Parkins C W
Division of Otolaryngology, University of Rochester School of Medicine and Dentistry, New York.
Hear Res. 1989 Sep;41(2-3):137-68. doi: 10.1016/0378-5955(89)90007-5.
Electroneural response patterns of single auditory-nerve neurons were studied in aminoglycoside-deafened squirrel monkeys. The electrical stimuli were delivered through bipolar electrodes implanted in the scala tympani. The effects of pulse width, shape, frequency, and intensity on neural adaptation, phase locking, and spectral content were evaluated. Our results did not demonstrate the characteristic adaptation seen in auditory-nerve neurons in response to acoustic stimulation. Phase locking to a broad stimulus pulse (3200 microseconds/phase) was found to a very restricted phase angle of the electrical stimulus which was broader for square wave than for sine wave stimulation. The latency of the phase locked response varied inversely with stimulus intensity with greater variation for square wave stimulation than for sine wave stimulation. Auditory neurons were capable of a very high degree of phase locking to a 200-microseconds/phase pulse presented at 156 pulses per second (PPS) and to the first pulse of a 2500-Hz pulse burst. Phase locking was much poorer for the subsequent 200-microseconds/phase pulses comprising the 2500-Hz pulse burst where the neuron's response was determined by its relative recovery status. These findings can be explained by an interaction between the neuron's relative refractory status and its integration of charge over the stimulatory half cycle of the electrical stimulus. These two factors also appear to determine the interspike interval of the neural response. This interval decreased monotonically with increasing stimulus intensity. The neural spike rate (150-500 Hz) producing this interval increased with intensity and may be a source of periodicity information which the central auditory nervous system could interpret as pitch. This may account for the proportional relationship between pitch and stimulus intensity seen in some cochlear implant patients. Our study demonstrates that auditory-nerve neurons comply with basic neurophysiological principles in their responses to electrical stimulation. These principles should be incorporated into the cochlear prosthesis stimulator if more normal neural response patterns are desired in the cochlear prosthesis patient.
在氨基糖苷类致聋的松鼠猴中研究了单个听神经神经元的电神经反应模式。电刺激通过植入鼓阶的双极电极施加。评估了脉冲宽度、形状、频率和强度对神经适应、锁相和频谱内容的影响。我们的结果未显示听神经神经元对声刺激产生的典型适应。发现对宽刺激脉冲（3200微秒/相位）的锁相局限于电刺激的非常有限的相位角，该相位角对于方波刺激比对正弦波刺激更宽。锁相反应的潜伏期与刺激强度成反比，方波刺激的变化比正弦波刺激更大。听觉神经元能够高度锁相于以每秒156次脉冲（PPS）呈现的200微秒/相位脉冲以及2500赫兹脉冲串的第一个脉冲。对于构成2500赫兹脉冲串的后续200微秒/相位脉冲，锁相要差得多，此时神经元的反应由其相对恢复状态决定。这些发现可以通过神经元的相对不应期状态与其在电刺激的刺激半周期内的电荷积分之间的相互作用来解释。这两个因素似乎也决定了神经反应的峰峰间隔。该间隔随刺激强度增加而单调减小。产生此间隔的神经放电率（150 - 500赫兹）随强度增加，可能是中央听觉神经系统可解释为音高的周期性信息的来源。这可能解释了一些人工耳蜗植入患者中音高与刺激强度之间的比例关系。我们的研究表明，听神经神经元在对电刺激的反应中符合基本的神经生理学原理。如果希望人工耳蜗植入患者有更正常的神经反应模式，这些原理应纳入人工耳蜗刺激器中。
