Bon L, Lucchetti C
Istituto di Fisiologia, Universita' di Trieste, Italy.
Exp Brain Res. 1994;102(2):259-71. doi: 10.1007/BF00227513.
We evoked both ear and eye movements in area 8b, the rostral area of frontal cortex, in two monkeys. In some sites it was possible to evoke only ear movements or only eye movements; in other locations we evoked both ear and eye movements by varying the intensity of electrical stimulation. The electrically evoked ear movements were forward, or backward, or oblique (upward-forward; upward-backward). In two penetrations the ear movements were bilateral, in the other penetrations they were contralateral. Ipsilateral ear movements were not observed. The evoked eye movements were mainly fixed-vector saccades, contralateral and with an upward orientation of about 45 degrees. If we considered only the sites where the threshold was equal to or lower than 50 microA, the stimulation of this area evoked mainly ear movements. In addition we recorded the electrical activity of 195 neurons. Of these neurons: 74% (145/195) discharged before ear movements (ear cells); 20% (40/195) discharged before ear and eye movements (ear-eye cells); 5% (10/195) discharged only before eye movements (eye cells). Ninety-one percent (132/145) of ear cells presented a preferred direction; 90% (36/40) of ear-eye cells presented a preferred direction for ear movements, and 15% (6/40) presented a preferred direction for eye movements. Eighty-five percent (34/40) of cells did not present a preferred direction for visually guided saccades and were active when the monkey made saccades toward the unlit targets (checking saccades). Our results show that a field of area 8b is related to ear movements and to eye-ear movements. The findings that it is possible to obtain both ear and eye movements with low-intensity currents and that there are cells firing for the two types of movements suggest that area 8b may be involved in the orientation and coordination of both ear and eye. This area might be considered a rostral extension of supplementary eye field (SEF) or a different region. However, based on its distinct functional characteristics and connectivity, it is probably better regarded as a separate field. Regardless, the combination of 8b and SEF may constitute a cortical center for orienting processes.
我们在两只猴子的额叶皮层嘴侧区域8b中诱发了耳部和眼部运动。在一些位点，仅能诱发耳部运动或仅能诱发眼部运动；在其他位点，我们通过改变电刺激强度来诱发耳部和眼部运动。电诱发的耳部运动包括向前、向后或倾斜（向上向前；向上向后）。在两次穿刺中，耳部运动是双侧的，在其他穿刺中则是对侧的。未观察到同侧耳部运动。诱发的眼部运动主要是固定矢量扫视，对侧且向上约45度。如果我们仅考虑阈值等于或低于50微安的位点，对该区域的刺激主要诱发耳部运动。此外，我们记录了195个神经元的电活动。在这些神经元中：74%（145/195）在耳部运动之前放电（耳部细胞）；20%（40/195）在耳部和眼部运动之前放电（耳部 - 眼部细胞）；5%（10/195）仅在眼部运动之前放电（眼部细胞）。91%（132/145）的耳部细胞有一个偏好方向；90%（36/40）的耳部 - 眼部细胞有耳部运动的偏好方向，15%（6/40）有眼部运动的偏好方向。85%（34/40）的细胞对于视觉引导的扫视没有偏好方向，并且在猴子向未点亮的目标进行扫视（检查性扫视）时活跃。我们的结果表明，8b区域的一个场与耳部运动以及眼 - 耳运动有关。能够用低强度电流获得耳部和眼部运动以及存在针对这两种运动类型放电的细胞这一发现表明，8b区域可能参与耳部和眼部的定向与协调。该区域可能被认为是辅助眼区（SEF）的嘴侧延伸或一个不同的区域。然而，基于其独特的功能特征和连接性，它可能更宜被视为一个独立的场。无论如何，8b区域和SEF的组合可能构成一个用于定向过程的皮层中心。
