Dissociation between frontal and temporal-parietal contributions to connected speech in acute stroke

Abstract

Humans are uniquely able to retrieve and combine words into syntactic structure to produce connected speech. Previous identification of focal brain regions necessary for production focused primarily on associations with the content produced by speakers with chronic stroke, where function may have shifted to other regions after reorganization occurred. Here, we relate patterns of brain damage with deficits to the content and structure of spontaneous connected speech in 52 speakers during the acute stage of a left hemisphere stroke. Multivariate lesion behaviour mapping demonstrated that damage to temporal-parietal regions impacted the ability to retrieve words and produce them within increasingly complex combinations. Damage primarily to inferior frontal cortex affected the production of syntactically accurate structure. In contrast to previous work, functional-anatomical dissociations did not depend on lesion size likely because acute lesions were smaller than typically found in chronic stroke. These results are consistent with predictions from theoretical models based primarily on evidence from language comprehension and highlight the importance of investigating individual differences in brain-language relationships in speakers with acute stroke.

Damage to Broca’s area does not contribute to long-term speech production outcome after stroke

“…Across the 27 subtests that comprise the CAT, we selected the spoken picture description task as our behavioural index of speech production abilities, with the goal of ensuring the ecological validity of our findings by assessing connected speech production (rather than single word production) in a setting that resembled those encountered in real-world scenarios more closely. Our decision was also motivated by recent efforts to characterise the complex nature of speech production, their deficits and neural correlates using samples of connected speech ( Stark et al , 2019 ; Alyahya et al , 2020; Ding et al ., 2020 ). The CAT spoken picture description task was administered to each patient and the spoken responses scored following standardized procedures described in the assessment battery manual.…”

Working Memory Capacities Neurally Dissociate: Evidence from Acute Stroke

“…A total of 94 acute LH stroke patients (51 males; 81 right handed; 88 ischemic stroke; 6 hemorrhagic stroke; age: M = 61 years; standard deviation [SD] = 12 years; range = 25–85 years; education: M = 14 years; SD = 4 years; range = 0–33 years) were recruited from the Memorial Hermann, Houston Methodist, and St. Luke’s hospitals in Houston, TX, USA, as part of an ongoing project ( Martin and Schnur 2019 ; Ding et al. 2020 ).…”

Working Memory Capacities Neurally Dissociate: Evidence from Acute Stroke

“…Semantic integration (e.g., integrating noun-noun, “apple core”, and verb-noun, “throw dart”, combinations) would seem to necessarily draw on semantic WM to maintain the two concepts such that an appropriate integration could be carried out. With respect to the pSTS, damage to a similar pSTS locus after acute stroke in a subset of patients studied here was associated with reduced ability to produce nouns and increasingly complex word combinations during a narrative production task (Ding et al 2020). In a behavioral analysis of another subset of these patients, semantic WM was necessary for producing increasingly complex word combinations (Martin and Schnur 2019).…”

“…While the current findings cannot distinguish the role of these two regions, other findings in the literature suggest that the LIFG region is involved in retrieving or refreshing semantic representations (Heim et al 2009: Johnson et al 2005; Martin and Chao 2001), whereas the AG is involved more directly in maintaining semantic representations to support meaning integration (Humphries et al 2006). The results showing the involvement of the pSTS are more novel but may underlie the maintenance of several word meanings during complex phrase construction (Ding et al 2020). Further investigation is needed to determine if the engagement of this region replicates and what its distinctive role might be.…”

“…= 12 years; range = 25-85 years; education: M = 14 years; S.D. = 4 years; range = 0-33 years) were recruited from the Memorial Hermann, Houston Methodist and St. Luke’s hospitals in Houston, Texas, USA, as part of an ongoing project (Martin and Schnur 2019; Ding et al 2020). Subjects met the following inclusion criteria: Native English speaker; No other neurological diseases (e.g., tumor, dementia); No neuroradiological evidence of previous non-lacunar left hemisphere stroke (cf.…”