It remains unclear how specific cortical regions contribute to the brain’s overall capacity for consciousness. Clarifying this could help distinguish between theories of consciousness. Here, we investigate the association between markers of regionally specific (de)activation and the brain’s overall capacity for consciousness. We recorded electroencephalographic responses to cortical electrical stimulation in six rats and computed Perturbational Complexity Index state-transition (PCIST), which has been extensively validated as an index of the capacity for consciousness in humans. We also estimated the balance between activation and inhibition of specific cortical areas with the ratio between high and low frequency power from spontaneous electroencephalographic activity at each electrode. We repeated these measurements during wakefulness, and during two levels of ketamine anaesthesia: with the minimal dose needed to induce behavioural unresponsiveness and twice this dose. We found that PCIST was only slightly reduced from wakefulness to light ketamine anaesthesia, but dropped significantly with deeper anaesthesia. The high-dose effect was selectively associated with reduced high frequency/low frequency ratio in the posteromedial cortex, which strongly correlated with PCIST. Conversely, behavioural unresponsiveness induced by light ketamine anaesthesia was associated with similar spectral changes in frontal, but not posterior cortical regions. Thus, activity in the posteromedial cortex correlates with the capacity for consciousness, as assessed by PCIST, during different depths of ketamine anaesthesia, in rats, independently of behaviour. These results are discussed in relation to different theories of consciousness.

中文翻译：

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氯胺酮麻醉下的意识能力与大鼠后内侧皮质的活动选择性相关


目前尚不清楚特定的皮质区域如何影响大脑的整体意识能力。澄清这一点有助于区分意识理论。在这里，我们研究了区域特异性（去）激活标记与大脑整体意识能力之间的关联。我们记录了六只大鼠对皮质电刺激的脑电图反应，并计算了扰动复杂性指数状态转换（PCIST），该指数已被广泛验证为人类意识能力的指数。我们还通过每个电极自发脑电图活动的高频功率和低频功率之间的比率来估计特定皮质区域的激活和抑制之间的平衡。我们在清醒时和两种氯胺酮麻醉期间重复了这些测量：诱导行为无反应所需的最小剂量和该剂量的两倍。我们发现，从清醒到轻度氯胺酮麻醉，PCIST 仅略有下降，但随着麻醉深度的加深，PCIST 显着下降。高剂量效应选择性地与后内侧皮层高频/低频比的降低相关，这与 PCIST 密切相关。相反，氯胺酮轻度麻醉引起的行为无反应与额叶区域的类似光谱变化有关，但与后皮质区域无关。因此，根据 PCIST 的评估，大鼠在不同深度的氯胺酮麻醉期间，后内侧皮质的活动与意识能力相关，与行为无关。这些结果是与不同的意识理论相关的讨论。