Regional cerebral blood flow and lateralized hemispheric dysfunction in depression

Functional connectivity of major depression disorder using ongoing EEG during music perception

OBJECTIVE

The functional connectivity (FC) of major depression disorder (MDD) has not been well studied under naturalistic and continuous stimuli conditions. In this study, we investigated the frequency-specific FC of MDD patients exposed to conditions of music perception using ongoing electroencephalogram (EEG).

METHODS

First, we applied the phase lag index (PLI) method to calculate the connectivity matrices and graph theory-based methods to measure the topology of brain networks across different frequency bands. Then, classification methods were adopted to identify the most discriminate frequency band for the diagnosis of MDD.

RESULTS

During music perception, MDD patients exhibited a decreased connectivity pattern in the delta band but an increased connectivity pattern in the beta band. Healthy people showed a left hemisphere-dominant phenomenon, but MDD patients did not show such a lateralized effect. Support vector machine (SVM) achieved the best classification performance in the beta frequency band with an accuracy of 89.7%, sensitivity of 89.4% and specificity of 89.9%.

CONCLUSIONS

MDD patients exhibited an altered FC in delta and beta bands, and the beta band showed a superiority in the diagnosis of MDD.

SIGNIFICANCE

Our study provided a promising reference for the diagnosis of MDD, and revealed a new perspective for understanding the topology of MDD brain networks during music perception.

A brain-based endophenotype for major depressive disorder

We have identified a brain-based endophenotype for major depressive disorder (MDD) that includes thinning of the cortex of the lateral aspect of the right hemisphere and the medial aspect of the left, as well as bilateral hypoplasia of frontal and parietal white matter. The endophenotype status of these abnormalities is supported by their presence in a multigenerational cohort of persons who themselves do not have MDD but who are at increased familial risk for developing the illness. Those who have the endophenotype but who are not ill nevertheless still suffer from inattention and poor visual memory for social stimuli in direct proportion to the magnitude of cortical thinning and white matter hypoplasia within the endophenotype. Identification of this endophenotype and its cognitive correlates provides targets for devising new preventive and therapeutic interventions for MDD.

Individualized alpha activity and frontal asymmetry in major depression

Lateralized differences in frontal alpha power in individuals with major depressive disorder (MDD) are thought to reflect an aberrant affective processing style. However research into anterior alpha asymmetry and MDD has often produced conflicting results. The current study aimed to investigate whether individualized alpha bandwidths provide a more sensitive measure of anterior alpha asymmetry in MDD than the traditional fixed 8-13 Hz alpha band. Resting EEG was recorded from 34 right-handed female participants (18 controls, 16 MDD). Each participant's Individual Alpha Frequency was used to delineate a broad individualized alpha band and three individualized narrow alpha sub-bands: lower alpha1, lower alpha 2 and upper alpha. Activity within the broad and narrow individualized bandwidths and within the traditional fixed alpha band were used to compare a) controls and acutely depressed individuals and b) medicated and unmedicated MDD participants. Individualizing and subdividing the alpha bandwidth did not add appreciably to the sensitivity of anterior alpha asymmetry in MDD as no significant differences in lateralized alpha power between controls and MDD participants were observed in any alpha bandwidth. This finding was consistent under two reference schemes and across multiple scalp locations. Within the MDD group, antidepressant use was associated with significantly greater right than left hemispheric power in the lower alpha 1 band. The relevance of this finding is discussed in relation to the electrophysiological correlates of antidepressant medication use, lateralized differences in affective processing and treatment resistant MDD.

Partial clinical response to 2 weeks of 2 Hz repetitive transcranial magnetic stimulation to the right parietal cortex in depression

The aim of this treatment study was to evaluate the therapeutic effects of repetitive transcranial magnetic stimulation (rTMS) over the right parietal cortex in depression. In a double-blind, sham-controlled design ten consecutive sessions of 2 Hz rTMS (inter-pulse interval 0.5 s) at 90% motor threshold to the right parietal cortex (2400 pulses per session) were applied to 34 patients with the primary diagnosis of DSM-IV depression and a score of > or =15 on the 17-item Hamilton Rating Scale for Depression (HAMD). The primary outcome measures were the percentage change from baseline on the 17-item HAMD scores after ten sessions, and the percentage of clinical (defined as > or =50% reduction in HAMD score) and partial clinical (defined as > or =30% reduction in HAMD score) responders. Reduction of HAMD scores in the real rTMS treatment (mean real+/-S.D., -19.9+/-32.5%) was not statistically different from the sham rTMS treatment (mean sham+/-S.D., -5.6+/-28.4%), and the number of clinical responders did not differ between treatments. However, a significant greater number of partial clinical responders were observed in the real (43.8%) compared to the sham rTMS treatment (6.3%). This study provides the first evidence showing that 2 Hz rTMS over the right parietal cortex may have antidepressant properties, and warrants further research.

Brain glucose metabolism difference between bipolar and unipolar mood disorders in depressed and euthymic states

BACKGROUND

Functional brain imaging studies have consistently demonstrated abnormalities in regional cerebral glucose metabolism in the prefrontal cortex in patients with mood disorders (MD). These studies, however, have not clarified the differential characteristics of glucose metabolism between depressed and euthymic states, or between bipolar mood disorder (BP) and unipolar mood disorder (UP).

METHODS

We used [(18)F]fluorodeoxyglucose (FDG) positron emission tomography (PET) to evaluate the differences in glucose metabolism at resting state. We compared 30 depressed and 17 euthymic female patients with mood disorders with age-, IQ-, and socioeconomically matched 20 healthy controls (HCs). Then, BP and UP patients were separately analyzed. The PET data were objectively analyzed by statistical parametric mapping (SPM).

RESULTS

Compared with HCs, the depressed MD patients showed significantly lower glucose metabolism in the bilateral frontal gyri, left cingulate gyrus, bilateral temporal gyri, right insula, bilateral inferior parietal lobules, and right occipital gyrus. In contrast, the euthymic MD patients demonstrated fewer areas with significant reduction. When the depressed BP patients were separately compared with HCs, the glucose metabolism was found to be significantly lower in the bilateral frontal gyri, right cingulate gyrus, and bilateral inferior parietal lobules. Meanwhile, the depressed UP patients showed a significantly lower metabolism in the bilateral frontal gyri, left cingulate gyrus, bilateral temporal gyri, bilateral insulae, bilateral inferior parietal lobules, and right occipital gyrus.

