Wylie D R, Crowder N A
Department of Psychology, University of Alberta, Edmonton, Alberta T6G 2E9, Canada.
J Neurophysiol. 2000 Nov;84(5):2529-40. doi: 10.1152/jn.2000.84.5.2529.
Neurons in the pretectal nucleus lentiformis mesencephali (LM) are involved in the analysis of optic flow that results from self-motion. Previous studies have shown that LM neurons have large receptive fields in the contralateral eye, are excited in response to largefield stimuli moving in a particular (preferred) direction, and are inhibited in response to motion in the opposite (anti-preferred) direction. We investigated the responses of LM neurons to sine wave gratings of varying spatial and temporal frequency drifting in the preferred and anti-preferred directions. The LM neurons fell into two categories. "Fast" neurons were maximally excited by gratings of low spatial [0.03-0.25 cycles/ degrees (cpd)] and mid-high temporal frequencies (0.5-16 Hz). "Slow" neurons were maximally excited by gratings of high spatial (0.35-2 cpd) and low-mid temporal frequencies (0.125-2 Hz). Of the slow neurons, all but one preferred forward (temporal to nasal) motion. The fast group included neurons that preferred forward, backward, upward, and downward motion. For most cells (81%), the spatial and temporal frequency that elicited maximal excitation to motion in the preferred direction did not coincide with the spatial and temporal frequency that elicited maximal inhibition to gratings moving in the anti-preferred direction. With respect to motion in the anti-preferred direction, a substantial proportion of the LM neurons (32%) showed bi-directional responses. That is, the spatiotemporal plots contained domains of excitation in addition to the region of inhibition. Neurons tuned to stimulus velocity across different spatial frequency were rare (5%), but some neurons (39%) were tuned to temporal frequency. These results are discussed in relation to previous studies of the responses of neurons in the accessory optic system and pretectum to drifting gratings and other largefield stimuli.
中脑豆状核前核（LM）中的神经元参与对自身运动所产生的视觉流的分析。先前的研究表明，LM神经元在对侧眼中具有大的感受野，对沿特定（偏好）方向移动的大视野刺激产生兴奋反应，而对沿相反（非偏好）方向的运动产生抑制反应。我们研究了LM神经元对在偏好和非偏好方向上漂移的不同空间和时间频率的正弦波光栅的反应。LM神经元分为两类。“快速”神经元对低空间频率[0.03 - 0.25周/度（cpd）]和中高时间频率（0.5 - 16赫兹）的光栅产生最大兴奋。“慢速”神经元对高空间频率（0.35 - 2 cpd）和低中时间频率（0.125 - 2赫兹）的光栅产生最大兴奋。在慢速神经元中，除一个之外，所有神经元都偏好向前（从颞侧到鼻侧）运动。快速组包括偏好向前、向后、向上和向下运动的神经元。对于大多数细胞（81%），在偏好方向上引起最大兴奋的空间和时间频率与在非偏好方向上移动的光栅引起最大抑制的空间和时间频率不一致。关于在非偏好方向上的运动，相当一部分LM神经元（32%）表现出双向反应。也就是说，时空图除了抑制区域外还包含兴奋区域。在不同空间频率上对刺激速度进行调谐的神经元很少见（5%），但一些神经元（39%）对时间频率进行调谐。这些结果结合先前关于副视系统和顶盖中神经元对漂移光栅和其他大视野刺激反应的研究进行了讨论。
