Relkin E M, Turner C W
Department of Bioengineering, Syracuse University, New York 13244-5290.
J Acoust Soc Am. 1988 Aug;84(2):584-91. doi: 10.1121/1.396836.
Forward masking, as measured behaviorally, is defined as an increase in a signal's detection threshold resulting from a preceding masker. Previously, forward masking in the auditory nerve has been measured as a reduction in the neural response to a signal when preceded by a masker. However, detection threshold depends on both the magnitude of the response to the signal and the variance of the response. Thus changes in detectability cannot be inferred from response reduction alone. Relkin and Pelli (1987) have described a two-interval forced-choice procedure that may be used to measure the threshold for the detection of a probe signal in recordings of spike counts in single auditory neurons. These methods have been used to study the forward masking of characteristic frequency probe tones by characteristic frequency maskers as masker intensity was varied. Although the masker does reduce the detectability of the probe tone, it was found that the threshold shifts are much less than those observed behaviorally, particularly for intense maskers. In part, the small threshold shifts can be attributed to the reduction in response variance following the masker, which is the result of the adaptation of spontaneous activity. These results imply that behavioral forward masking must result from suboptimal processing of spike counts from auditory neurons at a location central to the auditory nerve.
从行为学角度测量，前掩蔽被定义为由于先前的掩蔽声导致信号检测阈值升高。此前，听觉神经中的前掩蔽被测量为当掩蔽声先于信号出现时，神经对信号的反应减弱。然而，检测阈值既取决于对信号的反应幅度，也取决于反应的方差。因此，不能仅从反应减弱就推断出可检测性的变化。雷尔金和佩利（1987年）描述了一种双间隔强迫选择程序，可用于测量在单个听觉神经元的脉冲计数记录中检测探测信号的阈值。随着掩蔽声强度的变化，这些方法已被用于研究特征频率掩蔽声对特征频率探测音的前掩蔽。尽管掩蔽声确实会降低探测音的可检测性，但发现阈值变化远小于行为学上观察到的变化，尤其是对于高强度掩蔽声。部分而言，阈值变化小可归因于掩蔽声之后反应方差的降低，这是自发活动适应的结果。这些结果表明，行为学上的前掩蔽必定是由于在听觉神经中枢位置对听觉神经元脉冲计数的处理欠佳所致。
