Prediction of antidepressant effects of sleep deprivation by metabolic rates in the ventral anterior cingulate and medial prefrontal cortex

Neurocircuitry of mood disorders

This review begins with a brief historical overview of attempts in the first half of the 20th century to discern brain systems that underlie emotion and emotional behavior. These early studies identified the amygdala, hippocampus, and other parts of what was termed the 'limbic' system as central parts of the emotional brain. Detailed connectional data on this system began to be obtained in the 1970s and 1980s, as more effective neuroanatomical techniques based on axonal transport became available. In the last 15 years these methods have been applied extensively to the limbic system and prefrontal cortex of monkeys, and much more specific circuits have been defined. In particular, a system has been described that links the medial prefrontal cortex and a few related cortical areas to the amygdala, the ventral striatum and pallidum, the medial thalamus, the hypothalamus, and the periaqueductal gray and other parts of the brainstem. A large body of human data from functional and structural imaging, as well as analysis of lesions and histological material indicates that this system is centrally involved in mood disorders.

Imaging phenotypes of major depressive disorder: genetic correlates

Imaging techniques are a potentially powerful method of identifying phenotypes that are associated with, or are indicative of, a vulnerability to developing major depressive disorder (MDD). Here we identify seven promising MDD-associated traits identified by magnetic resonance imaging (MRI) or positron emission tomography (PET). We evaluate whether these traits are state-independent, heritable endophenotypes, or state-dependent phenotypes that may be useful markers of treatment efficacy. In MDD, increased activity of the amygdala in response to negative stimuli appears to be a mood-congruent phenomenon, and is likely moderated by the 5-HT transporter gene (SLC6A4) promoter polymorphism (5-HTTLPR). Hippocampal volume loss is characteristic of elderly or chronically-ill samples and may be impacted by the val66met brain-derived neurotrophic factor (BDNF) gene variant and the 5-HTTLPR SLC6A4 polymorphism. White matter pathology is salient in elderly MDD cohorts but is associated with cerebrovascular disease, and is unlikely to be a useful marker of a latent MDD diathesis. Increased blood flow or metabolism of the subgenual anterior cingulate cortex (sgACC), together with gray matter volume loss in this region, is a well-replicated finding in MDD. An attenuation of the usual pattern of fronto-limbic connectivity, particularly a decreased temporal correlation in amygdala-anterior cingulate cortex (ACC) activity, is another MDD-associated trait. Concerning neuroreceptor PET imaging, decreased 5-HT(1A) binding potential in the raphe, medial temporal lobe, and medial prefrontal cortex (mPFC) has been strongly associated with MDD, and may be impacted by a functional single nucleotide polymorphism in the promoter region of the 5-HT(1A) gene (HTR1A: -1019 C/G; rs6295). Potentially indicative of inter-study variation in MDD etiology or mood state, both increased and decreased binding potential of the 5-HT transporter has been reported. Challenges facing the field include the problem of phenotypic and etiological heterogeneity, technological limitations, the confounding effects of medication, and non-disease related inter-individual variation in brain morphology and function. Further advances are likely as epigenetic, copy-number variant, gene-gene interaction, and genome-wide association (GWA) approaches are brought to bear on imaging data.

The effects of psychotherapy on neural responses to rewards in major depression

BACKGROUND

Unipolar major depressive disorder (MDD) is characterized by anomalous neurobiological responses to pleasant stimuli, a pattern that may be linked to symptoms of anhedonia. However, the potential for psychotherapy to normalize neurobiological responses to pleasant stimuli has not been evaluated.

METHODS

Twelve adults with and 15 adults without MDD participated in two identical functional magnetic resonance imaging scans that used a Wheel of Fortune task. Between scans, MDD outpatients received Behavioral Activation Therapy for Depression, a psychotherapy modality designed to increase engagement with rewarding stimuli and reduce avoidance behaviors.

RESULTS

Seventy-five percent of adults with MDD were treatment responders, achieving post-treatment Hamilton Rating Scale for Depression score of six or below. Relative to changes in brain function in the matched nondepressed group, psychotherapy resulted in functional changes in structures that mediate responses to rewards, including the paracingulate gyrus during reward selection, the right caudate nucleus (i.e., the dorsal striatum), during reward anticipation, and the paracingulate and orbital frontal gyri during reward feedback. There was no effect of diagnostic status or psychotherapy on in-scanner task-related behavioral responses.

CONCLUSIONS

Behavioral Activation Therapy for Depression, a psychotherapy modality designed to increase engagement with rewarding stimuli and reduce avoidance behaviors, results in improved functioning of unique reward structures during different temporal phases of responses to pleasurable stimuli, including the dorsal striatum during reward anticipation.

