Neural organization of speech production: A lesion-based study of error patterns in connected speech

Brielle C Stark; Alexandra Basilakos; Gregory Hickok; Chris Rorden; Leonardo Bonilha; Julius Fridriksson

Despite differing distributions of paraphasias across the two tasks, verbal paraphasias made during connected speech and naming were associated with damage to shared neural substrates (i.e. semantically related and unrelated paraphasias in connected speech and naming both associated with an area of damage localized to left hemisphere ventral stream cortex), supporting prior evidence from single-word retrieval that lesion damage in this area is associated with semantically related and unrelated paraphasias. While this result-that paraphasias in both connected speech and naming associate with areas of shared damageseems straightforward and perhaps not novel, few studies have evaluated brain damage associated with paraphasias during connected speech (e.g. in primary progressive aphasia: Wilson et al., 2010) . As noted in the introduction, the two larger studies to do so focused on different populations (post-stroke aphasia; primary progressive aphasia) and also evaluated only one type of paraphasia (phonemic). In the present study, we find that verbal paraphasias, made during connected speech and naming, were associated with shared lesion damage to specific brain areas in the left hemisphere. Semantically related paraphasias have been long attributed to neurodegeneration (Jefferies and Lambon Ralph, 2006; Noppeney et al., 2007) or stroke damage (Cloutman et al., 2009; Schwartz et al., 2009; Lambon Ralph et al., 2012; Griffis et al., 2017) involving left anterior temporal cortex, and this is reflected in our conjunction analysis which demonstrated that semantically related paraphasias made during both connected speech and naming localized to this area. Further, brain damage associated with unrelated paraphasias made during both tasks was localized to left posterior temporal cortex, an area which has been implicated most often in lexical . CC-BY-NC-ND 4.0 International license is made available under a The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. It . https://doi.org/10.1101/544841 doi: bioRxiv preprint retrieval (Lau et al., 2008) . These results further support the role of the left hemisphere ventral stream of language in lexical-semantic processing (Hickok and Poeppel, 2007) .