Poster C14, Wednesday, August 21, 2019, 10:45 am – 12:30 pm, Restaurant Hall
Comparing multi-dimensionality in post-stroke aphasia and primary progressive aphasia using principle component analysis
Ruth Ingram1, Gorana Pobric1, Ajay Halai2, Seyed Sajjadi3, Karalyn Patterson2, Matthew Lambon Ralph2;1Division of Neuroscience and Experimental Psychology, School of Biological Sciences, University of Manchester, 2Department of Clinical Neurosciences, University of Cambridge & MRC Cognition & Brain Sciences Unit, 3Department of Neurology, University of California, Irvine
Language impairments caused by stroke (post-stroke aphasia) and neurodegeneration (primary progressive aphasia) have overlapping symptomatology and nomenclature and are both divided into categorical subtypes. Despite the apparent similarities, the few direct comparisons between primary progressive aphasia and post-stroke aphasia to date have often been limited either in the subtypes included (e.g., only fluent subtypes), or the cognitive/linguistic domains tested (e.g., only grammatical comprehension). The aim of this study was to compare a full range of linguistic and cognitive impairments in a cohort of post-stroke aphasia and primary progressive aphasia who were recruited without selection criteria for specific subtypes. We applied principal component analysis to explore the underlying structure of the variance in behavioural scores. Varimax rotation was applied to aid cognitive interpretation of the extracted components. Similar phonological, semantic and fluency-related components were found for post-stroke aphasia and primary progressive aphasia. A combined-principal component analysis across post-stroke aphasia and primary progressive aphasia highlighted varying degrees of overlap within and between these groups on all extracted components. Classification analysis was employed to quantify the ability to separate subtypes based on a potential categorical boundary within the principal component analysis-extracted behavioural ‘space’ for primary progressive aphasia and post-stroke aphasia respectively. Semantic dementia patients were most similar to the traditional idea of a diagnostic category (i.e. within group homogeneity and distinct between group differences), whereas the considerable overlap within and between other subtypes of primary progressive aphasia and post-stroke aphasia indicates a lack of categorical boundaries. Less overlap on the fluency component could suggest differences in the application of the fluent/non-fluent scale in PSA and PPA. The finding of graded variations between and within categories of both post-stroke aphasia and primary progressive aphasia suggests that a multidimensional rather than categorical classification system may be a better conceptualisation of both primary progressive aphasia and post-stroke aphasia. This may prove to be a productive alternative approach for relating behaviour to lesion/atrophy correlates and the underlying pathology, as has been demonstrated for post-stroke aphasia. The similar, graded language dimensions observed for primary progressive aphasia and post-stroke aphasia indicate comparability of the disorders despite very different types of damage.
Themes: Disorders: Acquired, Methods
Method: Behavioral