Semantic processing in aphasia: evidence from semantic priming and semantic interference

Semantic processing theories propose activation of concepts via semantic features, with interference from semantic neighbours arising due to shared features. Semantic impairment has been explained as damage to activation and interference mechanisms, and linked to impaired semantic control. This study investigated semantic activation and interference in 20 people with aphasia. We found normal semantic priming or hyper-priming, coupled with significant semantic interference effects, in most of the participants, regardless of scores on standard semantic tasks. There was little evidence of a relationship between executive functions and semantic processing. The data indicate that semantic activation is unimpaired in most people with aphasia. Apparent difficulties with semantic processing are predominantly found when tasks involve resolving competition from close semantic neighbours. These novel findings question the use of offline tasks involving semantic competitors in diagnosis of semantic deficits in aphasia – and other conditions such as dementia – and demand revised diagnostic methods.

语义加工理论提出，概念通过语义特征（semantic features）得以激活，而语义邻项（semantic neighbours）因共享特征会产生干扰效应。语义损伤（semantic impairment）被解释为激活与干扰机制受损，并与语义控制（semantic control）功能缺损相关联。本研究针对20名失语症（aphasia）患者考察了其语义激活与干扰效应。研究发现，无论受试者在标准化语义任务中的得分如何，大多数参与者均表现出正常的语义启动（semantic priming）或超启动效应（hyper-priming），同时伴随显著的语义干扰效应。几乎未发现执行功能（executive functions）与语义加工之间存在关联的证据。本研究数据表明，大多数失语症患者的语义激活功能并未受损。受试者在语义加工中表现出的明显困难，主要出现在任务需要解决与近义语义邻项的竞争时。这些全新的研究结果对采用包含语义竞争项的离线任务诊断失语症及痴呆（dementia）等其他病症的语义缺损这一做法提出了质疑，同时呼吁修订相关诊断方法。