Dynamic Spatial Coding within the Dorsal Frontoparietal Network during a Visual Search Task

• Published in: PloS one Vol. 3; no. 9; p. e3167
• Main Authors: Sommer, Wieland H., Kraft, Antje, Schmidt, Sein, Olma, Manuel C., Brandt, Stephan A.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 09.09.2008; Public Library of Science (PLoS)
• Subjects: Adult; Attention; Behavior; Brain; Coding; Eye movements; Form Perception; Frontal Lobe - physiology; Functional Laterality - physiology; Functional magnetic resonance imaging; Hemispheric laterality; Humans; Lesions; Localization; Magnetic Resonance Imaging - methods; Medical imaging; Memory; Neglect syndromes; Neural coding; Neurology; Neuroscience; Neuroscience/Cognitive Neuroscience; Neuroscience/Experimental Psychology; Neuroscience/Psychology; Neurosciences; Orientation - physiology; Parietal Lobe - physiology; Pattern Recognition, Visual - physiology; Receptive field; Research Design; Searching; Space Perception - physiology; Transcranial magnetic stimulation; Visual perception; Visual Perception - physiology; Visual task performance; Visual tasks; Germany
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0003167

To what extent are the left and right visual hemifields spatially coded in the dorsal frontoparietal attention network? In many experiments with neglect patients, the left hemisphere shows a contralateral hemifield preference, whereas the right hemisphere represents both hemifields. This pattern of spatial coding is often used to explain the right-hemispheric dominance of lesions causing hemispatial neglect. However, pathophysiological mechanisms of hemispatial neglect are controversial because recent experiments on healthy subjects produced conflicting results regarding the spatial coding of visual hemifields. We used an fMRI paradigm that allowed us to distinguish two attentional subprocesses during a visual search task. Either within the left or right hemifield subjects first attended to stationary locations (spatial orienting) and then shifted their attentional focus to search for a target line. Dynamic changes in spatial coding of the left and right hemifields were observed within subregions of the dorsal front-parietal network: During stationary spatial orienting, we found the well-known spatial pattern described above, with a bilateral hemifield representation in the right hemisphere and a contralateral preference in the left hemisphere. However, during search, the right hemisphere had a contralateral preference and the left hemisphere equally represented both hemifields. This finding leads to novel perspectives regarding models of visuospatial attention and hemispatial neglect.