Miller A L, Morris D J, Pfingst B E
Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan Medical Center, Ann Arbor 48109-0506, USA.
Hear Res. 1997 Jul;109(1-2):21-33. doi: 10.1016/s0378-5955(97)00037-3.
Interactions between pulse separation and pulse polarity order were examined using psychophysical studies of electrical detection thresholds in nonhuman primates. Subjects were trained using acoustic stimuli, then deafened in one ear and implanted with an electrode array for electrical stimulation of the cochlea. Threshold vs pulse separation functions for trains of biphasic electrical pulses were compared for constant and alternating leading phase polarity. When leading phase polarity was held constant, threshold vs pulse separation functions were nonmonotonic (U-shaped). Small polarity-dependent (cathodic vs anodic leading phase) differences in absolute thresholds were observed at long pulse separations, but function shape was independent of leading phase. When leading phase polarity alternated, there was a pronounced reduction in thresholds at short pulse separations (below about 1 ms), resulting in monotonically increasing threshold vs pulse separation functions. At long pulse separations, functions for alternating and constant polarity stimuli were similar. Polarity effects were most apparent for longer duration trains (20 pulses) at long pulse durations (1-2 ms/phase). For stimuli consisting of only two biphasic pulses, alternating polarity effects depended on whether cathodic or anodic phases were adjacent. The neural mechanisms underlying these effects probably include refractory properties and/or residual potentials.
通过对非人类灵长类动物电检测阈值的心理物理学研究，检验了脉冲间隔与脉冲极性顺序之间的相互作用。使用听觉刺激对受试者进行训练，然后使其中一只耳朵失聪，并植入电极阵列以对耳蜗进行电刺激。比较了恒定和交替领先相极性的双相电脉冲序列的阈值与脉冲间隔函数。当领先相极性保持恒定时，阈值与脉冲间隔函数是非单调的（U形）。在长脉冲间隔时，观察到绝对阈值存在小的极性依赖性（阴极与阳极领先相）差异，但函数形状与领先相无关。当领先相极性交替时，在短脉冲间隔（低于约1毫秒）时阈值明显降低，导致阈值与脉冲间隔函数单调增加。在长脉冲间隔时，交替和恒定极性刺激的函数相似。极性效应在长脉冲持续时间（1-2毫秒/相）的较长持续时间序列（20个脉冲）中最为明显。对于仅由两个双相脉冲组成的刺激，交替极性效应取决于阴极或阳极相是否相邻。这些效应背后的神经机制可能包括不应期特性和/或残余电位。
