Geranmayeh Fatemeh, Brownsett Sonia L E, Wise Richard J S
Computational Cognitive and Clinical Neuroimaging Laboratory, Division of Brain Sciences, Imperial College London, Hammersmith Hospital, London, W12 0NN, UK
Computational Cognitive and Clinical Neuroimaging Laboratory, Division of Brain Sciences, Imperial College London, Hammersmith Hospital, London, W12 0NN, UK.
Brain. 2014 Oct;137(Pt 10):2632-48. doi: 10.1093/brain/awu163. Epub 2014 Jun 28.
The estimated prevalence of aphasia in the UK and the USA is 250 000 and 1 000 000, respectively. The commonest aetiology is stroke. The impairment may improve with behavioural therapy, and trials using cortical stimulation or pharmacotherapy are undergoing proof-of-principle investigation, but with mixed results. Aphasia is a heterogeneous syndrome, and the simple classifications according to the Broca-Wernicke-Lichtheim model inadequately describe the diverse communication difficulties with which patients may present. Greater knowledge of how intact neural networks promote recovery after aphasic stroke, either spontaneously or in response to interventions, will result in clearer hypotheses about how to improve the treatment of aphasia. Twenty-five years ago, a pioneering study on healthy participants heralded the introduction of functional neuroimaging to the study of mechanisms of recovery from aphasia. Over the ensuing decades, such studies have been interpreted as supporting one of three hypotheses, which are not mutually exclusive. The first two predate the introduction of functional neuroimaging: that recovery is the consequence of the reconstitution of domain-specific language systems in tissue around the lesion (the 'perilesional' hypothesis), or by homotopic cortex in the contralateral hemisphere (the 'laterality-shift' hypothesis). The third is that loss of transcallosal inhibition to contralateral homotopic cortex hinders recovery (the 'disinhibition' hypothesis). These different hypotheses at times give conflicting views about rehabilitative intervention; for example, should one attempt to activate or inhibit a contralateral homotopic region with cortical stimulation techniques to promote recovery? This review proposes that although the functional imaging data are statistically valid in most cases, their interpretation has often favoured one explanation while ignoring plausible alternatives. In our view, this is particularly evident when recovery is attributed to activity in 'language networks' occupying sites not observed in healthy participants. In this review we will argue that much of the distribution of what has often been interpreted as language-specific activity, particularly in midline and contralateral cortical regions, is an upregulation of activity in intact domain-general systems for cognitive control and attention, responding in a task-dependent manner to the increased 'effort' when damaged downstream domain-specific language networks are impaired. We further propose that it is an inability fully to activate these systems that may result in sub optimal recovery in some patients. Interpretation of the data in terms of activity in domain-general networks affords insights into novel approaches to rehabilitation.
据估计，失语症在英国和美国的患病率分别为25万和100万。最常见的病因是中风。行为疗法可能会改善这种损伤，使用皮质刺激或药物疗法的试验正在进行原理验证研究，但结果不一。失语症是一种异质性综合征，根据布罗卡-韦尼克-利希海姆模型进行的简单分类不足以描述患者可能出现的各种沟通困难。更深入了解完整的神经网络如何在失语症中风后自发或响应干预促进恢复，将有助于更清晰地提出关于如何改善失语症治疗的假设。25年前，一项针对健康参与者的开创性研究预示着功能神经成像将被引入失语症恢复机制的研究。在随后的几十年里，此类研究被解释为支持三种假设之一，这三种假设并非相互排斥。前两种假设早于功能神经成像的引入：恢复是病变周围组织中特定领域语言系统重构的结果（“病变周围”假设），或者是对侧半球的同位皮层的结果（“偏侧性转移”假设）。第三种假设是胼胝体对侧同位皮层的抑制丧失阻碍了恢复（“去抑制”假设）。这些不同的假设有时对康复干预给出相互矛盾的观点；例如，是否应该尝试用皮质刺激技术激活或抑制对侧同位区域以促进恢复？本综述提出，虽然功能成像数据在大多数情况下在统计学上是有效的，但其解释往往倾向于一种解释而忽略了合理的替代解释。我们认为，当恢复归因于在健康参与者中未观察到的部位的“语言网络”活动时，这一点尤为明显。在本综述中，我们将论证，通常被解释为语言特异性活动的许多分布，特别是在中线和对侧皮质区域，是完整的认知控制和注意力通用系统活动的上调，当受损的下游特定领域语言网络受损时，这些系统以任务依赖的方式对增加的“努力”做出反应。我们进一步提出，一些患者恢复不佳可能是由于无法充分激活这些系统。从通用网络活动的角度解释数据有助于深入了解新的康复方法。
