Department of Neuroscience, Erasmus MC, University Medical Center Rotterdam, 3000 DR Rotterdam, The Netherlands.
Neuron. 2013 Jun 5;78(5):936-48. doi: 10.1016/j.neuron.2013.04.028.
Neurons in the medial superior olive (MSO) enable sound localization by their remarkable sensitivity to submillisecond interaural time differences (ITDs). Each MSO neuron has its own "best ITD" to which it responds optimally. A difference in physical path length of the excitatory inputs from both ears cannot fully account for the ITD tuning of MSO neurons. As a result, it is still debated how these inputs interact and whether the segregation of inputs to opposite dendrites, well-timed synaptic inhibition, or asymmetries in synaptic potentials or cellular morphology further optimize coincidence detection or ITD tuning. Using in vivo whole-cell and juxtacellular recordings, we show here that ITD tuning of MSO neurons is determined by the timing of their excitatory inputs. The inputs from both ears sum linearly, whereas spike probability depends nonlinearly on the size of synaptic inputs. This simple coincidence detection scheme thus makes accurate sound localization possible.
中脑上橄榄复合体（MSO）中的神经元对亚毫秒级的两耳时间差（ITD）非常敏感，从而实现声音定位。每个 MSO 神经元都有自己的“最佳 ITD”，在这个时间差下神经元会做出最优响应。然而，来自双耳的兴奋性输入的物理路径长度差异并不能完全解释 MSO 神经元的 ITD 调谐。因此，目前仍存在争议的是这些输入如何相互作用，以及输入到相反树突的分离、适时的突触抑制、或突触后电位或细胞形态的不对称性是否进一步优化了吻合检测或 ITD 调谐。通过在体全细胞和细胞外记录，我们在这里显示 MSO 神经元的 ITD 调谐由其兴奋性输入的时间决定。双耳的输入线性相加，而尖峰概率则取决于突触输入的大小呈非线性变化。因此，这种简单的吻合检测方案使得精确的声音定位成为可能。
