Brain Plasticity - Lecture Notes PDF

eu Neuroplasticity Roadmap Module 1- What is neuroplasticity? Module 2- Structural vs synaptic plasticity Module 3- Examples of neuroplasticity Module 4- Plasticity after brain damage Module 1 Neuroplasticity? Hemispherectomy Jody Miller Developed Rasmussen syndrome at age 3. E...

eu Neuroplasticity Roadmap Module 1- What is neuroplasticity? Module 2- Structural vs synaptic plasticity Module 3- Examples of neuroplasticity Module 4- Plasticity after brain damage Module 1 Neuroplasticity? Hemispherectomy Jody Miller Developed Rasmussen syndrome at age 3. Epilepsy originating in her right hemisphere. Almost constant seizures. Only one treatment option: hemispherectory- removal of right hemisphere https://www.youtube.com/watch? v=f2fCY_M7Vms A static view of the brain Until recently, the brain was thought of as a static entity, something that didn’t change much. Any change, was thought to be for the worse, a change of deterioration. Aging leads to neuronal loss, toxins (i.e., drugs, alcohol, chemicals) lead to neuronal loss. We are born with a number of neurons and the number of neurons was thought to only decrease over time. Today’s view The brain is plastic, undergoing constant change. As previously understood, the brain loses neurons and connections BUT crucially, the brain also make new neurons and new connections. Plasticity or Neuroplasticity The brain’s ability to change and reorganize itself over time. The brain is constantly changing (i.e., new memories). What leads to plasticity? New experiences New memories Gradual loss of neurons and synapses Brain damage Plasticity is higher early in life but still present throughout life. Implications: The brain is not a static entity. It is dynamic and it can undergo significant changes throughout life. Module 2 Structural vs synaptic plasticity What can change in the brain? Physical properties of neurons The number of neurons (increase or decrease) The dendrites, axon terminals and dendritic spines in existing neurons The ability of neurons to communicate The number of postsynaptic receptors The amount of neurotransmitter released What can change in the brain? Physical properties The ability to of the neuron- communicate Structural between neurons- plasticity Synaptic plasticity Structural Plasticity Changes to the number of neurons New neurons (very limited) Neuronal loss Changes to the number of axon terminals and dendrites. Leads to new connections between neurons and new information processing. Structural plasticity Synaptic Plasticity How strong synapses are? Like friendships, synapses grow stronger or weaker Potentiation- existing synapses grow stronger With repeated communication between neurons makes the synapse stronger More neurotransmitter is released OR More postsynaptic receptors Depression- existing synapses grow weaker. With repeated lack of communication between neurons makes the synapse weaker Less neurotransmitter is released OR Fewer postsynaptic receptors Module 3 Examples of neuroplasticity Plasticity after learning in animal models Rats raised in an enriched environment develop a thicker cortex and increased dendritic branching. Plasticity after stress Rats raised in a stressed environment develop a smaller dendritic branching. Plasticity after exercise Exercise is known to increase trophic factors that facilitate the survival of neurons. Measurable expansion of neurons has also been shown in humans as a function of physical activity. The thickness of the cerebral cortex declines in old age but much less in those that are physically active. Exercise is known to increase trophic factors that facilitate the survival of neurons. The plastic brain; Optional: https://www.youtube.com/watch?v=wFtc-NPl4Lc This is a 6.5-minute video that describes the research of two neuroscientists at the University of Alabama at Birmingham. Dr. Linda Wadiche describes her research on neurogenesis in the adult hippocampus. Dr. Erik Roberson describes his research on plaque formation in Alzheimers disease. The video includes several interesting and informative micrographs Module 4 Plasticity after brain damage Plasticity after brain damage Axon sprouting Collateral sprouts are new branches formed by other non-damaged axons that make synapses with vacant areas. Plasticity and phantom limbs A phantom limb is the sensation that an amputated or missing limb (even an organ, like the appendix) is still present and is moving appropriately with other body parts. The phantom limb can produce a very painful sensation. The patient can also experience sensation in the missing limb after touching a different area of the body. What explains phantom limbs After a limb is amputated: The cortical area that represents sensation of the missing limb is still intact. But that area is not receiving any input. The brain reorganizes so that nearby brain regions innervate the area of the missing limb. If the missing limb is a hand, the area next to it in the sensory cortex is the face. Over time, the neurons that innervate the face area, develop axon collaterals to the vacant area of the hand.  Phantom limbs In the next video, V.S. Ramachandran explains how phantom limbs is the result of brain reorganization. V.S. Ramachandran is Director of the Center for Brain and Cognition and Distinguished Professor with the Psychology Department and Neurosciences Program at the University of California, San Diego, and Adjunct Professor of Biology at the Salk Institute. Ramachandran initially trained as a doctor (MBBS) at Stanley Medical College, Madras, India, and subsequently obtained a Ph.D. from Trinity College at the University of Cambridge. After that, he received an honorary FRCP; London (Fellow of the Royal College of Physicians) and two honorary doctorates (DSc; honoris causa). Ramachandran’s early work was on visual perception but he is best known for his experiments in behavioral neurology which, despite their apparent simplicity, have had a profound impact on the way we think about the brain. He has been called “The Marco Polo of neuroscience” by Richard Dawkins and “The modern Paul Broca” by Eric Kandel.  Ramachandran on Phamton limbs. Not excellent quality video but e https://www.youtube.com/watch?v=s xcellent content q6u4XVrr58 Neuroplasticity Summary The brain reorganizes constantly in response to sensory input, motor output, learning, memory, stress, exercise etc. Neuroplasticity works in both directions: some areas become larger and synapses stronger, some areas become smaller and synapses weaker. eu