Cerebral Cortex Advance Access first published online on November 16, 2006
This version published online on December 18, 2006
Cerebral Cortex, doi:10.1093/cercor/bhl120
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Temporal Dynamics of Plastic Changes in Human Primary Somatosensory Cortex after Finger Webbing
1 Institute for Advanced Biomedical Technologies, "G. D'Annunzio University" Foundation, Chieti, Italy, 2 Department of Medical Physics, School of Medicine, University of Patras, Patras, Greece, 3 Department of Clinical Sciences and Bioimaging, "G. D'Annunzio University," Chieti, Italy, 4 IRCCS "Centro S. Giovanni di Dio" FBF, Brescia, Italy, 5 AFaR–CRCCS, "Isola Tiberina", Rome, Italy, 6 Clinical Neurology, University Campus Biomedico, Rome, Italy
Address correspondence to Maria L. Stavrinou, Department of Medical Physics, School of Medicine, University of Patras, Asclepiou Street, Rio Campus 26500, Patras, Greece. Email: maria{at}heart.med.upatras.gr.
The primary somatosensory cortex (SI) exhibits a detailed topographic organization of the hand and fingers, which has been found to undergo plastic changes following modifications of the sensory input. Although the spatial properties of these changes have been extensively investigated, little is known about their temporal dynamics. In this study, we adapted the paradigm of finger webbing, in which 4 fingers are temporarily webbed together, hence modifying their sensory feedback. We used magnetoencephalography, to measure changes in the hand representation in SI, before, during, and after finger webbing for about 5 h. Our results showed a decrease in the Euclidean distance (ED) between cortical sources activated by electrical stimuli to the index and small finger 30 min after webbing, followed by an increase lasting for about 2 h after webbing, which was followed by a return toward baseline values. These results provide a unique frame in which the different representational changes occur, merging previous findings that were only apparently controversial, in which either increases or decreases in ED were reported after sensory manipulation for relatively long or short duration, respectively. Moreover, these observations further confirm that the mechanisms that underlie cortical reorganization are extremely rapid in their expression and, for the first time, show how brain reorganization occurs over time.
Key Words: cortex • finger somatotopy • magnetoencephalography • short-term plasticity • somatosensory