The neuro-anatomical bases for the advantage of left periphery in neglect dyslexia

• ¹ San Camillo Hospital (IRCCS), Italy
• ² Department of Psychology, University of Milan-Bicocca, Italy
• ³ Ricerca in Advanced NeuroRehabilitation, Istituto S. Anna, Italy
• ⁴ Padova Neuroscience Center, University of Padua, Italy

*Daniela D'Imperio, Martina Abbondanza, First authorship shared. Syntactic structure has been shown to modulate reading in neglect dyslexia patients (Friedmann et al., 2011). The left periphery (LP) has recently been studied as a structure of interest. LP (Rizzi, 1997) is the highest layer of syntactic structure; it represents the interface between pragmatics and syntax. Topic and Focus are the two central projections of LP. Abbondanza et al. (2018) have recently shown neglect dyslexia patients have an advantage for sentences containing Topic and Focus, with respect to sentences with canonical word order (SVO). The present work investigates the anatomical underpinning of LP advantage. Eleven Italian-speaking right brain damage patients with acquired left neglect were recruited. There were seven males and three females, and mean age was 65 (range: 49-77). We used 103 sentences (Abbondanza et al. 2018), which were divided into two groups based on syntactic structure. In Group 1, 66 sentences included Topic and Focus elements as proper projections of the LP. These stimuli were both Clitic Left-Dislocation and Contrastive/Corrective Focus, because of their common syntactic features. Group 2 was composed of 37 control sentences, which were mainly SVO sentences with expressed or unexpressed subjects. Group sentences were matched for length (5 words and 23.5 graphemes on average) and word frequency. Participants were asked to read each sentence aloud. Both omissions and substitutions in the left side of the sentence were considered errors. Participants' percentage of errors show that in SVO sentences, more mistakes were committed overall in comparison to Topic and Focus structures (t-test=3.39, p=0.02) (Table 1). The difference between these two percentages were computed for each participant as index of LP benefit (i.e., less errors for Group 1). This index was used to investigate the lesion regions underpinning a lack of LP effect using voxel-based lesion symptom mapping (VLSM). VLSM analysis showed that right lesions in the middle and superior frontal lobe and anterior and middle cingulate cortex (Figure 1) seem to correspond with less benefit from LP, defining it as a relevant area for the LP activation. LP represents the interface between communicative intention and syntactic realization. Based on the present results, the attraction LP exerts on the attention of people with neglect dyslexia seems to require an intact frontal lobe. This finding is consistent with the idea that LP, despite its syntactic complexity, has a pragmatic function with a powerful influence on attention.