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

ABSTRACT

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.

KEYWORDS:

• Neglect dyslexia
• visuospatial neglect
• acquired dyslexia
• sentence-level neglect

Acknowledgments

This work was funded by Stroke Association UK awards to ND (TSA2015_LECT02) and to MJM (SA PGF 18\100031), the Wellcome Trust to CRG (101253/A/13/Z) and was supported by the National Institute for Health Research (NIHR) Oxford Biomedical Research Centre (BRC) based at Oxford University Hospitals NHS Trust. We would like to express our sincere gratitude and admiration to the late Prof Glyn W Humphreys, who led the BUCS study and initiated the OCS work. We also thank the many contributors to the BUCS study (including but not limited to Dr Wai-Ling Bickerton, Dr Dana Samson, Dr Pia Rotshtein, Dr Johnny King, Dr Lara Harris, Prof M Jane Riddoch) and the research facilitators from the then West-Midlands Stroke Research Network. The OCS study was supported by the National Institute for Health Research Clinical Research Network, where we would particularly like to thank Ms Rachel Teal and the Multidisciplinary Team at the acute stroke unit at the John Radcliffe Hospital. We also acknowledge the contributions to data collection and curation for the OCS data made by Ms Ellie Slavkova, Ms Grace Chiu and Ms Romina Basting. Finally, we would like to thank Professor Olaf Sporns for helping to supervise MJM during a preliminary version of this project.

Author contributions

MJM helped design the study, conducted analysis, and drafted manuscript. NS aided in study design, patient selection, and manuscript revision. CG assisted in patient selection and manuscript revision. ND conceived the study, assisted in patient selection and manuscript revision.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Stroke Association UK [SA PGF 18\100031, TSA2015_LECT02]; Wellcome Trust [101253/A/13/Z]; National Institute for Health Research (NIHR) Oxford Biomedical Research Centre (BRC) based at Oxford University Hospitals NHS Trust.