Anterior cingulate cortical volumes and treatment remission of geriatric depression

BACKGROUND

Structural abnormalities of the anterior cingulate cortex (ACC) may interfere with the interaction of cortical and limbic networks involved in emotional regulation and contribute to chronic depressive syndromes in the elderly. This study examined the relationship of regional anterior cingulate cortical volumes with treatment remission of elderly depressed patients. We hypothesized that patients who failed to remit during a 12-week controlled treatment trial of escitalopram would exhibit smaller anterior cingulate gray matter volumes than patients who remitted.

METHODS

The participants were 41 non-demented individuals with non-psychotic major depression. After a 2-week single-blind placebo period, subjects who still had a Hamilton Depression Rating Scale (HDRS) of 18 or greater received escitalopram 10 mg daily for 12 weeks. Remission was defined as a HDRS score of 7 or below for at least 2 consecutive weeks. The patient sample consisted of 22 depressed patients who achieved remission during the study and 19 depressed patients who remained symptomatic. High-resolution magnetization-prepared rapidly acquired gradient echo (MPRAGE) sequences were acquired on a 1.5 T scanner and regional ACC volumes were manually outlined (dorsal, rostral, anterior subgenual, and posterior subgenual).

RESULTS

Repeated measure analyses revealed that patients who failed to remit following escitalopram treatment had smaller dorsal and rostral anterior cingulate gray matter volumes than patients who remitted, whereas subgenual cortical volumes did not differ between the groups.

CONCLUSIONS

Structural abnormalities of the dorsal and rostral anterior cingulate may perpetuate late-life depression.

The functional neuroanatomy of geriatric depression

OBJECTIVE

Positron Emission Tomography (PET) studies of cerebral glucose metabolism have demonstrated sensitivity in evaluating the functional neuroanatomy of treatment response variability in depression, as well as in the early detection of functional changes associated with incipient cognitive decline. The evaluation of cerebral glucose metabolism in late life depression may have implications for understanding treatment response variability, as well as evaluating the neurobiological basis of depression in late life as a risk factor for dementia.

METHODS

Sixteen patients with geriatric depression and 13 comparison subjects underwent resting PET studies of cerebral glucose metabolism, as well as magnetic resonance (MR) imaging scans to evaluate brain structure.

RESULTS

Cerebral glucose metabolism was elevated in geriatric depressed patients relative to comparison subjects in anterior (right and left superior frontal gyrus) and posterior (precuneus, inferior parietal lobule) cortical regions. Cerebral atrophy (increased cerebrospinal fluid [CSF] and decreased grey and white matter volumes) were observed in some of these regions, as well. Regional cerebral metabolism was positively correlated with severity of depression and anxiety symptoms.

CONCLUSIONS

In contrast to decreased metabolism observed in normal aging and neurodegenerative conditions such as Alzheimer's disease, cortical glucose metabolism was increased in geriatric depressed patients relative to demographically matched controls, particularly in brain regions in which cerebral atrophy was observed, which may represent a compensatory response.

Pretreatment regional brain glucose uptake in the midbrain on PET may predict remission from a major depressive episode after three months of treatment

In order to test the hypotheses that pretreatment metabolic activity in the midbrain and the rostral anterior cingulate may predict remission in response to medications enhancing monoaminergic transmission, we compared relative regional cerebral metabolic rate of glucose (rCMRglu) using positron emission tomography (PET) in medication-free patients with major depression who remitted after 3 months of monoaminergic medication, with non-remitters on the same treatment. [(18)F]-FDG PET was conducted in a group of 33 drug-free DSM-IV major depression subjects prior to antidepressant treatment. Patients were prescribed paroxetine initially (61%) unless they had failed paroxetine previously. Treatment was then managed by the subjects' own physician with 91% receiving a selective serotonin reuptake inhibitor and 78% another non-selective monoamine reuptake inhibitor during the 3 months of treatment. Voxel-based parametric brain maps of remitters were compared with maps of non-remitters using SPM2. Remission was defined as a >50% decrease in and a final score of Collapse

Key Words

• depression
• pet
• fdg
• brain regions
• remission
• antidepressant treatment
• outcome
• positron emission tomography

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MESH Headings

• Adult
• Antidepressive Agents/therapeutic use
• Brain/metabolism
• Brain Mapping/methods
• Depressive Disorder, Major/diagnostic imaging
• Depressive Disorder, Major/drug therapy
• Depressive Disorder, Major/metabolism
• Depressive Disorder, Major/psychology
• Diagnostic and Statistical Manual of Mental Disorders
• Female
• Fluorodeoxyglucose F18/metabolism
• Functional Laterality
• Glucose/metabolism
• Gyrus Cinguli/metabolism
• Humans
• Image Processing, Computer-Assisted
• Male
• Mesencephalon/diagnostic imaging
• Mesencephalon/drug effects
• Mesencephalon/metabolism
• Middle Aged
• Paroxetine/therapeutic use
• Positron-Emission Tomography
• Psychiatric Status Rating Scales
• Selective Serotonin Reuptake Inhibitors/therapeutic use
• Treatment Outcome

