Hippocampus anatomy sagittal mri
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Recent interest in the subgenual cingulate gyrus (Brodmann area 25: BA25) as a deep brain stimulation (DBS) target for depression has triggered a wealth of neuroimaging research based on the hypothesis that BA25 and the white matter underlying it may represent a key central node of corticolimbic communication that underlies the pathophysiology of depression. White Matter Tracts Deep to the Subgenual Cingulate Gyrus One temporal ROI (blue shading) was placed over the left temporal lobe white matter stem, and a second subcaudate ROI (red shading) was placed over the subcaudate white matter. b Regions of interest (ROIs): 2 customized ovoid coronal plane ROIs used to seed the uncinate fasciculus overlaid onto an individual subject’s coronal T1-weighted anatomical image. Ī Anatomical structures: coronal T1-weighted anatomical image demonstrating the important anatomical structures surrounding the uncinate fasciculus including the medial temporal lobe, insula, and subgenual cingulate gyrus. Upon arrival in the prefrontal region, the traditional description has been a division into 2 prefrontal stems, extending to the lateral orbital gyri and the frontopolar cortex, respectively. From here the tract runs medially to the insula and ventrally/inferiorly to the head of the caudate nucleus (a location that would have likely been targeted in the once performed subcaudate tractotomy) – see Figure 1a.
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The temporal component connects with the uncus, anterior temporal pole, and basolateral amygdala, and extends posteriorly/caudally prior to the U-shaped hook. Structurally, the UF has a hook-shaped morphology that curves around the posterior insula within the temporal stem. In addition, the UF is one of the last association tracts to completely mature, with final myelination extending from the second and late into the third decade of life, corresponding to the age of onset of many of the implicated psychiatric conditions. Numerous studies have demonstrated reduced connectivity in the UF across a range of neuropsychiatric conditions including mood disorders, anxiety disorders, psychotic disorders, antisocial personality disorder/psychopathy, and in the frontotemporal dementias. Functionally, the UF is considered key in the prefrontal inhibition of the mesial temporal lobe structures.
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The uncinate fasciculus (UF) is the largest white matter association tract connecting the prefrontal cortex with the anteromedial temporal lobe. A probable medial subgenual prefrontal stem of the uncinate fasciculus was demonstrated in a cohort of healthy volunteers and is of potential significance in our understanding of neuropsychiatry and mood disorders. The medial subgenual stem fibers were inseparable from the caudal body and temporal stem of the main uncinate fasciculus and followed the same hook-shaped morphology. A medial prefrontal stem extending to the subgenual cingulate gyrus was demonstrated in 65/74 left and 70/74 right cerebral hemispheres, and had a mean fractional anisotropy value of 0.43 (95% CI 0.40–0.47). Using diffusion tensor imaging in 74 healthy volunteer humans, we seeded the uncinate fasciculus using 2 regions of interest centered over the temporal stem and the caudal body of the uncinate fasciculus in the coronal plane at the level of the anterior commissure. We hypothesized that these fibers represent a third, medial prefrontal stem of the uncinate fasciculus. Recent imaging studies of the white matter tracts deep to the subgenual cingulate gyrus (Brodmann area 25: BA25) suggest the presence of white matter fibers extending from BA25 to the amygdala, via a route that would run in close proximity to the uncinate fasciculus, that are of functional importance in mood disorders.
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The traditional anatomical description outlines a temporal stem that hooks around the posterior insula, a subinsular body, and 2 prefrontal stems extending to the lateral orbital gyri and the frontopolar cortex. The uncinate fasciculus is the largest white matter association tract connecting the prefrontal cortex and the anteromedial temporal lobe.