The Fourth Asian Conference on Vision (ACV2006)i¼]j

Differences of Dendritic Morphology of Layer III Pyramidal Cells among Cortical Areas in Infant Monkeys
Koji Ikezoe1, Guy N Elston2, 3, Tomofumi Oga4, Hiroshi Tamura3, 5, Ichiro Fujita3, 5
1Graduate School of Engineering Science, Osaka University, Osaka Japan
2 Centre for Cognitive Neuroscience, Australia
3Core Research for Evolutional Science and Technology, JST, Japan
4School of Engineering Science, Osaka University, Osaka Japan
5Graduate School of Frontier Biosciences, Osaka University, Osaka Japan

1. Introduction
Layer III pyramidal cells in adult monkeys exhibit systematic difference in their dendritic morphology among cortical areas. Basal dendrites of cells in visual association cortex such as inferior temporal area TE spread more extensively and are more branched than those in the primary visual cortex (V1). Pyramidal cells in prefrontal cortex, such as area 12, have even more dendritic branches than those in area TE. Here, we investigated whether a similar regional difference in the dendritic morphology was present in infant monkeys.

2. Materials and Methods
We stained individual layer III pyramidal cells in V1 (n=45), area TE (n=42), and area 12 (n=43) of a 3-week old monkey (Macaca fascicularis) using intracellular dye-injection techniques in lightly fixed tissues.

3. Results
The number of branches of basal dendrites was greatest in area 12, followed by area TE, and V1.
The tangential extent had a similar tendency with the number of branches. The tangential extent of V1 cells was greater than that of adults. However, in TE and area 12, the tangential extent was smaller than that of adults.

4. Discussion
Thus, heterogeneity in pyramidal cell dendrites already exists 3-weeks after birth. The results further suggest that developmental processes after this period also differ among the cortical areas.

Examples of reconstructed layer III pyramidal cells in V1, TE and area 12. Only the basal dendrites are drawn. Scale bar = 100ƒÊm

Acknowledgement This research was supported by CREST, JST (Japan) & NHMRC (Australia).
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