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Grants

• RR00645 NCRR NIH HHS
• MH40695 NIMH NIH HHS
• M01 RR000645 NCRR NIH HHS
• R01 MH040695 NIMH NIH HHS
• MH62185 NIMH NIH HHS
• P50 MH062185 NIMH NIH HHS

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Affiliation(s)

Matthew S Milak Department of Psychiatry, Columbia University, New York, NY, United States.
Ramin V Parsey
Leilani Lee
Maria A Oquendo
Doreen M Olvet
Francoise Eipper
Kevin Malone
J John Mann

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Rostral anterior cingulate cortex theta current density and response to antidepressants and placebo in major depression

OBJECTIVE

To assess whether pretreatment theta current density in the rostral anterior cingulate (rACC) and medial orbitofrontal cortex (mOFC) differentiates responders from non-responders to antidepressant medication or placebo in a double-blinded study.

METHODS

Pretreatment EEGs were collected from 72 subjects with Major Depressive Disorder (MDD) who participated in one of three placebo-controlled trials. Subjects were randomized to receive treatment with fluoxetine, venlafaxine, or placebo. Low-resolution brain electromagnetic tomography (LORETA) was used to assess theta current density in the rACC and mOFC.

RESULTS

Medication responders showed elevated rACC and mOFC theta current density compared to medication non-responders (rACC: p=0.042; mOFC: p=0.039). There was no significant difference in either brain region between placebo responders and placebo non-responders.

CONCLUSIONS

Theta current density in the rACC and mOFC may be useful as a biomarker for prediction of response to antidepressant medication.

SIGNIFICANCE

This is the first double-blinded treatment study to examine pretreatment rACC and mOFC theta current density in relation to antidepressant response and placebo response. Results support the potential clinical utility of this approach for predicting clinical outcome to antidepressant treatments in MDD.

The role of the tripartite glutamatergic synapse in the pathophysiology and therapeutics of mood disorders

Bipolar disorder and major depressive disorder are common, chronic, and recurrent mood disorders that affect the lives of millions of individuals worldwide. Growing evidence suggests that glutamatergic system dysfunction is directly involved in mood disorders. This article describes the role of the "tripartite glutamatergic synapse," comprising presynaptic and postsynaptic neurons and glial cells, in the pathophysiology and therapeutics of mood disorders. Glutamatergic neurons and glia directly control synaptic and extrasynaptic glutamate levels/ release through integrative effects that target glutamate excitatory amino acid transporters, postsynaptic density proteins, ionotropic receptors (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid [AMPA], N-methyl-D-aspartate [NMDA], and kainate), and metabotropic receptors. This article also explores the glutamatergic modulators riluzole and ketamine, which are considered valuable proof-of-concept agents for developing the next generation of antidepressants and mood stabilizers. In therapeutically relevant paradigms, ketamine preferentially targets postsynaptic AMPA/NMDA receptors, and riluzole preferentially targets presynaptic voltage-operated channels and glia.

Ketamine and the next generation of antidepressants with a rapid onset of action

Existing treatments for major depressive disorder (MDD) usually take weeks to months to achieve their antidepressant effects, and a significant number of patients do not have adequate improvement even after months of treatment. In addition, increased risk of suicide attempts is a major public health concern during the first month of standard antidepressant therapy. Thus, improved therapeutics that can exert their antidepressant effects within hours or a few days of their administration are urgently needed, as is a better understanding of the presumed mechanisms associated with these rapid antidepressant effects. In this context, the N-methyl-D-aspartate (NMDA) antagonist ketamine has consistently shown antidepressant effects within a few hours of its administration. This makes it a valuable research tool to identify biomarkers of response in order to develop the next generation of fast-acting antidepressants. In this review, we describe clinical, electrophysiological, biochemical, and imaging correlates as relevant targets in the study of the antidepressant response associated with ketamine, and their implications for the development of novel, fast-acting antidepressants. We also review evidence that alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) to NMDA throughput may represent a convergent mechanism for the rapid antidepressant actions of ketamine. Overall, understanding the molecular basis of this work will likely lead to the ultimate development of improved therapeutics for MDD.

