Regional brain gray matter abnormalities in patients with bipolar II disorder: A comparison study with bipolar I patients and healthy controls

Despite the high prevalence and clinical significance of bipolar II disorder (BD II), the underlying pathophysiology is not well explored in previous studies. The purpose of the current study was to investigate brain gray matter abnormalities in BD II. High resolution magnetic resonance brain images from 23 BD II patients, 23 sex- and age-matched patients with bipolar I disorder (BD I) and 23 healthy controls were acquired and processed according to the optimized voxel-based morphometry protocol. The processed gray matter tissue volumes were compared among the three groups. Both the BD II and BD I group showed gray matter deficits in the ventromedial prefrontal regions, compared to controls. The BD I group had widespread gray matter reductions in the bilateral frontal, temporal, parietal and parahippocampal cortices, compared to controls. However, gray matter reductions in these regions were not found in the BD II group. With a less conservative statistical threshold, the BD II group showed additional gray matter deficits in the anterior limbic cortices. Our data suggest that gray matter deficits in the ventromedial prefrontal and anterior limbic cortices are common in both BD II and BD I. On the other hand, different pattern of gray matter abnormalities between BD II and BD I found in this study supports that two subtypes may have different neurobiological characteristics.     

Systematic review and voxel-based meta-analysis of diffusion tensor imaging studies in bipolar disorder

Background

Diffusion tensor imaging (DTI) studies have shown changes in the microstructure of white matter in bipolar disorder. Studies suggest both localised, predominantly fronto-limbic, as well as more widespread changes in white matter, but with some apparent inconsistency. A meta-analysis of white matter alterations in adults with bipolar disorder was undertaken.

Method

Whole-brain DTI studies comparing adults with bipolar disorder to healthy controls on fractional anisotropy (FA) were retrieved using searches of MEDLINE and EMBASE from between 2003 and December 2012. White-matter tract involvement was collated and quantified. Clusters of significantly altered FA were meta-analysed using effect-size signed differential mapping (ES-SDM).

Results

Ten VBA studies (252 patients and 256 controls) and five TBSS studies (138 patients and 98 controls) met inclusion criteria. Sixty-one clusters of significantly different FA between bipolar disorder and healthy controls were identified. Analysis of white-matter tracts indicated that all major classes of tracts are implicated. ES-SDM meta-analysis of VBA studies revealed three significant clusters of decreased FA in bipolar disorder (a right posterior temporoparietal cluster and two left cingulate clusters). Findings limited to the Bipolar Type I papers were more robust.

Limitations

Voxel-based studies do not accurately identify tracts, and our ES-SDM analysis used only published peak voxels rather than raw DTI data.

Conclusions

There is consistent data indicating widespread white matter involvement with decreased white matter FA demonstrated in three disparate areas in bipolar disorder. White matter alterations are not limited to anterior fronto-limbic pathways in bipolar disorder.     

Structural brain alterations in bipolar disorder II: A combined voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) study

Background

Brain structural changes have been described in bipolar disorder (BP), but usually studies focused on both I and II subtypes indiscriminately and investigated changes in either brain volume or white matter (WM) integrity. We used combined voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) analysis to track changes in the grey matter (GM) and WM in the brains of patients affected by BPII, as compared to healthy controls.

Methods

Using VBM and DTI, we scanned 20 DSM-IV-TR BPII patients in their euthymic phase and 21 healthy, age- and gender-matched volunteers with no psychiatric history.

Results

VBM showed decreases in GM of BPII patients, compared to controls, which were diffuse in nature and most prominent in the right middle frontal gyrus and in the right superior temporal gurus. DTI showed significant and widespread FA reduction in BPII patients in all major WM tracts, including cortico-cortical association tracts.

Limitations

The small sample size limits the generalisability of our findings.

Conclusions

Reduced GM volumes and WM integrity changes in BPII patients are not prominent like those previously reported in bipolar disorder type-I and involve cortical structures and their related association tracts.     

