The article illustrates findings describing separate visual pathways within the cortex that play different roles in interpreting visual information. These visual pathways include the ventral and dorsal streams which elicit visual perception and visual control of action, respectively. An important model for these findings was patient D.F., an individual afflicted with visual form agnosia, resulting in difficulties perceiving visual objects. In determining the origin of this patient's condition, high-resolution anatomical MRI scans were used showing damage in a location that was bilateral to the lateral occipital cortex (LO). More specifically, damage was seen bilateral to patient D.F.'s occipitotemporal visual system, otherwise known as the ventral stream.
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Functional MRI scans were also used to view activation within the ventral and dorsal stream regions when given the task of object recognition and object-guided grasping. When comparing activation within the ventral stream when shown line drawings of common objects and scrambled line drawings, it was found that there was no difference in activation level in this region when presented with the two stimuli, which is contrary to the results found in healthy control participants. Now, despite abnormal functioning of the ventral stream, patient D.F. showed considerable activation in dorsal stream regions or more specifically the anterior intraparietal sulcus when asked to perform grasping actions, which was similar to activation found in healthy control participants. Thus, from the information gathered, they were able to link patient D.F.'s object recognition inabilities to ventral stream damage, while the patient's visual control of action was associated with the dorsal stream.
Functional MRI scans were also used to view activation within the ventral and dorsal stream regions when given the task of object recognition and object-guided grasping. When comparing activation within the ventral stream when shown line drawings of common objects and scrambled line drawings, it was found that there was no difference in activation level in this region when presented with the two stimuli, which is contrary to the results found in healthy control participants. Now, despite abnormal functioning of the ventral stream, patient D.F. showed considerable activation in dorsal stream regions or more specifically the anterior intraparietal sulcus when asked to perform grasping actions, which was similar to activation found in healthy control participants. Thus, from the information gathered, they were able to link patient D.F.'s object recognition inabilities to ventral stream damage, while the patient's visual control of action was associated with the dorsal stream.