CONCLUSIONS

The results of this study provide evidence of persistent hypometabolism in depressed MD patients, particularly in the frontal gyrus. Although the conclusions are limited in the cross-sectional study, these findings suggest that abnormalities in the right frontal gyrus, left temporal gyrus, and left cingulate gyrus tend to normalize as the depression symptoms improve, although those in the left frontal gyrus, right cingulate gyrus, and right temporal gyrus persist. This study also elucidated the cerebral hypofunction specific to each BP and UP. BP patients showed a decrease in glucose metabolism in the right anterior cingulate and UP patients did in the right temporal gyrus, right insula, and left posterior cingulate. This study clarified the differences between subtypes.

The regulation of sleep and arousal: Development and psychopathology

Throughout early development, a child spends more time asleep than in any waking activity. Yet, the specific role of sleep in brain maturation is a complete mystery. In this article, the developmental psychobiology of sleep regulation is conceptualized within the context of close links to the control of arousal, affect, and attention. The interactions among these systems are considered from an ontogenetic and evolutionary biological perspective. A model is proposed for the development of sleep and arousal regulation with the following major tenets:

1. Sleep and vigilance represent opponent processes in a larger system of arousal regulation.

2. The regulation of sleep, arousal, affect, and attention overlap in physiological, neuroanatomical, clinical, and developmental domains.

3. Complex interactions among these regulatory systems are modulated and integrated in regions of the prefrontal cortex (PFC).

4. Changes at the level of PFC underlie maturational shifts in the relative balance across these regulatory systems (such as decreases in the depth/length of sleep and increased capacity for vigilance and attention), which occur with normal development.

5. The effects of sleep deprivation (including alterations in attention, emotions, and goal-directed behaviors) also involve changes at the level of PFC integration across regulatory systems.

This model is then discussed in the context of developmental pathology in the control of affect and attention, with an emphasis on sleep changes in depression.

Prefrontal Cortex, Emotion, and Approach/Withdrawal Motivation

This article provides a selective review of the literature and current theories regarding the role of prefrontal cortex, along with some other critical brain regions, in emotion and motivation. Seemingly contradictory findings have often appeared in this literature. Research attempting to resolve these contradictions has been the basis of new areas of growth and has led to more sophisticated understandings of emotional and motivational processes as well as neural networks associated with these processes. Progress has, in part, depended on methodological advances that allow for increased resolution in brain imaging. A number of issues are currently in play, among them the role of prefrontal cortex in emotional or motivational processes. This debate fosters research that will likely lead to further refinement of conceptualizations of emotion, motivation, and the neural processes associated with them.

Clinical value of 99mTc-HMPAO SPECT in depressed bipolar I patients

Regional cerebral blood flow was studied in 17 bipolar I depressed patients (DSM-IV criteria) with single photon emission computed tomography (SPECT). Visual analysis of images revealed no abnormality in eight patients and abnormal findings in nine patients. In the nine patients with abnormal findings, all showed regional decreases of the uptake of (99m)Tc-D,L-hexamethylpropylene amine oxime (HMPAO, four in the frontal region, two in the basal ganglia, and three in both the frontal region and the basal ganglia). The patients with visible SPECT abnormalities had significantly higher scores on the Hamilton Rating Scale for Depression (HDRS).

The relationship of regional cerebral blood flow with subtypes of major depression

The aim of the present study was to search for differences between subtypes of major depression with the use of single photon emission tomography.

MATERIALS AND METHODS

Fifty (50) patients aged 21-60 years suffering from Major Depression according to DSM-IV took part in the study. The SCAN v 2.0 was used to assist clinical diagnosis. The psychometric assessment included the HDRS, the HAS, the GAF, the Newcastle scales and the Diagnostic Melancholia Scale (DMS). Single Photon Emission Computerized Tomography (HMPAO SPECT) was used to assess regional cerebral blood flow. The methods of analysis included chi-square test, ANCOVA, and Discriminant Function Analysis.

RESULTS

Forty one (82%) depressed patients had abnormal SPECT findings. The most consistent finding in all patients across all subtypes was a global brain hypoperfusion, which did not include the frontal lobes. The most impressive finding was the relative increase of right frontal lobe perfusion in atypicals, in contrast to the relative decrease of perfusion in both the melancholic and the 'undifferentiated' patients in that particular region. The reverse was true for the right occipital lobe.

CONCLUSION

The results of the current study provide support for the old hypothesis on the existence of two distinct types of depression, characterized by different underlying psychopathologies, but also provide strong evidence for a neurobiological abnormality underlying atypical depression, the subtype closer to the old concept of 'neurotic' depression, which was considered to be psychological or reactive in origin.

Principal component and volume of interest analyses in depressed patients imaged by 99mTc-HMPAO SPET: a methodological comparison

Previous regional cerebral blood flow (rCBF) studies on patients with unipolar major depressive disorder (MDD) have analysed clusters of voxels or single regions and yielded conflicting results, showing either higher or lower rCBF in MDD as compared to normal controls (CTR). The aim of this study was to assess rCBF distribution changes in 68 MDD patients, investigating the data set with both volume of interest (VOI) analysis and principal component analysis (PCA). The rCBF distribution in 68 MDD and 66 CTR, at rest, was compared. Technetium-99m d, l-hexamethylpropylene amine oxime single-photon emission tomography was performed and the uptake in 27 VOIs, bilaterally, was assessed using a standardising brain atlas. Data were then grouped into factors by means of PCA performed on rCBF of all 134 subjects and based on all 54 VOIs. VOI analysis showed a significant group x VOI x hemisphere interaction ( P<0.001). rCBF in eight VOIs (in the prefrontal, temporal, occipital and central structures) differed significantly between groups at the P<0.05 level. PCA identified 11 anatomo-functional regions that interacted with groups ( P<0.001). As compared to CTR, MDD rCBF was relatively higher in right associative temporo-parietal-occipital cortex ( P<0.01) and bilaterally in prefrontal ( P<0.005) and frontal cortex ( P<0.025), anterior temporal cortex and central structures ( P<0.05 and P<0.001 respectively). Higher rCBF in a selected group of MDD as compared to CTR at rest was found using PCA in five clusters of regions sharing close anatomical and functional relationships. At the single VOI level, all eight regions showing group differences were included in such clusters. PCA is a data-driven method for recasting VOIs to be used for group evaluation and comparison. The appearance of significant differences absent at the VOI level emphasises the value of analysing the relationships among brain regions for the investigation of psychiatric disease.