Sex dimorphism in gray/white matter volume and diffusion tensor during normal aging

The purpose of this study is to elucidate sex differences in global and regional gray/white matter volume, mean diffusivity (MD), and fractional anisotropy (FA) during normal aging using voxel‐based analysis. We studied 245 healthy right‐handed subjects with a wide range of ages (115 women, 22–70 years; 130 men, 21–71 years). Regarding global effects, inclusion of a quadratic age term improved the fit to data for white matter fraction and MD, but not for global gray matter volume/fraction or FA. Regarding regional effects, we found anterior‐dominant volume loss, FA decrease predominantly in the anterior white matter, and MD increase predominantly in perisylvian regions and periventricular white matter against age for both sexes. Compared with women, we found a steeper FA decline for men in the right inferior fronto‐temporal areas, extending to the anterior cingulate cortex, and an accelerated MD increase for men in the bilateral frontal, temporal, and parietal areas. There was no area in which interaction of sex with age was significant for regional volume, or in which a steeper FA decline or accelerated MD increase for women was significant. Our results provide strong evidence of sex dimorphism in global and focal diffusion characteristics during normal aging. Copyright © 2010 John Wiley & Sons, Ltd.     

Glial fibrillary acidic protein mRNA levels in the cingulate cortex of individuals with depression, bipolar disorder and schizophrenia

Recent studies have shown a decrease in glial number and glial fibrillary acidic protein (GFAP) levels in the frontal and cingulate cortices of individuals with mood disorders and schizophrenia. In an attempt to verify and expand these findings we examined GFAP messenger ribonucleic acid (mRNA) levels in postmortem sections of the anterior cingulate cortex (ACC) from the Stanley Neuropathology Consortium (SNC). The consortium consists of 15 cases in each of four groups (schizophrenia, bipolar disorder, non-psychotic depression and unaffected controls). By in situ hybridization, we found higher levels of GFAP mRNA in white matter and at the pial surface as compared with gray matter levels in all cases. In the white matter of ACC we detected a significant effect of diagnosis (P<0.04) with GFAP mRNA levels decreased in individuals with schizophrenia and bipolar disorder as compared with normal controls. In the gray matter there was a significant effect of layer (P<0.01) with the highest levels of GFAP mRNA in layer VI in all groups. As in the white matter, the mean GFAP mRNA levels were decreased in individuals with schizophrenia and bipolar disorder as compared with the unaffected controls, however the difference failed to reach statistical significance. Thus, astrocytes positive for GFAP may contribute to the decrease in glial density previously described in subjects with major mental illness, however the relative contribution of astrocytes may vary with diagnosis.     

Event related oscillations in euthymic patients with bipolar disorder

Bipolar disorder involves dysfunction in gamma amino butyric acid (GABA)/glutamatergic systems and neural circuits that regulate cognitive processing. Valproate, a mood stabilizing anticonvulsant, modulates GABA/glutamate and shows neuroprotective effect. Electroencephalographic oscillatory activity assessment is an alternative brain imaging technique with high time resolution. It presents integrative brain functioning. We aimed to assess the oscillatory responses of patients with bipolar disorder in euthymic state of bipolar disorder and the changes after treatment with valproate. Event related potentials to visual odd-ball paradigm in 10 euthymic medication free, bipolar patients were measured before and after 6 weeks of valproate monotherapy and compared with sex- and age-matched healthy controls. Delta frequency bands, as representative of signal detection and decision-making, were obtained by digital filtering. At baseline, patients showed higher delta responses to target stimuli in all but significantly left frontal channels in comparison to controls. After 6 weeks of treatment, delta responses decreased significantly in central frontal (Fz) (p: 0.028), left frontal (F3) (p: 0.028), left (T3) (p: 0.015), right anterior (T4) (p: 0.011), and left posterior temporal (T5) (p: 0.011) channels compared to baseline and became no different to the controls, which did not differ between two assessments. The findings point to a diffuse increase in low frequency electrical activity which was prominent in the left frontal location in euthymic patients with bipolar disorder. Reduction of the electrical activity of the left frontal and bilateral anterior temporal areas with treatment may be through modulation of glutamatergic and GABAergic mechanisms and indicative of valproate's neuroprotective effect.     

