TY - JOUR
T1 - Patchy and laminar terminations of medial geniculate axons in monkey auditory cortex
AU - Hashikawa, T.
AU - Molinari, M.
AU - Rausell, E.
AU - Jones, E. G.
PY - 1995
Y1 - 1995
N2 - The object of this study was to identify the terminal distributions of thalamocortical axons arising in chemically characterized subdivisions of the medial geniculate complex. Large injections of wheat germ agglutinin- conjugated horseradish peroxidase or small injections of Phaseolus vulgaris leucoagglutinin were made in the medial geniculate complex of Macaca fuscata. The terminal distributions of labeled axons in the cortex were correlated with auditory cortical fields demonstrable by different intensities of immunoreactivity for parvalbumin. Fibers from the ventral nucleus terminated mainly in layer IV and deep portion of layer III (IIIB), with additional terminations in layers I-IIIA and in layer VI. In layers IIIB-IV, a major terminal plexus was formed by a small number of dense patches, 300-500 μm in diameter, surrounded by smaller satellite patches. The patches conformed to a similarly lobulated pattern of parvalbumin fiber immunoreactivity. Terminations of some individually labeled thalamocortical fibers were restricted to a single patch, whereas others innervated more than one patch by collateral branches. Fibers from the dorsal nuclei ending in areas of less dense parvalbumin immunoreactivity surrounding the primary auditory cortex formed much larger terminal patches centered largely in layer IIIB. Fibers from the magnocellular nucleus had relatively few terminal branches but innervated extremely wide areas by collaterals of single axons. Two types of axons arose from the magnocellular nucleus, one terminating preferentially in middle cortical layers and the other exclusively in layer I. These may arise respectively from parvalbumin- and calbindin-immunoreactive cell populations in the magnocellular nucleus.
AB - The object of this study was to identify the terminal distributions of thalamocortical axons arising in chemically characterized subdivisions of the medial geniculate complex. Large injections of wheat germ agglutinin- conjugated horseradish peroxidase or small injections of Phaseolus vulgaris leucoagglutinin were made in the medial geniculate complex of Macaca fuscata. The terminal distributions of labeled axons in the cortex were correlated with auditory cortical fields demonstrable by different intensities of immunoreactivity for parvalbumin. Fibers from the ventral nucleus terminated mainly in layer IV and deep portion of layer III (IIIB), with additional terminations in layers I-IIIA and in layer VI. In layers IIIB-IV, a major terminal plexus was formed by a small number of dense patches, 300-500 μm in diameter, surrounded by smaller satellite patches. The patches conformed to a similarly lobulated pattern of parvalbumin fiber immunoreactivity. Terminations of some individually labeled thalamocortical fibers were restricted to a single patch, whereas others innervated more than one patch by collateral branches. Fibers from the dorsal nuclei ending in areas of less dense parvalbumin immunoreactivity surrounding the primary auditory cortex formed much larger terminal patches centered largely in layer IIIB. Fibers from the magnocellular nucleus had relatively few terminal branches but innervated extremely wide areas by collaterals of single axons. Two types of axons arose from the magnocellular nucleus, one terminating preferentially in middle cortical layers and the other exclusively in layer I. These may arise respectively from parvalbumin- and calbindin-immunoreactive cell populations in the magnocellular nucleus.
KW - cortical columns
KW - hearing
KW - parallel auditory pathways
KW - single axons
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U2 - 10.1002/cne.903620204
DO - 10.1002/cne.903620204
M3 - Article
C2 - 8576433
AN - SCOPUS:0028857084
VL - 362
SP - 195
EP - 208
JO - Journal of Comparative Neurology
JF - Journal of Comparative Neurology
SN - 0021-9967
IS - 2
ER -