Functional dissociation between action and perception of object shape in developmental visual object agnosia

Area of Science:

• Neuroscience
• Cognitive Psychology
• Visual Perception

Background:

• The two visual systems model posits separate ventral (object recognition) and dorsal (visuomotor control) pathways.
• Developmental visual object agnosia presents a unique case to study the interplay between perception and action.

Purpose of the Study:

• To investigate if visuomotor control can develop normally despite early-onset, severe visual perceptual impairments.
• To examine the dissociation between object perception and the visual control of action.

Main Methods:

• A case study of LG, an individual with developmental visual object agnosia.
• LG manually estimated block widths (perceptual task) and grasped blocks of varying widths (action task).
• Comparison of LG's performance to matched controls on perceptual sensitivity and grasping parameters (e.g., maximum grip aperture, reaction time).

Main Results:

• LG showed profoundly impaired perceptual sensitivity to object width.
• Grasping actions, including maximum grip aperture and movement times, were largely normal.
• Sensitivity to object shape during grasping emerged later in LG's movement compared to controls.

Conclusions:

• Demonstrates a clear dissociation between the perception and action of object shape.
• Suggests distinct stages within the grasping movement (planning vs. online control) may be differentially affected.
• Visuomotor abilities can develop and function typically even with severely impaired visual perceptual abilities.