Inoue Y, Takemura A, Kawano K, Kitama T, Miles F A
Electrotechnical Laboratory, Tsukubashi, Ibaraki, Japan.
Exp Brain Res. 1998 Jul;121(2):135-44. doi: 10.1007/s002210050445.
Motion of a large-field pattern elicits short-latency ocular following responses (OFR) in the monkey, which are mediated at least in part by the medial superior temporal area of the cortex (MST). The magnitude of the OFR is known to be inversely related to viewing distance, and we investigated the dependence of OFR and the associated neuronal activity in the MST on a major cue to viewing distance, ocular vergence, in alert monkeys (Macaca fuscata). The vergence angle, expressed in terms of the apparent viewing distance, ranged from infinity to 16.6 cm (0-6 m(-1)). The magnitude of the initial OFR increased monotonically with increases in convergence at a mean (+/-SD) rate of 19.6+/-4.5%/m(-1) in four monkeys (over the range 0-4 m(-1)). In two monkeys, we recorded the single unit activity of 160 MST neurons that responded to motion of a large-field pattern with directional selectivity. The mean latency (+/-SD) of the MST discharges elicited by large-field motion was 50+/-7.5 ms (n=115), which preceded the onset of OFR by an average of 10+/-9.9 ms. The discharge modulation elicited by large-field motion showed a significant dependence on vergence in 91/160 neurons (57%), 72 of which (79%) increased their firing rate with increasing convergence ("near" neurons), and the remainder increasing their firing rate with decreasing convergence ("far" neurons). However, on average, the sensitivity of these MST neurons to vergence was only about 30% of that shown by the OFR. It could be that only those neurons that are very sensitive to vergence angle contribute to the OFR, but it is also possible that much of the modulation of OFR with vergence occurs downstream from the MST or in alternative pathways (yet to be discovered) that contribute to OFR.
大视野模式的运动在猴子中引发短潜伏期的眼球跟踪反应（OFR），这至少部分是由皮层的内侧颞上区（MST）介导的。已知OFR的幅度与观察距离成反比，我们在警觉的猕猴（食蟹猴）中研究了OFR以及MST中相关神经元活动对观察距离的主要线索——眼的辐辏的依赖性。以表观观察距离表示的辐辏角范围从无穷远到16.6厘米（0 - 6米⁻¹）。在四只猴子中（在0 - 4米⁻¹范围内），初始OFR的幅度随着辐辏增加以平均（±标准差）19.6 ± 4.5%/米⁻¹的速率单调增加。在两只猴子中，我们记录了160个对大视野模式运动有方向选择性反应的MST神经元的单位活动。大视野运动引发的MST放电的平均潜伏期（±标准差）为50 ± 7.5毫秒（n = 115），比OFR开始平均提前10 ± 9.9毫秒。大视野运动引发的放电调制在91/160个神经元（57%）中显示出对辐辏的显著依赖性，其中72个（79%）随着辐辏增加而增加放电率（“近”神经元），其余的随着辐辏减小而增加放电率（“远”神经元）。然而，平均而言，这些MST神经元对辐辏的敏感性仅约为OFR的30%。可能只有那些对辐辏角非常敏感的神经元才对OFR有贡献，但也有可能OFR随辐辏的大部分调制发生在MST的下游或在尚未发现的有助于OFR的替代通路中。
