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4/25/17 Using Brain Plasticity to Facilitate Rehabilitation Sarah A. Raskin Connecticut Speech Language Hearing Association [email protected] Structural Basis of Brain Plasticity What is learning? Learning involves physiological brain changes A recovering brain is in a dynamic and plastic state We know from non-injured brains that experience causes brain changes, including cognitive improvement New treatments have been designed with plasticity in mind The Nature of Learning Learning refers to the process by which experiences change our nervous system and hence our behavior. We refer to these changes as memories. Experiences are not “stored”; rather, they change the way we perceive, perform, think, and plan. They do so by physically changing the structure of the nervous system, altering neural circuits that participate in perceiving, performing, thinking, and planning. 4 1 4/25/17 Structural Basis of Brain Plasticity But what is plasticity? At the neural level, learning is associated with changes that take place at the synapse Can refer to any change from the molecular level to synaptic change to cortical reorganization to behavior Neurons that wire together fire together The Hebb Rule Donald Hebb argued that synapses that are active at the same time are strengthened over time Implies that repeated neural activity will produce physical changes in the nervous system 14.7 copyright 2010 Pearson 2 4/25/17 Experience Based Changes Neurogenesis in brain regions when songbirds learn new songs Nottebohm, 1985 Experience Based Changes Rats in enriched environments heavier brains with new granule cells higher levels of some neurotransmitters more nerve cell connections increased neuronal branching performed better on learning tasks Kempermann, Kuhn, & Gage, 1997 Experience Based Changes Experience Based Changes Participation in a learning task alone leads to new neurons generated by stem cells Gould et al., 1999 This was true compared to both animals in an impoverished environment and animals in a social environment Kempermann, Kuhn, & Gage, 1997 3 4/25/17 Adult Brains Can Grow New Cells New nerve cells in the hippocampus of humans Cortical Plasticity New nerve cells in the hippocampus of adult humans are functional Eriksson, 1998 Gould & McEwan, 1998 Cortical Plasticity Before: Reorganization Perceptual Reorganization has been shown in all sensory modalities The organization can be modified by damage, pharmacologic intervention, or change in the sensory environment After: Kaas, Merzenich, Killacky, 1983 Copyright 2010 Pearson 4 4/25/17 Sign Language Braille Reading Although sign language is a visual and motor process, it is processed in the same language areas used for speech in hearing individuals Reorganization of sensory cortex Reorganization of cortex Increased representation for fingers of string musicians Ebert et al., 1995 The representation of the fingers of blind Braille readers who use several fingers simultaneously to read was both enlarged and disordered; a perceptual disturbance in which the subjects could not discriminate which of their fingers was being touched Sterr et al., 1998 5 4/25/17 Changes in hippocampus in London taxi drivers The more demanding the task Performed by that area, the more Complex the cells and the networks And the change correlates with time spent as taxi driver 6 4/25/17 Plasticity after Injury The percent prevalence of low idea density in early life autobiographies by late life cognitive state for 180 participants in the Nun Study. Sensory or Motor Training and Plasticity Manipulating Experience Experimentally Ramachandran (1993) Indirectly measured the cortical maps in individuals with limb amputations When the face was stroked softly with a cotton swab, amputees reported sensations of being touched in the amputated hand May explain “phantom limb” pain Copyright 2010 Worth Copyright 2010 Worth 7 4/25/17 Reorganization of sensory cortex Human studies with amputees Recovery from damage to the brain So what happens when someone is recovering from brain injury? Elbert, et al., 1994 Theories of Restoration Vicariance due to equipotentiality Redundancy Functional substitution Recovery from diaschisis (posttraumatic neural depression) Theories of Restoration Vicariance due to equipotentiality Different brain parts can do the same job Redundancy Functional substitution Recovery from diaschisis 8 4/25/17 Theories of Restoration Vicariance due to equipotentiality Different brain parts can do the same job Redundancy Some parts already did the same job Functional substitution Recovery from diaschisis Theories of Restoration Vicariance due to equipotentiality Different brain parts can do the same job Redundancy Some parts already did the same job Functional substitution A new region can learn to do the job Recovery from diaschisis Swelling, shock, etc. Other injury-induced plasticity Collateral growth or sprouting Not always