Longitudinal MRI study of cortical thickness, perfusion, and metabolite levels in major depressive disorder

Low docosahexaenoic acid status is associated with reduced indices in cortical integrity in the anterior cingulate of healthy male children: a 1H MRS Study

Docosahexaenoic acid (DHA, 22:6n-3) is the principal omega-3 fatty acid in mammalian brain gray matter, and emerging preclinical evidence suggests that DHA has neurotrophic and neuroprotective properties. This study investigated relationships among DHA status, neurocognitive performance, and cortical metabolism measured with proton magnetic resonance spectroscopy (1H MRS) in healthy developing male children (aged 8-10 years, n = 38). Subjects were segregated into low-DHA (n = 19) and high-DHA (n = 19) status groups by a median split of erythrocyte DHA levels. Group differences in 1H MRS indices of cortical metabolism, including choline (Cho), creatine (Cr), glutamine + glutamate + γ-aminobutyric acid (Glx), myo-inositol (mI), and n-acetyl aspartate (NAA), were determined in the right and left dorsolateral prefrontal cortex (R/L-DLPFC, BA9) and bilateral anterior cingulate cortex (ACC, BA32/33). Group differences in neurocognitive performance were evaluated with the Kaufman Brief Intelligence Test and identical-pairs version of the continuous performance task (CPT-IP). Subjects in the low-DHA group consumed fish less frequently (P = 0.02), had slower reaction times on the CPT-IP (P = 0.007), and exhibited lower mI (P = 0.007), NAA (P = 0.007), Cho (P = 0.009), and Cr (P = 0.01) concentrations in the ACC compared with the high-DHA group. There were no group differences in ACC Glx or any metabolite in the L-DLPFC and R-DLPFC. These data indicate that low-DHA status is associated with reduced indices of metabolic function in the ACC and slower reaction time during sustained attention in developing male children.

Altered cerebral perfusion in executive, affective, and motor networks during adolescent depression

OBJECTIVE

Although substantial literature has reported regional cerebral blood flow (rCBF) abnormalities in adults with depression, these studies commonly necessitated the injection of radioisotopes into subjects. The recent development of arterial spin labeling (ASL), however, allows noninvasive measurements of rCBF. Currently, no published ASL studies have examined cerebral perfusion in adolescents with depression. Thus, the aim of the present study was to examine baseline cerebral perfusion in adolescent depression using a newly developed ASL technique: pseudocontinuous arterial spin labeling (PCASL).

METHOD

A total of 25 medication-naive adolescents (13-17 years of age) diagnosed with major depressive disorder (MDD) and 26 well-matched control subjects underwent functional magnetic resonance imaging. Baseline rCBF was measured via a novel PCASL method that optimizes tagging efficiency.

RESULTS

Voxel-based whole brain analyses revealed significant frontal, limbic, paralimbic, and cingulate hypoperfusion in the group with depression (p < .05, corrected). Hyperperfusion was also observed within the subcallosal cingulate, putamen, and fusiform gyrus (p < .05, corrected). Similarly, region-of-interest analyses revealed amygdalar and insular hypoperfusion in the group with depression, as well as hyperperfusion in the putamen and superior insula (p < .05, corrected).

CONCLUSIONS

Adolescents with depression and healthy adolescents appear to differ on rCBF in executive, affective, and motor networks. Dysfunction in these regions may contribute to the cognitive, emotional, and psychomotor symptoms commonly present in adolescent depression. These findings point to possible biomarkers for adolescent depression that could inform early interventions and treatments, and establishes a methodology for using PCASL to noninvasively measure rCBF in clinical and healthy adolescent populations.

The vascular depression hypothesis: mechanisms linking vascular disease with depression

The 'Vascular Depression' hypothesis posits that cerebrovascular disease may predispose, precipitate or perpetuate some geriatric depressive syndromes. This hypothesis stimulated much research that has improved our understanding of the complex relationships between late-life depression (LLD), vascular risk factors, and cognition. Succinctly, there are well-established relationships between LLD, vascular risk factors and cerebral hyperintensities, the radiological hallmark of vascular depression. Cognitive dysfunction is common in LLD, particularly executive dysfunction, a finding predictive of poor antidepressant response. Over time, progression of hyperintensities and cognitive deficits predicts a poor course of depression and may reflect underlying worsening of vascular disease. This work laid the foundation for examining the mechanisms by which vascular disease influences brain circuits and influences the development and course of depression. We review data testing the vascular depression hypothesis with a focus on identifying potential underlying vascular mechanisms. We propose a disconnection hypothesis, wherein focal vascular damage and white matter lesion location is a crucial factor, influencing neural connectivity that contributes to clinical symptomatology. We also propose inflammatory and hypoperfusion hypotheses, concepts that link underlying vascular processes with adverse effects on brain function that influence the development of depression. Testing such hypotheses will not only inform the relationship between vascular disease and depression, but also provide guidance on the potential repurposing of pharmacological agents that may improve LLD outcomes.

