Hemispheric asymmetry in a dissociation between the visuomotor and visuoperceptual streams.
We have explored the level of interaction between the putative visuoperceptual (VP) and visuomotor (VM) processing streams within each cerebral hemisphere. Six patients with unilateral brain lesions and 26 intact-brain participants were tested. We presented three-dimensional versions of the Mueller-Lyer illusion separately to the left and to the right hemifields of each participant. In one condition, the participant grasped the central shaft of the illusion object between the thumb and forefinger (visuomotor task). In the other, the participant estimated the size of the shaft using the same fingers (visuoperceptual task). We calculated the magnitude of the illusion in each task for each hemifield. Intact-brain participants had a significantly larger illusion in estimation than in grasping in both hemifields. The two patients with right-hemisphere damage showed a large dissociation between grasping and estimation illusions, whereas the four patients with left-hemisphere damage showed no detectable dissociation. These results are consistent with the idea that the visuomotor and visuoperceptual streams are more dissociated in the left hemisphere than in the right.
Radoeva
Petya D
PD
Program in Neuroscience and Behavior, Mount Holyoke College, 50 College Street, South Hadley, MA 01075, USA. petya@mail.upenn.edu
Cohen
Joseph D
JD
Corballis
Paul M
PM
Lukovits
Timothy G
TG
Koleva
Svetlinka G
SG
D000368:Aged; D001930:Brain Injuries / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009903:Optical Illusions; D010468:Perceptual Disorders / Q000473:pathology / Q000503:physiopathology*; D010775:Photic Stimulation / Q000379:methods; D011597:Psychomotor Performance / Q000502:physiology*; D011601:Psychophysics / Q000379:methods; D011930:Reaction Time / Q000502:physiology; D013028:Space Perception / Q000502:physiology*; D013997:Time Factors; D014652:Vascular Diseases / Q000150:complications; D014796:Visual Perception / Q000502:physiology*