of Gaussian random fields. This paper describes the steps involved in VBM, with particular emphasis on segmenting gray matter from MR images with nonuniformity artifact. We provide evaluations of the assumptions that underpin the method, including the accuracy of the segmentation and the assumptions made about the statistical distribution of the data.

Adult brain neurogenesis and psychiatry: a novel theory of depression

Neurogenesis (the birth of new neurons) continues postnatally and into adulthood in the brains of many animal species, including humans. This is particularly prominent in the dentate gyrus of the hippocampal formation. One of the factors that potently suppresses adult neurogenesis is stress, probably due to increased glucocorticoid release. Complementing this, we have recently found that increasing brain levels of serotonin enhance the basal rate of dentate gyrus neurogenesis. These and other data have led us to propose the following theory regarding clinical depression. Stress-induced decreases in dentate gyrus neurogenesis are an important causal factor in precipitating episodes of depression. Reciprocally, therapeutic interventions for depression that increase serotonergic neurotransmission act at least in part by augmenting dentate gyrus neurogenesis and thereby promoting recovery from depression. Thus, we hypothesize that the waning and waxing of neurogenesis in the hippocampal formation are important causal factors, respectively, in the precipitation of, and recovery from, episodes of clinical depression.

Reduction of frontal neocortical grey matter associated with affective aggression in patients with temporal lobe epilepsy: an objective voxel by voxel analysis of automatically segmented MRI

BACKGROUND

Interictal episodes of aggression are often reported in patients with epilepsy. Some have characteristics of what has been referred to as episodic dyscontrol or intermittent explosive disorder (IED). Although structural brain abnormalities are thought to play a part in the pathophysiology of aggression, there are few in vivo studies of structural cerebral changes in patients with epilepsy and aggression. Using quantitative MRI, subtle structural brain abnormalities can be investigated in subgroups of patients with both epilepsy and episodes of affective aggression.

METHODS

After automated segmentation of cerebral grey matter from T1 weighted MRI, the objective technique of statistical parametric mapping (SPM) was applied to the analysis of 35 control subjects, 24 patients with temporal lobe epilepsy (TLE) with a history of repeated, interictal episodes of aggression, and 24 patients with TLE without episodes of aggression. Both TLE patient groups were compared with each other and with the control subjects on a voxel by voxel basis for increases and decreases of grey matter.

RESULTS

The patients with TLE with aggressive episodes had a decrease of grey matter, most markedly in the left frontal lobe, compared with the control group and with patients with TLE without aggressive episodes.

CONCLUSION

These findings suggest that a reduction of frontal neocortical grey matter might underly the pathophysiology of aggression in TLE. These voxel by voxel comparisons can guide further in vivo studies into aggression.

Late-life chronic depression: a 399-case study in private practice

OBJECTIVE

Aims of the study were to find the prevalence of chronic depression in elderly patients compared with younger patients, and to compare chronic depression between elderly and younger patients, to find if there were clinical differences. A major feature of the study was the inclusion of a large number of bipolar II patients, usually not included in previous studies.

METHODS

Three hundred and ninety-nine consecutive unipolar (N=200) and bipolar II (N=199) depression outpatients were interviewed with the Structured Clinical Interview for DSM-IV and depression rating scales in a private practice.

RESULTS

Chronic depression was more common in elderly patients than in younger patients (53.6% vs 40.1%, p=0.0299). Late-life chronic depression patients had later age at onset, longer duration of illness, fewer bipolar II cases, more unipolar cases and more relapses than younger chronic depression patients.

CONCLUSIONS

Results suggest that late-life depression is more likely to be chronic than depression in younger patients. The subtyping of chronic depression according to age seems supported by a different age at onset and some clinical differences.

Abnormal cerebral structure in juvenile myoclonic epilepsy demonstrated with voxel-based analysis of MRI

MRI scans of patients with idiopathic generalized epilepsy (IGE) are normal on visual assessment. Using an interactive anatomical segmentation technique and volume-of-interest measurements of MRI, we showed recently that patients with IGE had significantly larger cortical grey matter than control subjects. Further, 40% of individual patients with juvenile myoclonic epilepsy (JME), a syndrome of IGE in adolescence, had significant abnormalities of cerebral structure. In this study, we applied the automated and objective technique of statistical parametric mapping (SPM) to the analysis of structural MRI from 20 patients with JME and 30 control subjects. The cortical grey matter of each individual JME patient and the group of JME patients was contrasted with that of the group of 30 normal subjects. The voxel-based SPM comparison between the group of JME patients and the control subjects showed an increase in cortical grey matter in the mesial frontal lobes of the patients. Analysis of individual patients revealed significant abnormalities of cortical grey matter in five out of 20 JME patients, four of whom had been shown to have widespread abnormalities using the previous volume of interest technique. These findings indicate a structural cerebral abnormality in JME, with involvement of mesiofrontal cortical structures.