EEG mapping in seasonal affective disorder

Given that the nature of hemispheric dysfunction is different in heterogeneous disorders, in the present investigation EEG power mapping was applied to establish neurophysiological profiles that might potentially discriminate patients with seasonal affective disorder (SAD) among other affective disorders. The baseline resting EEG activity was recorded from 31 depressed SAD patients and 30 controls. Power in the delta, theta-1, theta-2, alpha, beta-1 and beta-2 frequency bands was extracted by Fourier transformation. Patients were found to have a lower delta (in central, parietal, occipital, temporal, posterior-temporal areas), theta-1 (in central and parietal), theta-2 (in anterior-frontal, parietal, occipital) and alpha activity (in anterior-frontal, midfrontal, central, parietal and occipital areas) than controls. SAD subjects showed, compared to controls, an asymmetrical distribution of delta, theta-1, theta-2 and alpha activity in parietal and temporal regions due to an increase of EEG power over the right electrode sites, and beta activity in the lateral frontal region due to an increase of beta power over the right electrode site. It is assumed that differential hemispheric contributions of EEG spectra may discriminate between the varieties of depression or different depressive states.

Seasonal affective disorder: spatial organization of EEG power and coherence in the depressive state and in light-induced and summer remission

The present study analyzed EEG power and coherence in subjects with seasonal affective disorder (SAD) during depressive episodes and during light-induced and summer remission. Baseline EEG activity was recorded during the winter period before light treatment (31 SAD patients, 30 control subjects); after 10 days of 2-h morning light treatment (10 SAD subjects); and during the summer period (14 SAD subjects, 27 control subjects). EEG power and coherence were calculated for the delta, theta-1, theta-2, alpha, beta-1 and beta-2 frequency bands. Compared with control subjects, SAD subjects had lower than normal EEG power in most frequency bands; asymmetrical distribution of delta, theta-1, theta-2 and alpha activity in parietal and temporal regions due to increased EEG power over the left electrode sites; and beta activity in the lateral frontal region due to increased beta power over the right electrode site. The foci of decreased EEG coherence were mainly in the right and left frontal and the right posterior regions. Remitted SAD subjects showed normalization of inter-hemispheric asymmetry in lateral frontal areas; increases of delta, theta-2, and alpha activity compared with control values; theta-1 activity in excess of control values; and disappearance of the foci of decreased coherence in anterior areas of the left hemisphere.

Cerebrovascular disease and late life depression: an age old association revisited

OBJECTIVES

To examine the relationship between depression and cerebrovascular disease in three distinct settings: depression in established cerebrovascular disease, cerebrovascular disease in established depression and depression in vascular dementia.

METHODS

Medline, EMBASE, PsychLit and PsychInfo databases were scanned to locate relevant articles. Data were also extracted from other articles, cited by those articles generated from the above databases.

RESULTS

Using operational criteria, the prevalence of depression is higher than controls only within the first year after stroke, but most studies have not employed control groups. The prevalence of depression in vascular dementia compared with Alzheimer's disease is higher in the majority of studies, but matching for sociodemographic factors and severity of cognitive impairment has been inconsistent. An association between frontal/subcortical cerebrovascular lesions and depression in later life has been observed, but there may be methodological flaws underlying this observation in some computerized tomography studies.

CONCLUSION

There is some evidence that cerebrovascular disease has an aetiopathological role in late life depression. The increased likelihood of damage to frontal/subcortical brain circuitry following stroke, transient ischaemia and hypertension may explain the high prevalence of depression in older people with vascular risk factors. More valid definitions of lesion location and the use of appropriately matched control groups would seek to clarify this issue. The extrapolation to care settings from the high prevalence of depression accompanying cerebrovascular disease and the prolongation of disability in depressed people with stroke, suggests closer liaison between old age psychiatrists, neurologists and physicians caring for the elderly.

Functional and neuroanatomic correlations in poststroke depression: the Sunnybrook Stroke Study

BACKGROUND AND PURPOSE

The purpose of our study was to determine the functional and neuroanatomic correlates of poststroke depressive symptoms.

METHODS

Patients with consecutive admissions to a regional stroke center for new-onset unilateral hemispheric stroke who met World Health Organization and National Institute of Neurological and Communicative Disorders and Stroke criteria were eligible for inclusion in a longitudinal study. Acutely, patients underwent CT scanning, and at 3 months and 1 year after stroke, depressive symptoms were assessed by using both the Montgomery-Asberg Depression Rating Scale and the Zung Self-Rating Depression Scale. The Functional Independence Measure (FIM) served as an indication of functional outcome and was obtained at 1 month, 3 months, and 1 year after stroke, along with other demographic information. The Talairach and Tournoux stereotactic atlas was used for the primary determination of CT lesion localization. Lesion proximity to the anterior frontal pole was also measured.

RESULTS

Eighty-one patients participated in the longitudinal study. Stepwise linear regression analyses generated a highly significant model (F(3,76)=9.8, R(2)=28%, P<0.0005), with lower 1-month total FIM scores, living at home, and damage to the inferior frontal region predicting higher depression scores at 3 months. Similarly, lower 3-month total FIM scores correlated with higher 3-month depression scores, and lower 1-year total FIM scores correlated with higher 1-year depression scores.

CONCLUSIONS

Functional measures correlated with poststroke depression across time and, together with neuroanatomic measures, predicted depressive symptoms longitudinally. Although inferior frontal lesion location, irrespective of side, appeared to play a role as a risk factor in this study, the degree of functional dependence after stroke imparted the greatest risk.