Targeted electrode-based modulation of neural circuits for depression

During the last 20 years of neuroscience research, we have witnessed a fundamental shift in the conceptualization of psychiatric disorders, with the dominant psychological and neurochemical theories of the past now complemented by a growing emphasis on developmental, genetic, molecular, and brain circuit models. Facilitating this evolving paradigm shift has been the growing contribution of functional neuroimaging, which provides a versatile platform to characterize brain circuit dysfunction underlying specific syndromes as well as changes associated with their successful treatment. Discussed here are converging imaging findings that established a rationale for testing a targeted neuromodulation strategy, deep brain stimulation, for treatment-resistant major depression.

Increased anterior cingulate cortical activity in response to fearful faces: a neurophysiological biomarker that predicts rapid antidepressant response to ketamine

BACKGROUND

Most patients with major depressive disorder (MDD) experience a period of lengthy trial and error when trying to find optimal antidepressant treatment; identifying biomarkers that could predict response to antidepressant treatment would be of enormous benefit. We tested the hypothesis that pretreatment anterior cingulate cortex (ACC) activity could be a putative biomarker of rapid antidepressant response to ketamine, in line with previous findings that investigated the effects of conventional antidepressants. We also investigated patterns of ACC activity to rapid presentation of fearful faces compared with the normal habituation observed in healthy subjects.

METHODS

We elicited ACC activity in drug-free patients with MDD (n = 11) and healthy control subjects (n = 11) by rapidly presenting fearful faces, a paradigm known to activate rostral regions of the ACC. Spatial-filtering analyses were performed on magnetoencephalographic (MEG) recordings, which offer the temporal precision necessary to estimate ACC activity elicited by the rapid presentation of stimuli. Magnetoencephalographic recordings were obtained only once for both patients and control subjects. Patients were subsequently administered a single ketamine infusion followed by assessment of depressive symptoms 4 hours later.

RESULTS

Although healthy subjects had decreased neuromagnetic activity in the rostral ACC across repeated exposures, patients with MDD showed robust increases in pretreatment ACC activity. Notably, this increase was positively correlated with subsequent rapid antidepressant response to ketamine. Exploratory analyses showed that pretreatment amygdala activity was negatively correlated with change in depressive symptoms.

CONCLUSIONS

Pretreatment rostral ACC activation may be a useful biomarker that identifies a subgroup of patients who will respond favorably to ketamine's antidepressant effects.

Cerebral glucose metabolic response to combined total sleep deprivation and antidepressant treatment in geriatric depression: a randomized, placebo-controlled study

A randomized, placebo-controlled study was performed to evaluate whether the onset of the glucose metabolic effects of a selective serotonin reuptake inhibitor (paroxetine) would be accelerated by total sleep deprivation (TSD). Patients were randomly assigned to one of three groups: TSD and paroxetine treatment, TSD and 2 weeks of placebo followed by paroxetine treatment, or 2 weeks of paroxetine treatment. Sixteen elderly depressed patients who met DSM-IV criteria for major depressive disorder and nine age-matched comparison subjects underwent positron emission tomography (PET) studies of cerebral glucose metabolism at baseline, post-TSD (or a normal night's sleep for the paroxetine- only group), post-recovery sleep and 2 weeks post-paroxetine or placebo treatment (patients only). TSD was not consistently associated with a decrease in depressive symptoms between groups nor with decreases in cerebral metabolism in cortical regions that have been associated with rapid and sustained clinical improvement (e.g. anterior cingulate gyrus). The observation of a synergistic antidepressant effect of combined TSD and paroxetine treatment that was observed in a previous "open label" pilot study was not observed in the present randomized study, consistent with lack of a cerebral metabolic effect in brains regions previously shown to be associated with improvement of depressive symptoms.

The subgenual anterior cingulate cortex in mood disorders

The anterior cingulate cortex (ACC) ventral to the genu of the corpus callosum has been implicated in the modulation of emotional behavior on the basis of neuroimaging studies in humans and lesion analyses in experimental animals. In a combined positron emission tomography/magnetic resonance imaging study of mood disorders, we demonstrated that the mean gray matter volume of this "subgenual" ACC (sgACC) cortex is abnormally reduced in subjects with major depressive disorder (MDD) and bipolar disorder, irrespective of mood state. Neuropathological assessments of sgACC tissue acquired postmortem from subjects with MDD or bipolar disorder confirmed the decrement in gray matter volume, and revealed that this abnormality was associated with a reduction in glia, with no equivalent loss of neurons. In positron emission tomography studies, the metabolic activity was elevated in this region in the depressed relative to the remitted phases of the same MDD subjects, and effective antidepressant treatment was associated with a reduction in sgACC activity. Other laboratories replicated and extended these findings, and the clinical importance of this treatment effect was underscored by a study showing that deep brain stimulation of the sgACC ameliorates depressive symptoms in treatment-resistant MDD. This article discusses the functional significance of these findings within the context of the preclinical literature that implicates the putative homologue of this region in the regulation of emotional behavior and stress response. In experimental animals, this region participates in an extended "visceromotor network" of structures that modulates autonomic/neuroendocrine responses and neurotransmitter transmission during the neural processing of reward, fear, and stress. These data thus hold important implications for the development of neural models of depression that can account for the abnormal motivational, neuroendocrine, autonomic, and emotional manifestations evident in human mood disorders.

