Synaptic and intrinsic mechanisms underlying development of cortical direction selectivity

Modifications of synaptic inputs and cell-intrinsic properties both contribute to neuronal plasticity and development. To better understand these mechanisms, we undertook an intracellular analysis of the development of direction selectivity in the ferret visual cortex, which occurs rapidly over a few days after eye opening. We found strong evidence of developmental changes in linear spatiotemporal receptive fields of simple cells, implying alterations in circuit inputs. Further, this receptive field plasticity was accompanied by increases in near-spike-threshold excitability and input-output gain that resulted in dramatically increased spiking responses in the experienced state. Increases in subthreshold membrane responses induced by the receptive field plasticity and the increased input-output spiking gain were both necessary to explain the elevated firing rates in experienced ferrets. These results demonstrate that cortical direction selectivity develops through a combination of plast...突触输入与细胞内在特性的改变，均参与神经元可塑性与神经系统发育进程。为深入阐明此类机制，我们针对雪貂视觉皮层内方向选择性的发育开展了细胞内分析——该方向选择性于动物睁眼后数日内快速形成。研究发现，视觉皮层简单细胞的线性时空感受野存在显著的发育性变化，提示其上游神经环路输入发生了重塑。此外，此类感受野可塑性伴随近动作电位阈值兴奋性与输入输出增益的提升，最终使觉醒状态下的动作电位发放响应显著增强。由感受野可塑性诱导的阈下膜反应增强，以及输入输出放电增益的提升，二者均为解释觉醒雪貂皮层放电频率升高的必要条件。本研究结果表明，皮层方向选择性的发育是通过协同的可塑性机制