Imas Olga A, Ropella Kristina M, Ward B Douglas, Wood James D, Hudetz Anthony G
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA.
Neurosci Lett. 2005 Oct 28;387(3):145-50. doi: 10.1016/j.neulet.2005.06.018.
We seek to understand neural correlates of anesthetic-induced unconsciousness. We hypothesize that cortical integration of sensory information may underlie conscious perception and may be disrupted by anesthetics. A critical role in frontal-posterior interactions has been proposed, and gamma (20-60 Hz) oscillations have also been assigned an essential role in consciousness. Here we investigated whether general anesthetics may interfere with the exchange of information encoded in gamma oscillations between frontal and posterior cortices. Bipolar electrodes for recording of event-related potentials (ERP) were chronically implanted in the primary visual cortex, parietal association and frontal association cortices of six rats. Sixty light flashes were presented every 5s, and ERPs were recorded at increasing concentrations of halothane or isoflurane (0-2%). Information exchange was estimated by transfer entropy, a novel measure of directional information transfer. Transfer entropy was calculated from 1-s wavelet-transformed ERPs. We found that (1) feedforward transfer entropy (FF-TE) and feedback transfer entropy (FB-TE) were balanced in conscious-sedated state; (2) anesthetics at concentrations producing unconsciousness augmented both FF-TE and FB-TE at 30 Hz but reduced them at 50 Hz; (3) reduction at 50 Hz was more pronounced for FB-TE, especially between frontal and posterior regions; (4) at high concentrations, both FF-TE and FB-TE at all frequencies were at or below conscious-sedated baseline. Our findings suggest that inhalational anesthetics preferentially impair frontal-posterior FB information transfer at high gamma frequencies consistent with the postulated role of frontal-posterior interactions in consciousness.
我们试图了解麻醉诱导无意识状态的神经关联。我们假设感觉信息的皮层整合可能是意识感知的基础，并且可能会被麻醉剂破坏。有人提出了额叶 - 后部相互作用中的关键作用，并且γ（20 - 60赫兹）振荡也被认为在意识中起着重要作用。在这里，我们研究了全身麻醉剂是否可能干扰额叶和后部皮层之间以γ振荡编码的信息交换。用于记录事件相关电位（ERP）的双极电极被长期植入六只大鼠的初级视觉皮层、顶叶联合皮层和额叶联合皮层。每5秒呈现60次闪光，并在增加浓度的氟烷或异氟烷（0 - 2%）下记录ERP。通过转移熵来估计信息交换，转移熵是一种用于定向信息传递的新度量。转移熵是根据1秒的小波变换ERP计算得出的。我们发现：（1）在清醒 - 镇静状态下，前馈转移熵（FF - TE）和反馈转移熵（FB - TE）是平衡的；（2）产生无意识状态的麻醉剂浓度会使30赫兹时的FF - TE和FB - TE都增加，但在50赫兹时会降低；（3）50赫兹时的降低对于FB - TE更为明显，尤其是在额叶和后部区域之间；（4）在高浓度下，所有频率的FF - TE和FB - TE都处于或低于清醒 - 镇静基线。我们的研究结果表明，吸入性麻醉剂优先损害高γ频率下的额叶 - 后部FB信息传递，这与额叶 - 后部相互作用在意识中的假定作用一致。
