Nodal F R, Bajo V M, Parsons C H, Schnupp J W, King A J
Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
Neuroscience. 2008 Jun 12;154(1):397-408. doi: 10.1016/j.neuroscience.2007.12.022. Epub 2007 Dec 23.
Auditory localization experiments typically either require subjects to judge the location of a sound source from a discrete set of response alternatives or involve measurements of the accuracy of orienting responses made toward the source location. To compare the results obtained by both methods, we trained ferrets by positive conditioning to stand on a platform at the center of a circular arena prior to stimulus presentation and then approach the source of a broadband noise burst delivered from 1 of 12 loudspeakers arranged at 30 degrees intervals in the horizontal plane. Animals were rewarded for making a correct choice. We also obtained a non-categorized measure of localization accuracy by recording head-orienting movements made during the first second following stimulus onset. The accuracy of the approach-to-target responses declined as the stimulus duration was reduced, particularly for lateral and posterior locations, although responses to sounds presented in the frontal region of space and directly behind the animal remained quite accurate. Head movements had a latency of approximately 200 ms and varied systematically in amplitude with stimulus direction. However, the final head bearing progressively undershot the target with increasing eccentricity and rarely exceeded 60 degrees to each side of the midline. In contrast to the approach-to-target responses, the accuracy of the head orienting responses did not change much with stimulus duration, suggesting that the improvement in percent correct scores with longer stimuli was due, at least in part, to re-sampling of the acoustical stimulus after the initial head turn had been made. Nevertheless, for incorrect trials, head orienting responses were more closely correlated with the direction approached by the animals than with the actual target direction, implying that at least part of the neural circuitry for translating sensory spatial signals into motor commands is shared by these two behaviors.
听觉定位实验通常要么要求受试者从一组离散的反应选项中判断声源的位置，要么涉及测量朝向声源位置的定向反应的准确性。为了比较这两种方法得到的结果，我们通过正向条件训练雪貂，使其在刺激呈现前站在圆形竞技场中心的平台上，然后接近从水平面上以30度间隔排列的12个扬声器中的1个发出的宽带噪声爆发源。动物做出正确选择会得到奖励。我们还通过记录刺激开始后第一秒内的头部定向运动，获得了一种非分类的定位准确性测量方法。随着刺激持续时间的缩短，接近目标反应的准确性下降，特别是对于侧向和后方位置，尽管对空间前部区域和动物正后方呈现的声音的反应仍然相当准确。头部运动的潜伏期约为200毫秒，并且振幅随刺激方向系统地变化。然而，最终的头部方位随着离心率的增加逐渐低于目标，并且很少超过中线两侧60度。与接近目标反应相反，头部定向反应的准确性并没有随着刺激持续时间而有太大变化，这表明较长刺激下正确得分百分比的提高至少部分是由于在最初头部转动后对声学刺激的重新采样。然而，对于错误的试验，头部定向反应与动物接近的方向比与实际目标方向更密切相关，这意味着将感觉空间信号转化为运动指令的神经回路至少有一部分是这两种行为所共有的。
