Lesion correlates of patholinguistic profiles in chronic aphasia: comparisons of syndrome-, modality- and symptom-level assessment

Abstract

One way to investigate the neuronal underpinnings of language competence is to correlate patholinguistic profiles of aphasic patients to corresponding lesion sites. Constituting the beginnings of aphasiology and neurolinguistics over a century ago, this approach has been revived and refined in the past decade by statistical approaches mapping continuous variables (providing metrics that are not simply categorical) on voxel-wise lesion information (voxel-based lesion-symptom mapping). Here we investigate whether and how voxel-based lesion-symptom mapping allows us to delineate specific lesion patterns for differentially fine-grained clinical classifications. The latter encompass 'classical' syndrome-based approaches (e.g. Broca's aphasia), more symptom-oriented descriptions (e.g. agrammatism) and further refinement to linguistic sub-functions (e.g. lexico-semantic deficits for inanimate versus animate items). From a large database of patients treated for aphasia of different aetiologies (n = 1167) a carefully selected group of 102 first ever ischaemic stroke patients with chronic aphasia (; 12 months) were included in a VLSM analysis. Specifically, we investigated how performance in the Aachen Aphasia Test-the standard clinical test battery for chronic aphasia in German-relates to distinct brain lesions. The Aachen Aphasia Test evaluates aphasia on different levels: a non-parametric discriminant procedure yields probabilities for the allocation to one of the four 'standard' syndromes (Broca, Wernicke, global and amnestic aphasia), whereas standardized subtests target linguistic modalities (e.g. repetition), or even more specific symptoms (e.g. phoneme repetition). Because some subtests of the Aachen Aphasia Test (e.g. for the linguistic level of lexico-semantics) rely on rather coarse and heterogeneous test items we complemented the analysis with a number of more detailed clinically used tests in selected mostly mildly affected subgroups of patients. Our results indicate that: (i) Aachen Aphasia Test-based syndrome allocation allows for an unexpectedly concise differentiation between 'Broca's' and 'Wernicke's' aphasia corresponding to non-overlapping anterior and posterior lesion sites; whereas (ii) analyses for modalities and specific symptoms yielded more circumscribed but partially overlapping lesion foci, often cutting across the above syndrome territories; and (iii) especially for lexico-semantic capacities more specialized clinical test-batteries are required to delineate precise lesion patterns at this linguistic level. In sum this is the first report on a successful lesion-delineation of syndrome-based aphasia classification highlighting the relevance of vascular distribution for the syndrome level while confirming and extending a number of more linguistically motivated differentiations, based on clinically used tests. We consider such a comprehensive view reaching from the syndrome to a fine-grained symptom-oriented assessment mandatory to converge neurolinguistic, patholinguistic and clinical-therapeuti...

Partly segregated cortico-subcortical pathways support phonologic and semantic verbal fluency: A lesion study

“…Dorsal/ventral dissociations have also been found in aphasic patients, where expressive impairments can occur at the lexical-semantic or lexical-phonological levels. Semantic impairments in aphasia can occur at different levels of language processing but have been associated with left temporal, and inferior frontal areas, while lexical-phonological difficulties occur after supramarginal and arcuate lesions (Henseler et al, 2014;Parker Jones et al, 2014). Our results suggest that dorsal/ventral dissociations found in aphasic patients can also be found in an unselected brain-damaged patients population and confirm the role of temporal structure in accessing the meaning of words.…”

“…A meta-analysis of 30 neuropsychological studies including tests of verbal fluency in patients with brain damage indeed reports that while temporal structures are more important for semantic fluency, frontal damages impact similarly on phonologic and semantic fluency (Henry and Crawford, 2004). Of note, dorsal/ventral dissociations for phonologic and semantic processing have also been found related to other types of language impairments; deficits in oral expression can for example occur at the lexical-semantic or lexical-phonological levels (Henseler et al, 2014;Parker Jones et al, 2014).…”

Shared neural substrates of apraxia and aphasia

“…The supramarginal gyrus borders Wernicke's area at the posterior end of the superior temporal gyrus. Its lesions have been associated with defects of the phonological loop of verbal working memory (Baddeley, 2004;Leyton et al, in press);Henseler et al, 2014) but also with deficient comprehension and naming of categorical spatial relations and mechanically complex tools (Kemmerer et al, 2012;Pelgrims et al, 2013;Orban and Caruana, 2014;Watson and Buxbaum, 2015). It is remarkable that these symptoms include disturbances of spatial, semantic, and linguistic processing.…”

Factors predicting post-stroke aphasia recovery

“…Aphasia recovery is generally predicted not only by size but also lesion location in critical language areas, logically a small lesion in a speech area is more likely to impact on language severity and recovery, while a large lesion elsewhere may affect speech minimally (Naeser et al 1998(Naeser et al , 1989Henseler et al 2014).…”