Unravelling the mystery of the left temporoparietal junction: Speech comprehension impairments in stroke and progressive aphasia.

"Living well" with dementia or stroke refers to the ability to adapt to impairments/symptoms to enable social connectedness, life-participation, mental wellbeing and independent living. This is supported by accurate diagnosis and management which, in-turn, is predicated on an accurate understanding of dementia/stroke conditions. This PhD concerns three acquired communication impairments: dementia-related Logopenic variant Primary Progressive Aphasia (LvPPA); post-stroke Wernicke's aphasia (WA) and post-stroke Conduction aphasia (CA).

Despite shared patterns of brain damage affecting the left temporoparietal junction and apparent similarities in neuropsychological profile, they are purported to have categorically different speech comprehension impairments with different underlying causes. This indicates an incomplete understanding of the conditions: How can different conditions arise from the same neural and cognitive profile?

Two explanations are proposed to resolve this paradox: (1) that clinical and theoretical distinctions are erroneous, caused by researchers with different theoretical lenses examining the disorders separately, using measures of differing sensitivity and that the conditions appear dissimilar due to differences in impairment severity. (2) that traditional "offline" clinical testing methodologies fail to capture the way in which cognitive mechanisms are recruited during naturalistic, real-world speech comprehension in the three conditions. Unifying WA, CA and LvPPA within the same methodological framework, this PhD will merge neuropsychology methods with contemporary electrophysiology neural tracking methods.

These studies will provide a comprehensive evaluation of speech comprehension and its constituent processes under clinical and naturalistic conditions.

This research has medium-term implications for the clinical assessment and management of WA, CA and LvPPA. By applying sensitive neuropsychological and online measures to fully profile language comprehension capacity across the three conditions, potential unmet language comprehension need may be identified. This information could reshape the clinical conceptualization, assessment, and management of the conditions.

Additionally, resolving theoretical inconsistencies between the conditions will provide convergent evidence for the linguistic and cognitive mechanisms supporting real-time language comprehension. These findings can be used to refinement the specificity of our current interventions.

Results from this PhD will be disseminated to stroke and dementia clinical audiences. Further collaborations with existing industry partners will be sought to identify potential routes for translation of findings into management and interventions, including digital health interventions, environmental modifications, and communication partner training.

Domains relevant to ESRC remit:

The proposed PhD research spans linguistic, psychological and neuroscientific disciplines. This approach has been designed to elucidate whether apparent differences between the populations of interest are a consequence of different methods, theoretical or observation perspectives. This research falls into the ESRC remit as it aims to understand the processes that underpin communication in language impaired populations, therefore aligning with the ESRC's remit for healthy ageing research, and living well with cognitive and communication impairments.