Semantic impairment in aphasia: A problem of control?

Abstract

Purpose

The relationship between cognitive processes and language ability in aphasia has recently gained increasing attention, with some authors suggesting that control impairments may underlie difficulties with semantic tasks in aphasia. This paper aims to present an overview of the current research on the involvement of cognitive processes in semantic processing tasks and discuss the proposed relationship between cognitive control and semantic processing in aphasia.

Method

The role of cognitive processes in semantic processing tasks commonly used in the aphasiology literature is discussed and two theoretical approaches to semantic processing that contribute to the understanding of the nature of semantic breakdown in aphasia are outlined. Finally, we examine the evidence put forward in the Controlled Semantic Cognition framework with regard to the interpretation of impaired performance on semantic processing tasks in people with aphasia.

Result

Non-linguistic cognitive abilities such as working memory, inhibition and control are required by semantic processing tasks, in addition to access to conceptual information, making it difficult to dissociate these abilities. Several issues exist regarding the evidence put forward for a control deficit as the underlying cause of poor performance on semantic processing tasks in aphasia.

Conclusion

It remains unclear whether impairment on semantic tasks in people with aphasia is related to problems with the representation and/or processing (activation/retrieval) of meaning or problems with cognitive control (or both). Further research is still needed to fully understand how non-linguistic cognitive processes interact with semantic processing, as well as clarify and consistency the definition of control.

Keywords:

• Aphasia
• semantics
• cognitive-linguistic interactions

Acknowledgements

The authors thank the editor and three anonymous reviewers for helpful comments on an earlier version.

Notes

1 As Mirman and Britt (2014) note, what is meant by an access disorder varied across accounts with different terms and scope of meanings (e.g., activation, retrieval, selection).

2 A population that they label as having semantic aphasia (Jefferies & Lambon Ralph, 2006). As this is not a standard aphasia syndrome, we have mostly avoided using this term except in the context of the Controlled Semantic Cognition account. Instead we refer to this population as people with aphasia who perform poorly on tasks requiring semantic processing or use the terminology “people with aphasia with a semantic impairment”.

3 Please note that the terms executive control, cognitive control, executive functions and control are used interchangeably in the semantic control literature. Here, for consistency, we use the term control only.

4 Note that the control mechanism required to select one lexical item over another in a competitive environment (e.g., in a picture-word inference task) would not be specifically regarded as semantic control, although this does not necessarily mean that this task would not require some degree of control.

Additional information

Funding

During the preparation of this manuscript Bruna Tessaro was supported by the International Macquarie University Research Excellence Scholarship (IDEALAB) 20191485 and a Newcastle University Postgraduate Scholarship, and Solène Hameau by an Australian Research Council Discovery Project DP190101490.