Mourning and melancholia revisited: correspondences between principles of Freudian metapsychology and empirical findings in neuropsychiatry

Freud began his career as a neurologist studying the anatomy and physiology of the nervous system, but it was his later work in psychology that would secure his place in history. This paper draws attention to consistencies between physiological processes identified by modern clinical research and psychological processes described by Freud, with a special emphasis on his famous paper on depression entitled 'Mourning and melancholia'. Inspired by neuroimaging findings in depression and deep brain stimulation for treatment resistant depression, some preliminary physiological correlates are proposed for a number of key psychoanalytic processes. Specifically, activation of the subgenual cingulate is discussed in relation to repression and the default mode network is discussed in relation to the ego. If these correlates are found to be reliable, this may have implications for the manner in which psychoanalysis is viewed by the wider psychological and psychiatric communities.

Rapid onset of antidepressant action: a new paradigm in the research and treatment of major depressive disorder

OBJECTIVE

Current therapeutics of depression are similar in their time to antidepressant action and often take weeks to months to achieve response and remission, which commonly results in considerable morbidity and disruption in personal, professional, family, and social life, as well as risk for suicidal behavior. Thus, treatment strategies presenting a rapid improvement of depressive symptoms--within hours or even a few days--and whose effects are sustained would have an enormous impact on public health. This article reviews the published data related to different aspects of rapid improvement of depressive symptoms.

DATA SOURCES

Literature for this review was obtained through a search of the MEDLINE database (1966-2007) using the following keywords and phrases: rapid response, antidepressant, time to, glutamate, sleep, therapeutics, latency, and depression. The data obtained were organized according to the following topics: clinical relevance and time course of antidepressant action, interventions showing evidence of rapid response and its potential neurobiological basis, and new technologies for better understanding rapid anti-depressant actions.

DATA SYNTHESIS

A limited number of prospective studies evaluating rapid antidepressant actions have been conducted. Currently, only a few interventions have been shown to produce antidepressant response in hours or a few days. The neurobiological basis of these rapid antidepressant actions is only now being deciphered.

CONCLUSIONS

Certain experimental treatments can produce antidepressant response in a much shorter period of time than existing medications. Understanding the molecular basis of these experimental interventions is likely to lead to the development of improved therapeutics rather than simply furthering our knowledge of current standard antidepressants.

Chronic vagus nerve stimulation for treatment-resistant depression decreases resting ventromedial prefrontal glucose metabolism

Vagus nerve stimulation (VNS) is used as an adjunctive therapy for treatment-resistant depression (TRD). Its mechanism of action is not fully understood. Longitudinal measurement of changes in brain metabolism associated with VNS can provide insights into this new treatment modality. Eight severely depressed outpatients who were highly treatment-resistant underwent electrical stimulation of the left vagus nerve for approximately one year. The main outcome measures were resting regional brain glucose uptake measured with positron emission tomography (PET) and the 24-item Hamilton Depression Scale. The most significant and extensive change over one year of chronic VNS localized to the ventromedial prefrontal cortex extending from the subgenual cingulate to the frontal pole. This region continued to decline in metabolism even toward the end of the study. Clinically, this cohort showed a trend for improvement. No correlations surfaced between change in glucose uptake and depression scores. However, the sample size was small; none remitted; and the range of depression scores was limited. Chronic VNS as adjunctive therapy in patients with severe TRD produces protracted and robust declines in resting brain activity within the ventromedial prefrontal cortex, a network with dense connectivity to the amygdala and structures monitoring the internal milieu.

Dissociable recruitment of rostral anterior cingulate and inferior frontal cortex in emotional response inhibition

The integrity of decision-making under emotionally evocative circumstances is critical to navigating complex environments, and dysfunctions in these processes may play an important role in the emergence and maintenance of various psychopathologies. The goal of the present study was to examine the spatial and temporal dynamics of neural responses to emotional stimuli and emotion-modulated response inhibition. High-density event-related brain potentials (ERPs) were measured as participants (N=25) performed an emotional Go/NoGo task that required button presses to words of a "target" emotional valence (i.e., positive, negative, neutral) and response inhibition to words of a different "distractor" valence. Using scalp ERP analyses in conjunction with source-localization techniques, we identified distinct neural responses associated with affective salience and affect-modulated response inhibition, respectively. Both earlier (approximately 300 ms) and later (approximately 700 ms) ERP components were enhanced with successful response inhibition to emotional distractors. Only ERPs to target stimuli differentiated affective from neutral cues. Moreover, source localization analyses revealed right ventral lateral prefrontal cortex (VLPFC) activation in affective response inhibition regardless of emotional valence, whereas rostral anterior cingulate activation (rACC) was potentiated by emotional valence but was not modulated by response inhibition. This dissociation was supported by a significant Region x Trial Type x Emotion interaction, confirming that distinct regional dynamics characterize neural responses to affective valence and affective response-inhibition. The results are discussed in the context of an emerging affective neuroscience literature and implications for understanding psychiatric pathologies characterized by a detrimental susceptibility to emotional cues, with an emphasis on major depressive disorder.