Monorhinal odor identification and depression scores in patients with seasonal affective disorder

BACKGROUND

Visual and olfactory pathways are interconnected. Olfactory deafferentation unmasks photoperiodic responsiveness in some nonphotoperiodic animals such as laboratory rats. By analogy, we hypothesized that olfactory deficits may unmask seasonal rhythms in certain individuals, namely those with seasonal affective disorder (SAD). Since previous studies suggest lateralized hemispheric dysfunction in SAD, and since olfactory neurons' primary projections are largely ipsilateral, we assessed olfactory identification performance on both the right and left side of the nose.

METHODS

Twenty-four patients with SAD and 24 matched controls were studied using a phenyl ethyl alcohol detection threshold test bilaterally and the University of Pennsylvania Smell Identification Test unilaterally. Subjects rated their mood using the Self Assessment Mood Scale for SAD. Patients' testing was done in both 'depressed' and 'improved on light' states.

RESULTS

No difference in olfactory performance was found between patients and controls or between patients before and after light treatment. However, right-side identification scores were negatively correlated with 'typical' depression scores (r = -0.56, P = 0.006), while left-side olfactory scores were not. Atypical depression scores were unrelated to olfactory performance. Similar correlations emerged between the olfactory identification laterality quotient (Right - Left)/(Right + Left) and typical depressive scores (r = - 0.64, P < 0.001) and total depression scores (r = - 0.59, P < 0.004).

LIMITATIONS

We studied a demographically heterogeneous sample and did not control for menstrual factors.

DISCUSSION

Our results add to previous evidence of lateralized hemispheric involvement in SAD and suggest that olfaction may be related to seasonal emotional rhythms in humans.

Brain metabolic changes in major depressive disorder from pre- to post-treatment with paroxetine

Functional brain imaging studies of subjects with Major Depressive Disorder (MDD) have suggested that decreased dorsolateral (DLPFC) and increased ventrolateral (VLPFC) prefrontal cortical activity mediate the depressed state. Pre- to post-treatment studies indicate that these abnormalities normalize with successful treatment. We performed [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) scans on 16 outpatients with MDD before and after treatment with paroxetine (target dose = 40 mg/day). Regions of interest (ROIs) for this analysis were drawn by a rater blind to subject identity on the magnetic resonance image of each subject and transferred onto their coregistered PET scans. We hypothesized that DLPFC metabolism would increase, while ventral frontal metabolism [in the VLPFC, the orbitofrontal cortex (OFC), and the inferior frontal gyrus (IFG)] would decrease with successful treatment. Treatment response was defined as a decrease in the Hamilton Depression Rating Scale of > 50% and a Clinical Global Improvement Scale rating of 'much' or 'very much' improved. By these criteria, nine of the subjects were classified as treatment responders. These responders had significantly greater decreases in normalized VLPFC and OFC metabolism than did non-responders. There were no significant effects of treatment response on change in the DLPFC or IFG in this sample. However, there was a positive correlation between change in HAM-D scores and change in normalized IFG and VLPFC metabolism. There were no significant interactions with laterality. On pre-treatment scans, lower metabolism in the left ventral anterior cingulate gyrus was associated with better treatment response. These findings implicate ventral prefrontal-subcortical brain circuitry in the mediation of response to serotonin reuptake inhibitors in MDD.

Changes in regional cerebral blood flow demonstrated by single photon emission computed tomography in depressive disorders: comparison of unipolar vs. bipolar subtypes

Single photon emission tomography (SPECT) with 99mTc-HMPAO was used to compare regional cerebral blood flow (rCBF) in patients with unipolar and bipolar depression. The study group consisted of 10 unipolar depressed patients and seven bipolar depressed patients who met the DSM-III-R criteria for major depressive disorder (MDD). Nine physically and mentally healthy volunteers served as control subjects. SPECT images were obtained in the patients at two time points: (1) during the major depressive episode before patients had received medication; and (2) at the beginning of the remitted state while patients were receiving antidepressant medication. During the depressive episode, unmedicated unipolar depressed patients showed relatively increased left frontal rCBF compared both with the control subjects and the bipolar patients (P < 0.05). No significant differences in rCBF emerged between the bipolar patients and the control subjects. The data suggest that unipolar depressed patients, unlike bipolar patients, have relatively increased rCBF in the left frontal lobes during the depressive episode, but these differences tend to disappear during the period of remission.

A voxel-based analysis of cerebral perfusion in dementia and depression of old age

Thirty-nine elderly depressed patients as well as 15 demented patients with Alzheimer's disease and 11 healthy volunteers were imaged at rest with a high resolution single-slice 12-detector head scanner (SME-Neuro 900) and the cerebral perfusion marker 99mTc-Exametazime (HM-PAO). Statistical parametric maps were computed to compare early- and late-onset depressed, Alzheimer patients and healthy volunteers and to examine associations between regional perfusion and clinical and MRI variables. Patients with late-onset depression showed reductions in temporal lobe perfusion compared with early-onset depression and controls. Alzheimer patients had the expected reduced perfusion in temporoparietal and prefontal cortex, as well as basal ganglia, compared with healthy controls. Compared with depressed patients, they showed a relative reduction in temporoparietal cortex, only. This difference was more pronounced between Alzheimer patients and early onset, compared to late-onset patients with depression. Periventricular white matter changes on MRI were associated with temporal lobe reductions of tracer uptake in depression. In the Alzheimer group, deep white matter MRI changes were associated with frontal perfusion deficits. Our results support a vulnerability hypothesis, which predicts that patients with late-onset depression will show more brain changes than patients with an early onset of their illness. Statistical parametric mapping in patients with organic psychiatric brain syndromes is feasible and promising as a clinical and research method.

