Sound intensity is encoded by auditory neuron subgroups that differ in thresholds and spontaneous rates. Whether variations in neuronal biophysics contributes to this functional diversity is unknown. Because intensity thresholds correlate with synaptic position on sensory hair cells, we combined patch clamping with fiber labeling in semi-intact cochlear preparations in neonatal rats from both sexes. The biophysical properties of auditory neurons vary in a striking spatial gradient with synaptic position. Neurons with high thresholds to injected currents contact hair cells at synaptic positions where neurons with high thresholds to sound-intensity are found in vivo. Alignment between in vitro and in vivo thresholds suggests that biophysical variability contributes to intensity coding. Biophysical gradients were evident at all ages examined, indicating that cell diversity emerges in early post-natal development and persists even after continued maturation. This stability enabled a remarkably successful model for predicting synaptic position based solely on biophysical properties.

中文翻译：

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新生儿听觉神经元生物物理特性的梯度与突触接触位置和内毛细胞的强度编码图一致


声音强度由阈值和自发率不同的听觉神经元亚群编码。神经元生物物理学的变化是否有助于这种功能多样性尚不清楚。由于强度阈值与感觉毛细胞上的突触位置相关，因此我们将膜片钳与纤维标记结合起来，用于两性新生大鼠的半完整耳蜗制备物中。听觉神经元的生物物理特性随突触位置的不同而呈现显着的空间梯度变化。对注入电流具有高阈值的神经元在突触位置接触毛细胞，在体内发现对声音强度具有高阈值的神经元。体外和体内阈值之间的一致性表明生物物理变异性有助于强度编码。在所检查的所有年龄段，生物物理梯度都很明显，表明细胞多样性在出生后早期发育中出现，甚至在持续成熟后仍然存在。这种稳定性使得一个非常成功的模型能够仅根据生物物理特性来预测突触位置。