UCLPartners Centre for Neurorehabilitation Seminar: Prof Beth Jefferies

Abstract:
Semantic cognition brings meaning to our world – it allows us to not only recognise objects and to understand words but also to retrieve the varied features of concepts in a way that is appropriate for the task or context. When we retrieve weaker aspects of knowledge, or when there is competition from irrelevant aspects of meaning, we require control processes to shape the multimodal meanings we retrieve. This aspect of control is underpinned by a left-lateralised distributed neural network, distinct from but adjacent to the domain-general “multiple-demand” executive network. Patients who have multimodal semantic problems following left hemisphere stroke have damage to this semantic control network, and consequently their capacity to retrieve meanings is highly dependent on the context. Their semantic deficits are qualitatively different from semantic dementia, even though they fail the same range of verbal and non-verbal semantic tasks: I will show evidence that this difference reflects degradation of conceptual knowledge in semantic dementia versus controlled access impairment in aphasia. I will present evidence that people with aphasia following lesions to the anterior and posterior left-hemisphere nodes of the semantic control network have comparable semantic deficits. I will show that lesion-disconnection mapping can distinguish semantic control from general executive impairment, with non-semantic difficulties associated with more cross-hemisphere disconnection. Finally, I will explore the implications of these insights for speech and language therapy targeting the rehabilitation of multimodal semantic impairment in aphasia. 

Lecture Theatre, 33 Queen Square, London WC1N 3BG Or Online (via Zoom)

 Please send enquiries to: cnr@ucl.ac.uk

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