regeneration

regeneration - Journal of Cerebral Blood Flow &...

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Review Article Regeneration and plasticity in the brain and spinal cord Barbro B Johansson Wallenberg Neuroscience Center, Department of Clinical Neuroscience, Lund University, Lund, Sweden The concept of brain plasticity covers all the mechanisms involved in the capacity of the brain to adjust and remodel itself in response to environmental requirements, experience, skill acquisition, and new challenges including brain lesions. Advances in neuroimaging and neurophysiologic techniques have increased our knowledge of task-related changes in cortical representation areas in the intact and injured human brain. The recognition that neuronal progenitor cells proliferate and differentiate in the subventricular zone and dentate gyrus in the adult mammalian brain has raised the hope that regeneration may be possible after brain lesions. Regeneration will require that new cells differentiate, survive, and integrate into existing neural networks and that axons regenerate. To what extent this will be possible is difficult to predict. Current research explores the possibilities to modify endogenous neurogenesis and facilitate axonal regeneration using myelin inhibitory factors. After apoptotic damage in mice new cortical neurons can form long-distance connections. Progenitor cells from the subventricular zone migrate to cortical and subcortical regions after ischemic brain lesions, apparently directed by signals from the damaged region. Postmortem studies on human brains suggest that neurogenesis may be altered in degenerative diseases. Functional and anatomic data indicate that myelin inhibitory factors, cell implantation, and modification of extracellular matrix may be beneficial after spinal cord lesions. Neurophysiologic data demonstrating that new connections are functioning are needed to prove regeneration. Even if not achieving the goal, methods aimed at regeneration can be beneficial by enhancing plasticity in intact brain regions. (2007) 27, 1417–1430; doi:10.1038/sj.jcbfm.9600486; published online 28 March 2007 Keywords: axonal regeneration; focal brain ischemia; myelin inhibitory factors; neurogenesis; olfactory ensheathing cells Brain plasticity The concept of brain plasticity is not new. In 1890 William James proposed in his book ‘Principles of Psychology’ that the habits in living beings are because of the plasticity of the brain, defining plasticity as the possession of a structure weak enough to yield to an influence, but strong enough not to yield all at once. Detailed discussions on brain plasticity together with experimental data and beauti- ful drawings can be found in the papers by Ramon y Cajal. In ‘Textura del sistema nervioso del hombre y de los vertebrados’ (Textbook on the nervous system of man and the vertebrates 1897–1899), he wrote thatr to explain skill acquisition is necessary to assume formation of new pathways through ramification and progressive growth of dendrite arborization
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regeneration - Journal of Cerebral Blood Flow &...

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