Ozgoren Murat, Bayazit Onur, Kocaaslan Sibel, Gokmen Necati, Oniz Adile
Department of Biophysics, Faculty of Medicine, Dokuz Eylul University, Izmir, 35340, Turkey.
Nonlinear Biomed Phys. 2010 Jun 3;4 Suppl 1(Suppl 1):S6. doi: 10.1186/1753-4631-4-S1-S6.
The study of brain functioning is a major challenge in neuroscience fields as human brain has a dynamic and ever changing information processing. Case is worsened with conditions where brain undergoes major changes in so-called different conscious states. Even though the exact definition of consciousness is a hard one, there are certain conditions where the descriptions have reached a consensus. The sleep and the anesthesia are different conditions which are separable from each other and also from wakefulness. The aim of our group has been to tackle the issue of brain functioning with setting up similar research conditions for these three conscious states.
In order to achieve this goal we have designed an auditory stimulation battery with changing conditions to be recorded during a 40 channel EEG polygraph (Nuamps) session. The stimuli (modified mismatch, auditory evoked etc.) have been administered both in the operation room and the sleep lab via Embedded Interactive Stimulus Unit which was developed in our lab. The overall study has provided some results for three domains of consciousness. In order to be able to monitor the changes we have incorporated Bispectral Index Monitoring to both sleep and anesthesia conditions.
The first stage results have provided a basic understanding in these altered states such that auditory stimuli have been successfully processed in both light and deep sleep stages. The anesthesia provides a sudden change in brain responsiveness; therefore a dosage dependent anesthetic administration has proved to be useful. The auditory processing was exemplified targeting N1 wave, with a thorough analysis from spectrogram to sLORETA. The frequency components were observed to be shifting throughout the stages. The propofol administration and the deeper sleep stages both resulted in the decreasing of N1 component. The sLORETA revealed similar activity at BA7 in sleep (BIS 70) and target propofol concentration of 1.2 microg/mL.
The current study utilized similar stimulation and recording system and incorporated BIS dependent values to validate a common approach to sleep and anesthesia. Accordingly the brain has a complex behavior pattern, dynamically changing its responsiveness in accordance with stimulations and states.
由于人类大脑具有动态且不断变化的信息处理能力，大脑功能的研究是神经科学领域的一项重大挑战。当大脑在所谓的不同意识状态下发生重大变化时，情况会变得更糟。尽管意识的确切定义很难确定，但在某些情况下，描述已达成共识。睡眠和麻醉是彼此可分离且与清醒状态也可分离的不同状态。我们团队的目标是通过为这三种意识状态设置相似的研究条件来解决大脑功能问题。
为了实现这一目标，我们设计了一种在40通道脑电图多导记录仪（Nuamps）记录过程中随条件变化的听觉刺激组。刺激（改良失配、听觉诱发电位等）通过我们实验室开发的嵌入式交互式刺激单元在手术室和睡眠实验室中进行。总体研究为意识的三个领域提供了一些结果。为了能够监测变化，我们在睡眠和麻醉条件下都采用了脑电双频指数监测。
第一阶段的结果为这些改变的状态提供了基本的理解，即听觉刺激在浅睡眠和深睡眠阶段均已成功处理。麻醉会使大脑反应性突然改变；因此，剂量依赖性麻醉给药已被证明是有用的。以N1波为靶点举例说明了听觉处理过程，并从频谱图到标准化低分辨率脑电磁断层成像进行了全面分析。观察到频率成分在各个阶段都在变化。丙泊酚给药和较深睡眠阶段均导致N1成分减少。标准化低分辨率脑电磁断层成像显示，睡眠状态下（脑电双频指数为70）的BA7区域和目标丙泊酚浓度为1.2微克/毫升时具有相似的活动。
当前研究采用了相似的刺激和记录系统，并纳入了依赖脑电双频指数的值，以验证一种针对睡眠和麻醉的通用方法。因此，大脑具有复杂的行为模式，会根据刺激和状态动态改变其反应性。
