Visual processing in the ketamine-anesthetized monkey - Optokinetic and blood oxygenation level-dependent responses
Visual processing in the ketamine-anesthetized monkey - Optokinetic and blood oxygenation level-dependent responses
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DOI：
10.1007/s00221-001-0998-0
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发表时间：
2002-04-01
影响因子：
2
通讯作者：
Logothetis, NK
中科院分区：
文献类型：
--
作者：
Leopold, DA;Plettenberg, HK;Logothetis, NK
我们用视动反应和功能磁共振成像(FMRI)研究了小剂量(1-2 mg/kg)氯胺酮麻醉调节清醒状态猴的视觉加工过程。我们发现，尽管动物处于分离状态，尽管氯胺酮对眼球运动系统有特定的影响，但视动性眼球震颤(OKN)可以可靠地在大的、移动的视觉模式中诱发。对于单眼刺激，反应是水平双向的，这表明氯胺酮并没有消除运动刺激的皮层处理。此外，功能磁共振成像的结果直接表明，皮层血氧水平依赖(BOLD)对视觉模式的反应在相同剂量的氯胺酮诱导OKN时得到保存。最后，在氯胺酮麻醉状态下，知觉双稳态运动刺激产生了自发交替的OKN模式，这种模式通常与知觉变化紧密相连。综上所述，这些结果表明，在给予氯胺酮后，尽管动物的行为发生了分离，但皮层回路继续以剂量依赖的方式处理视觉模式。虽然在这种情况下很难评估知觉体验，但眼动模式显示，大脑不仅记录，而且还对其感觉输入做出反应，利用它来驱动感觉运动回路，甚至通过参与与感知相关的自发状态变化来对感觉冲突做出反应。因此，氯胺酮麻醉的猴子制剂为与意识知觉和麻醉相关的行为和电生理研究以及基本感觉加工的神经机制提供了一个安全和可行的范例。
We used optokinetic responses and functional magnetic resonance imaging (fMRI) to examine visual processing in monkeys whose conscious state was modulated by low doses (1-2 mg/kg) of the dissociative anesthetic ketamine. We found that, despite the animal's dissociated state and despite specific influences of ketamine on the oculomotor system, optokinetic nystagmus (OKN) could be reliably elicited with large, moving visual patterns. Responses were horizontally bidirectional for monocular stimulation, indicating that ketamine did not eliminate cortical processing of the motion stimulus. Also, results from fMRI directly demonstrated that the cortical blood oxygenation level-dependent (BOLD) response to visual patterns was preserved at the same ketamine doses used to elicit OKN. Finally, in the ketamine-anesthetized state, perceptually bistable motion stimuli produced patterns of spontaneously alternating OKN that normally would be tightly coupled to perceptual changes. These results, taken together, demonstrate that after ketamine administration cortical circuits continue to processes visual patterns in a dose-dependent manner despite the animal's behavioral dissociation. While perceptual experience is difficult to evaluate under these conditions, oculomotor patterns revealed that the brain not only registers but also acts upon its sensory input, employing it to drive a sensorimotor loop and even responding to a sensory conflict by engaging in spontaneous perception-related state changes. The ketamine-anesthetized monkey preparation thereby offers a safe and viable paradigm for the behavioral and electrophysiological investigation of issues related to conscious perception and anesthesia, as well as neural mechanisms of basic sensory processing.