From the Departments of Anesthesiology (W.L.G., K.K.L., C.J.R., S.L., S.G.) Radiology (X.L.) Neurology (J.R.B., S.-J.L.), Medical College of Wisconsin, Milwaukee, Wisconsin the Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan (A.G.H.).
Anesthesiology. 2019 Aug;131(2):254-265. doi: 10.1097/ALN.0000000000002669.
Elucidating networks underlying conscious perception is important to understanding the mechanisms of anesthesia and consciousness. Previous studies have observed changes associated with loss of consciousness primarily using resting paradigms. The authors focused on the effects of sedation on specific cognitive systems using task-based functional magnetic resonance imaging. The authors hypothesized deepening sedation would degrade semantic more than perceptual discrimination.
Discrimination of pure tones and familiar names were studied in 13 volunteers during wakefulness and propofol sedation targeted to light and deep sedation. Contrasts highlighted specific cognitive systems: auditory/motor (tones vs. fixation), phonology (unfamiliar names vs. tones), and semantics (familiar vs. unfamiliar names), and were performed across sedation conditions, followed by region of interest analysis on representative regions.
During light sedation, the spatial extent of auditory/motor activation was similar, becoming restricted to the superior temporal gyrus during deep sedation. Region of interest analysis revealed significant activation in the superior temporal gyrus during light (t [17] = 9.71, P < 0.001) and deep sedation (t [19] = 3.73, P = 0.001). Spatial extent of the phonologic contrast decreased progressively with sedation, with significant activation in the inferior frontal gyrus maintained during light sedation (t [35] = 5.17, P < 0.001), which didn't meet criteria for significance in deep sedation (t [38] = 2.57, P = 0.014). The semantic contrast showed a similar pattern, with activation in the angular gyrus during light sedation (t [16] = 4.76, P = 0.002), which disappeared in deep sedation (t [18] = 0.35, P = 0.731).
Results illustrate broad impairment in cognitive cortex during sedation, with activation in primary sensory cortex beyond loss of consciousness. These results agree with clinical experience: a dose-dependent reduction of higher cognitive functions during light sedation, despite partial preservation of sensory processes through deep sedation.
阐明意识知觉的相关网络对于理解麻醉和意识的机制非常重要。之前的研究主要使用静息范式观察与意识丧失相关的变化。作者使用基于任务的功能磁共振成像来关注镇静对特定认知系统的影响。作者假设，随着镇静程度的加深，语义辨别能力的下降将超过知觉辨别能力。
在 13 名志愿者清醒和丙泊酚镇静时（目标为轻度和深度镇静），研究了纯音和熟悉名字的辨别。对比突出了特定的认知系统：听觉/运动（音调和注视）、语音（不熟悉的名字与音调和语义（熟悉与不熟悉的名字），并在镇静条件下进行了对比，然后在代表性区域进行了感兴趣区分析。
在轻度镇静时，听觉/运动激活的空间范围相似，在深度镇静时局限于颞上回。感兴趣区分析显示，在轻度镇静时（t[17]=9.71，P<0.001）和深度镇静时（t[19]=3.73，P=0.001），颞上回有显著的激活。随着镇静程度的加深，语音对比的空间范围逐渐减小，在轻度镇静时，下额回有显著的激活（t[35]=5.17，P<0.001），而在深度镇静时则未达到显著水平（t[38]=2.57，P=0.014）。语义对比也呈现出类似的模式，在轻度镇静时，角回有激活（t[16]=4.76，P=0.002），而在深度镇静时则消失（t[18]=0.35，P=0.731）。
结果表明，在镇静期间，认知皮层广泛受损，即使在深度镇静时，初级感觉皮层也有激活。这些结果与临床经验一致：在轻度镇静时，随着镇静程度的加深，高级认知功能逐渐降低，尽管通过深度镇静，感觉过程得到部分保留。