Functional neuroimaging studies of depression: the anatomy of melancholia

Functional brain imaging techniques, which permit noninvasive measures of neurophysiology and neuroreceptor binding, are powerful and sensitive tools for research aimed at elucidating the pathophysiology of major depression. The application of these technologies in depression research has produced several studies of resting cerebral blood flow (BF) and glucose metabolism in subjects imaged during various phases of illness and treatment. This review examines these data and the principles relevant to their interpretation and discusses the insights they provide into the anatomical correlates of depression. Within the anatomical networks implicated in emotional processing by other types of evidence, these BF and metabolic data demonstrate that major depression is associated with reversible, mood state-dependent, neurophysiological abnormalities in some structures and irreversible, trait-like abnormalities in other structures. In some of the regions in which trait-like abnormalities appear, abnormal metabolic activity appears at least partly related to the anatomical abnormalities identified in magnetic resonance imaging (MRI) studies of depression.

Regional cerebral blood flow abnormalities in late-life depression: relation to refractoriness and chronification

We examined patterns of regional cerebral blood flow (rCBF) abnormalities in 18 patients with major depressive disorder in late life using single photon emission computed tomography (SPECT) and 99mTc-hexamethylpropylenamine oxime (99mTc-HMPAO). Compared with 13 age-matched controls, relative rCBF was significantly decreased bilaterally in the anterior cingulate gyrus, the prefrontal cortex, the temporal cortex, the parietal cortex, the hippocampus and the caudate nucleus. However, it was not correlated with the severity of depression or global cognitive dysfunction. In 10 patients with a prolonged depressive episode or prolonged residual symptoms (the refractory subgroup), robust and extensive decreases in rCBF were found compared with controls and the rCBF decreased significantly in the anterior cingulate gyrus and the prefrontal cortex compared with that in the non-refractory subgroup. In the non-refractory subgroup, rCBF decreased significantly in the caudate nucleus and tended to decrease in the anterior cingulate gyrus compared with controls. These findings indicate that dysfunction of the limbic system, the cerebral association cortex and the caudate nucleus may be implicated in late-life depression and that robust and extensive hypoperfusion, especially in the anterior cingulate and the prefrontal regions, may relate to refractoriness or chronification of depression.

Brain electrical asymmetries during cognitive task performance in depressed and nondepressed subjects

BACKGROUND

Studies using electroencephalogram (EEG) measures of activation asymmetry have reported differences in anterior asymmetry between depressed and nondepressed subjects. Several studies have suggested reciprocal relations between measures of anterior and posterior activation asymmetries. We hypothesized that depressed subjects would fail to show the normal activation of posterior right hemisphere regions in response to an appropriate cognitive challenge.

METHODS

EEG activity was recorded from 11 depressed and 19 nondepressed subjects during the performance of psychometrically matched verbal (word finding) and spatial (dot localization) tasks. Band power was extracted from all epochs of artifact-free data and averaged within each condition. Task performance was also assessed.

RESULTS

Depressed subjects showed a specific deficit in the performance of the spatial task, whereas no group differences were evident on verbal performance. In posterior scalp regions, nondepressed controls had a pattern of relative left-sided activation during the verbal task and relative right-sided activation during the spatial task. In contrast, depressed subjects failed to show activation in posterior right hemisphere regions during spatial task performance.

CONCLUSIONS

These findings suggest that deficits in right posterior functioning underlie the observed impairments in spatial functioning among depressed subjects.

rCBF SPECT in Parkinson's disease patients with mental dysfunction

Functional imaging of the brain using SPECT provides information correlative to the alterations of regional blood flow. In this paper we review the literature pertaining to SPECT in Parkinson's disease with and without dementia and depression. Parkinson's disease itself is not associated with a consistent pattern of cerebral blood flow alterations in the basal ganglia, but reduced parietal blood flow is more often reported. The heterogeneity of blood flow changes possibly reflects the multifactorial pathophysiology of the disease. In demented Parkinson's disease patients frontal hypoperfusion is often found or bilateral temporoparietal deficits, probably indicative of concomitant Alzheimer's disease. The SPECT studies undertaken in depressed patients with and without Parkinson's disease show highly conflicting and inconsistent results, probably due to methodological and diagnostic flaws (especially the inclusion of demented Parkinson patients). Several lines of reasoning point to a prefrontal dysfunction and future SPECT studies are planned to study this region in non-demented Parkinson's disease patients with and without major depression.

Right hemisphere abnormalities in major depression: quantitative electroencephalographic findings before and after treatment

The quantitative EEGs of drug-free depressed patients were analyzed and compared to age and sex-matched controls, using spectral analysis. In addition, QEEGs of depressed patients after clinical improvement resulting from 6 weeks of antidepressant treatment were also analyzed. The subjects were 20 patients suffering from major depression (DSM-III-R). Scores on the Hamilton Rating Scale for Depression (HRSD) of all patients showed a reduction of more than 50% at the end of the 6th week. The results show: (1) delta and theta bipolar absolute powers of the right hemisphere increased in drug-free depressed patients, compared to controls. (2) No changes in all bands of QEEG were found after clinical improvement resulting from 6 weeks of treatment. These results suggest that the right hemisphere plays an important role in major depression, and that a reduction in symptoms is not necessarily indicative of an improvement in underlying major depression.

Region-dependent asymmetrical or symmetrical variations in the oxygenation and hemodynamics of the brain due to different mental stimuli

The present paper demonstrates region-dependent variations in the oxygenation and hemodynamics of the brain hemispheres due to three different types of mental stimulation. The variations were observed with a four-channel optical imaging system using tissue-transparent near-infrared light and described changes from baseline of both the hemoglobin oxygenation state and blood volume during three kinds of psychological or mental tasks. During the mirror drawing task, a lateralized hemisphere response (the dominant hemisphere response pattern) was observed in 57% of 14 right handed volunteers in the frontal region (Brodmann's area 10), while in the temporal region (area 38), 80% showed the bilateral response pattern. A large majority of the subjects showed the bilateral response pattern in the frontal and temporal regions while calculating. A smaller majority showed this while looking at anatomical charts, though 30% did not show any response at all in the temporal region. This showed that there were region-dependent asymmetrical or symmetrical variations of the oxygen delivery-oxygen utilization relationship due to different types of mental stimuli.

