Interaural time difference discrimination thresholds for single neurons in the inferior colliculus of guinea pigs
Interaural time difference discrimination thresholds for single neurons in the inferior colliculus of guinea pigs
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DOI：
10.1523/jneurosci.23-02-00716.2003
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发表时间：
2003-01-15
影响因子：
5.3
通讯作者：
Palmer, AR
中科院分区：
文献类型：
--
作者：
Shackleton, TM;Skottun, BC;Palmer, AR
在乌拉坦麻醉的豚鼠下丘，以单个单位测量耳间时差(ITD)变化的敏感性。以100次重复和细小间隔(每个周期100分)测量ITD功能。利用受试者工作特征(ROC)分析每个ITD的棘波计数分布，确定ITD的刚刚可察觉差异(JND)。JND随着信号频率从50赫兹增加到800赫兹而逐渐变小，但在1千赫以上变得无法测量。最低的JND(30Musec)与人类的JND相当，这表明在单个神经元的放电中有足够的信息，允许在不强制合并的情况下进行区分。ROC分析需要选择参考ITD，通过通过ITD功能步进目标ITD，可以从该参考ITD找到JND。对于每个神经元，选择参照物以最小化JND。最低的JND通常是同侧导联的参考，接近ITD函数的最小值，方差也很小，但斜率接近最陡。这是尽管ITD功能的峰值出现在对侧的前导刺激。当参考的ITD在中线时，可以通过寻找大于或小于中线的射速来获得JND。较低的JND通常是通过寻找发射率的降低来获得的。随着持续时间的增加，JND要么减少，要么增加，这取决于单位类型，而当水平增加时，JND通常增加。
Sensitivity to changes in the interaural time difference (ITD) of 50 msec tones was measured in single units in the inferior colliculus of urethane-anesthetized guinea pigs. ITD functions were measured with 100 repeats and fine spacing (100 points per cycle). The just noticeable difference (jnd) for ITD was determined using receiver operating characteristic (ROC) analysis of the spike-count distribution at each ITD. The jnd became progressively smaller as the signal frequency increased from 50 to 800 Hz but became unmeasurable above 1 kHz. The lowest jnds (30 musec) were comparable with human jnds, indicating that there is sufficient information in the firings of individual neurons to permit discrimination without obligatory pooling. ROC analysis requires the choice of a reference ITD from which the jnd may be found by stepping the target ITD through the ITD function. For each neuron the reference was chosen to minimize the jnd. The lowest jnd was usually for ipsilateral leading references, near the minimum of the ITD function where the variance was also low, but where the slope was nearing its steepest. This was despite the peak of the ITD function occurring for contralateral leading stimuli. When the reference ITD was on midline, a jnd could be obtained by looking for firing rates either greater or smaller than the firing rate at midline. The lower jnd was usually obtained by looking for a decrease in firing rate. As duration increased, jnds either decreased or increased, depending on unit type, whereas when level increased, jnds generally increased.