Kumar Arun N, Han Yanning H, Kirsch Robert F, Dell'Osso Louis F, King W Michael, Leigh R John
Department of Biomedical Engineering, Department of Veterans Affairs Medical Center and University Hospitals, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106-5040, USA.
Biol Cybern. 2006 Aug;95(2):143-57. doi: 10.1007/s00422-006-0073-9. Epub 2006 May 13.
During natural activities, two types of eye movements - saccades and vergence - are used in concert to point the fovea of each eye at features of interest. Some electrophysiological studies support the concept of independent neurobiological substrates for saccades and vergence, namely saccadic and vergence burst neurons. Discerning the interaction of these two components is complicated by the near-synchronous occurrence of saccadic and vergence components. However, by positioning the far target below the near target, it is possible to induce responses in which the peak velocity of the vertical saccadic component precedes the peak velocity of the horizontal vergence component by approximately 75 ms. When saccade-vergence responses are temporally dissociated in this way, the vergence velocity waveform changes, becoming less skewed. We excluded the possibility that such change in skewing was due to visual feedback by showing that similar behavior occurred in darkness. We then tested a saccade-related vergence burst neuron (SVBN) model proposed by Zee et al. in J Neurophysiol 68:1624-1641 (1992), in which omnipause neurons remove inhibition from both saccadic and vergence burst neurons. The technique of parameter estimation was used to calculate optimal values for responses from human subjects in which saccadic and convergence components of response were either nearly synchronized or temporally dissociated. Although the SVBN model could account for convergence waveforms when saccadic and vergence components were nearly synchronized, it could not when the components were temporally dissociated. We modified the model so that the saccadic pulse changed the parameter values of the convergence burst units if both components were synchronized. The modified model accounted for velocity waveforms of both synchronous and dissociated convergence movements. We conclude that both the saccadic pulse and omnipause neuron inhibition influence the generation of vergence movements when they are made synchronously with saccades.
在自然活动中，两种眼动——扫视和辐辏——协同作用，将每只眼睛的中央凹对准感兴趣的特征。一些电生理研究支持扫视和辐辏具有独立神经生物学基质的概念，即扫视爆发神经元和辐辏爆发神经元。由于扫视和辐辏成分几乎同时出现，辨别这两个成分之间的相互作用变得复杂。然而，通过将远目标置于近目标下方，可以诱发垂直扫视成分的峰值速度比水平辐辏成分的峰值速度提前约75毫秒的反应。当扫视 - 辐辏反应以这种方式在时间上分离时，辐辏速度波形会发生变化，变得不那么偏斜。我们通过表明在黑暗中也会出现类似行为，排除了这种偏斜变化是由于视觉反馈的可能性。然后，我们测试了Zee等人在《神经生理学杂志》68:1624 - 1641（1992年）中提出的扫视相关辐辏爆发神经元（SVBN）模型，其中全暂停神经元消除对扫视爆发神经元和辐辏爆发神经元的抑制。参数估计技术用于计算人类受试者反应的最佳值，这些反应中扫视和会聚成分要么几乎同步，要么在时间上分离。尽管当扫视和辐辏成分几乎同步时，SVBN模型可以解释会聚波形，但当成分在时间上分离时则不能。我们修改了模型，使得如果两个成分同步，扫视脉冲会改变会聚爆发单元的参数值。修改后的模型解释了同步和分离的会聚运动的速度波形。我们得出结论，当扫视和辐辏运动与扫视同步进行时，扫视脉冲和全暂停神经元抑制都会影响辐辏运动的产生。
