Tuesday, February 8, 2011

Uncinate Fasciculus

The uncinate fasciculus is a band of cortical neuron myelinated axons in the human brain that connects the inferior part of the frontal lobe with the anterior temporal lobe and parts of the limbic system, such as the hippocampus and amygdala that are located in this lobe. It is the last fasciculus to mature in the brain (beyond the age of 30). The average length of the uncinate fasciculus is 45 mm. It has three parts: a frontal extension, an intermediary segment, and a temporal segment. The uncinate fasciculus is a hook-shaped tract of fibers which go from the inferior frontal gyrus and the lower surfaces of the frontal lobe to the forward portions of the temporal lobe.

Uncinate Fasciculus and Schizophrenia

Evidence suggests that a disruption in connectivity between different brain regions, especially between the frontal and temporal lobes, linked up by the uncinate fasciculus, may partly explain some of the primary symptoms of schizophrenia. This idea, first proposed by Wernicke in 1906, posits a disturbance in functional connectivity between the frontal and temporal cortices in schizophrenia that might have as its basis a disruption in the white matter tracts connecting them. Abnormalities within the fiber bundles of the uncinate fasciculus associate with social anxiety, Alzheimer's disease, bipolar disorder, and depression in the elderly that had first had it in adolescence or early adulthood. Such abnormalities also link to schizophrenia.