1 C3NL, Centre for Restorative Neuroscience, Division of Brain Sciences, Department of Medicine, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK.
Brain. 2014 Feb;137(Pt 2):586-97. doi: 10.1093/brain/awt350. Epub 2013 Dec 26.
Self-awareness is commonly impaired after traumatic brain injury. This is an important clinical issue as awareness affects long-term outcome and limits attempts at rehabilitation. It can be investigated by studying how patients respond to their errors and monitor their performance on tasks. As awareness is thought to be an emergent property of network activity, we tested the hypothesis that impaired self-awareness is associated with abnormal brain network function. We investigated a group of subjects with traumatic brain injury (n = 63) split into low and high performance-monitoring groups based on their ability to recognize and correct their own errors. Brain network function was assessed using resting-state and event-related functional magnetic resonance imaging. This allowed us to investigate baseline network function, as well as the evoked response of networks to specific events including errors. The low performance-monitoring group underestimated their disability and showed broad attentional deficits. Neural activity within what has been termed the fronto-parietal control network was abnormal in patients with impaired self-awareness. The dorsal anterior cingulate cortex is a key part of this network that is involved in performance-monitoring. This region showed reduced functional connectivity to the rest of the fronto-parietal control network at 'rest'. In addition, the anterior insulae, which are normally tightly linked to the dorsal anterior cingulate cortex, showed increased activity following errors in the impaired group. Interestingly, the traumatic brain injury patient group with normal performance-monitoring showed abnormally high activation of the right middle frontal gyrus, putamen and caudate in response to errors. The impairment of self-awareness was not explained either by the location of focal brain injury, or the amount of traumatic axonal injury as demonstrated by diffusion tensor imaging. The results suggest that impairments of self-awareness after traumatic brain injury result from breakdown of functional interactions between nodes within the fronto-parietal control network.
自我意识在创伤性脑损伤后通常会受损。这是一个重要的临床问题，因为意识会影响长期预后，并限制康复尝试。可以通过研究患者如何对自己的错误做出反应以及监测他们在任务中的表现来进行研究。由于意识被认为是网络活动的涌现性质，我们假设受损的自我意识与异常的大脑网络功能有关。我们调查了一组创伤性脑损伤患者（n = 63），根据他们识别和纠正自己错误的能力将他们分为低和高表现监测组。使用静息状态和事件相关功能磁共振成像来评估大脑网络功能。这使我们能够研究基线网络功能，以及网络对特定事件（包括错误）的诱发反应。低表现监测组低估了自己的残疾程度，并表现出广泛的注意力缺陷。在表现自我意识受损的患者中，被称为额顶控制网络的神经活动异常。背侧前扣带皮层是该网络的关键部分，涉及表现监测。该区域在“休息”时与额顶控制网络的其余部分的功能连接减少。此外，在受损组中，通常与背侧前扣带皮层紧密相连的前岛叶在错误后显示出增加的活动。有趣的是，具有正常表现监测的创伤性脑损伤患者组在错误响应中表现出右侧额中回、壳核和尾状核的异常高激活。自我意识的损害既不能用局灶性脑损伤的位置，也不能用弥散张量成像显示的创伤性轴索损伤的程度来解释。研究结果表明，创伤性脑损伤后自我意识的损害是由于额顶控制网络内节点之间的功能相互作用中断所致。