Brain structural changes in obstructive sleep apnea

STUDY OBJECTIVES: Determine whether obstructive sleep apnea (OSA) subjects show indications of axonal injury. DESIGN: We assessed fiber integrity in OSA and control subjects with diffusion tensor imaging (DTI). We acquired four whole-brain DTI series from each subject. The four series were realigned, and the diffusion tensor calculated at each voxel. Fractional anisotropy (FA), a measure of fiber integrity, was derived from the diffusion tensor, resulting in a whole brain FA "map." The FA maps were spatially normalized, smoothed, and compared using voxel-based statistics to determine differences between OSA and control groups, with age as a covariate (P < 0.05, corrected for multiple comparisons). SETTING: University medical center. SUBJECTS: We studied 41 patients with untreated OSA (mean age +/- SD: 46.3 +/- 8.9 years; female/male: 7/34) with apnea-hypopnea index 15 to 101 (mean +/- SD: 35.7 +/- 18.1 events/hour), and 69 control subjects (mean age +/- SD: 47.5 +/- 8.79 years; female/male: 25/44). MEASUREMENTS AND RESULTS: Multiple regions of lower FA appeared within white matter in the OSA group, and included fibers of the anterior corpus callosum, anterior and posterior cingulate cortex and cingulum bundle, right column of the fornix, portions of the frontal, ventral prefrontal, parietal and insular cortices, bilateral internal capsule, left cerebral peduncle, middle cerebellar peduncle and corticospinal tract, and deep cerebellar nuclei. CONCLUSIONS: White matter is extensively affected in OSA patients; the alterations include axons linking major structures within the limbic system, pons, frontal, temporal and parietal cortices, and projections to and from the cerebellum.     

Combined analyses of gray matter voxel-based morphometry and white matter tract-based spatial statistics in pediatric bipolar mania

Background

Ample evidence has suggested the presence of gray matter (GM) and white matter (WM) abnormalities in bipolar disorder (BD) patients, including pediatric bipolar disorder (PBD). However, little research has been done in PBD patients that carefully classify the mood states. The aim of the present study is to investigate the brain structural changes in PBD-mania children and adolescents.

Methods

Eighteen children and adolescents with bipolar mania (male/female, 6/12) aged 10–18 years old and 18 age- and sex-matched healthy controls were included in the present study. The 3D T1-weighted magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) data were obtained on a Siemens 3.0 T scanner. Voxel-based morphometry (VBM) analysis and tract-based spatial statistics (TBSS) analysis were conducted to compare the gray matter volume and white matter fractional anisotropy (FA) value between patients and controls. Correlations of the MRI data of each survived area with clinical characteristics in PBD patients were further analyzed.

Results

As compared with the control group, PBD-mania children showed decreased gray matter volume in the left hippocampus. Meanwhile, significant lower FA value was detected in the right anterior cingulate (AC) in the patient group. No region of increased gray matter volume or FA value was observed in PBD-mania. The hippocampal volume was negatively associated with the Young Mania Rating Scale (YMRS) score when controlling for clinical characteristics in PBD-mania patients, however, there was no significant correlation of FA value of the survived area with illness duration, the onset age, number of episodes, or the YMRS score in PBD-mania patients.

Limitation

The present outcomes require replication in larger samples and verification in medication free subjects.

Conclusions

Our findings highlighted that extensive brain structural lesions (including GM and WM) were existed in PBD-mania. The widespread occurrence of structural abnormalities mainly located in the anterior limbic network (ALN) which suggested that this network might contribute to emotional and cognitive dysregulations in PBD.     

