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DOI: 10.1055/s-2008-1078688
Unsuspected Plasticity of Single Neurons after Connection of the Corticospinal Tract with Peripheral Nerves in Spinal Cord Lesions
Publication History
Publication Date:
17 June 2008 (online)
ABSTRACT
We sought to understand an unsuspected plasticity of single neurons found after connection of the cord with peripheral nerves in paraplegics. Our research aimed at making paraplegics walk again, after 20 years of experimental surgery in animals that, among other things, demonstrated the alteration of the motor end plate receptors from cholinergic to glutamatergic; the same connection was done in humans. The grafts were put in the corticospinal tract of the cord randomly, without possibility of choosing the axons coming from different areas of the brain cortex. As a result, the patient was able to selectively activate the muscles she wanted without cocontractions of the other muscles connected with the same cortical areas. We believe that unlike in nerve or tendon transfers, where the whole cortical area corresponding to the transfer changes its function (a phenomenon that we call “brain plasticity by areas”), in the connection of the lateral bundle of the thoracic cord (the CST) with different peripheral nerves and muscles, the brain plasticity occurs by single neurons; in fact, there are no cocontractions. We propose to call it “brain plasticity by single neurons.” We speculate that this phenomenon is due to the simultaneous activation of neurons spread in different cortical areas for a given specific movement while the other neurons of the same areas connected with peripheral nerves of different muscles are not activated. Why different neurons of the same area fire at different times according to different voluntary demands remains to be discovered, and we are committed to solve this enigma.
KEYWORDS
Brain plasticity - neuron activity - paraplegia - corticospinal tract - central nervous system–peripheral nervous system connection - cocontractions
REFERENCES
- 1 Richardson P M, McGuinness U M, Aguayo A J. Axons from CNS neurons regenerate into PNS grafts. Nature. 1980; 284 264-265
- 2 David S, Aguayo A J. Avonal elongation into peripheral nervous system “bridges” after central nervous system injury in adult rats. Science. 1981; 214 931-933
- 3 Brunelli G, Milanesi S, Bartolaminelli P, De Filippo G, Brunelli F, Bottonelli P V. Experimental grafts in spinal cord lesions (preliminary report). Ital J Orthop Traumatol. 1983; 9(suppl) 53-56
- 4 Brunelli G, Milanesi S. Experimental repair of spinal cord lesions by grafting from CNS to PNS. J Reconstr Microsurg. 1988; 4 245-250
- 5 Brunelli G A, Brunelli G R, Mattiuzzo V et al.. Spinal cord experimental repair: CNS PNS graphiting gives functional connection. Monograph. Brescia, Italy; Gruppo Editoriale Delfo 1996: 1-55
- 6 Brunelli G A, Brunelli G R. Experimental surgery in spinal cord lesions by connecting upper motoneurons directly to peripheral targets. J Periph Nerv Syst. 1996; 1 111-118
- 7 Friedman B, Aguayo A J. Injured neurons in the olfactory bulb of the adult rat grow axons along grafts of peripheral nerve. J Neurosci. 1985; 5 1616-1625
- 8 Horvat J C, Pecot-Dechavassine M, Mira J C, Davarpanah Y. Formation of functional endplates by spinal axons regeneration through a peripheral nerve graft: a study in the adult rat. Brain Res Bull. 1989; 22 103-114
- 9 Bertelli J A, Orsal D, Mira J C. Median nerve neurotization by peripheral verve grafts directly implated into the spinal cord: anatomical, behavioural and electrophysiological evidences of sensorimotor recovery. Brain Res. 1994; 644 150-159
- 10 Brunelli G A, Brunelli G R, Mattiuzzo V. Experimental spinal cord repair (by means of direct connection of the above lesions CNS with PNS). Surg Technol Int. 1997; 6 391-395
- 11 Brunelli G A. Direct neurotization of muscles by presynaptic motoneurons. J Reconstr Microsurg. 2001; 17 631-636
- 12 Brunelli G, Spano P F, Barlati S et al.. Glutamatergic reinnervation through peripheral nerve graft dictates assembly of glutamatergic synapses at rat skeletal muscle. Proc Natl Acad Sci U S A. 2005; 102 8752-8757
- 13 Pizzi M, Brunelli G, Barlati S, Spano P. Glutamatergic innervation of rat skeletal muscle by supraspinal neurons: a new paradigm in spinal cord injury repair. Curr Opin Neurobiol. 2006; 16 323-328
Professor Giorgio Brunelli
Fondazione Midollo, Via Galvani 26
25123 Brescia, Italy