Regional cerebral blood flow changes following chronic administration of antidepressant drugs

1. Twenty-six patients with major unipolar depression were rated clinically and regional cerebral blood flow (rCBF) determined prior to and after six months of treatment with 75-100 mg/day amitriptyline (n. 16) or 200 mg/day amineptine (n. 10). 2. rCBF was measured in 16 regions over each hemisphere by the Xenon 133 inhalation method and was computed as the initial slope index (ISI). The severity of depression was quantified by the Hamilton rating scale for depression. 3. Baseline rCBF values of depressed patients tended to be lower than those of normal subjects. Significant reductions were observed for all probes exploring the frontal region of the left hemisphere and for some probes exploring the frontal region of the right hemisphere. Chronic treatment with amitriptyline induced a significant increase in rCBF in the left frontal region. Similar results were obtained after treatment with amineptine. 4. Besides confirming frontal lobe dysfunction in depressed patients which is reversed by treatment with classic tricyclic antidepressants, the present results show that this dysfunction may also be reversed by treatment with dopaminergic drugs.

Changes in regional cerebral blood flow on recovery from depression

We have previously described focal abnormalities of regional cerebral blood flow (rCBF) in the left dorsolateral prefrontal cortex (DLPFC), anterior cingulate cortex and angular gyrus in 40 patients with major depression. We now report on the patterns of change in rCBF in a subgroup of 25 of the same patients who were rescanned following clinical remission of depression. Fifteen patients were scanned when optimally matched for drug treatment (4) or drug free on both occasions (11). The other 10 patients were fully recovered but could not be matched for drug status for clinical and ethical reasons. In a paired comparison of the same patients when ill and following recovery it was evident that remission was associated with a significant increase in rCBF in the left DLPFC and medial prefrontal cortex including anterior cingulate. Increases in rCBF in the angular gyrus were not seen when the comparison of depressed and recovered scans was matched for medication. The previously described relationship between clinical symptoms and brain perfusion in the depressed state was no longer present in the recovered state; this supports the hypothesis of state relatedness. Thus, recovery from depression is associated with increases in rCBF in the same areas in which focal decreases in rCBF are described in the depressed state in comparison with normal controls.

The P300 ERP component: an index of cognitive dysfunction in depression?

A number of measures of brain function have suggested that depression is associated with cerebral hypoactivity. This study examines the late components of the event-related potential (ERP), in particular the P300 component, in depression. The P300 component is thought to index the updating of neurocognitive models which are concerned with the prediction of future events. Cognitive theories of depression include the proposition that depression may be characterized by abnormalities in the prediction of future events. The P300 component may therefore provide one neurophysiological index of cognitive dysfunction in depression. Twenty-seven subjects (14 medicated, 13 drug-free) fulfilling DSM-III criteria for Major Depression were compared to 27 age- and sex-matched normal controls. The amplitudes and latencies of N100, P200, N200 and P300 ERP components, reaction time and task accuracy were recorded during a standard auditory discrimination task. No significant differences were found in any ERP component measure or in reaction-time between the groups. Depressed subjects performed the experimental task significantly less accurately than normal controls, but this was not reflected in the ERPs.

State changes in brain activity shown by the uptake of 99mTc-exametazime with single photon emission tomography in major depression before and after treatment

Twenty-eight patients with a major depressive episode previously investigated at rest using Single Photon Emission Tomography (SPET or SPECT) with 99mTc-exametazime, were followed up at an interval of 9-28 months with the same investigation after full recovery. All patients were unipolar and were rated on the Newcastle scale and with the 17-item Hamilton scale. The uptake of 99mTc-Exametazime was expressed relative to calcarine/occipital cortex. Sixteen patients were scanned when optimally matched for drug treatment (4) or on both occasions drug free (12). The other 12 patients were fully recovered but could not be matched for drug status; these patients showed significantly more retardation, diurnal mood variation and guilt at presentation. Significant bilateral increases in tracer uptake were confined to basal ganglia and inferior anterior cingulate cortex in the matched group, where there were additional increases in thalamus and posterior cingulate cortex on the right side. There were no statistically discernible changes in the neocortex in the matched sample. The unmatched sample yielded inconclusive evidence of increased tracer uptake in left temporal cortex. The findings give a potential focus to the neuropharmacological analysis of depressive illness because the topography of the state change in brain function implicates dopamine function.

Cerebral blood flow in major depression and dysthymia

Using single photon emission computerized tomography (SPECT) with a 99mTc-HMPAO perfusion technique, we studied the regional cerebral blood flow (rCBF) of 42 drug-free inpatients suffering from Major Depression' (n = 21) or dysthymia with the super-imposed diagnosis of a major depressive episode (n = 21). The patients with Major Depression had a significantly lower frontal and posterior rCBF ratio than those with Double Depression. Left frontal region indices showed a slight overlap between the two groups. There was no correlation between the severity of the illness and the rCBF indices. Different qualitative cerebral dysfunctions may be implicated in these two affective disorder sub-types.

Regional cerebral blood flow alterations in unipolar depression

Forty-seven symptomatic inpatients and outpatients with major depression (13 nonendogenous, 23 endogenous, and 11 psychotic by Research Diagnostic Criteria) were compared with 138 normal control subjects. Absolute regional cerebral blood flow (rCBF, ml/minute/100 g) was measured with 133Xe single photon emission computed tomography. Flow ratios (region of interest/global flow) and residual scores (the difference between patient flow ratios and expected normal flow ratios, as derived from the control population) were also computed. Results revealed significant age x region x depression subtype interactions for absolute, ratio, and residual flow data. Consequently, a test of group means (or analysis of covariance) could not be used to examine between-group differences. Multiple regression analyses were employed to study the effects of age on rCBF. This analysis revealed that different, though sometimes overlapping, regions exhibited different age effects on rCBF in different depressive subtypes. Thus, diagnostic-subtype-dependent age effects on rCBF precluded comparisons of mean values within or across regions for subject groups, but distinguished between symptomatic depressed patients and control subjects and among patient groups. Possible causes of such effects include variations in duration of illness or medication history or sensitization phenomena.

