Shaikh Aasef G, Green Andrea M, Ghasia Fatema F, Newlands Shawn D, Dickman J David, Angelaki Dora E
Department of Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Curr Biol. 2005 Sep 20;15(18):1657-62. doi: 10.1016/j.cub.2005.08.009.
Our inner ear is equipped with a set of linear accelerometers, the otolith organs, that sense the inertial accelerations experienced during self-motion. However, as Einstein pointed out nearly a century ago, this signal would by itself be insufficient to detect our real movement, because gravity, another form of linear acceleration, and self-motion are sensed identically by otolith afferents. To deal with this ambiguity, it was proposed that neural populations in the pons and midline cerebellum compute an independent, internal estimate of gravity using signals arising from the vestibular rotation sensors, the semicircular canals. This hypothesis, regarding a causal relationship between firing rates and postulated sensory contributions to inertial motion estimation, has been directly tested here by recording neural activities before and after inactivation of the semicircular canals. We show that, unlike cells in normal animals, the gravity component of neural responses was nearly absent in canal-inactivated animals. We conclude that, through integration of temporally matched, multimodal information, neurons derive the mathematical signals predicted by the equations describing the physics of the outside world.
我们的内耳配备了一组线性加速度计，即耳石器官，它们能够感知自身运动过程中所经历的惯性加速度。然而，正如爱因斯坦近一个世纪前所指出的，仅靠这个信号本身不足以检测我们的实际运动，因为重力（另一种线性加速度形式）和自身运动在耳石传入神经中产生的感觉是相同的。为了解决这种模糊性，有人提出脑桥和中线小脑的神经群体利用前庭旋转传感器（半规管）产生的信号来计算一个独立的、内部的重力估计值。关于放电率与假定的对惯性运动估计的感觉贡献之间的因果关系的这一假设，在此通过记录半规管失活前后的神经活动进行了直接测试。我们发现，与正常动物的细胞不同，在半规管失活的动物中，神经反应的重力成分几乎不存在。我们得出结论，通过整合时间上匹配的多模态信息，神经元能够得出描述外部世界物理规律的方程所预测的数学信号。
