复合听神经动作电位与调幅刺激声包络的时序相关分析
Temporal sequential correlation analysis on compound action potentials of the auditory nerve versus the stimulating AM-sound envelope
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摘要: 在豚鼠用植入内听道出口处的电极记录了调幅声诱发的复合听神经动作电位,并研究了在声参数系统地变化时反应与调制波之间的时序相关性。所用的调制波有三种:频率固定的连续或短段正弦波(频率范围40Hz~5kHz),频率变化的短段正弦波及小段语音信号。其它声参数变化范围为:载波500Hz~20kHz,调制深度5%~95%,强度20~90dBSPL。对于频率固定的连续或短段正弦调制波,在大多数参数条件下,反应与调制波之间的相关系数(r)相当高:0.80~0.95,在由于参数不适当、反应幅度下降时,r相应地变小。对于频率变化的短段正弦调制波,r在0.66~0.86之间变化。当用语音信号片段作调制波时,反应与调制波之间仍存在一定的相关性(r在0.50左右变化),表明对语音信息在耳蜗水平的编码,时间模式是有效的。文中对听觉时间机理的一些理论及技术要点作了讨论。Abstract: Compound action potentials of the auditory nerve in response to amplitude-modulating tones were recorded in guinea pigs with electrode implanted to the exit of the internal auditory meatus and temporal sequential correlation between the responses and the modulators was studied in a paradigm of systematically changing acoustic parameters. Three kinds of modulator were used:continuous or burst sinusoids of fixed frequency (in the range of 40 Hz~5 kHz),short bursts of sinusoids with changing frequency and short segments of speech signal. Ranges of parametric variation were 500 Hz~20 kHz for carrier frequency, 5%~95% for modulation depth and 20~90 dB SPL for intensity. For continuous or burst sinusoidal modulators of fixed frequencies, the correlation coefficient (r) remained quite high in most parametric conditions,amounting from 0.80 to 0.95. It became smaller mainly in instances of decreased response amplitude on account of unfavourable parameters. For burst modulators of changing frequency, r varied around 0.66~0.86. When segments of speech signal served as the modulators, significant correlation (r around 0.50) also existed, indicating the validity of the timing mode of information encoding for speech sound at the cochlear nerve level. Some theoretical and technical points in studying the timing mechanism of audition is discussed.