Interaural time difference tuning in the rat inferior colliculus is predictive of behavioral sensitivity

Recent studies have shown that rats are a useful model for binaural cochlear implant (CI) research, with behavioral sensitivity to interaural time differences (ITDs) of CI stimuli which are better than those of human patients. Here, we characterize ITD tuning in the rat inferior colliculus (IC) and explore whether quality of tuning can predict behavioral performance. We recorded IC responses to stimuli of varying pulse rates and envelope types and quantified both mutual information (MI) and neural d' as measures of ITD sensitivity. Neural d' values paralleled behavioral ones, declining with increasing click rates or when envelopes changed from rectangular to Hanning windows. While MI values increased with experience, neural d' did not. However, neural d' values correlated much better with behavioral performance than MI. Thus, neural d' appears to be a particularly well suited to predicting how stimulus parameters will impact behavioral performance.已有研究表明，大鼠是双耳人工耳蜗（cochlear implant, CI）研究的理想动物模型，其对人工耳蜗刺激的双耳时间差（interaural time differences, ITDs）的行为敏感性优于人类患者。本研究对大鼠下丘（inferior colliculus, IC）的ITD调谐特性进行了系统表征，并探讨调谐质量能否预测行为表现。我们记录了大鼠下丘对不同脉冲速率与包络类型刺激的响应，量化了互信息（mutual information, MI）与神经d'值作为ITD敏感性的评估指标。神经d'值与行为学结果趋势一致：随着点击速率升高，或当刺激包络从矩形窗转为汉宁窗时，神经d'值均会下降。尽管互信息值会随实验经验增加而上升，但神经d'值并无此类变化。然而，神经d'值与行为表现的相关性远高于互信息。综上，神经d'值似乎尤其适用于预测刺激参数对行为表现的影响。