adaptive So a recovering brain is in a very plastic and dynamic state Copyright 2010 Worth 9 4/25/17 Can we use this to design training? Environmental Therapy Rats were given hippocampul damage leading to deficits in new learning Exposure to a complex and enriched environment for one month was sufficient to enhance and sustain recovery compared to an impoverished environment Will et al., 1990 Environmental Therapy The problem is defining enriched environments for people And defining the numbers of hours required Kolb et al., 2011 Reorganization of sensory cortex-specific training First mapped out parts of sensorimotor cortex active when a finger stimulated Cut the nerve fibers to that finger Same areas of cortex now become active when a different finger is stimulated within hours 10 4/25/17 Reorganization of sensory cortex Now, once again map out receptive fields Extensive training with rotating disk Cortical fields enlarged for the trained finger which endured for some time Structural Basis of Brain Plasticity Sensory or Motor Training and Plasticity Manipulating Experience Experimentally Nudo and colleagues (1997) Had monkeys retrieve food from small or large food wells Small wells required dexterous movements of one or two fingers, whereas the monkeys could put their entire hand in the large wells The digit representation on the motor cortex was larger for animals that had to retrieve food from the smaller wells Effect of Motor Practice Lasted up to 8 weeks Copyright 2010 Pearson 11 4/25/17 Constraint Induced Movement Therapy The animals with cortical damage recovered more quickly after training with small wells Has been used with success in patients with stroke, brain injury, spinal cord injury and hip replacement Copyright 2010 Worth 12 4/25/17 Sensory Reorganization Individuals with cortical blindness who were given intensive training dramatically enlarged their visual fields Unclear whether due to stimulation of neurons in the blind spot, neurons from other regions or islands of spared neurons in the injury zone Zihl, 1990 Cortical Plasticity Cognitive Tasks Reorganization can also occur with practice on a cognitive task with humans PET study during naïve and practiced performance of a simple verbal task--saying an appropriate verb for a visually presented noun Cortical Plasticity Reorganization During naïve performance areas most activated were the anterior cingulate, left prefrontal and left posterior temporal cortices During practiced performance they were insular cortex, left medial extra-striate cortex 13 4/25/17 Cortical Plasticity Reorganization Reorganization can also occur after practice with a cognitive task in humans General Principles of Plasticity Changes in the brain require repetition The brain can be altered by a wide range of experiences Training must be aware of the specific systems being trained and the ways that system responds to training Experience-dependent changes interact Kolb, B., Cioe, J. & Williams, P. (2011) Neuronal organization and change after brain injury. In: Raskin, S. (ed) Neuroplasticity and rehabilitation. Guilford Press: NY. Raichle, Fiez, Videen, MacLeod, Pardo, Fox, & Petersen, 1994 Cognitive Rehabilitation Future Directions There is some evidence that cognitive rehabilitation techniques that are intensive and take place over many months lead to changes in brain function Sohlberg & Posner, 1998 Raskin & Buckheit, 1998 14 4/25/17 Brain-Computer Interface Brain Gate Or a computer mouse Virtual Reality Cognitive Rehabilitation The process of relearning skills that have been lost or altered as a result of damage to brain cells or altered brain chemistry. If skills cannot be relearned, then new ones have to be taught. Malia, 2014 Rizzo, et al. (2010) 15 4/25/17 Approaches to Treatment Environmental Modifications changing the environment to alleviate the need for the deficient function Compensation making up for what is deficient by some external means Approaches to Treatment Direct Interventions Functional Skills Training Behavior Modification Medications Process-specific Training Direct Intervention attempting to retrain specific impaired cognitive functions Aim of Cognitive Rehabilitation To improve the ability to carry out everyday tasks. Impact on real life Improve quality of life Approaches Cognitive-Didactic (bottom-up) Functional-Experiential (top-down) Integrative Holistic—training skills in a hierarchical manner while ensuring these skills generalize to daily life 16 4/25/17 First Plan for Generalization Actively plan for generalization from the beginning Identify reinforcements in the natural environment Program common stimuli between training and the real world Use sufficient examples in therapy Select a method for measuring Sohlberg & Raskin, 1996 generalization Levels of Generalization Level I: Improvement on treatment tasks Level II: Improvement on related neuropsychological tests Level III: Improvement in daily life (Gordon, 1987) 17