McKay C M, McDermott H J, Clark G M
Department of Otolaryngology, University of Melbourne, Australia.
J Acoust Soc Am. 1995 Mar;97(3):1777-85. doi: 10.1121/1.412054.
An experiment was conducted with four cochlear implantees, which investigated the pitch evoked by amplitude-modulating current pulse trains delivered to a single cochlear location. These stimuli produce a pitch percept which may be similar to that of acoustic stimuli such as modulated noise for modulation frequencies in the range 80-300 Hz, approximately. The experiments investigated the effect of modulation depth on the way pitch was matched to that of unmodulated pulse trains. The method of constant stimuli was used, in which the variable parameter was the rate of the unmodulated stimulus. The modulated stimuli comprised pulses having one of two possible current values, with the higher value occurring once in every modulation period. The results showed that the matched rate fell exponentially from a value close to the carrier rate towards a value equal to the modulation frequency as the modulation depth increased. The results were compared to the predictions of a simple model in which the matched rate corresponded to a weighted average of carrier and modulation frequencies, with the weightings proportional to the number of neurons firing at each of these frequencies. The results agreed with the predictions of the model reasonably well, except in cases where the carrier rate was 700 Hz or higher, and for one subject at the highest intensity level.
对四名人工耳蜗植入者进行了一项实验，该实验研究了传递到单个耳蜗位置的调幅电流脉冲序列所诱发的音高。这些刺激产生的音高感知可能类似于调制频率在80 - 300 Hz范围内的声学刺激（如调制噪声）所产生的音高感知。实验研究了调制深度对音高与未调制脉冲序列音高匹配方式的影响。采用了恒定刺激法，其中可变参数是未调制刺激的速率。调制刺激包括具有两种可能电流值之一的脉冲，较高的值在每个调制周期中出现一次。结果表明，随着调制深度的增加，匹配率从接近载波速率的值呈指数下降至等于调制频率的值。将结果与一个简单模型的预测进行了比较，在该模型中，匹配率对应于载波频率和调制频率的加权平均值，权重与在每个频率下放电的神经元数量成比例。结果与模型的预测相当吻合，除了载波速率为700 Hz或更高的情况，以及一名受试者在最高强度水平时的情况。
