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THE ANATOMICAL BASIS OF FUNCTIONAL LOCALIZATION IN THE CORTEX
Richard E. Passingham*, Klaas E. Stephan|| and Rolf Ktter
The functions of a cortical area are determined by its extrinsic connections and intrinsic properties. Using the database CoCoMac, we show that each cortical area has a unique pattern of cortico-cortical connections a connectional fingerprint. We present examples of such fingerprints and use statistical analysis to show that no two areas share identical patterns. We suggest that the connectional fingerprint underlies the observed cell-firing differences between areas during different tasks. We refer to this pattern as a functional fingerprint and present examples of such fingerprints. In addition to electrophysiological analysis, functional fingerprints can be determined by functional brain imaging. We argue that imaging provides a useful way to define such fingerprints because it is possible to compare activations across many cortical areas and across a wide range of tasks.
*Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK.
Wellcome Department of Imaging Neuroscience, Institute of Neurology, University College London,12 Queen Square, London WC1N 3BG, UK.
Institute for Medicine, Research Centre Jlich, 52045 Jlich, Germany.
||Department of Psychology, University of Newcastle upon Tyne, Ridley Building, Claremont Place, Newcastle NE1 7RU, UK.
C. & O. Vogt Brain Research Institute and Department of Morphological Endocrinology & Histochemistry, Heinrich-Heine-Universitt Dsseldorf, Universittsstr. 1, 40225 Dsseldorf, Germany. Correspondence to R.E.P. e-mail: dick.passingham@ psy.ox.ac.ukdoi:10.1038/nrn893
Historically, there has been a long controversy concerning functional localization in the cortex. Franz and Lashley1 were the first to devise an experimental method for tackling the question, making lesions in the cortex and testing their effects on the performance of behavioural tasks. Although experimental lesions had been made before, it was the use of psychological tasks that was crucial in these studies. Experiments of this sort led Lashley2 to challenge the degree to which functions were localized in the cerebral cortex.
Lashley worked with rats, which have a lissencephalic brain, and he was not able to make lesions reliably in specific cytoarchitectural areas. It was not until the 1950s that lesions were placed in specific cytoarchitec-tonic areas in non-human primates3,4. These and subsequent studies supported a greater degree of localization than Lashley had been prepared to accept. It could be shown, for example,...