School of Psychology and Counselling, The Open University, Milton Keynes, UK.
School of Social and Community Medicine, University of Bristol, UK.
Cortex. 2022 Nov;156:71-85. doi: 10.1016/j.cortex.2022.05.022. Epub 2022 Jul 8.
Semantic control allows us to focus semantic activation on currently relevant aspects of knowledge, even in the face of competition or when the required information is weakly encoded. Diverse cortical regions, including left prefrontal and posterior temporal cortex, are implicated in semantic control, however; the relative contribution of these regions is unclear. For the first time, we compared semantic aphasia (SA) patients with damage restricted to temporoparietal cortex (TPC; N = 8) to patients with infarcts encompassing prefrontal cortex (PF+; N = 22), to determine if prefrontal lesions are necessary for semantic control deficits. These SA groups were also compared with semantic dementia (SD; N = 10), characterised by degraded semantic representations. We asked whether TPC cases with semantic impairment show controlled retrieval deficits equivalent to PF+ cases or conceptual degradation similar to patients with SD. Independent of lesion location, the SA subgroups showed similarities, whereas SD patients showed a qualitatively distinct semantic impairment. Relative to SD, both TPC and PF+ SA subgroups: (1) showed few correlations in performance across tasks with differing control demands, but a strong relationship between tasks of similar difficulty; (2) exhibited attenuated effects of lexical frequency and concept familiarity, (3) showed evidence of poor semantic regulation in their verbal output - performance on picture naming was substantially improved when provided with a phonological cue, and (4) showed effects of control demands, such as retrieval difficulty, which were equivalent in severity across TPC and PF+ groups. These findings show that semantic impairment in SA is underpinned by damage to a distributed semantic control network, instantiated across anterior and posterior cortical areas.
语义控制使我们能够将语义激活集中在知识的当前相关方面，即使在存在竞争或所需信息编码较弱的情况下也是如此。然而，包括左前额叶和后颞叶皮层在内的多种皮质区域都与语义控制有关；这些区域的相对贡献尚不清楚。我们首次将语义性失语症（SA）患者与仅限于颞顶叶皮层（TPC；N=8）的损伤患者与包括前额叶皮层（PF+；N=22）的损伤患者进行了比较，以确定前额叶损伤是否对语义控制缺陷是必需的。还将这些 SA 组与语义性痴呆（SD；N=10）进行了比较，SD 患者的语义表现明显下降。我们询问了是否 TPC 有语义障碍的病例表现出与 PF+病例相当的受控检索缺陷，或者是否与 SD 患者相似的概念退化。独立于病变位置，SA 亚组表现出相似性，而 SD 患者表现出明显不同的语义障碍。与 SD 相比，TPC 和 PF+SA 亚组：（1）在具有不同控制要求的任务中表现出很少的相关性，但在难度相似的任务之间具有很强的关系；（2）表现出词汇频率和概念熟悉度的减弱效应；（3）在言语输出中表现出较差的语义调节证据 - 在提供语音提示时，图片命名的表现得到了极大改善；（4）表现出控制要求的影响，例如检索难度，在 TPC 和 PF+组中严重程度相当。这些发现表明，SA 中的语义障碍是由分布式语义控制网络的损伤引起的，该网络分布在前后皮质区域。
