fMRI of global visual perception in simultanagnosia.
The integration of visual elements into global perception seems to be implemented separately to single object perception. This assumption is supported by the existence of patients with simultanagnosia who can identify single objects but are incapable of integrating multiple visual items. We investigated a case of simultanagnosia due to posterior cortical atrophy without structural brain damage who demonstrated an incomplete simultanagnosia. The patient successfully recognized a global stimulus in one trial but failed to do so just a few seconds later. Using event-related fMRI, we contrasted post hoc selected trials of successful global perception with trials of global recognition failure. We found circumscribed clusters of activity at the right and left primary intermediate sulci and a bilateral cluster at the ventral precuneus. The integration of multiple visual elements resulting in a conscious perception of their gestalt seems to rely on these bilateral structures in the human lateral and medial inferior parietal cortex.
Himmelbach
Marc
M
Hertie-Institute for Clinical Brain Research, Eberhard Karls University, Hoppe-Seyler-Str. 3, D-72076 Tübingen, Germany. marc.himmelbach@uni-tuebingen.de
Erb
Michael
M
Klockgether
Thomas
T
Moskau
Susanna
S
Karnath
Hans-Otto
HO
D000377:Agnosia / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000098:blood supply / Q000473:pathology / Q000503:physiopathology; D016009:Chi-Square Distribution; D005260:Female; D019788:Fluorodeoxyglucose F18; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D049268:Positron-Emission Tomography / Q000379:methods; D011601:Psychophysics
D019788:Fluorodeoxyglucose F18; D010100:Oxygen