Poster A20, Thursday, August 16, 10:15 am – 12:00 pm, Room 2000AB

Word-Level Spelling Performance in Patients with Parietal versus Temporal-Frontal Lobe Lesions: Implications for the Dual Lexica Model

Venugopal Balasuramanian1,2, Maureen Costello-Yacano3, Maha Alders4, Judith Koebli1;1School of Health and Medical Sciences, Seton Hall University, South Orange, New Jersey, 2SCORE Lab, Johns Hopkins School of Medicine, 3LaSalle University, Philadelphia, PA, USA, 4King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia

Hickok and Poeppel (2004; 2016) proposed their dual (dorsal and ventral) stream model to account for the neural underpinnings of speech and language processing from auditory input and, it is evident that it gave a new impetus to research in the field of neurobiology of language/speech. Based on this model, Gow (2012) proposed a dual lexica model: Dorsal and ventral lexica. The two lexica, according to Gow, will facilitate different processes in the dual streams. Gow localizes the dorsal lexicon (DL) in the inferior parietal lobe, including the supramarginal gyrus. The DL provides interface between the articulatory and phonetic representations. The ventral lexicon (VL), neurologically rooted in the superior posterior temporal sulcus and mid-temporal gyrus, provides interface between word and meaning. The present study aimed at using the dual lexica model of spoken language processing (Gow, 2012) to discuss the performance of two persons with aphasia on a few lexical tasks, in particular, spelling to dictation and reading tasks. If the dorsal lexicon is impaired due to parietal lobe lesions, one would expect phonological paraphasias in reading and phonologically-related substitutions in spelling. If the ventral lexicon is implicated due to temporal lobe lesions, one would expect semantic paraphasias/deep dyslexias in oral reading and deep dysgraphia in spelling to dictation. Method. Subjects. LK, a 45 year-old male with a stroke induced lesion in temporal region extending up to a portion of the frontal lobe and the basal ganglia of the LH. CBH is a 59-year-old female aphasic with bilateral parietal lobe lesion. Procedures. Clinical testing (BDAE, BNT), Experimental Testing:1) Johns Hopkins University Dysgraphaia Battery, 2) Psycholinguistic Assessment of Language Performance of Aphasics (reading and writing sub-tests). Using the performance profiles, the cognitive components implicated in the subjects’ performance were identified. Results and Discussion. Lk’s reading is less severely affected, compared to his writing, such a disparity in performance is expected because writing is a harder task. He has symptoms of deep dyslexia without the symptoms of deep dysgraphia. Semantic errors (9% of all reading errors) were found only in reading. If the interface between semantic representations and the auditory input (dictation) is interrupted, then the errors will include semantically related ones. At this point in time, the VL’s relation to orthographic representation of words is not specified. CBH’s writing performance revealed impaired lexical-semantic component, whereas her reading performance fails to show a matching deficit. This finding does not accord well with the prediction about the phonologic/articulatory relationship in spelling errors. Thus the DL in Gow’s model is underspecified to account for semantic nature of the error pattern in CBH. The role of the supramarginal gyrus in semantics is attested in clinical literature as evidenced in Luria’s category of semantic aphasia. A recent meta-analysis of fMRI studies of semantic processing (Binder, Desai, Graves and Conant, 2009) identified three cortical systems for semantic processing, including the posterior multimodal and heteromodal association areas. To account for language processing in reading and writing, both the dual stream and dual lexica models will require further extension.

Topic Area: Writing and Spelling