The role of parieto-temporal connectivity in pure neglect dyslexia

Abstract

a b s t r a c tThe initial stages of reading are characterised by parallel and effortless access to letters constituting a word. Neglect dyslexia is an acquired reading disorder characterised by omission or substitution of the initial or the final letters of words. Rarely, the disorder appears in a'pure' form that is, without other signs of spatial neglect. Neglect dyslexia is linked to damage involving the inferior parietal lobe and regions of the temporal lobe, but the precise anatomical basis of the pure form of the disorder is unknown. Here, we show that pure neglect dyslexia is associated with decreased structural connectivity between the inferior parietal and lateral temporal lobe. We examined patient DM, who following bilateral occipito-parietal damage presented left neglect dyslexia together with right visual field loss, but no signs of spatial neglect. DM's reading errors were affected by word length and were much more frequent for pseudowords than for existing words. Most errors were omissions or substitutions of the first or second letter, and the spatial distribution of errors was similar for stimuli presented left or right of fixation. The brain lesions of DM comprised the inferior and superior parietal lobule as well as the cuneus and precuneus of the left hemisphere, and the angular gyrus and lateral occipital cortex of the right hemisphere. Diffusion tensor imaging revealed bilateral decrease of fibre tracts connecting the inferior parietal lobule with the superior and middle temporal cortex. These findings suggest that parieto-temporal connections play a significant role for the deployment of attention within words during reading.

What role for prism adaptation in the rehabilitation of pure neglect dyslexia?

“…Patients with neglect dyslexia omit or substitute the initial letters of a word, which may lead to productions that are partly visually similar with the target word, but bear no semantic connection with it (e.g., "pillow" for YELLOW, or "hair" for CHAIR). About one half of all patients with neglect dyslexia also have a left-sided visual field defect such as hemianopia (Lee et al, 2009;Ptak, Di Pietro, & Schnider, 2012), but cases with opposite impairments have been described (e.g., right visual field impairment with left neglect dyslexia; Arduino, Daini and Silveri, 2005;Ptak, Di Pietro, & Pignat, 2016), indicating that hemianopia is not the main explanatory factor of neglect dyslexia.…”

Dissociation between Selecting and Orienting Attentional Reading Deficits: A Study in Adults with Epilepsy

“…For example, in spatial neglect, a deficit in which patients ignore stimuli located on the contralesional side, patients make frequent errors reading words located in the contralesional space in a text or in a two-word bilateral display [ 13 , 14 , 15 ], or reading letters located in the contralesional part of a single word, mainly involving letter omission and substitution errors [ 16 , 17 ]. This type of deficit, namely neglect dyslexia, is frequent after lesions of the posterior part of the brain, and can sometimes occur without spatial neglect for nonverbal stimuli [ 18 , 19 ]. The asymmetric errors in text and in single-words can be dissociated [ 20 ], the first errors being sometimes related to an egocentric deficit, where the neglected side is defined with reference to the patients’ body, and the second to an allocentric or object-based deficit, defined with reference to the word spatial coordinates [ 19 ].…”