Antidepressant response to partial sleep deprivation in unipolar depression is not related to state anxiety

One night of total or partial sleep deprivation (SD) produces a temporary remission in up to 60% of patients with major depression, yet mechanisms remain unclear. We investigated whether the antidepressant effects of SD are caused, even partially, by an improvement in anxiety. As part of a functional magnetic resonance imaging study, 19 unmedicated major depression patients and eight controls completed the Spielberger State/Trait Anxiety Inventory (STAI) (state version) at baseline and sleep-deprived scanning sessions. We found (1) greater anxiety in patients than controls; (2) no baseline or SD STAI difference between responders and nonresponders; (3) no STAI change with SD in any subject group; and (4) no significant correlation between any STAI and Hamilton Depression Rating Scale measures. Our findings did not provide support for an anxiolytic process associated with the antidepressant effects of SD.

[Executive functions in patients with depression. The role of prefrontal activation]

Depression is a multifarious disease, having an impact on most aspects of everyday life. Cognitive deficits cause considerable impairments and restraints in performance and have become one of the major clinical and research foci in recent years. According to previous work, deficits in executive functioning seem to be particularly prominent. At present only a few functional neuroimaging studies investigated the neurofunctional correlates aimed at these deficits by using specific activation tasks. These findings are somewhat controversial, revealing prefrontal hypo- as well as hyperactivation as a substrate of executive performance. This paper reviews current functional neuroimaging findings within a framework of depression as a dysfunction in limbic-cortical circuits. As a conclusion, the concept of "simple" hypofrontality does not offer a satisfactory explanation. Rather, a more dynamic model will be necessary in order to achieve a more realistic concept of executive deficits in depression.

Methylphenidate-induced activation of the anterior cingulate but not the striatum: a [15O]H2O PET study in healthy volunteers

The dopaminergic system has been implicated in the pathogenesis and treatment of a variety of neuropsychiatric disorders, such as schizophrenia, depression, and addiction. (Dys)function of the dopaminergic system may be studied by combining [15O]H2O PET with a dopaminergic drug challenge. In this pilot study we investigated the suitability of the dopamine reuptake blocker methylphenidate (MP) as a dopaminergic probe. Measurements of regional cerebral blood flow (rCBF) were made at 10 and 30 min after placebo and MP (0.25 mg/kg) injection to seven healthy volunteers. During scanning the behavioral condition of the subjects was standardized using a continuous performance task. Growth hormone levels were assessed and subjective ratings were obtained. MP significantly elevated growth hormone levels. After receiving MP, the subjective experience varied from neutral to highly pleasurable. Ten minutes after MP administration, significant relative increases in rCBF were found in the rostral anterior cingulate (AC), temporal poles, and the supplementary motor area. Significant reductions were seen in the superior temporal gyri, right medial frontal gyrus, and right inferior parietal cortex. At 30 min after MP administration, increases were seen in the AC, temporal pole, and right cerebellum. No changes were observed in the striatum. The activation in the right rostral AC was significantly higher in the subjects with the highest euphoria scores compared to the subjects with minimal MP-induced changes in euphoria. We suggest that the combined MP challenge with functional imaging, as described in our study, may be a useful tool to study the functional integrity of the dopaminergic system in psychiatric disorders.

Polysomnography and criteria for the antidepressant response to sleep deprivation

BACKGROUND

One night of total or partial sleep deprivation (SD) produces a temporary remission in 40-60% of patients with major depression. Yet no attempts to determine the optimum response criterion(a) for the antidepressant response to SD have been published.

METHODS

Twenty-three unmedicated major depression patients received polysomnography (PSG) on an adaptation night; a baseline night; a partial SD (PSD) night (awake after 3 a.m.); and a "recovery" night. Subjects received the Hamilton Depression Rating Scale (HDRS17) at standard times during baseline and PSD days and at 8 a.m. after the "recovery" night. Response was defined as percent decrease in the modified HDRS17 (HDRS17Mod) (omitting sleep and weight loss items) from baseline to the minimum following PSD. Using cutoffs of 30%, 35%, 40%, and 50% to dichotomize responders and nonresponders, PSG variables were analyzed for between-group differences.