Melatonin rhythms in seasonal affective disorder

We examined 24-hour melatonin rhythms from 20 patients with seasonal affective disorder (SAD) and 20 healthy volunteers. Patients and controls were individually matched for age, sex, and month of study. Plasma samples were taken at hourly intervals, and were assayed for melatonin by radio-immunoassay. The 24-hourly melatonin estimations for each individual were fitted to a cosine curve, and the significance of the curve fits was calculated. Two analyses were performed. In analysis 1 the following were calculated: (a) cosine fit, (b) significance of fits, (c) mean amplitude and acrophase (peak) and (d) mean melatonin levels. The curve fits were highly significant for all but three subjects (two patients, one control), but there were no significant differences in any measure between the two groups. In analysis 2 the comparisons were repeated and restricted to the 18 patients and 19 controls in whom there was a significantly significant melatonin rhythm. Again there were no significant differences between groups. These results suggest that the circadian rhythm of melatonin is not abnormal in SAD, and that the therapeutic effect of light in SAD is not mediated by phase shifts in melatonin secretion.

Regional cerebral glucose metabolism in late-life depression and Alzheimer disease: a preliminary positron emission tomography study

Eight subjects with late-life depression, eight subjects with probable Alzheimer disease, and eight healthy age-matched controls were studied using 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography in the resting state with their eyes open and ears unoccluded. The depressed subjects showed widespread reductions in the regional cerebral metabolic rate for glucose in most major neocortical, subcortical, and paralimbic regions that were significantly different from control values (P < 0.01). The metabolic decrements in the depressed group were comparable in magnitude to those seen in the Alzheimer disease group. These data demonstrate widespread nonfocal decline in glucose metabolism in late-life depression that is comparable to the hypometabolism seen in Alzheimer disease. These findings have pathophysiological implications in major depressive disorder in the elderly.

Regional cerebral blood flow in depression measured by positron emission tomography: the relationship with clinical dimensions

We have previously reported focal abnormalities of regional cerebral blood flow (rCBF) in a group of 33 patients with major depression. This report, on an extended sample of 40 patients who demonstrated identical regional deficits to those previously described, examines the relationships between depressive symptoms and patterns of rCBF. Patients' symptom ratings were subjected to factor analysis, producing a three-factor solution. The scores for these three factors, which corresponded to recognizable dimensions of depressive illness, were then correlated with rCBF. The first factor had high loadings for anxiety and correlated positively with rCBF in the posterior cingulate cortex and inferior parietal lobule bilaterally. The second factor had high loadings for psychomotor retardation and depressed mood and correlated negatively with rCBF in the left dorsolateral prefrontal cortex and left angular gyrus. The third factor had a high loading for cognitive performance and correlated positively with rCBF in the left medial prefrontal cortex. These data indicate that symptomatic specificity may be ascribed to regional functional deficits in major depressive illness.

Regional cerebral blood flow in unipolar depression measured with Tc-99m-HMPAO single photon emission computed tomography: negative findings

Recent studies have reported that patients with unipolar major depression may show a lower whole brain cerebral blood flow (CBF) and reduced regional CBF in frontal, temporal, and parietal lobes. The present study used single photon emission computed tomography (SPECT) with the CBF marker Tc-99m-hexamethylpropyleneamineoxine (HMPAO) to measure the cortical CBF of six individual regions of interest (ROIs), total ROI, and left or right hemispheric total ROI in 43 unipolar depressed subjects and 12 normal control subjects. There were no significant differences in the distribution of Tc-99m-HMPAO uptake into total ROI, right or left global ROI, prefrontal, motor frontal, parietal, temporal, visual cortex, or associative visual cortex between patients with melancholic depression, simple major depression, or minor depression and healthy control subjects. There were also no significant differences in the right-left distribution of uptake between the patients and the control subjects. Hypoperfusion was observed in motor frontal and parietal cortex of patients who had been taking benzodiazepines during the study period. It is concluded that cortical CBF, as assessed with Tc-99m-HMPAO SPECT, is relatively intact in the present sample of patients with severe depression.

Is the mechanism of prefrontal hypofunction in depression the same as in schizophrenia? Regional cerebral blood flow during cognitive activation

To test the hypothesis that depressed and schizophrenic patients have a common pathophysiological mechanism for hypofunction of the prefrontal cortex ('hypofrontality'), we measured regional cortical blood flow (rCBF) in ten depressed patients, ten patients with schizophrenia, and 20 age- and sex-matched normal controls. Blood flow was measured during three different cognitive conditions: a resting state, a simple number-matching sensorimotor control task, and the Wisconsin Card Sorting test (WCS). The schizophrenic patients had lower prefrontal rCBF during the WCS. There were no differences in global or regional flow between the depressed patients and the normal subjects during any testing condition. Analysis of rCBF lateralisation showed that during the WCS normal subjects had relatively more left parietal blood flow than depressed patients, who had more right parietal blood flow. Since the testing condition that has most consistently revealed hypofrontality in schizophrenia (i.e. the WCS) was not associated with abnormal rCBF in the depressed patients, these data suggest that the pathophysiological mechanisms underlying prefrontal hypofunction in depression and schizophrenia are different.

Reconsidering Depression in the Elderly

The authors present a literature review and a scientific commentary. The prevalence of depressive disorders in the elderly and their association with significant morbidity and mortality are discussed in relation to study of clinical heterogeneity, which may provide useful insights into etiologic and pathophysiologic variability. The authors summarize findings regarding clinical and associated features of late-life depression, explore the limitations of current factual knowledge and conceptual approaches, and propose directions for future research. They argue that current sample selection procedures minimize the variability of the very phenomena under study; therefore, few phenomenologic differences or risk factors for long-term outcome have been noted consistently. Factors such as medical illness account for much of the observed heterogeneity in presentation and outcome. Future studies must include a broader range of subjects and carefully examine in a multidimensional fashion a wider range of "comorbid" conditions, personality and social assessments, and neuropsychologic and neurobiologic measures. Such approaches will enhance our understanding of the pathophysiologic mechanisms of depression in the elderly and across the lifespan.

