Neural mechanisms underlying selectivity for the rate and direction of frequency-modulated sweeps in the inferior colliculus of the pallid bat
Neural mechanisms underlying selectivity for the rate and direction of frequency-modulated sweeps in the inferior colliculus of the pallid bat
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DOI：
10.1152/jn.00021.2006
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发表时间：
2006-09-01
影响因子：
2.5
通讯作者：
Coburn, Michael S.
中科院分区：
文献类型：
--
作者：
Fuzessery, Zoltan M.;Richardson, Marlin D.;Coburn, Michael S.
本研究描述了苍白蝙蝠(Antrozous Pallidus)下丘中央核(ICC)中神经元选择性频率扫描的方向和速度的机制。这个ICC含有很高比例的神经元(66%)，这些神经元选择性地对蝙蝠回声定位脉冲的向下扫描方向做出反应。一些人(19%)是只对向下扫荡做出反应的专家。大多数神经元(83%)也会调整到扫频。双音抑制范式被用来描述形成扫描方向和速度选择性的抑制机制。两种不同的机制可以创建类似的速率调整。第一个是形成时长调谐的早期最佳频率抑制，而时长调谐又决定了速率调谐。在大多数没有调整时长的神经元中，延迟的高频抑制会产生频率调整。这些神经元对快速扫描速度做出反应，但随着扫描速度的减慢而受到抑制，延迟抑制与兴奋重叠。在这些神经元中，在兴奋性调谐曲线内开始向下扫描可以消除频率调谐。但是，如果速率调整是由持续时间调整决定的，则此操作不起作用。向下扫描方向的选择性是通过早期的低频抑制来创建的，该低频抑制阻止了对向上扫描的响应。除了低频和高频抑制的到达时间的这种不对称性外，低频边带的带宽更宽。带宽会影响FM扫描期间抑制的到达时间，因为将很快遇到更宽的边带。这些发现表明，可以通过不同的机制创建类似的光谱时相滤光器。
This study describes mechanisms that underlie neuronal selectivity for the direction and rate of frequency-modulated sweeps in the central nucleus of the inferior colliculus (ICC) of the pallid bat (Antrozous pallidus). This ICC contains a high percentage of neurons (66%) that respond selectively to the downward sweep direction of the bat's echolocation pulse. Some (19%) are specialists that respond only to downward sweeps. Most neurons (83%) are also tuned to sweep rates. A two-tone inhibition paradigm was used to describe inhibitory mechanisms that shape selectivity for sweep direction and rate. Two different mechanisms can create similar rate tuning. The first is an early on-best frequency inhibition that shapes duration tuning, which in turn determines rate tuning. In most neurons that are not duration tuned, a delayed high-frequency inhibition creates rate tuning. These neurons respond to fast sweep rates, but are inhibited as rate slows, and delayed inhibition overlaps excitation. In these neurons, starting a downward sweep within the excitatory tuning curve eliminates rate tuning. However, if rate tuning is shaped by duration tuning, this manipulation has no effect. Selectivity for the downward sweep direction is created by an early low-frequency inhibition that prevents responses to upward sweeps. In addition to this asymmetry in arrival times of low- and high-frequency inhibitions, the bandwidth of the low- frequency sideband was broader. Bandwidth influences the arrival time of inhibition during an FM sweep because a broader sideband will be encountered sooner. These findings show that similar spectrotemporal filters can be created by different mechanisms.