RESULTS

All cutoffs differentiated responders' and nonresponders' mood response to PSD despite similar baseline values. Sleep continuity measures most consistently differed between responders and nonresponders on baseline and recovery nights. None of the response cutoffs tested were clearly "best" in terms of detecting the most PSG differences between groups.

LIMITATIONS

More subjects may be needed.

CONCLUSIONS

Given the increasing interest in SD for clinical and research applications, as well as its proposed use for subtyping depression, further study to determine the optimal response criterion(a) for the antidepressant response to SD is warranted. Planned pooling of multisite data on standardized SD protocols could help determine the optimal cutpoint for response.

Measurement of cerebral perfusion with arterial spin labeling: Part 2. Applications

Arterial spin labeling (ASL) uses magnetic resonance imaging methods to measure cerebral blood flow (CBF) non-invasively. ASL CBF validly localizes brain function and may be especially useful for studies where the time frame of behavioral change is more than a few minutes, such as in longitudinal and treatment studies. ASL measures of cerebral perfusion are highly accurate in detecting lesion laterality in temporal lobe epilepsy, stenotic-occlusive disease, and brain tumors. Among lesioned patients, ASL CBF has excellent concurrent validity when correlated with CBF measured by Positron Emission Tomography or with dynamic susceptibility-weighted magnetic resonance. ASL CBF can predict tumor grading in vivo and can predict six-month response to the surgical treatment of brain tumors. ASL's capability to selectively and non-invasively tag flow in major vessels may refine the monitoring of treatment of cerebrovascular disease and brain tumors. Conclusions about the utility of ASL are limited by the small sample sizes of the studies currently in the literature and by the uncertainty caused by the effect of brain disease on transit times of the magnetic tag. As the method evolves, ASL techniques will likely become more widely used in clinical research and practice.

Improved anatomic delineation of the antidepressant response to partial sleep deprivation in medial frontal cortex using perfusion-weighted functional MRI

This study used functional magnetic resonance imaging (fMRI) to clarify the sites of brain activity associated with the antidepressant effects of sleep deprivation (SD). We hypothesized: 1) depressed responders' baseline ventral anterior cingulate (AC) perfusion will be greater than that of nonresponders and controls; 2) following partial sleep deprivation (PSD), ventral AC perfusion will significantly decrease in responders only. Seventeen unmedicated outpatients with current major depression and eight controls received perfusion-weighted fMRI and structural MRI at baseline and following 1 night of late-night PSD. Talairach-transformed gray matter masks were merged with Talairach Daemon-based region of interest (ROI) templates. Baseline left ventral AC (LVAC) perfusion was greater in responders than nonresponders. There was no difference involving the medial frontal cortex. Responders' LVAC perfusion dropped from baseline to PSD scans compared with nonresponders and controls, as did perfusion in the right dorsal AC. In the patient group as a whole, decrease in LVAC perfusion from baseline to PSD scans correlated directly with the decrease in the modified 17-item Hamilton Depression Rating Scale (HDRS17) between baseline and PSD conditions. These data--the first using fMRI--show greater anatomic specificity than previous findings of SD and depression in linking decreased brain activity in this area with clinical improvement.

Resting anterior cingulate activity and abnormal responses to errors in subjects with elevated depressive symptoms: a 128-channel EEG study

Depression has been associated with dysfunctional executive functions and abnormal activity within the anterior cingulate cortex (ACC), a region critically involved in action regulation. Prior research invites the possibility that executive deficits in depression may arise from abnormal responses to negative feedback or errors, but the underlying neural substrates remain unknown. We hypothesized that abnormal reactions to error would be associated with dysfunctional rostral ACC activity, a region previously implicated in error detection and evaluation of the emotional significance of events. To test this hypothesis, subjects with low and high Beck Depression Inventory (BDI) scores performed an Eriksen Flanker task. To assess whether tonic activity within the rostral ACC predicted post-error adjustments, 128-channel resting EEG data were collected before the task and analyzed with low-resolution electromagnetic tomography (LORETA) using a region-of-interest approach. High BDI subjects were uniquely characterized by significantly lower accuracy after incorrect than correct trials. Mirroring the behavioral findings, high BDI subjects had significantly reduced pretask gamma (36.5-44 Hz) current density within the affective (rostral; BA24, BA25, BA32) but not cognitive (dorsal; BA24', BA32') ACC subdivision. For low, but not high, BDI subjects pretask gamma within the affective ACC subdivision predicted post-error adjustments even after controlling for activity within the cognitive ACC subdivision. Abnormal responses to errors may thus arise due to lower activity within regions subserving affective and/or motivational responses to salient cues. Because rostral ACC regions have been implicated in treatment response in depression, our findings provide initial insight into putative mechanisms fostering treatment response.