Structural brain correlates of IQ changes in bipolar disorder

BACKGROUND: There is increasing evidence that cognitive deficits are present in bipolar disorder (BP), but their neural correlates have not been fully explored. The aim of this study is to correlate structural brain abnormalities with cognitive performance in BP and to explore differences between clinical subtypes. METHOD: Thirty-six BP patients (13 men, 23 women) with a mean age of 39 years (range 21-63 years) underwent neuropsychological testing and imaging. Twenty-five patients had bipolar disorder I (BP I) and 11 had bipolar disorder II (BP II). Patients with co-morbid psychiatric diagnosis, drug and alcohol abuse or systemic illness were excluded. Correlations between cognitive performance and structural brain changes were explored using high-resolution anatomical imaging and magnetization transfer imaging (MTI). RESULTS: In the whole BP group the difference between estimated pre-morbid IQ and current IQ was significantly correlated with left-sided reduction of the magnetization transfer ratio (MTR) in the superior temporal gyrus, uncus and para-hippocampal gyrus. In BP II patients the areas where these correlations were significant extended to the right superior and middle temporal gyri, cingulate gyrus, pre-cuneus and adjacent frontal and parietal white matter. The volume of superior temporal white matter was also correlated with IQ difference in this subgroup. CONCLUSIONS: The study highlights the association between fronto-temporal abnormalities and decline in IQ in BP. The more extensive abnormalities present in BP II patients suggest that persistent depression, rather than mania, may be a key pathophysiological factor or that BP II represents a clinical phenotype with a higher risk of developing cognitive abnormalities.     

White matter alterations in narcolepsy patients with cataplexy: tract‐based spatial statistics

Functional imaging studies and voxel‐based morphometry analysis of brain magnetic resonance imaging showed abnormalities in the hypothalamus–thalamus–orbitofrontal pathway, demonstrating altered hypocretin pathway in narcolepsy. Those distinct morphometric changes account for problems in wake–sleep control, attention and memory. It also raised the necessity to evaluate white matter changes. To investigate brain white matter alterations in drug‐naïve narcolepsy patients with cataplexy and to explore relationships between white matter changes and patient clinical characteristics, drug‐naïve narcolepsy patients with cataplexy (n = 22) and healthy age‐ and gender‐matched controls (n = 26) were studied. Fractional anisotropy and mean diffusivity images were obtained from whole‐brain diffusion tensor imaging, and tract‐based spatial statistics were used to localize white matter abnormalities. Compared with controls, patients showed significant decreases in fractional anisotropy of white matter of the bilateral anterior cingulate, fronto‐orbital area, frontal lobe, anterior limb of the internal capsule and corpus callosum, as well as the left anterior and medial thalamus. Patients and controls showed no differences in mean diffusivity. Among patients, mean diffusivity values of white matter in the bilateral superior frontal gyri, bilateral fronto‐orbital gyri and right superior parietal gyrus were positively correlated with depressive mood. This tract‐based spatial statistics study demonstrated that drug‐naïve patients with narcolepsy had reduced fractional anisotropy of white matter in multiple brain areas and significant relationship between increased mean diffusivity of white matter in frontal/cingulate and depression. It suggests the widespread disruption of white matter integrity and prevalent brain degeneration of frontal lobes according to a depressive symptom in narcolepsy.     

Klinefelter's syndrome (XXY) as a genetic model for psychotic disorders.

Males with an extra-X chromosome (Klinefelter's syndrome) frequently, although not always, have an increased prevalence of psychiatric disturbances that range from attention deficit disorder in childhood to schizophrenia or severe affective disorders during adulthood. In addition, they frequently have characteristic verbal deficits. Thus, examining brain magnetic resonance imaging (MRI) scans of these individuals may yield clues to the influence of X chromosome genes on brain structural variation corresponding to psychiatric and cognitive disorders. Eleven adult XXY and 11 age matched XY male controls were examined with a structured psychiatric interview, battery of cognitive tests, and an MRI scan. Ten of eleven of the XXY men had some form of psychiatric disturbance, four of whom had auditory hallucinations compared with none of the XY controls. Significantly smaller frontal lobe, temporal lobe, and superior temporal gyrus (STG) cortical volumes were observed bilaterally in the XXY men. In addition, diffusion tensor imaging (DTI) of white matter integrity resulted in four regions of reduced fractional anisotropy (FA) in XXY men compared with controls, three in the left hemisphere, and one on the right. These correspond to the left posterior limb of the internal capsule, bilateral anterior cingulate, and left arcuate bundle. Specific cognitive deficits in executive functioning attributable to frontal lobe integrity and verbal comprehension were noted. Thus, excess expression of one or more X chromosome genes influences both gray and white matter development in frontal and temporal lobes, as well as white matter tracts leading to them, and may in this way contribute to the executive and language deficits observed in these adults. Future prospective studies are needed to determine which gene or genes are involved and whether their expression could be modified with appropriate treatments early in life. Brain expressed genes that are known to escape inactivation on extra-X chromosomes would be prime candidates.     

