Takahashi Katsumasa, Gu Yong, May Paul J, Newlands Shawn D, DeAngelis Gregory C, Angelaki Dora E
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Neurosci. 2007 Sep 5;27(36):9742-56. doi: 10.1523/JNEUROSCI.0817-07.2007.
Recent studies have shown that most neurons in the dorsal medial superior temporal area (MSTd) signal the direction of self-translation (i.e., heading) in response to both optic flow and inertial motion. Much less is currently known about the response properties of MSTd neurons during self-rotation. We have characterized the three-dimensional tuning of MSTd neurons while monkeys passively fixated a central, head-fixed target. Rotational stimuli were either presented using a motion platform or simulated visually using optic flow. Nearly all MSTd cells were significantly tuned for the direction of rotation in the absence of optic flow, with more neurons preferring roll than pitch or yaw rotations. The preferred rotation axis in response to optic flow was generally the opposite of that during physical rotation. This result differs sharply from our findings for translational motion, where approximately half of MSTd neurons have congruent visual and vestibular preferences. By testing a subset of neurons with combined visual and vestibular stimulation, we also show that the contributions of visual and vestibular cues to MSTd responses depend on the relative reliabilities of the two stimulus modalities. Previous studies of MSTd responses to motion in darkness have assumed a vestibular origin for the activity observed. We have directly verified this assumption by recording from MSTd neurons after bilateral labyrinthectomy. Selectivity for physical rotation and translation stimuli was eliminated after labyrinthectomy, whereas selectivity to optic flow was unaffected. Overall, the lack of MSTd neurons with congruent rotation tuning for visual and vestibular stimuli suggests that MSTd does not integrate these signals to produce a robust perception of self-rotation. Vestibular rotation signals in MSTd may instead be used to compensate for the confounding effects of rotatory head movements on optic flow.
最近的研究表明，背内侧颞上区（MSTd）的大多数神经元会响应视觉流和惯性运动，发出自我平移方向（即前进方向）的信号。目前，关于MSTd神经元在自我旋转过程中的反应特性了解较少。我们在猴子被动注视一个固定在头部中央的目标时，对MSTd神经元的三维调谐特性进行了表征。旋转刺激要么通过运动平台呈现，要么使用视觉流进行视觉模拟。在没有视觉流的情况下，几乎所有的MSTd细胞对旋转方向都有显著的调谐，更喜欢翻滚旋转的神经元比俯仰或偏航旋转的更多。响应视觉流时的首选旋转轴通常与物理旋转时相反。这一结果与我们对平移运动的研究结果截然不同，在平移运动中，大约一半的MSTd神经元具有一致的视觉和前庭偏好。通过对一部分神经元进行视觉和前庭联合刺激测试，我们还表明，视觉和前庭线索对MSTd反应的贡献取决于两种刺激模式的相对可靠性。先前关于MSTd对黑暗中运动反应的研究假设观察到的活动起源于前庭。我们通过双侧迷路切除术后记录MSTd神经元，直接验证了这一假设。迷路切除术后，对物理旋转和平移刺激的选择性消失，而对视觉流的选择性不受影响。总体而言，缺乏对视觉和前庭刺激具有一致旋转调谐的MSTd神经元表明，MSTd不会整合这些信号以产生对自我旋转的稳健感知。MSTd中的前庭旋转信号可能反而用于补偿旋转头部运动对视觉流的混淆影响。
