Deficient allo-centric visuospatial processing contributes to apraxic deficits in sub-acute right hemisphere stroke

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurology

Background:

• Visuospatial deficits are common after right hemisphere (RH) stroke, but apraxic deficits are less understood.
• The relationship between apraxic and visuospatial deficits and their underlying pathophysiology in RH stroke requires further investigation.

Purpose of the Study:

• To examine the behavioral and lesion patterns of apraxic and visuospatial deficits in sub-acute RH stroke patients.
• To characterize the relationship between these deficits using principal component analysis (PCA).
• To explore the role of ego-centric/space-based and allo-centric/object-based processing.

Main Methods:

• Studied 50 sub-acute RH stroke patients assessing pantomime of object use, bucco-facial imitation, line bisection, and letter cancellation.
• Utilized principal component analysis (PCA) to analyze the relationship between deficit patterns.
• Performed statistical lesion analyses correlating component scores with brain lesions.

Main Results:

• Over half of RH stroke patients exhibited visuospatial deficits, and about one-third showed apraxic deficits.
• PCA identified distinct components: PCA1 linked to allo-centric/object-based processing (pantomime, imitation, line bisection overall deviation), and PCA2 to ego-centric/space-based processing (letter cancellation, line bisection contra- vs. ipsilesional deviation).
• Lesion analyses supported the interpretation of PCA1 and PCA2 representing distinct processing types.

Conclusions:

• Allo-centric/object-based processing disturbances contribute to apraxic pantomime and imitation deficits in RH stroke.
• Findings suggest distinct neural substrates for object-based and space-based processing in the RH.
• This research clarifies the nature of apraxic deficits following RH stroke and their relationship with visuospatial impairments.