The ability to speak coherently, maintaining focus on the topic at hand, is critical for effective communication and is commonly impaired following brain damage. Recent data suggests that executive processes that regulate access to semantic knowledge (i.e., semantic control) are critical for maintaining coherence during speech. To test this hypothesis, we assessed speech coherence in a case-series of stroke patients who exhibited deficits in semantic control. Patients were asked to speak about a series of topics and their responses were analysed using computational linguistic methods to derive measures of their global coherence (the degree to which they spoke about the topic given) and local coherence (the degree to which they maintained a topic from one utterance to the next). Compared with age-matched controls, patients showed severe impairments to global coherence but not to local coherence. Global coherence was strongly correlated with the patients' performance on tests of semantic control, with greater semantic control deficits associated with poorer ability to maintain global coherence. Other aspects of speech production were also impaired but were not significantly correlated with semantic control deficits. These results suggest that semantic control deficits give rise to speech that is poorly regulated at the macrolinguistic “message” level. The preservation of local coherence in the patients suggests that automatic activation of semantic associations is relatively intact, such that each utterance they produce is connected meaningfully to the next. However, in the absence of control processes to constrain semantic activation, the content of their speech becomes increasingly distant from the original topic of discourse. This study is the first to investigate the impact of semantic control impairments on speech production at the discourse level and suggests that patients with these impairments are likely to have difficulties maintaining coherence in conversation.

中文翻译：

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走出困境：语义控制缺陷患者的语音连贯性受损

连贯的讲话能力，保持对当前话题的关注是有效交流的关键，并且在大脑受损后通常会受损。最新数据表明，调节对语义知识（即语义控制）的访问的执行过程对于在语音中保持连贯性至关重要。为了验证这一假设，我们评估了一系列在语义控制方面表现出缺陷的中风患者的语音连贯性。要求患者谈论一系列主题，并使用计算语言方法分析其反应，以得出其整体连贯性（他们对给定话题的谈论程度）和局部连贯性（他们保持话题的程度）的度量。从一种说话到另一种说话）。与年龄匹配的对照组相比，患者表现出对整体连贯性的严重损害，但对局部连贯性没有损害。整体连贯性与患者在语义控制测试中的表现密切相关，语义控制缺陷更大，而维持整体连贯性的能力较弱。语音产生的其他方面也受到损害，但与语义控制缺陷没有显着相关。这些结果表明，语义控制缺陷会导致语音在宏观语言“消息”级别上的管理不善。患者中局部连贯性的保留表明语义关联的自动激活相对完整，因此他们产生的每个话语都与下一个有意义地建立了联系。但是，由于没有控制流程来限制语义激活，他们演讲的内容越来越远离话语的原始主题。这项研究是第一个在语篇水平上研究语义控制障碍对言语产生的影响的研究，并表明患有这些障碍的患者可能难以保持对话的连贯性。