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Abstract：
In the central nucleus of the inferior colliculus (ICC), which acts as the hub of the auditory pathways, how the sound is coded by distinct cell types is largely unknown. Large GABAergic cells are tuned broadly to pure tones and respond more strongly to frequency-modulated sweeps than small GABAergic and glutamatergic (GLU) cells. Neurons, especially GLU cells, which share sharpness of tuning and sweep sensitivity, were spatially clustered inside the ICC. The difference in responsiveness between cell types was partially explained by the morphology of dendritic trees and the spatial distributions of excitatory and inhibitory inputs. The results suggest that each ICC cell type has a particular sound-encoding strategy, which is partially determined by the morphological characteristics and location of cells, and contributes information coding in higher centres in different ways.
The rules governing the encoding of sound information in the higher auditory centres are largely unknown. In the central nucleus of the inferior colliculus (ICC), which acts as the hub of the auditory pathways, the presence of functional maps other than tonotopicity has been suggested but not established, due to significant heterogeneity in the response properties of single microdomains. Since each ICC cell type has distinct neuronal circuitry, each cell type might encode sound information differently. Here, juxtacellular recording from rat ICC of both sexes revealed that large GABAergic (LG), small GABAergic (SG) and glutamatergic (GLU) cells encode sound information differently. LG cells are broadly tuned and respond more strongly to frequency-modulated sweeps than SG and GLU cells. At a population level, responsiveness to sweeps is location dependent: the responsiveness to sweeps is shared in local clusters of GLU cells, whereas that to directional selectivity of sweeps is shared in local clusters of LG cells. The difference in responsiveness between cell types was partially explained by the morphology of dendritic trees and the spatial distributions of excitatory and inhibitory inputs. LG neurons had a dense local axonal plexus with projection fibres to multiple distant targets, whereas GLU projection neurons mainly aimed at a single, distant target and had less dense local collaterals. These results suggest that each ICC cell type has a particular sound-encoding strategy, which is partially determined by the morphological characteristics and location of the cell, and the different cell types contribute information coding in higher centres in different ways.
The rules governing the encoding of sound information in the higher auditory centres are largely unknown. In the central nucleus of the inferior colliculus (ICC), which acts as the hub of the auditory pathways, the presence of functional maps other than tonotopicity has been suggested but not established, due to significant heterogeneity in the response properties of single microdomains. Since each ICC cell type has distinct neuronal circuitry, each cell type might encode sound information differently. Here, juxtacellular recording from rat ICC of both sexes revealed that large GABAergic (LG), small GABAergic (SG) and glutamatergic (GLU) cells encode sound information differently. LG cells are broadly tuned and respond more strongly to frequency-modulated sweeps than SG and GLU cells. At a population level, responsiveness to sweeps is location dependent: the responsiveness to sweeps is shared in local clusters of GLU cells, whereas that to directional selectivity of sweeps is shared in local clusters of LG cells. The difference in responsiveness between cell types was partially explained by the morphology of dendritic trees and the spatial distributions of excitatory and inhibitory inputs. LG neurons had a dense local axonal plexus with projection fibres to multiple distant targets, whereas GLU projection neurons mainly aimed at a single, distant target and had less dense local collaterals. These results suggest that each ICC cell type has a particular sound-encoding strategy, which is partially determined by the morphological characteristics and location of the cell, and the different cell types contribute information coding in higher centres in different ways.
摘要：
在下丘（ICC）的中央核，作为听觉通路的枢纽，声音如何被不同的细胞类型编码在很大程度上是未知的。与小的GABA能和谷氨酸能（GLU）细胞相比，大的GABA能细胞被广泛调节为纯音，并且对调频扫描的反应更强烈。神经元,尤其是GLU细胞，它们共享调谐和扫描灵敏度的清晰度，在空间上聚集在ICC内部。树突树的形态以及兴奋性和抑制性输入的空间分布部分解释了细胞类型之间反应性的差异。结果表明，每个ICC细胞类型具有特定的声音编码策略，这部分是由细胞的形态特征和位置决定的，并以不同的方式在更高的中心贡献信息编码。
在较高的听觉中枢中控制声音信息编码的规则在很大程度上是未知的。在下丘（ICC）的中央核，作为听觉通路的枢纽，已经提出但尚未建立除音调视性以外的功能图的存在，由于单个微域的响应特性存在明显的异质性。由于每个ICC细胞类型都有不同的神经元电路，每种细胞类型可能编码不同的声音信息。这里,来自男女大鼠ICC的细胞间记录显示，大的GABA能（LG），小GABA能（SG）和谷氨酸能（GLU）细胞编码不同的声音信息。与SG和GLU单元相比,LG单元被广泛地调谐并且对调频扫描的响应更强。在人口层面,对扫描的响应取决于位置：对扫描的响应在GLU单元的本地集群中共享，而扫描的方向选择性在LG细胞的本地集群中共享。树突树的形态以及兴奋性和抑制性输入的空间分布部分解释了细胞类型之间反应性的差异。LG神经元有一个密集的局部轴突丛，向多个远处的目标投射纤维，而GLU投射神经元主要针对单个，远离目标，局部络脉密度较低。这些结果表明，每个ICC细胞类型具有特定的声音编码策略，这部分是由细胞的形态特征和位置决定的，不同的细胞类型以不同的方式在较高的中心贡献信息编码。
在较高的听觉中枢中控制声音信息编码的规则在很大程度上是未知的。在下丘（ICC）的中央核，作为听觉通路的枢纽，已经提出但尚未建立除音调视性以外的功能图的存在，由于单个微域的响应特性存在明显的异质性。由于每个ICC细胞类型都有不同的神经元电路，每种细胞类型可能编码不同的声音信息。这里,来自男女大鼠ICC的细胞间记录显示，大的GABA能（LG），小GABA能（SG）和谷氨酸能（GLU）细胞编码不同的声音信息。与SG和GLU单元相比,LG单元被广泛地调谐并且对调频扫描的响应更强。在人口层面,对扫描的响应取决于位置：对扫描的响应在GLU单元的本地集群中共享，而扫描的方向选择性在LG细胞的本地集群中共享。树突树的形态以及兴奋性和抑制性输入的空间分布部分解释了细胞类型之间反应性的差异。LG神经元有一个密集的局部轴突丛，向多个远处的目标投射纤维，而GLU投射神经元主要针对单个，远离目标，局部络脉密度较低。这些结果表明，每个ICC细胞类型具有特定的声音编码策略，这部分是由细胞的形态特征和位置决定的，不同的细胞类型以不同的方式在较高的中心贡献信息编码。
