Dissociations within neglect-related reading impairments: Egocentric and allocentric neglect dyslexia

Consistently lateralized reading errors are commonly understood as side-effects of visuospatial neglect impairment. There is however a qualitative difference between systematically omitting full words presented on one side of passages (egocentric neglect dyslexia) and lateralized errors when reading single words (allocentric neglect dyslexia). This study aims to investigate the relationship between egocentric and allocentric neglect dyslexia and visuospatial neglect. 1209 stroke survivors completed standardized reading and cancellation tests. Stringent criteria identified unambiguous cases of allocentric neglect dyslexia (N = 17) and egocentric neglect dyslexia (N = 35). These conditions were found to be doubly dissociated with all cases of egocentric and allocentric neglect dyslexia occurring independently. Allocentric neglect dyslexia was dissociated from both egocentric and allocentric visuospatial neglect. Additionally, two cases of allocentric neglect dyslexia which co-occurred with oppositely lateralized domain-general visuospatial neglect were identified. Conversely, all cases of egocentric neglect dyslexia were found in the presence of domain-general visuospatial neglect. These findings suggest that allocentric neglect dyslexia cannot be fully understood as a consequence of visuospatial neglect. In contrast, we found no evidence for a dissociation between egocentric neglect dyslexia and visuospatial neglect. These findings highlight the need for new, neglect dyslexia specific rehabilitation strategies to be designed and tested.