Poster E67, Thursday, August 22, 2019, 3:45 – 5:30 pm, Restaurant Hall
Relationships between phonological working memory and language processing in adults with dyslexia
Terri Scott1, Yaminah Carter1, Ja Young Choi2, Tyler Perrachione1;1Boston University, 2Harvard University
Phonological working memory (PWM) is the ability to encode and maintain representations of speech sounds in short-term memory. PWM is believed to play an important role during language and reading development (Duvfa et al. 2001) and deficits in PWM are found in a wide variety of developmental language disorders (DLD), including dyslexia (Larrivee et al. 1999; Peter et al. 2011). In order to better understand the relationship between PWM and language in DLD, this work explores the brain basis of these abilities in typically developing adults and adults with persistent PWM deficits associated with dyslexia. The most widely used theoretical framework for conceptualizing PWM is Baddeley’s model of working memory (Baddeley & Hitch 1974; Baddeley 1986; 2003). This model operationalizes PWM as a separate ability from language processing; however, more recent studies have challenged this view by showing that established PWM assessments, such as nonword repetition, recruit brain areas associated with speech and language (Strand et al. 2008; McGettigan et al. 2011; Perrachione et al. 2017; Scott et al. 2018). Using functional magnetic resonance imaging (fMRI), we investigated the extent to which language and PWM overlap in the brains of typically developing adults and adults with dyslexia. Twenty typically developing adults (12 female; age 19-32, M=24.1 years) and twenty-two adults with dyslexia (18 female; age 19-29, M=23.5 years) underwent fMRI while completing a PWM task (nonword and real-word repetition) and a passive listening language localizer (Scott et al. 2017). Nonword/real-word repetition activation was measured during a sparse-sampling block design fMRI (TR=2.25s, TA=0.75s, 3mm isotropic, 45 slices, 5 simultaneous slices). Language localizer activation was measured during continuous-sampling fMRI (same acquisition parameters with no silent delay; TR = 0.75s). Separately from the scanning session, participants completed a battery of cognitive tests including the TOWRE (Torgesen et al. 1999) and WRMT (Woodcock 1998), which were used to confirm reading difficulties in dyslexia. Group-constrained subject-specific analysis (GCSS; Fedorenko et al. 2010; Julian et al. 2012) was used to account for individual variability in local organization of functional neuroanatomy among members of both our control and dyslexia groups. Surprisingly, we found no differences in the mean level of activation in core PWM areas (bilateral STG, LPT, LPreCG, and RCereb; identified in Scott et al., 2018) once we accounted for individual variation in functional neuroanatomy; however, we uncovered subtle differences in the degree to which language areas were recruited during PWM in adults with dyslexia. Most notably, left IFG was the only region to show a significant group-by-condition interaction during nonword repetition, and this overlapped with significant group differences during real-word repetition and language processing. These results suggest that the persistent PWM deficits in dyslexia may be related to the extent to which language regions are recruited to support PWM, rather than disruption to domain-general working memory systems.
Themes: Phonology and Phonological Working Memory, Speech Perception
Method: Functional Imaging