Brain phosphorous metabolism in depressive disorders detected by phosphorus-31 magnetic resonance spectroscopy

Brain phosphorus metabolism was measured in 22 patients with depressive disorders. Ten of them had DSM-III-R bipolar disorder, and 12 had major depression. In bipolar patients, phosphomonoester (PME) and intracellular pH were significantly increased in the depressive state than in the euthymic state, while those values in the euthymic state were significantly low as compared to age-matched normal controls. Phosphocreatine (PCr) was significantly decreased in severely depressed patients compared to mild depressives. These findings suggest that high energy phosphate metabolism, intracellular pH and membrane phospholipid metabolism are altered in depressive disorders.

Longitudinal study of regional cerebral blood flow changes in depression after stroke

BACKGROUND

We studied 60 patients longitudinally to examine relations between regional cerebral blood flow and depressive states after stroke.

METHODS

Poststroke depressive states were assessed by the Zung Self-Rating Depression Scale (SDS). Regional cerebral blood flow was measured using the 133xenon inhalation method with patients in the resting state on the same day as the SDS assessment. All patients were followed for an average of 14 months after the initial assessment.

RESULTS

Severity of depression was inversely correlated with regional cerebral blood flow values in the parieto-occipital regions of the right hemisphere and in the anterior temporal region of the left hemisphere at the initial evaluation. Patients with lesions in left frontal or right parieto-occipital regions were more depressive in comparison with those with other brain lesions. Follow-up study showed significant inverse correlations between changes in SDS score and changes in regional cerebral blood flow at all scalp sites. Furthermore, higher inverse correlations were observed at specific brain regions in each hemisphere, including the parietal and parieto-occipital regions of the right hemisphere and the anterior temporal and inferior frontal regions of the left hemisphere. This relation was independent of recovery from neurological deficits.

CONCLUSIONS

These results suggest that dysfunction of specific cortical and subcortical regions in both hemispheres asymmetrically contributes to depressive state after stroke.

Evaluation of the effects of total sleep deprivation on cerebral blood flow using single photon emission computerized tomography

HMPAO-single photon emission computerized tomography (SPECT) is a useful technique in studying cerebral blood flow (CBF). This method is suitable to evaluate the differences of CBF with reference to total sleep deprivation (TSD) within 24 h because of the short half-life of the radiopharmaceutical compound. In the present study, CBF before and after TSD was analysed in patients suffering from major depression. The morning before and after TSD, Tc-HMPAO-SPECT was performed in 20 patients. Hamilton Rating Scale for Depression scores and subjective ratings were obtained daily. Eleven patients responded to TSD; 9 were nonresponders. The main finding was a significant left temporal and mainly right parietal increase of CBF, which was observed in the responders only. CBF values and the severity of depression correlated inversely.

Single photon emission tomography with 99mTc-exametazime in major depression and the pattern of brain activity underlying the psychotic/neurotic continuum

Forty patients with a major depressive episode were investigated at rest using Single Photon Emission Tomography (SPET or SPECT) with 99mTc-exametazime, an intravenous ligand taken into brain in proportion to regional cerebral blood flow, thereby providing an estimate of regional metabolism. All patients were unipolar and were rated on the Newcastle scale and with the 17-item Hamilton scale. They also completed a range of neuropsychological tests. They were compared with 20 control subjects matched for age, gender, premorbid intelligence and education. The uptake of 99mTc-exametazime was expressed for a range of anatomically defined regions of interest relative to calcarine/occipital cortex. The depressed group showed reduced uptake in the majority of cortical and sub-cortical regions examined, most significantly in temporal, inferior frontal and parietal areas. Unexpectedly, there was a strong positive association between uptake and scores on the Newcastle scale, especially in cingulate areas and frontal cortex. After removing the variance attributable to the Newcastle ratings, however, there emerged the expected negative association between Hamilton scores and anterior tracer uptake. The associations between neuropsychological impairment and regional brain uptake of tracer in part reflected the pattern seen with the Newcastle scale: for example, impairment of memory function correlated with higher uptake into posterior cingulate areas. We propose that depressive illness may be characterised by two processes. One leads to an overall reduction in anterior neocortical function, perhaps related to symptom severity. The other mechanism is manifest as relatively increased function, most notably within cingulate and frontal areas of the cerebral cortex in association with psychotic symptoms. The findings offer new understanding of the brain states underlying depressive illness and a potential focus to subsequent neuropharmacological analysis.

SPECT imaging in psychiatry. A review

In the last two decades, brain imaging has become an integral part of clinical and research psychiatry. Single photon computed emission tomography (SPECT) is rapidly gaining acceptance as one of the major imaging techniques available, along with computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). Each of these techniques has its assets and drawbacks. This review concerns SPECT, a highly prevalent imaging technique whose potential value in brain imaging has not been appreciated until recently. Its purpose is to expose practicing clinicians and research psychiatrists alike to the attributes of this instrument, which is available in most nuclear medicine departments today. An effort is made to provide a comprehensive account of this technique, including a brief summary of the basic principles, the various methods of its application, and recent findings in most psychiatric disorders. Analogies to its "aristocratic cousin," PET, are presented to emphasize similarities and differences. Finally, directions for future development and implementation of SPECT are suggested.

A practical approach to children failing in school

The most likely causes of failure in school in otherwise capable children who come from homes in which they are loved and cared for are learning disabilities, affective illness, primary disorder of vigilance and, on occasion, narcolepsy. The various learning disabilities are often accompanied by problems of attention, concentration, organization, mood and feelings, and social interaction. These latter problems are reflections of biochemical disorders that respond effectively to judicious pharmacologic intervention. When this type of medical management is combined with constructive counseling and suitable curriculum adjustments, the child can attain his or her maximum education potential and become a productive and contributing adult member of society.

Impaired recognition of affect in facial expression in depressed patients

Measures of recognition of seven affects in facial and verbal expressions to 17 depressed patients and 31 controls were administered. Depressed patients were significantly impaired in the recognition of affect in the facial, but not verbal, expressions. Among the seven affects examined, depressed patients made significantly or near significantly fewer correct matches for sad, happy, and interested face items. The performance of the depressed patients was similar to that observed by Kolb and Taylor in patients with right, but not left, hemisphere cortical excisions. The neurobiology of facial recognition is reviewed, and the relevance of the observed perceptual deficit in depressed patients to the pathophysiology and symptomatology of depression is discussed.