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25 PLASTICITY, RECOVERY AND REHABILITATION OF THE ADULT BRAIN 25.1 Principles of Brain Plasticity How plastic is the brain? -In past – adult brain is like a rock – chip things off but that is it, once lost, it cannot regenerate or do anything-Now we still know we cannot regrow but can see neuroplasticity – RECREATE NEW PATHWAYS-Reading: Reconceptualize Brain Injury Rehabilitation in the Future: A Peak Over the Horizon– trying to understand where does the brain fall on the spectrum of neuroplasticity – how much can really occur?o“a perfectly plastic brain would be infinitely malleable, able to learn new information and skills and b able to reorganize after insult, but it would be slow to automatize learning. A perfectly specialized brain would be fixed, always poised to respond optimally to the old and to provide rapid routines, but w little capacity for an adaptive respond to new challenges and experiences or to insult”1.Plasticity is common to all nervous systems and the principles are conserved -As you get older, you’re always learning new info -Ex. C. elegans oSmall worms that can learn oCan habituate – stop responding to a continually presented stimulates oSomething in NS changes – ALL NERVOUS SYSTEMS SHOW NEUROPLASTICITY -Behavioral changes are accompanied by changes in the NS oThe neural record of learned information 2.Plasticity can be analyzed at many levels/studied through a.Behavior -Ex. Prism adaption oSubjects fitted w prisms can adapt to the shifted visual world, Reverses left to right and upside down oAt first confusing debilitating – cannot hit ball bc brain doesn’t register where it is properly but can show habituation and eventually learn to hit ball properly oIn a few days, subjects adapt and can eat, dress, walk and eventually can engage in very complex behaviors such as skiing and riding a bike oAdjustment time needed upon removal -Premotor cortex– important in re-adaption oIf this region is inactive in monkey studies, the animal has great difficulty adapting to the change -Posterior parietal cortex oPET human studies show increased activation in posterior parietal cortex during adaption -In monkeys, cells in the visual cortex (V1 and V4) begin to respond to stimuli from ipsilateral visual field -Rapidity of adaption suggest that the connections r already there and just need to be activated and broken in b.Neural imaging -Changes in grey matter induced by trainingEx juggling study oTeach non jugglers how to juggle – 3 months training, scanned b4 and after, (3 months after w/o juggling) oIncrease in temporal lobes when juggling, decreased when didn’t juggle oWas transient – didn’t last if didn’t keep juggling – brain increased w juggling then decreased after training when didn’t juggle for 3 months -Growth of language related brain areas after foreign language learningEx swiss army interpreters (multiple languages in a short amount of time) oIncrease in size of hippocampus, Inferior frontal gyrus