Clinical applications of arterial spin labeling

MR arterial spin labeling is primarily applied as a neuroimaging method to measure cerebral blood flow. As this technique becomes more widely available, a basic understanding of the clinical applications is necessary for optimal utilization in the setting of patient care. This review focuses on the use of arterial spin labeling imaging for the evaluation of cerebrovascular disease, brain tumors and neuropsychiatric illness.

Novel biomarkers in major depression

PURPOSE OF REVIEW

This article reviews literature published over the period January 2011-June 2012 on biomarkers in major depression.

RECENT FINDINGS

Although a large body of research accumulated over the past decades points to distinct biological mechanisms being involved in the pathophysiology of major depressive disorder (MDD), its precise pathobiology is not yet fully understood. In the last 2 years, substantial new research has been generated in an attempt to identify and characterize novel candidate biomarkers for MDD. This review provides an update on biomarker research in MDD and summarizes the most recent results from neuroimaging, genetic, epigenetic, and neurochemical studies in MDD.

SUMMARY

Promising new findings report high diagnostic accuracy for metabonomic and epigenetic approaches as well as combinatorial functional neuroimaging approaches, which are currently representing the forefront of MDD biomarker development.

Correlating anterior insula gray matter volume changes in young people with clinical and neurocognitive outcomes: an MRI study

BACKGROUND

The anterior insula cortex is considered to be both the structural and functional link between experience, affect, and behaviour. Magnetic resonance imaging (MRI) studies have shown changes in anterior insula gray matter volume (GMV) in psychosis, bipolar, depression and anxiety disorders in older patients, but few studies have investigated insula GMV changes in young people. This study examined the relationship between anterior insula GMV, clinical symptom severity and neuropsychological performance in a heterogeneous cohort of young people presenting for mental health care.

METHODS

Participants with a primary diagnosis of depression (n = 43), bipolar disorder (n = 38), psychosis (n = 32), anxiety disorder (n = 12) or healthy controls (n = 39) underwent structural MRI scanning, and volumetric segmentation of the bilateral anterior insula cortex was performed using the FreeSurfer application. Statistical analysis examined the linear and quadratic correlations between anterior insula GMV and participants' performance in a battery of clinical and neuropsychological assessments.

RESULTS

Compared to healthy participants, patients had significantly reduced GMV in the left anterior insula (t = 2.05, p = .042) which correlated with reduced performance on a neuropsychological task of attentional set-shifting (ρ = .32, p = .016). Changes in right anterior insula GMV was correlated with increased symptom severity (r = .29, p = .006) and more positive symptoms (r = .32, p = .002).

CONCLUSIONS

By using the novel approach of examining a heterogeneous cohort of young depression, anxiety, bipolar and psychosis patients together, this study has demonstrated that insula GMV changes are associated with neurocognitive deficits and clinical symptoms in such young patients.

Distinct neurometabolic profiles are evident in the anterior cingulate of young people with major psychiatric disorders

Currently, there are no validated neurobiological methods for distinguishing different pathophysiological pathways in young patients presenting in the early phases of major psychiatric disorders. Hence, treatments are delivered simply on the basis of their possible effects on nonspecific symptom constructs such as depression, cognitive change or psychotic symptoms. In this study, the ratios (relative to creatine) of key metabolites (N-acetyl aspartate, myoinositol, glutamate and glutathione) were measured with proton magnetic resonance spectroscopy ((1)H-MRS) within the anterior cingulate cortex of 88 young persons presenting with major mood or psychotic symptoms. We derived empirically (using a cluster analytical technique) three subgroups of subjects on the basis of their patterns of in vivo brain biochemistry. The three subgroups were distinguished (from each other) by all the four metabolites, in particular, glutathione and glutamate. By contrast, the groups could not be distinguished by differences in terms of other demographic, functional or clinical measures. We propose that this (1)H-MRS-based subclassification system could be used as the basis for much more specific tests of novel intervention strategies (notably, antioxidant and glutamatergic therapies) early in the course of major psychiatric disorders.