Ilg Uwe J, Churan Jan
Oculomotor Lab, Dept. of Cognitive Neurology, Hertie-Institute for Clinical Brain Research, University of Tübingen, Hoppe-Seyler-Strasse 3, D-72076 Tübingen, Germany.
J Neurophysiol. 2004 Sep;92(3):1512-23. doi: 10.1152/jn.01174.2003. Epub 2004 Apr 14.
It is widely accepted that middle temporal (MT) and middle superior temporal (MST) cortical areas in the brain of rhesus monkeys are essential for processing visual motion. We asked whether this assumption holds true if the moving stimulus consists of a second-order motion stimulus. In addition, we asked whether neurons in area MT and MST code for moving sound sources. To answer these questions, we trained three rhesus monkeys on a direction-discrimination task. Our monkeys were able to correctly report the direction of all motion stimuli used in this study. Firing rates of directionally selective neurons from area MT (n = 38) and MST (n = 68) were recorded during task performance. These neurons coded only for the stimulus movement if the motion stimulus was separated from the background by luminance or flicker (Fourier and drift-balanced motion). If these segregation cues were absent (in the case of theta motion and of the moving sound source), firing rates did not code for the stimulus' direction. Therefore we conclude that although areas MT and MST are undoubtedly involved in processing a moving stimulus, they are not the final cortical stages responsible for perceiving it.
人们普遍认为，恒河猴大脑中的颞中（MT）和颞上中（MST）皮质区域对于处理视觉运动至关重要。我们询问，如果移动刺激由二阶运动刺激组成，这一假设是否成立。此外，我们还询问MT和MST区域的神经元是否对移动声源进行编码。为了回答这些问题，我们训练了三只恒河猴完成一项方向辨别任务。我们的猴子能够正确报告本研究中使用的所有运动刺激的方向。在任务执行期间，记录了来自MT区域（n = 38）和MST区域（n = 68）的方向选择性神经元的放电率。如果运动刺激通过亮度或闪烁（傅里叶和漂移平衡运动）与背景分离，这些神经元仅对刺激运动进行编码。如果没有这些分离线索（在θ运动和移动声源的情况下），放电率就不会对刺激方向进行编码。因此，我们得出结论，尽管MT和MST区域无疑参与了处理移动刺激，但它们并不是负责感知移动刺激的最终皮质阶段。
