Anxiety Disorders: Trimble M

Drevets WC, Savitz J, Trimble M. · Section on Neuroimaging in Mood and Anxiety Disorders, Molecular Imaging Branch, National Institute of Mental Health, Bethesda, MD, USA. · CNS Spectr. · Pubmed #18704022 links to  free full text

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

Zahm DS, Trimble M. · Saint Louis University School of Medicine, Department of Pharmacological and Physiological Science, St Louis, MO 63104, USA. · CNS Spectr. · Pubmed #18204412 links to  free full text

Abstract: This review begins with a description of some problems that recently have beset an influential circuit model of fear conditioning and goes on to look at neuroanatomy that may subserve conditioning viewed in a broader perspective, including not only fear but also appetitive conditioning. The column will then focus on basal forebrain functional-anatomical systems, or macrosystems, as they have come to be called. Yet, more specific attention is then given to the relationships of the dorsal and ventral striatopallidal systems and extended amygdala with the dopaminergic mesotelencephalic projection systems, culminating with the hypothesis that all macrosystems contribute to behavioral conditioning.