Biology Program, Bard College, Annandale-on-Hudson, New York.
J Neurophysiol. 2019 Sep 1;122(3):1084-1096. doi: 10.1152/jn.00099.2019. Epub 2019 Jul 10.
For a biological neural network to be functional, its neurons need to be connected with synapses of appropriate strength, and each neuron needs to appropriately respond to its synaptic inputs. This second aspect of network tuning is maintained by intrinsic plasticity; yet it is often considered secondary to changes in connectivity and mostly limited to adjustments of overall excitability of each neuron. Here we argue that even nonoscillatory neurons can be tuned to inputs of different temporal dynamics and that they can routinely adjust this tuning to match the statistics of their synaptic activation. Using the dynamic clamp technique, we show that, in the tectum of tadpole, neurons become selective for faster inputs when animals are exposed to fast visual stimuli but remain responsive to longer inputs in animals exposed to slower, looming, or multisensory stimulation. We also report a homeostatic cotuning between synaptic and intrinsic temporal properties of individual tectal cells. These results expand our understanding of intrinsic plasticity in the brain and suggest that there may exist an additional dimension of network tuning that has been so far overlooked. We use dynamic clamp to show that individual neurons in the tectum of tadpoles are selectively tuned to either shorter (more synchronous) or longer (less synchronous) synaptic inputs. We also demonstrate that this intrinsic temporal tuning is strongly shaped by sensory experiences. This new phenomenon, which is likely to be mediated by changes in sodium channel inactivation, is bound to have important consequences for signal processing and the development of local recurrent connections.
为了使生物神经网络能够正常运行,其神经元需要通过适当强度的突触连接,并且每个神经元需要对其突触输入做出适当的响应。网络调谐的第二个方面由内在可塑性维持;然而,它通常被认为次于连接变化,并且主要局限于每个神经元整体兴奋性的调整。在这里,我们认为即使是非振荡神经元也可以针对不同时间动态的输入进行调谐,并且它们可以常规地调整这种调谐以匹配其突触激活的统计数据。使用动态钳技术,我们表明,在蝌蚪的顶盖中,当动物暴露于快速视觉刺激时,神经元对更快的输入变得具有选择性,而在动物暴露于较慢的、逼近的或多感觉刺激时,它们仍然对较长的输入有反应。我们还报告了单个顶盖细胞的突触和内在时间特性之间的稳态共调。这些结果扩展了我们对大脑内在可塑性的理解,并表明可能存在一个迄今为止被忽视的网络调谐的附加维度。我们使用动态钳来表明,蝌蚪顶盖中的单个神经元对较短(更同步)或较长(不同步)的突触输入具有选择性调谐。我们还证明,这种内在时间调谐强烈地受到感官体验的影响。这种新现象可能是由钠通道失活的变化介导的,它必然会对信号处理和局部递归连接的发展产生重要影响。