Differential tuning of excitation and inhibition shapes direction selectivity in ferret visual cortex.
Differential tuning of excitation and inhibition shapes direction selectivity in ferret visual cortex.
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DOI：
10.1038/s41586-018-0354-1
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发表时间：
2018-08
期刊：
影响因子：
64.8
通讯作者：
Fitzpatrick D
中科院分区：
文献类型：
--
作者：
Wilson DE;Scholl B;Fitzpatrick D
为了编码特定的感觉输入，皮层神经元必须针对不同的刺激特征产生选择性反应。原则上，多种因素影响皮质神经元的反应选择性：兴奋性和抑制性突触输入的调整和强度、树突非线性和尖峰阈值。在这里，我们采用了多种技术的组合，包括体内全细胞记录、体内突触和细胞分辨率双光子钙成像以及 GABA 选择性光遗传学操作来剖析雪貂视觉皮层 (V1) 2/3 层神经元方向选择性反应的影响因素。树突棘的双光子钙成像显示，每个神经元接收针对体细胞首选或零运动方向选择性的兴奋性突触输入的混合物。首选和零调节兴奋性输入的相对数量预测了神经元的体细胞方向偏好，但未能解释方向选择性的程度。相比之下，体内全细胞膜片钳记录揭示了阈下反应中显着程度的方向选择性，这与尖峰方向选择性显着相关。亚阈值方向选择性是通过对运动零方向的响应的幅度和方差来预测的，包括电导测量在内的几条证据表明，兴奋和抑制的差异调节会抑制对运动零方向的响应。与这一想法一致，2/3 层 GABA 能神经元的光遗传学失活通过增强对零方向的响应来降低方向选择性。此外，使用一种新技术对体内 2/3 层抑制性神经元的连接进行光遗传学映射，我们发现 2/3 层抑制性神经元对喜欢相反运动方向的兴奋性神经元进行长距离、柱间投射。我们得出的结论是，皮质内抑制通过抑制对运动零方向的反应，对雪貂 V1 2/3 层的方向选择性程度产生重大影响。
To encode specific sensory inputs, cortical neurons must generate selective responses for distinct stimulus features. In principle, a variety of factors contribute to a cortical neuron’s response selectivity: the tuning and strength of excitatory and inhibitory synaptic inputs, dendritic nonlinearities, and spike threshold. Here we employ a combination of techniques including in vivo whole-cell recording, synaptic and cellular resolution in vivo two photon calcium imaging, and GABAergic-selective optogenetic manipulation to dissect the factors contributing to direction selective responses of layer 2/3 neurons in ferret visual cortex (V1). Two-photon calcium imaging of dendritic spines revealed that each neuron receives a mixture of excitatory synaptic inputs selective for the somatic preferred or null direction of motion. The relative number of preferred- and null-tuned excitatory inputs predicted a neuron’s somatic direction preference, but failed to account for the degree of direction selectivity. In contrast, in vivo whole-cell patch clamp recordings revealed a striking degree of direction selectivity in subthreshold responses that was significantly correlated with spiking direction selectivity. Subthreshold direction selectivity was predicted by the magnitude and variance of the response to the null direction of motion, and several lines of evidence including conductance measurements demonstrate that differential tuning of excitation and inhibition suppresses responses to the null direction of motion. Consistent with this idea, optogenetic inactivation of GABAergic neurons in layer 2/3 reduced direction selectivity by enhancing responses to the null direction. Furthermore, using a new technique to optogenetically map connections of inhibitory neurons in layer 2/3 in vivo, we find that layer 2/3 inhibitory neurons make long-range, intercolumnar projections to excitatory neurons that prefer the opposite direction of motion. We conclude that intracortical inhibition exerts a major influence on the degree of direction selectivity in layer 2/3 of ferret V1 by suppressing responses to the null direction of motion.
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