Abstract
A typical consequence of stroke in the right hemisphere is unilateral spatial neglect. Distinct forms of neglect have been described, such as space-based (egocentric) and object-based (allocentric) neglect. However, the relationship between these two forms of neglect is still far from being understood, as well as their neural substrates. Here, we further explore this issue by using voxel lesion symptoms mapping (VLSM) analyses on a large sample of early subacute right-stroke patients assessed with the Apples Cancellation Test. This is a sensitive test that simultaneously measures both egocentric and allocentric neglect. Behaviourally, we found no correlation between egocentric and allocentric performance, indicating independent mechanisms supporting the two forms of neglect. This was confirmed by the VLSM analysis that pointed out a link between a damage in the superior longitudinal fasciculus and left egocentric neglect. By contrast, no association was found between brain damage and left allocentric neglect. These results indicate a higher probability to observe egocentric neglect as a consequence of white matter damages in the superior longitudinal fasciculus, while allocentric neglect appears more “globally” related to the whole lesion map. Overall, these findings on early subacute right-stroke patients highlight the role played by white matter integrity in sustaining attention-related operations within an egocentric frame of reference.
Highlights
A common consequence of stroke in the right hemisphere is visuospatial neglect (‘neglect’), a complex syndrome associated with a reduced ability to orient towards the contralesional side of space
We considered the severity of neglect by including egocentric and allocentric scores as continuous variables
We conducted voxel lesion symptoms mapping (VLSM) analyses on a large sample of early subacute right-stroke patients assessed by the Apples Cancellation Test (ACT)
Summary
A common consequence of stroke in the right hemisphere is visuospatial neglect (‘neglect’), a complex syndrome associated with a reduced ability to orient towards the contralesional side of space. It is becoming increasingly clearer that neglect is not a monolithic disorder with a unique neural substrate, but rather a collection of symptoms (attentional bias towards the ipsilesional space, impaired spatial orienting in presence of competing stimuli, perceptual extinction, etc.) supported by different neural substrates (Vuilleumier, 2013). An important distinction has been drawn between space-based (egocentric) and object-based (allocentric) neglect (Robertson & Marshall, 1993). Egocentric neglect (EN) is characterized by failing to attend to the contralesional side of space with respect to a subject-centered view; allocentric neglect (AN) is characterized by failing to attend to the contralesional side of objects (Gainotti & Ciaraffa, 2013).
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