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Quarter Century after the Direct and Indirect Pathways: Towards Comprehensive Understandings of the Basal Ganglia

開催日 2014/9/13
時間 9:00 - 11:00
会場 Room B(501)
Chairperson(s) 南部 篤 / Atsushi Nambu (生理学研究所 生体システム研究部門 / Division of System Neurophysiology, National Institute for Physiological Sciences, Japan)
藤山 文乃 / Fumino Fujiyama (同志社大学・脳科学研究科 / Laboratory of Neural Circuitry, Graduate School of Brain Science, Doshisha University, Kyoto, Japan)

Anatomical aspect of the basal ganglia circuitry, in relation to cortical projection

  • S3-B-1-2
  • 苅部 冬紀 / Fuyuki Karube:1,2 藤山 文乃 / Fumino Fujiyama:1,2 
  • 1:同志社大学・脳科学研究科 / Graduate School of Brain Science, Doshisha University, Kyoto, Japan 2:CREST, JST / CREST, JST, Tokyo, Japan 

The concept of "direct/indirect pathways" has been widely accepted as an attractive model of the basal ganglia (BG). However, recent experiments have bit by bit challenged this model, promoting to request researches on more minute neural circuits to explain actual complicated behaviors.
Here we re-examined anatomical circuitry of the rodent BG, focusing on cortical projections and subregions of the each BG nucleus. Cortex provides massive excitatory inputs to the striatum and subthalamic nucleus (STN), and strongly affects the BG circuitry. Calcium binding protein calbindin-D28K (CB) is known to be expressed heterogeneously among striatal projection neurons, showing CB-immunopositive (matrix) and immunonegative (patch) components. Globus pallidus external segment (GPe) can be also divided into CB-expression subregions that reflect the striato-pallidal terminal distribution. Thus, here we used CB immunohistochemistry to identify the subregions of the nuclei to uncover how multiple cortical areas relate to the BG circuitry.
Firstly, we found that the primary motor, secondary motor, and non-motor area differentially innervated both the striatum and STN. The cortico-striatal terminal distribution partially related to the CB expression pattern of the striatum. Secondary, the pallidal projection was evaluated by a small injection of a neural tracer in the CB-subregions of GPe. Each GPe subregion possessed characteristic projection patterns toward both up- and down-streams of the BG. Single cell reconstructions by a viral infection supported this view. In addition, STN subregions distinguished by either cortical or GPe innervation patterns seemed to be well matched with each other, namely, the STN subregions innervated by the frontal (no-motor) cortical area mainly received pallidal projections from the CB-immunopositive GPe, whereas the central STN subregion was often innervated by the primary motor cortex and the CB-immunonegative GPe subregion.
These data suggest that topographic organization of cortico-BG projections could well correlated with that of the intra- BG micro circuitry. These correlated circuits could contribute to control coordinated behaviors efficiently.

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