Cerebral Cortex Advance Access published online on February 4, 2009
Cerebral Cortex, doi:10.1093/cercor/bhp001
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Functional Selectivity of Interhemispheric Connections in Cat Visual Cortex
1 Department of Neurophysiology, MA 4/149, Ruhr-Universität, D-44780 Bochum, Germany, 2 International Graduate School of Neuroscience (IGSN), Ruhr-Universität, D-44780 Bochum, Germany, 3 Laboratoire de Physiologie de la Perception et de l'Action, Collège-de-France, UMR CNRS 7152, 75005 Paris, France, 4 Institute of Physiology, University of Pécs, H-7633 Pécs, Hungary, 5 Department of General Zoology and Neurobiology, University of Pécs, H-7633 Pécs, Hungary, 6 Laboratory for Cortical Systems Neuroscience, Department of Anatomy, Histology and Embryology, University of Debrecen, Nagyerdei krt. 98, 4012 Debrecen, Hungary
Address correspondence to Nathalie Rochefort, Institute of Neuroscience of the Technical University Munich, Biedersteiner Str.29, D-80802 Munich, Germany. Email: nathalie.rochefort{at}lrz.tu-muenchen.de.
The functional specificity of callosal connections was investigated in visual areas 17 and 18 of adult cats, by combining in vivo optical imaging of intrinsic signals with labeling of callosal axons. Local injections of neuronal tracers were performed in one hemisphere and eight single callosal axons were reconstructed in the opposite hemisphere. The distributions of injection sites and callosal axon terminals were analyzed with respect to functional maps in both hemispheres. Typically, each callosal axon displayed 2 or 3 clusters of synaptic boutons in layer II/III and the upper part of layer IV. These clusters were preferentially distributed in regions representing the same orientation and the same visuotopic location as that at the corresponding injection sites in the opposite hemisphere. The spatial distribution of these clusters was elongated and its main axis correlated well with the preferred orientation at the injection site. These results demonstrate a specific organization of interhemispheric axons that link cortical regions representing the same orientation and the same location of visual stimuli. Visual callosal connections are thus likely involved in the processing of coherent information in terms of shape and position along the midline of the visual field, which may facilitate the fusion of both hemifields into the percept of a single visual scene.
Key Words: area 17 • area 18 • callosal connections • corpus callosum • long-range connections • primary visual cortex