Kiley Caitlin W, Usrey W Martin
Center for Neuroscience, University of California, Davis, California 95618.
Center for Neuroscience, University of California, Davis, California 95618
J Neurosci. 2017 Nov 29;37(48):11549-11558. doi: 10.1523/JNEUROSCI.3762-16.2017. Epub 2017 Oct 24.
Neural circuits and the cells that comprise them undergo developmental changes in the spatial organization of their connections and in their temporal response properties. Within the lateral geniculate nucleus (LGN) of the dorsal thalamus, these changes have pronounced effects on the spatiotemporal receptive fields (STRFs) of neurons. An open and unresolved question is how STRF maturation affects stimulus-evoked correlated activity between pairs of LGN neurons during development. This is an important question to answer because stimulus-evoked correlated activity likely plays a role in establishing the specificity of thalamocortical connectivity and the receptive fields (RFs) of postsynaptic cortical neurons. Using multielectrode recording methods and white noise stimuli, we recorded neural activity from ensembles of LGN neurons in cats across early development. As expected, there was a progressive maturation of the spatial and temporal properties of visual responses. Using drifting bar stimuli and cross-correlation analysis, we also determined the orientation-tuning bandwidth of correlated activity between pairs of LGN neurons at different stages of development (Sillito and Jones, 2002; Andolina et al., 2007; Stanley et al., 2012; Kelly et al., 2014). Despite the larger RFs and slower responses of immature LGN neurons compared with mature neurons, our results show that correlated activity in the LGN was as tightly tuned for orientation early in development as it was in the adult. Closer examination revealed this age-invariant orientation tuning of correlated activity likely involves cellular mechanisms related to spike fatigue in young animals and a progressive decrease in response latency with development. Orientation tuning is a fundamental property of neurons in primary visual cortex. An important and unresolved question is how orientation tuning emerges during brain development. This study explores a potential mechanism for the establishment of orientation tuning based on correlated activity patterns among ensembles of maturing neurons in the lateral geniculate nucleus (LGN) of the thalamus. Results show that correlated activity between pairs of LGN neurons is more tightly tuned than predictions based simply on receptive field size, indicating that correlated activity has the properties needed to play an important role in the development of geniculocortical circuits and the emergence of cortical orientation tuning.
神经回路以及构成它们的细胞，在其连接的空间组织和时间响应特性方面会经历发育变化。在背侧丘脑的外侧膝状核（LGN）内，这些变化对神经元的时空感受野（STRF）有显著影响。一个尚未解决的开放性问题是，在发育过程中，STRF的成熟如何影响LGN神经元对之间由刺激诱发的相关活动。这是一个需要回答的重要问题，因为由刺激诱发的相关活动可能在建立丘脑皮质连接的特异性以及突触后皮质神经元的感受野（RF）方面发挥作用。我们使用多电极记录方法和白噪声刺激，记录了猫在早期发育过程中LGN神经元群体的神经活动。正如预期的那样，视觉反应的空间和时间特性逐渐成熟。我们还使用漂移条形刺激和互相关分析，确定了不同发育阶段LGN神经元对之间相关活动的方向调谐带宽（西利托和琼斯，2002年；安多利纳等人，2007年；斯坦利等人，2012年；凯利等人，2014年）。尽管与成熟神经元相比，未成熟LGN神经元的RF更大且反应更慢，但我们的结果表明，LGN中的相关活动在发育早期对方向的调谐与成年时一样紧密。进一步检查发现，这种与年龄无关的相关活动方向调谐可能涉及与幼小动物的峰电位疲劳相关的细胞机制，以及随着发育反应潜伏期的逐渐缩短。方向调谐是初级视觉皮层中神经元的基本特性。一个重要且未解决的问题是，方向调谐在大脑发育过程中是如何出现的。本研究探索了一种基于丘脑外侧膝状核（LGN）中成熟神经元群体之间相关活动模式建立方向调谐的潜在机制。结果表明，LGN神经元对之间的相关活动比仅基于感受野大小的预测调谐更紧密，这表明相关活动具有在膝状体皮质回路发育和皮质方向调谐出现中发挥重要作用所需的特性。
