Neuroplasticity+PPT

Neuroplasticity Overview

  • Neuroplasticity refers to the brain's ability to change and reorganize itself throughout life.

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: Understanding Neuroplasticity

  • Definition of Neuroplasticity: The brain's capacity to undergo constant change due to various factors such as learning, memory, and damage.

Case Study: Jody Miller

  • Developed Rasmussen syndrome at age 3.

  • Experienced epilepsy in the right hemisphere leading to severe seizures.

  • The only treatment was a hemispherectomy (removal of the right hemisphere).

Historical Perspective on the Brain

  • Static View: Previously believed the brain did not change after a certain developmental stage; change was considered a sign of deterioration.

  • Current View: The brain is dynamic, capable of neurogenesis (birth of new neurons) and forming new connections.

Module 2: Structural vs. Synaptic Plasticity

Physical Changes in the Brain

  • Structural Changes (Structural Plasticity):

    • Can include neuron growth, loss, and the alteration of axon terminals, dendrites, and dendritic spines.

  • Synaptic Changes (Synaptic Plasticity):

    • Involves the strength of communication between neurons, influenced by the number of neurotransmitter receptors and the amount of neurotransmitter released.

Synaptic Plasticity

  • Potentiation: Strengthening of existing synapses due to repeated stimulation, resulting in increased neurotransmitter release and receptor sensitivity.

  • Depression: Weakening of synapses due to lack of communication, leading to reduced neurotransmitter release and fewer receptors.

Module 3: Examples of Neuroplasticity

Learning-Related Changes

  • Animal Studies: Rats in enriched environments demonstrate thicker cortices and enhanced dendritic branching.

  • Human Studies:

    • MRI shows professional musicians' auditory cortex is significantly larger.

    • Increased gray matter in areas responsible for motor skills (e.g., keyboard players).

    • Differences in Brain Structure: Violinists vs. pianists have distinct brain patterns related to their instruments.

Effects of Stress

  • Environment with high-stress levels leads to reduced dendritic branching in rats.

Impact of Exercise

  • Exercise and Neurogenesis:

    • Regular physical activity promotes neuronal survival and enhances brain structure over time.

    • Evidence: Aging effects on the cortex are mitigated in physically active individuals.

Module 4: Plasticity after Brain Damage

Recovery Mechanisms

  • Recovery from brain injuries often involves neuroplasticity.

  • Example: An American soldier lost the ability to speak after a left hemisphere injury but showed gradual improvement over months.

Causes of Brain Damage

  • Common causes include:

    • Brain tumors, infections, degenerative diseases (e.g., Alzheimer's, Parkinson's).

    • Physical trauma (closed head injuries or strokes).

Treatment Approaches

  • Recent advances, such as tissue plasminogen activator (tPA) for ischemic strokes, improve recovery outcomes.

Types of Plasticity

  • Axon Regrowth:

    • Peripheral nervous system can regrow axons; central nervous system has limited regenerative capacity.

  • Axon Sprouting: Formation of new connections by nearby healthy axons targeting vacant synaptic sites.

Phenomenon of Phantom Limbs

  • Description: Individuals experiencing sensations in amputated limbs due to neural reorganization and cortical representation of the missing limb.

  • Mechanism: Nearby brain areas innervate regions left vacant by the loss of the limb, leading to phantom sensations.

General Principles of Neuroplasticity

  • Neuronal function is determined by connections rather than identity; neurons can adapt and take over functions of lost neurons.

Concluding Summary on Neuroplasticity

  • The brain is consistently adapting in response to various stimuli such as learning, stress, and exercise.

  • Neuroplasticity indicates that some areas of the brain can grow and strengthen connections, while others can weaken in the context of absence or reduced stimulus.