Neural recruitment during failed motor inhibition differentiates youths with bipolar disorder and severe mood dysregulation

Controversy exists about whether non-episodic irritability (operationalized as severe mood dysregulation, SMD) should be considered a developmental presentation of pediatric bipolar disorder (BD). While assessments of brain function may address this controversy, only one fMRI study has compared BD versus SMD. We compared neural activation in BD, SMD, and controls during a motor inhibition task, since motor disinhibition is an important clinical feature in both BD and SMD. During failed inhibition, BD youths exhibited less activation in the right anterior cingulate cortex (ACC) and right nucleus accumbens relative to both SMD and healthy youths. Exploratory analyses indicate that, in BD youths, reduced activation in the right ACC may be independent of comorbid ADHD. These findings highlight neural distinctions between the phenotypically related BD and SMD populations.     

Major depressive disorder and white matter abnormalities: A diffusion tensor imaging study with tract-based spatial statistics

BackgroundA few diffusion tensor imaging (DTI) studies have shown abnormalities in areas of white matter tracts involved in mood regulation in geriatric depressive patients, using a region-of-interest technique. A voxel-based morphometry DTI study of young depressive patients reported similar results. In this study, we explored the structure of the white matter of the whole brain with DTI in middle-aged major depressive disorder (MDD) patients, using novel tract-based spatial statistics.MethodsSixteen MDD patients and 20 controls underwent DTI. An automated tract-based spatial method (TBSS) was used to analyze the scans.ResultsCompared with controls, the MDD patients showed a trend for lower values of fractional anisotropy (FA) in the left sagittal stratum, and suggestive decreased FA in the right cingulate cortex and posterior body of corpus callosum. Regressing out the duration and severity of disorder in the model did not change the finding in the sagittal stratum, but dissipated the decrease of FA in latter regions.LimitationsPossibly by reason of a relatively small study sample for a TBSS, the results are suggestive, and should be replicated in further studies.ConclusionsA novel observer-independent DTI method showed decreased FA in the middle-aged MDD patients in white matter regions that have previously connected to the emotional regulation. Lower FA might imply underlying structural abnormalities that contribute to the dysfunction detected in the limbic-cortical network of depressive patients.     

Association between prior alcohol use disorders and decreased prefrontal gray matter volumes in bipolar I disorder patients

Up to 50% of bipolar disorder (BD) patients present a lifetime diagnosis of alcohol use disorders (AUD). BD patients with comorbid AUD, even when in remission from the AUD, have a poorer outcome and functional impairment than patients with BD alone. The neurobiological abnormalities that potentially characterize this severe subgroup of BD patients are unknown. Our goal was to investigate gray matter (GM) volume abnormalities in BD I patients with comorbid AUD. Twenty-one BD-AUD patients, 21 BD-nonAUD BD patients, and 25 healthy controls (HC), matched by age, gender, and handedness were studied. The BD-AUD patients were in remission from AUD on average for 6.8 years. 3D SPGR MRIs (TR = 25 ms, TE = 5 ms, slice thickness = 1.5 mm) were acquired from all subjects using a 1.5 T GE Signa Imaging System. We used an optimized voxel-based morphometry protocol to compare GM volumes among the groups. BD-AUD patients presented smaller GM volumes in the left medial frontal and the right anterior cingulate gyri compared to BD-nonAUD patients. BDnon-AUD patients did not present GM volume differences compared to HC. These findings provide evidence for an effect of comorbid AUD on regional brain structure of BD I patients and warrant further research on neurobiological aspects of this prevalent and severe comorbidity.     

