Relkin E M, Pelli D G
Department of Bioengineering, Syracuse University, New York 13244-5290.
J Acoust Soc Am. 1987 Nov;82(5):1679-91. doi: 10.1121/1.395159.
An important goal of auditory physiology is to relate the coding of signals in the auditory nerve to behavioral sensitivity. A useful step towards that goal is to measure physiological thresholds for the detection of tones in the neural spike train that are comparable to psychophysical thresholds. Detectability depends on the variability as well as the mean value of the response. A two-interval forced-choice task provides a criterion-free measure of detectability. On each trial of our experiments a probe tone was taken to be correctly detected if the number of spikes in response to the tone exceeded the number of spikes in an otherwise identical interval that did not contain the probe tone. (Analysis of the pulse-number distributions also allowed construction of ROC curves directly comparable to psychophysical ROC curves.) The proportion of trials that yielded correct detections was measured as a function of stimulus intensity to form a neurometric function, directly comparable to a psychophysical psychometric function. Threshold was defined as the intensity that produced a given proportion correct. The threshold intensity was also measured by an up-down procedure. Agreement between the two measures of threshold was excellent. Using the up-down procedure we could measure threshold in about 1 min, making it practical to measure the thresholds of a single neuron for many conditions. Comparisons of physiological and psychophysical ROC curves and neurometric and psychometric functions show systematic differences indicating that the animal makes its decisions inefficiently, perhaps by basing its decision on the maximum response among many neurons, rather than just the activity of the single most sensitive neuron.
听觉生理学的一个重要目标是将听神经中信号的编码与行为敏感性联系起来。朝着这个目标迈出的有益一步是测量神经冲动序列中检测音调的生理阈值，使其与心理物理学阈值相当。可检测性取决于反应的变异性以及平均值。双间隔强迫选择任务提供了一种无标准的可检测性测量方法。在我们实验的每次试验中，如果对音调做出反应的尖峰数量超过了在其他方面相同但不包含探测音调的间隔中的尖峰数量，则认为探测音调被正确检测到。（对脉冲数分布的分析还允许构建与心理物理学ROC曲线直接可比的ROC曲线。）测量产生正确检测的试验比例作为刺激强度的函数，以形成神经测量函数，直接与心理物理学心理测量函数可比。阈值被定义为产生给定正确比例的强度。阈值强度也通过升降程序进行测量。两种阈值测量方法之间的一致性非常好。使用升降程序，我们可以在大约1分钟内测量阈值，这使得在许多条件下测量单个神经元的阈值变得切实可行。生理和心理物理学ROC曲线以及神经测量和心理测量函数的比较显示出系统差异，表明动物做出决策的效率低下，可能是通过基于许多神经元中的最大反应而不是仅仅基于最敏感的单个神经元的活动来做出决策。
