Nakajima Ryuichi, Baker Bradley J
Center for Functional Connectomics, Korea Institute of Science and Technology, Seongbuk-gu, Seoul, 136-791, Republic of Korea.
Department of Neuroscience, University of Science and Technology, Daejeon, Republic of Korea.
J Phys D Appl Phys. 2018 Dec 19;51(50). doi: 10.1088/1361-6463/aae2e3. Epub 2018 Oct 16.
To understand the circuitry of the brain, it is essential to clarify the functional connectivity among distinct neuronal populations. For this purpose, neuronal activity imaging using genetically-encoded calcium sensors such as GCaMP has been a powerful approach due to its cell-type specificity. However, calcium (Ca) is an indirect measure of neuronal activity. A more direct approach would be to use genetically encoded voltage indicators (GEVIs) to observe subthreshold, synaptic activities. The GEVI, ArcLight, which exhibits large fluorescence transients in response to voltage, was expressed in excitatory neurons of the mouse CA1 hippocampus. Fluorescent signals in response to the electrical stimulation of the Schaffer collateral axons were observed in brain slice preparations. ArcLight was able to map both excitatory and inhibitory inputs projected to excitatory neurons. In contrast, the Ca signal detected by GCaMP6f, was only associated with excitatory inputs. ArcLight and similar voltage sensing probes are also becoming powerful paradigms for functional connectivity mapping of brain circuitry.
为了理解大脑的神经回路，明确不同神经元群体之间的功能连接至关重要。为此，使用诸如GCaMP等基因编码钙传感器的神经元活动成像因其细胞类型特异性而成为一种强大的方法。然而，钙（Ca）是神经元活动的间接测量指标。一种更直接的方法是使用基因编码电压指示剂（GEVIs）来观察阈下突触活动。在小鼠CA1海马体的兴奋性神经元中表达了对电压有大荧光瞬变反应的GEVI——ArcLight。在脑片制备中观察到了对海马体联合轴突电刺激的荧光信号。ArcLight能够绘制投射到兴奋性神经元的兴奋性和抑制性输入。相比之下，GCaMP6f检测到的钙信号仅与兴奋性输入相关。ArcLight和类似的电压传感探针也正成为大脑神经回路功能连接图谱绘制的强大范例。
