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Updated: May 25, 2025

Methods to Explore the Influence of Top-down Visual Processes on Motor Behavior
Published on: April 16, 2014
Differential affection of the visual information sub-streams in a patient with visual agnosia
Kirstin Lederer1, Bruno Fimm2, Jorn Munzert3
1Division for Clinical Cognitive Research, Department of Neurology, University Hospital RWTH Aachen, Aachen, Germany.
Introduction:
Visual agnosia is a deficit of object recognition addressed to the damage of the ventral stream (VS). The dorsal stream (DS) is usually intact in these patients, and it can be derived from well-preserved reaching and grasping of visually presented objects. In this study, we presented a new case of a visual agnosic patient (AC) with an extensive lesion of the secondary visual cortex.
Methods:
We examined the kinematics of his grasping behavior towards common day-to-day objects compared to a healthy control group. Both colored and color-masked objects were presented, and participants were instructed to grasp-then-name and name-then-grasp them.
Results:
The agnosic deficit was particularly evident when no color information was available to the patient: Although AC was able to recognize most colored objects with marked delay, his recognition of color-masked objects was very poor. Furthermore, the color-masked condition determined larger impairments in kinematic performance relative to the control group.
Discussion:
Results support the view that spared color processing in the VS allows for partial compensation of deficits. Color information is also processed along the DS, contributing to visuomotor transformations.
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