Cortical and structural‐connectivity damage correlated with impaired syntactic processing in aphasia

Abstract

Agrammatism in aphasia is not a homogeneous syndrome, but a characterization of a nonuniform set of language behaviors in which grammatical markers and complex syntactic structures are omitted, simplified, or misinterpreted. In a sample of 71 left-hemisphere stroke survivors, syntactic processing was quantified with the Northwestern Assessment of Verbs and Sentences (NAVS). Classification analyses were used to assess the relation between NAVS performance and morphosyntactically reduced speech in picture descriptions. Voxel-based and connectivity-based lesion-symptom mapping were applied to investigate neural correlates of impaired syntactic processing. Despite a nonrandom correspondence between NAVS performance and morphosyntactic production deficits, there was variation in individual patterns of syntactic processing. Morphosyntactically reduced production was predicted by lesions to left-hemisphere inferior frontal cortex. Impaired verb argument structure production was predicted by damage to left-hemisphere posterior superior temporal and angular gyrus, as well as to a ventral pathway between temporal and frontal cortex. Damage to this pathway was also predictive of impaired sentence comprehension and production, particularly of noncanonical sentences. Although agrammatic speech production is primarily predicted by lesions to inferior frontal cortex, other aspects of syntactic processing rely rather on regional integrity in temporoparietal cortex and the ventral stream.

Functional differentiation in the language network revealed by lesion-symptom mapping

“…Matchin & Hickok suggest that the pIFG is hypothesized to underlie a linear morpho-syntactic system that sequences words and morphemes during speech production, but is not critical for lexical retrieval or syntactic structure building in comprehension. As we have shown previously in subsets of these data (den Ouden et al, 2019;, and consistent with previous research (Sapolsky et al, 2010;, damage to the pIFG was significantly associated with agrammatic speech deficits, but was not associated with any comprehension deficits. The fact that the voxel-wise analysis identified the main locus of damage with the IFG, and that the interaction between pIFG and pMTG only approached significance, suggests that the role for middle frontal regions in syntax should be further investigated.…”

Resting-State Functional Magnetic Resonance Imaging Connectivity Between Semantic and Phonological Regions of Interest May Inform Language Targets in Aphasia

“…Additional measures were administered to rule out auditory discrimination deficits (Psycholinguistic Assessments of Language Processing in Aphasia: Same-Different Discrimination Using Word Minimal Pairs subtest; Kay et al, 1992) and nonverbal cognitive deficit (Raven's Progressive Colored Matrices;Raven, 1978). The Motor Speech Examination (Duffy, 2013) and Apraxia Battery for Adults-Second Edition (ABA-2; Dabul, 2000) Increasing Word Length subtest characterized motor speech. For published tests that involve perceptual judgment and scoring (e.g., WAB-R Fluency subtest), research assistants were trained by author K. J.…”

Brain Damage Associated with Impaired Sentence Processing in Acute Aphasia

“…Despite being widely studied, the brain areas crucial for successful sentence processing are still disputed in the literature (Hagoort & Indefrey, 2014;Rogalsky et al, 2018). Functional brain imaging and lesion-symptom mapping studies have implicated distributed cortical and subcortical areas as important for sentence processing, including inferior frontal areas (Caramazza & Zurif, 1976;Grodzinsky, 2000), anterior (Magnusdottir et al, 2013) and posterior (Den Ouden et al, 2019;Rogalsky et al, 2018) temporal areas, and temporo-parietal areas (Dronkers et al, 2004). While functional divisions between these areas have been proposed by previous studies, these remain controversial (Indefrey, 2012).…”