Semantic categorization in aphasic patients with impaired language comprehension: An event–related potentials study
Semantic categorization in aphasic patients with impaired language comprehension: An event–related potentials study

Summary/Abstract: Many studies have tackled the question of the organization of our conceptual knowledge in the brain, mainly conducting behaviour studies in healthy and impaired individuals. Animacy and inanimacy are among the most frequently studied categories and there are three main theories or models that explain semantic processing of animate and inanimate objects: the sensory/functional theory, the domain–specific semantic knowledge representation model and the connectionist model of the conceptual structure. Although the event– related potentials (ERP) technique has been used in aphasia research and many studies have used some variation of the semantic categorization task in healthy individuals, to our knowledge there are no studies that were intended to answer the question about semantic categorization in the aphasic population using the ERP technique. The aim of this study is to determine the differences in processing animate and inanimate objects between patients with aphasia with language comprehension difficulties and age, gender and education matched controls using the ERP technique. Results in this study show that the group of aphasic patients with impaired language comprehension have a lower amplitude and a longer latency of the N400 and the LPC amplitude, fewer correct behavioural responses and a slower reaction time on the behavioural categorization task than their controls. It can be concluded that aphasic patients have difficulties in both phases of lexico–semantic processing, the lexical retrieval or recognition phase and the categorization phase. The absence of differences in the processing of animate and inanimate objects in the N400 window and similar topographic distribution for animate and inanimate objects in both groups are consistent with the connectionist model of a single semantic system which claims that the same semantic system is active no matter which category is being processed. However, the observed differences between animate and inanimate objects in the LPC time window in the control group lead to the conclusion that inanimate objects are harder to categorize due to a smaller number of common features needed for the categorization processes.

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