Auditory Areas
Thalamocortical axons project primarily from the Medial geniculate Body (MGB) via sublenticular region of the internal capsule and terminate in an organized topographic manner in the transverse temporal gyri of Heschl. MGBm radiations terminate in specific locations while TC fibers from the MGBv terminate in nonspecific clusters of cells and form collateral connections to neighboring cells. Research done by staining the brains of macaque monkeys reveals projections from the ventral nucleus mainly terminating in layers IV and IIIB, with some nonspecific clusters of PIR cells terminating in layers I, II, IIIA, and VI. Fibers from the dorsal nuclei were found to project more directly to the primary auditory area, with most axons terminating in layer IIIB. The magnocellular nucleus projected a small amount of PIR cells with axons mainly terminating in layer 1, though large regions of the middle cortical layers were innervated through collaterally connected CIR neurons. Past research suggests that the thalamocortical-auditory pathway may be the only neural correlate that can explain a direct translation of frequency information to the cortex via specific pathways.
Read more about this topic: Thalamocortical Radiations
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