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Orthographic Amnesia in Developmental Dysgraphia
Poster Session C, Saturday, September 13, 11:00 am - 12:30 pm, Field House
Brenda Rapp1, Yuan Tao1, Jennifer Shea1, Michael McCloskey1, Wiley Robert2; 1Johns Hopkins University, 2University of North Carolina Greensboro
Introduction Hepner et al. (2017) reported on multiple cases of developmental spelling dysgraphia in which individuals with normal/superior cognitive skills exhibited highly selective, severe difficulties in learning the spellings of irregular words in the face of normal pseudoword spelling accuracy. Despite extensive testing, it has been challenging to identify the stage at which these selective learning difficulties arise. Here we report on an investigation that builds on Tao et al. (2024) which examined the neural bases of the initial stages of orthographic learning as neurotypical adults learned spellings for novel pseudowords during fMRI scanning. We found a distinctive bilateral hippocampal increase in BOLD response with the increasing memory strength of learning trials. Currently, we administered the same orthographic learning paradigm to two individuals with severe acquired spelling dysgraphia. To evaluate the selectivity of the effects, we also administered a similar paradigm involving in-scanner learning of complex visual patterns (Law et al., 2005). Methods Participants are a father (RBT, 56 years old) and son (TBT, 19 years old) diagnosed with severe developmental surface dysgraphia. Both are native English speakers and right-handed, with no history of neurological disease. They exhibit severe difficulties specifically in spelling irregular words (TBT: 0.7%ile and RBT: 4%ile) compared to normal performance in pseudo-word spelling. Nonetheless, both demonstrate normal-to-superior: spoken language vocabulary (PPVT), digit span, learning (verbal, visual and face), working memory (span), and executive functions (card sorting). Participants were administered two learning tasks during fMRI scanning: (1) Orthographic learning: Participants learned the mapping between 10 Auditorily presented pseudowords and their target spellings, with 16 repetitions of each item; (2) Visual pattern learning: Participants learned the mapping between 8 kaleidoscopic patterns and one of four button presses, with 18 repetitions of each item. In-scanner accuracy was recorded and used to bin learning trials into different levels of memory strength (based on Smith et al., 2004), for later analysis. Results Behavioral results. Orthographic Learning: TBT and RBT had in-scanner accuracies of 45% and 38%, respectively, significantly below the control mean of 78% (p <0.04 and 0.02). Visual pattern learning: TBT and RBT had in-scanner accuracies of 78% and 56%, comparable to controls (p=0.58; p=0.39). Neuroimaging results. Orthographic Learning: Neurotypical controls showed increasing BOLD response with increasing memory strength of the learning trials in bilateral Hippocampi (p < 0.001). In contrast, TBT and RBT did not (p=0.74), with a significant interaction between groups (p<.0.03). Visual Pattern Learning: TBT and RBT exhibited the expected increase in BOLD response with increasing memory strength of the learning trials, in bilateral Hippocampi. Conclusions The profound and highly selective nature of the difficulties these individuals experienced in learning word spellings can be described as selective “orthographic amnesia”. In fact, we report a lack of responsiveness of the bilateral Hippocampi during orthographic learning, despite appropriate Hippocampal responsiveness during other similarly structured complex visual pattern learning. Future work is needed to understand whether the abnormal Hippocampal responses are primary or derivative.
Topic Areas: Disorders: Developmental, Writing and Spelling