Changes of Brain Structure and Function in ADHD Children

To explore the changes of brain structure and function in attention-deficit/hyperactivity disorder (ADHD), fifteen ADHD patients (inattention subtype) and 15 normal control participants were recruited, the brain structure and function of these subjects were investigated by combining structural magnetic resonance imaging (MRI), diffusion tensor imaging and resting-state functional MRI. The results showed that ADHD patients had a significant decrease in the volume of the white matter (P?=?0.04), and a trend toward decreased volume of brain structures except for the putamen and globus pallidus. The visualization of statistical difference maps of the cortical thickness showed that ADHD patients had focal thinning in bilateral frontal regions and the right cingulate cortex (P?相似文献   

Improvements in white matter micro-structural integrity of right uncinate fasciculus and left fronto-occipital fasciculus of remitted first-episode medication-naïve panic disorder patients

Objective:

We designed this study to investigate neural correlates of white matter micro-structural integrity of remitted patients with first-episode, medication-naïve and very late-onset panic disorder

Method:

Twenty-one remitted patients with panic disorder completed treatment course with treatment of escitalopram (dose range around 10–15 mg/d). Twenty-one healthy controls were also enrolled into this study. Patients and controls all received 3-Tesla magnetic resonance imaging diffusion tensor imaging scanning at baseline and 6th week. We utilized FDT (FMRIB's Diffusion Toolbox v2.0) function of FSL (FMRIB Software Library) to calculate fractional anisotropy (FA). We compared FA values of patients and controls at baseline and 6th week to estimate the changes of FA of remitted patient group and inter-scan bias of controls. FA outputs of remitted patients and controls were compared by independent t test.

Results:

We found increased FA in some regions of right uncinate fasciculus and left fronoto-occipital fasciculus after remission in patient group (corrected p<0.05). Reduced FA of other regions of right uncinate fasciculus was still observed in remitted patients when they were compared to the control group.

Conclusion:

Subtle changes of white matter micro-structural integrity after remission might represent neural correlates of treatment effects for first-episode, medication-naïve and very late-onset panic disorder.     

White matter impairment in heroin addicts undergoing methadone maintenance treatment and prolonged abstinence: a preliminary DTI study

Methadone maintenance treatment (MMT) might cause the impairments of neuropsychological and neurotransmitter function in opioid addicts. Whether long-term MMT could lead to the impairment of white matter (WM) in heroin addiction brain is unclear. This study compared the WM integrity in the bilateral frontal lobe, temporal lobe, splenium and genu of corpus collasum (CC) between MMT patients (n=13), former heroin addicts (n=11) in prolonged abstinence (PA), and healthy control subjects (n=15) using diffusion tensor imaging (DTI). Fractional anisotropy (FA), apparent diffusion coefficient (ADC) and eigenvalues (λ(⊥), λ(||)) were measured. The correlation between DTI measures and accumulated former heroin dose, total methadone consumption, and PA duration were determined. Although the PA subjects showed no difference in DTI measures relative to the controls, the extensive correlations between the former heroin consumption and the DTI measures were noted. The MMT subjects showed a decreased FA values in the left genu, as well as the increased ADC and λ(⊥) values in the left splenium of CC in comparison to the controls. Compared with the PA, the MMT subjects had a significantly increased ADC value in the bilateral splenium of CC. Importantly, the methadone dosage used in the MMT group was correlated with the FA value in the left splenium of CC and in the right frontal lobe. Our preliminary results suggest that methadone plays a role in the impairment of WM integrity in heroin users on long-term MMT and the normalization of WM injury may occur during abstinence.     

