大脳皮質の単位回路

The Basic Modules of the Neocortex

大脳皮質に単位回路が繰り返した構造があるかは不明だった。われわれはさまざまな皮質領野において第Ⅴ層の神経細胞が細胞タイプ特異的なクラスター（マイクロカラム）を形成し六方格子状に並ぶことを見出した。マイクロカラムの細胞は共通な神経入力を持ち，類似した神経活動を示した。これらは第Ⅴ層がマイクロカラムを単位とした繰返し構造を持つことを示し，多数のマイクロカラムによる並列処理が多様な皮質機能を担うことを示唆する。

Abstract

The mammalian neocortex contains diverse cell types but whether they organize into repeated modular circuits remains unknown. We discovered that major cell types in neocortical layer 5 form a lattice structure in many areas of the brain. Large-scale three-dimensional imaging revealed that distinct types of excitatory and inhibitory neurons form cell type-specific radial clusters termed microcolumns. Microcolumns form a hexagonal lattice tessellating a wide region of the neocortex. Neurons within individual microcolumns exhibit synchronized in vivo activity and visual responses with similar orientation preference and ocular dominance. During early postnatal development, microcolumns are coupled by cell type-specific gap junctions and later received convergent synaptic inputs. Thus, layer 5 neurons organize into a brain-wide modular system providing a template for cortical processing.