生长期视觉皮层柱状结构的重组
Reorganization of columnar architecture in the growing visual cortex
摘要：
在出生后的发育过程中，许多皮质区域的大小会显著增加，逐渐使神经元细胞体相互移位。目前，人们对皮质生长如何影响神经回路的发育知之甚少。在这里，在急性和慢性实验中，我们研究的布局视觉优势（OD）列猫初级视觉皮层（V1）在一段时间内的大量出生后的增长。我们发现，尽管V1的相当大的尺寸增加，列之间的间距在很大程度上被保留。相反，它们的空间布局在这一时期发生了系统性的变化。而在年轻的动物列更带状，布局变得更加各向同性的成熟动物。我们提出了一种新的机制，生长诱导的重组是基于“之字形不稳定性”，在几个无生命的图案形成系统中观察到的动态不稳定性。我们认为，这种机制是固有的广泛的一类模型的活动依赖的OD列的形成。分析这个类的一个成员，弹性网络模型，我们表明，这种机制可以解释的列间距的保存和我们观察到的OD列的重组的特定模式。我们的结论是，神经元系统转移其选择性在正常的发展过程中，这种重组是由生长过程中的皮质扩张。我们的工作表明，皮层回路在发育过程中保持可塑性很长一段时间，以促进神经元回路的修改，以适应皮层的生长。
英文摘要：
Many cortical areas increase in size considerably during postnatal development, progressively displacing neuronal cell bodies from each other. At present, little is known about how cortical growth affects the development of neuronal circuits. Here, in acute and chronic experiments, we study the layout of ocular dominance (OD) columns in cat primary visual cortex (V1) during a period of substantial postnatal growth. We find that despite a considerable size increase of V1, the spacing between columns is largely preserved. In contrast, their spatial arrangement changes systematically over this period. While in young animals columns are more band-like, layouts become more isotropic in mature animals. We propose a novel mechanism of growth-induced reorganization that is based on the `zigzag instability', a dynamical instability observed in several inanimate pattern forming systems. We argue that this mechanism is inherent to a wide class of models for the activity-dependent formation of OD columns. Analyzing one member of this class, the Elastic Network model, we show that this mechanism can account for the preservation of column spacing and the specific mode of reorganization of OD columns that we observe. We conclude that neurons systematically shift their selectivities during normal development and that this reorganization is induced by the cortical expansion during growth. Our work suggests that cortical circuits remain plastic for an extended period in development in order to facilitate the modification of neuronal circuits to adjust for cortical growth.
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