White matter damage of patients with Alzheimer’s disease correlated with the decreased cognitive function

Increasing evidence demonstrates that there is marked damage and dysfunction in the white matter in Alzheimer’s disease (AD). The present study investigates the nature of white matter damage of patients with Alzheimer’s disease with diffusion tensor magnetic resonance imaging (DTI) and analyses the relationship between the white matter damage and the cognition function. DTI, as well as T1 fluid attenuated inversion recovery (FLAIR) and T2-FLAIR, was performed on probable patients of Alzheimer’s disease, and sex and age matched healthy volunteers to measure the fractional anisotropy (FA) and mean diffusivity (MD) in the genu and splenium of the corpus callosum, anterior and posterior limbs of the internal capsule, and the white matter of frontal, temporal, parietal, and occipital lobes. FA was lower in the splenium of corpus callosum, as well as in the white matter of the frontal, temporal, and parietal lobes from patients with Alzheimer’s disease than in the corresponding region from healthy controls and was strongly positive correlated with MMSE scores, whereas FA appeared no different in the anterior and posterior limbs of internal capsule, occipital lobes white matter, and the genu of corpus callosum between the patients and healthy controls. MD was significantly higher in the splenium of corpus callosum and parietal lobes white matter from patients than in that those from healthy controls and was strongly negative correlated with MMSE scores, whereas MD in the anterior and posterior limbs of internal capsule, as well as in frontal, temporal, occipital lobes white matter and the genu of corpus callosum, was not different between the patients and healthy controls. The most prominent alteration of FA and MD was in the splenium of corpus callosum. Our results suggested that white matter of patients with Alzheimer’s disease was selectively impaired and the extent of damage had a strong correlation with the cognitive function, and that selective impairment reflected the cortico–cortical and cortico–subcortical disconnections in the pathomechanism of Alzheimer’s disease. The values of FA and MD in white matter, especially in the splenium of corpus callosum in AD patients, might be a more appropriate surrogate marker for monitoring the disease progression.     

Aging in the CNS: comparison of gray/white matter volume and diffusion tensor data

This study investigated the global and regional effects of aging on brain volume, mean diffusivity (MD), and fractional anisotropy (FA) in 73 normal female subjects using voxel-based analysis. On a global scale, gray matter volume and FA were negatively correlated, whereas MD was positively correlated with age. Voxel-wise analyses showed brain volume and FA were negatively correlated predominantly in anterior structures, whereas MD was positively correlated in the cortical gray matter and periventricular white matter. Volume preservation was observed in the cingulate gyrus and subjacent white matter. FA increase was observed in the putamen. Voxel-based direct comparisons of volume and diffusion properties showed FA was more strongly negatively correlated in the fronto-temporal white matter, compared with volume and MD. Stronger positive correlation of MD was observed in the thalamus, caudate nucleus, and midbrain and stronger negative correlation of brain volume was observed in the frontal lobe and basal ganglia, compared with the other. These results indicate that diffusion properties and brain volume are complementary markers to the effects of aging.     

Anatomical measurements of the orbitofrontal cortex in child and adolescent patients with bipolar disorder

Imaging studies indicate smaller orbitofrontal cortex (OFC) volume in mood disorder patients compared with healthy subjects. We sought to determine whether child and adolescent patients with bipolar disorder have smaller OFC volumes than healthy controls. Fourteen children and adolescents meeting DSM-IV criteria for bipolar disorder (six males and eight females with a mean age+/-S.D.=15.5+/-3.2 years) and 20 healthy controls (11 males and nine females with mean age+/-S.D.=16.9+/-3.8 years) were studied. Orbitofrontal cortex volume was measured using magnetic resonance imaging. Male bipolar patients had smaller gray matter volumes in medial (p=0.044), right medial (0.037) and right (p=0.032) lateral OFC subdivisions compared to male controls. In contrast, female patients had larger gray matter volumes in left (p=0.03), lateral (p=0.012), left lateral (p=0.007), and trends for larger volumes in right lateral and left medial OFC subdivisions compared with female controls. Male patients exhibit smaller gray matter volumes, while female patients exhibit larger volumes in some OFC sub-regions. Gender differences in OFC abnormalities may be involved in illness pathophysiology among young bipolar patients.