Does amygdalar perfusion correlate with antidepressant response to partial sleep deprivation in major depression?

This study used functional MRI (fMRI) to clarify the sites of brain activity associated with the antidepressant effects of sleep deprivation (SD). We hypothesized: (1) baseline perfusion in right and left amygdalae will be greater in responders than in nonresponders; (2) following partial sleep deprivation (PSD), perfusion in responders' right and left amygdalae would decrease. Seventeen unmedicated outpatients with current major depression and eight controls received perfusion-weighted fMRI and structural MRI at baseline and following 1 night of late-night PSD. Baseline bilateral amygdalar perfusion was greater in responders than nonresponders. Clusters involving both amygdalae decreased from baseline to PSD specifically in responders. Right amygdalar perfusion diverged with PSD, increasing in nonresponders and decreasing in responders. These novel amygdalar findings are consistent with the overarousal hypothesis of SD as well as other functional imaging studies showing increased baseline amygdalar activity in depression and decreased amygdalar activity with remission or antidepressant medications.

Posterior cingulate cortex activation by emotional words: fMRI evidence from a valence decision task

Functional imaging studies consistently find that emotional stimuli activate the posterior cingulate cortex, a region that appears to have memory-related functions. However, prior imaging studies have not controlled for non-emotional stimulus features that might activate this region by engaging memory processes unrelated to emotion. This study examined whether emotional words activated the posterior cingulate cortex when these potentially confounding factors were controlled. Sixty-four pleasant and 64 unpleasant words were matched with neutral words on non-emotional features known to influence memory. Eight subjects underwent block-designed functional magnetic resonance imaging scans while evaluating the valence of these words. The posterior cingulate cortex was significantly activated bilaterally during both unpleasant and pleasant compared to neutral words. The strongest activation peak with both unpleasant and pleasant words was observed in the left subgenual cingulate cortex. Anteromedial orbital and left inferior and middle frontal cortices were also activated by both pleasant and unpleasant words. Right amygdala and auditory cortex were activated only by unpleasant words, while left frontal pole was activated only by pleasant words. The results show that activation of the posterior cingulate cortex by emotional stimuli cannot be attributed to the memory-enhancing effects of non-emotional stimulus features. The findings are consistent with the suggestion that this region may mediate interactions of emotional and memory-related processes. The results also extend prior findings that evaluating emotional words consistently activates the subgenual cingulate cortex, and suggest a means of probing this region in patients with mood disorders.

Changes in neural circuitry of language before and after treatment of major depression

Language tasks requiring semantic analysis of word meaning activate distinct brain areas including the anterior cingulate gyrus at about 200 msec after the stimulus onset, the left lateral prefrontal cortex at about 250 msec, and the left temporo-parietal (Wernicke's) area at 500-600 msec. Reading the same words activate the insula around 800 msec and left occipital cortex around 200 msec stronger than the semantic analysis in normal subjects. Many of these brain areas also show abnormal activity in resting state in patients with major unipolar depression. We measured 128-channel event-related brain potentials (ERPs) and statistical probability mapping in the use generation task carried out with single visual nouns to explore the topography and time course of these cortical activations related to semantic processing in 11 patients with major unipolar depression before and 8 weeks after treatment with the selective serotonin reuptake inhibitor (SSRI) citalopram. Before treatment in depressed state, the time course for the left prefrontal cortex activation did not show slowing, but was accompanied by the right prefrontal activation with a similar time course. The left posterior temporo-parietal activation appeared later than in normals. Treatment was accompanied by the complete elimination of the right prefrontal activation in the same use generation task. Time course of the posterior left temporo-parietal area showed a trend toward normalization. Insula-related activation in reading task was not seen in depressed state, but was evident in the same patient group after the depression has lifted, presumably as a result of treatment with citalopram.

Identifying a series of candidate genes for mania and psychosis: a convergent functional genomics approach

We have used methamphetamine treatment of rats as an animal model for psychotic mania. Specific brain regions were analyzed comprehensively for changes in gene expression using oligonucleotide GeneChip microarrays. The data was cross-matched against human genomic loci associated with either bipolar disorder or schizophrenia. Using this convergent approach, we have identified several novel candidate genes (e.g., signal transduction molecules, transcription factors, metabolic enzymes) that may be involved in the pathogenesis of mood disorders and psychosis. Furthermore, for one of these genes, G protein-coupled receptor kinase 3 (GRK3), we found by Western blot analysis evidence for decreased protein levels in a subset of patient lymphoblastoid cell lines that correlated with disease severity. Finally, the classification of these candidate genes into two prototypical categories, psychogenes and psychosis-suppressor genes, is described.