Dickman J David, Angelaki Dora E
Department of Otolaryngology, Washington University, 660 S Euclid, St Louis, MO 63110, USA.
Exp Brain Res. 2004 Mar;155(1):91-101. doi: 10.1007/s00221-003-1692-1. Epub 2003 Nov 11.
The temporal processing in the encoding of head rotation was investigated by comparing the dynamics of vestibular nuclei neurons with those of the regularly and irregularly firing semicircular canal afferents in alert rhesus monkeys. During earth-vertical axis rotations, neurons without eye movement sensitivity differed in their response dynamics from both regularly and irregularly firing semicircular canal afferents. At high frequencies, central responses increased in sensitivity and maintained phase leads of nearly 30 degrees relative to head velocity. These persistent high-frequency phase leads resembled those of irregularly firing (but not regularly firing) semicircular canal afferents. However, at low frequencies, central responses exhibited significantly smaller phase leads than those of irregularly firing semicircular canal afferents, and dynamics resembled more those of the regularly firing afferents. The response dynamics of central non-eye movement cells were significantly different from those of position-vestibular-pause and eye-head neurons (collectively referred to as eye movement cells). In contrast to the persistent phase leads of non-eye movement neurons, all eye movement cells modulated closely in phase with head velocity at all frequencies down to 0.05 Hz during visual suppression tasks. Vertical canal non-eye movement neurons that were insensitive to both translations and static head tilts led head velocity by approximately 5-30 degrees during high-frequency earth-horizontal axis rotations. Unlike the earth-vertical axis responses that led head velocity at low frequencies by as much as 20-40 degrees, vertical canal neurons only slightly led or even lagged behind head velocity during low-frequency earth-horizontal axis rotations. Posterior canal central non-eye movement cells lagged behind head velocity significantly more than anterior canal neurons. These frequency dependencies of central vestibular neurons in comparison with those of the afferents suggest that both low- and high-pass filtering might be necessary to convert primary semicircular canal afferent response dynamics to central neuron ones.
通过比较警觉的恒河猴前庭核神经元与规则和不规则发放的半规管传入神经的动态变化，研究了头部旋转编码中的时间处理。在地球垂直轴旋转期间，无眼动敏感性的神经元在反应动态上与规则和不规则发放的半规管传入神经均有所不同。在高频时，中枢反应的敏感性增加，相对于头部速度保持近30度的相位超前。这些持续的高频相位超前类似于不规则发放（而非规则发放）的半规管传入神经的相位超前。然而，在低频时，中枢反应的相位超前明显小于不规则发放的半规管传入神经，其动态更类似于规则发放的传入神经。中枢非眼动细胞的反应动态与位置 - 前庭 - 暂停和眼 - 头神经元（统称为眼动细胞）的反应动态显著不同。与非眼动神经元持续的相位超前相反，在视觉抑制任务期间，所有眼动细胞在低至0.05Hz的所有频率下均与头部速度紧密同相调制。对平移和静态头部倾斜均不敏感的垂直半规管非眼动神经元在高频地球水平轴旋转期间领先头部速度约5 - 30度。与在低频时领先头部速度多达20 - 40度的地球垂直轴反应不同，垂直半规管神经元在低频地球水平轴旋转期间仅略微领先甚至落后于头部速度。后半规管中枢非眼动细胞比前半规管神经元更显著地落后于头部速度。与传入神经相比，中枢前庭神经元的这些频率依赖性表明，可能需要低通和高通滤波才能将初级半规管传入神经的反应动态转换为中枢神经元的反应动态。
