Towards a unified, computationally-implemented neural network for understanding semantic cognition and its disorders.

语义记忆指的是我们拥有的关于单词，物体，人和我们环境中所有刺激的意义的丰富知识数据库。当我们理解一个单词或识别一个物体时，我们会激活这个信息。我们使用相同的知识来启动言语或非言语活动，如使用物体。沟通的目的，本身，是为了在人与人之间传达意义。因此，很明显，语义知识对于工作和家庭中的许多日常活动都至关重要。当这种类型的知识在脑损伤后瓦解或变得无法获取时，患者在生活的许多方面都会变得严重残疾。想象一下，例如，在日常对话中，一封信或报纸中只能理解一小部分单词;被困在重要的单词查找问题中;或者无法理解日常符号或路标。可悲的是，这类问题是许多类型的大脑疾病的共同特征。语义障碍是某些类型的痴呆症、脑感染和中风后的特征。在过去对中风后语言问题患者的研究中，我们发现大约1/3的患者存在可测量的语义处理问题。因此，我们持续研究计划的核心目标是：（a）建立一个正式的工作模型，以了解大脑如何支持语义处理;（B）对所有类型的语义障碍患者进行分类和调查;以及（c）利用我们的语义处理"大脑模型"来了解患者不同障碍的原因。这些步骤将用于改善：语义缺陷的检测;鉴别诊断;临床管理;和基于证据的干预措施。在我们上一个研究项目中，我们发现了不同患者组语义障碍性质的重要质的变化。除了这些临床研究，我们还开发和应用了新的基础科学方法来探测各种特定大脑区域的功能。这使我们能够检查正常运作的大脑中的患者结果，然后使用这些方法来扩展我们对语义过程的理解，以及涉及哪些特定的大脑子区域。在下一阶段的研究中，我们将利用这些重要的发现和方法作为一系列新研究的基础。我们的最终目标是建立一个支持语义处理的大脑区域网络的完整图片和模型。我们将使用这个模型来重现每个患者组的表现模式，并将其高精度地分类。这将通过采用各种临床和基础科学方法来实现。这些措施包括：（a）对现有和新的病人组别作进一步的临床调查，以搜集各类有关病人组别的语义处理问题的完整目录（包括痴呆症、中风和其他形式的脑损伤）;（B）脑刺激研究，以模拟类似病人的缺陷，并测试有关语义功能的关键概念;（c）功能性脑成像，以绘制出健康参与者和各种患者群体的语义处理;（d）其他事项通过一种新的数学建模形式（其中包含有关大脑区域的信息）合并来自所有这些研究领域的信息并将它们"连接"到模型中--这样我们不仅可以模拟病人的行为，还可以模拟大脑损伤的潜在模式。然后，我们将能够使用这个模型，不仅要了解所有这些不同的患者群体的语义问题的性质，但也使用该模型，以获得新的见解，最大限度地减少这些问题，并产生新的干预措施，可以使用这些患者群体的语言治疗师。

Semantic memory refers to the rich database of knowledge we have about the meanings of words, objects, people and all the stimuli present in our environment. We activate this information when we comprehend a word or recognise an object. We use the same knowledge to initiate speech or non-verbal activities such as object use. The aim of communication, itself, is for meaning to be conveyed between people. It is evident, therefore, that semantic knowledge is crucial for many everyday activities both at work and at home. When this type of knowledge disintegrates or becomes inaccessible after brain damage, patients become significantly disabled in many aspects of their lives. Imagine, for example, being able to comprehend only a small proportion of the words in everyday conversation, a letter or newspaper; being stuck with significant word-finding problems; or being unable to understand everyday symbols or road signs. Sadly, these kinds of problems are a common feature of many types of brain disease. Semantic impairment is a characteristic of certain types of dementia, brain infections and after stroke. In a past study of patients with language problems after stroke, we found measurable problems with semantic processing in around 1/3 of them. The core aims of our continuing research programme, therefore, are (a) to build up a formal, working model of how the brain supports semantic processing; (b) to catalogue and investigate all types of patient with semantic impairment; and (c) to use our "brain model" of semantic processing to understand the causes of the patients' different impairments. These steps will be used to improve: detection of semantic deficits; differential diagnosis; clinical management; and evidence-based interventions. In our last research programme we discovered important qualitative variations in the nature of semantic impairment in different patient groups. In addition to these clinical investigations, we developed and applied new basic science methods to probe the functioning of various specific brain regions. This allowed us to check the patient results in normally-functioning brains and then to use the methods to extend our understanding of semantic processes and which specific brain subregions are involved. In the next phase of our research, we will use these important findings and methods as a foundation for a new series of studies. Our ultimate aim is to build up a complete picture and model of the network of brain regions that support semantic processing. We will use this model to reproduce each patient group's pattern of performance, which will be catalogued with high precision. This will be achieved by adopting a variety of clinical and basic science methods. These will include: (a) further clinical investigations of existing and new patient groups - leading to a complete catalogue of the semantic processing problems in all types of relevant patient groups (covering dementia, stroke and other forms of brain damage); (b) brain stimulation studies to mimic patient-like deficits and to test key ideas about semantic functioning; (c) functional brain imaging in order to map out the semantic processing, in both healthy participants and various patient groups; (d) to amalgamate the information from all these lines of enquiry through a new form of mathematical modelling which incorporates information about brain regions and their 'wiring' into the model - such that we can simulate not only the patients' behaviour but also the underlying pattern of brain damage. We will then be able to use this model not only to understand the nature of semantic problems across all these different patient groups but also to use the model to gain new insights about minimising these problems and for generating new interventions that could be used by speech therapists with these patient groups.