Depressive illness

WHO estimate that by the beginning of the next century major unipolar depression will be one of the most important causes of ill health overall. Whereas the cause of depression is still obscure, it is becoming clear that a number of diverse factors are likely to be implicated, both genetic and environmental. Effective treatment of depression similarly involves a variety of methods, from electro-convulsive therapy to inter-personal psychotherapy. The pathophysiology of depression is gradually becoming accessible through research strategies, such as functional neuroimaging paired with mood altering interventions.

Voxel-by-voxel comparison of automatically segmented cerebral gray matter--A rater-independent comparison of structural MRI in patients with epilepsy

Quantitative evaluation of MRI in patients with epilepsy can give more information than qualitative assessment. Previously developed volume-of-interest-based methods identified subtle widespread structural changes in the neocortex beyond the visualized lesions in patients with malformations of cortical development (MCD) and hippocampal sclerosis (HS) and also in MRI-negative patients with juvenile myoclonic epilepsy (JME). This study evaluates a voxel-based automated analysis of structural MRI in epilepsy. After fully automated segmentation of cerebral gray matter from structural T1-weighted, high-resolution MRI scans, we applied the automated and objective technique of statistical parametric mapping (SPM) to the analysis of gray matter of 35 control subjects, 10 patients with partial seizures and MCD, 10 patients with left temporal lobe epilepsy (TLE) and HS, 10 patients with left TLE and normal MR quantitation of the hippocampus, and 20 patients with JME. At a corrected threshold of P < 0.05, significant abnormalities were found in 3/35 controls; in all 10 patients with MCD, 6 of whom had additional lesions beyond the margins of the visualized abnormalities; in 2/10 TLE patients with HS; in 2/10 MRI-negative TLE; and in 4/20 JME patients. Group comparisons between control subjects and HS patients identified the affected left temporal lobe with an increase in gray matter in the posterior temporal lobe, but did not identify hippocampal atrophy. The group of MRI-negative TLE patients showed no abnormalities compared with control subjects. Group comparison between control subjects and JME patients identified a mesial frontal increase in gray matter. The SPM-based voxel-by-voxel comparison of gray matter distribution identified MCD and abnormalities beyond the visualized lesion in individual MCD patients. The method did not reliably identify HS in individual patients or identify abnormalities in individual MRI-negative patients with TLE or JME in a proportion larger than the chance findings in the control group. Using group comparisons, structural abnormalities in the neocortical gray matter of patients with TLE and HS were lateralized to the affected temporal lobe. In patients with JME as a group, an increase in gray matter was localized to the mesial frontal area, corroborating earlier quantitative MRI findings.

Localizing age-related changes in brain structure between childhood and adolescence using statistical parametric mapping

Volumetric studies have consistently shown reductions in cerebral gray matter volume between childhood and adolescence, with the most dramatic changes occurring in the more dorsal cortices of the frontal and parietal lobes. The purpose of this study was to examine the spatial location of these changes employing methods typical of functional imaging studies. T1-weighted structural MRI data (1.2 mm) were analyzed for nine normally developing children and nine normal adolescents. Validity and reliability of the tissue segmentation protocol were assessed as part of several preprocessing analyses prior to statistical parametric mapping (SPM). Using SPM96, a simple contrast of average gray matter differences between the two age groups revealed 57 significant clusters (SPM[Z] height threshold, P<0.001, extent threshold 50, uncorrected). The pattern and distribution of differences were consistent with earlier findings from the volumetric assessment of the same subjects. Specifically, more differences were observed in dorsal frontal and parietal regions with relatively few differences observed in cortices of the temporal and occipital lobes. Permutation tests were conducted to assess the overall significance of the gray matter differences and validity of the parametric maps. Twenty SPMs were created with subjects randomly assigned to groups. None of the random SPMs approached the number of significant clusters observed in the age difference SPM (mean number of significant clusters = 5.8). The age effects observed appear to result from regions that consistently segment as gray matter in the younger group and consistently segment as white matter in the older group. The utility of these methods for localizing relatively subtle structural changes that occur between childhood and adolescence has not previously been examined.