Cullen K E, Guitton D
Aerospace Medical Research Unit and the Montreal Neurological Institute, McGill University, Montreal, Quebec H3G 1Y6, Canada.
J Neurophysiol. 1997 Dec;78(6):3283-306. doi: 10.1152/jn.1997.78.6.3283.
We have investigated the relationships among the firing frequency B(t) of inhibitory burst neurons (IBNs) and the metrics and dynamics of the eye, head, and gaze (eye + head) movements generated during voluntary combined eye-head gaze shifts in monkey. The same IBNs were characterized during head-fixed saccades in our first of three companion papers. In head-free gaze shifts, the number of spikes (NOS) in a burst was, for 82% of the neurons, better correlated with gaze amplitude than with the amplitude of either the eye or head components of the gaze shift. A multiple regression analysis confirmed that NOS was well correlated to the sum of head and eye amplitudes during head-free gaze shifts. Furthermore, the mean slope of the relationship between NOS and gaze amplitude was significantly less for head-free gaze shifts than for head-fixed saccades. NOS is a global parameter. To refine we used system identification techniques to evaluate a series of dynamic models in which IBN spike trains were related to gaze or eye movements. We found that gaze- and eye-based models predicted the discharges of IBNs equally well. However, the bias values required by gaze-based models were comparable to those required in our head-fixed models whereas those required by eye-based models were significantly larger. The difference in biases between gaze- and eye-based models was very strongly correlated to the mean head velocity () during gaze shifts [R = -0.93 +/- 0.15 (SD)]. This result suggested that the increased bias required by the eye-based models reflected an unmodeled input onto these cells. To pursue this argument further we investigated a series of dynamic models that included both eye velocity () and terms and this confirmed the importance of these two terms. As in our head-fixed analysis of companion paper I, the most valuable model formulation also included an eye saccade amplitude term (DeltaE) and was given by B(t) = r0 + r1DeltaE + b1 + g1 where r0, r1, b1, and g1 are constants. The amplitude of the head velocity coefficient was significantly less than that of the eye velocity coefficient. Furthermore, in our population long-lead IBNs tended to have a smaller head velocity coefficients than short-lead IBNs. We conclude that during head-free gaze shifts, the head velocity signal carried to the abducens nucleus by primate excitatory burst neurons (EBNs; if EBNs and IBNs carry similar signals) must be offset by other premotor cells.
我们研究了抑制性爆发神经元（IBNs）的发放频率B(t)与猴子在自愿性联合眼-头注视转移过程中产生的眼睛、头部和注视（眼睛+头部）运动的指标及动力学之间的关系。在我们三篇配套论文的第一篇中，对这些相同的IBNs在头部固定扫视过程中的特征进行了描述。在自由头部注视转移中，对于82%的神经元，爆发中的尖峰数量（NOS）与注视幅度的相关性比与注视转移的眼睛或头部成分的幅度的相关性更好。多元回归分析证实，在自由头部注视转移过程中，NOS与头部和眼睛幅度之和密切相关。此外，自由头部注视转移时NOS与注视幅度之间关系的平均斜率显著小于头部固定扫视时的平均斜率。NOS是一个全局参数。为了进一步细化，我们使用系统识别技术来评估一系列动态模型，其中IBN尖峰序列与注视或眼睛运动相关。我们发现基于注视和基于眼睛的模型对IBNs放电的预测效果同样好。然而，基于注视的模型所需的偏差值与我们头部固定模型所需的偏差值相当，而基于眼睛的模型所需的偏差值则显著更大。基于注视和基于眼睛的模型之间偏差的差异与注视转移过程中的平均头部速度（）密切相关[R = -0.93 +/- 0.15（标准差）]。这一结果表明，基于眼睛的模型所需的增加的偏差反映了这些细胞上未建模的输入。为了进一步探讨这一观点，我们研究了一系列包括眼睛速度（）和项的动态模型，这证实了这两个项的重要性。与我们配套论文I中头部固定分析一样，最有价值的模型公式还包括一个眼睛扫视幅度项（DeltaE），并由B(t) = r0 + r1DeltaE + b1 + g1给出，其中r0、r1、b1和g1是常数。头部速度系数的幅度显著小于眼睛速度系数的幅度。此外，在我们的群体中，长潜伏期IBNs的头部速度系数往往比短潜伏期IBNs的小。我们得出结论，在自由头部注视转移过程中，灵长类兴奋性爆发神经元（EBNs；如果EBNs和IBNs携带相似信号）传递到展神经核的头部速度信号必须被其他运动前细胞抵消。
