Notes on Neuroplasticity and Recovery

Introduction to Neuroplasticity

  • Dr. Jill Seale presents a discussion on the concept of neuroplasticity.

  • Objectives of the session:

    • Describe neurological recovery.

    • Define neuroplasticity.

    • Compare and contrast recovery and compensation.

Theories of Recovery

  1. Reversal of Diaschisis:

    • Definition: Diaschisis generally means "shocked throughout." It refers to the loss of function in areas of the brain that are not directly damaged but are connected to the damaged area.

    • Example: In the case of a stroke affecting a specific brain region, areas connected to that damaged region also suffer loss of function.

    • Physiological Changes:

      • Metabolic changes occur, often involving reduced blood flow and oxygenation to the affected area.

      • As physiological processes begin to recover (normalization of metabolism and blood flow), spontaneous recovery can occur, which can happen without rehabilitation.

      • Spontaneous recovery refers to the natural recovery of function due to the resolution of immediate physiological disruptions, despite the presence of permanent damage.

  2. Compensation:

    • Functional improvement occurs but significant impairment remains.

    • Example: A patient with right-sided weakness may relearn to dress using only their left arm, thus compensating for the lack of function in the right side.

    • In this case, while they can complete tasks, they do not utilize the affected side.

    • The same logic applies to activities like walking, where a patient may over-rely on their unaffected leg for mobility.

  3. Physiological and Anatomical Reorganization:

    • The nervous system undergoes changes in response to the intrinsic neural networks following injury.

    • Changes Include:

      • Alterations in neurotransmitter levels.

      • Neurological growth, which includes dendritic branching, axonal sprouting, synaptic genesis, and possibly neurogenesis (creation of new neurons).

    • This type of recovery is the most desirable as it focuses on restoring function in the affected area rather than relying on compensatory mechanisms.

Definition of Neuroplasticity

  • Neuroplasticity is defined as the brain's innate capability to:

    • Grow new neurons.

    • Reorganize and adapt structurally and functionally.

    • Access unused neural circuits and bypass damaged ones, a process often described as rewiring.

  • From a therapeutic perspective, neuroplasticity can be viewed as an opportunity to train a damaged brain to perform previously learned functions effectively again.

  • True recovery involves the ability to perform tasks using the affected parts in a similar manner to how they were accomplished before the injury.

Analogy of Neuroplasticity

  • Jill Bolte Taylor's analogy from her book My Stroke of Insight:

    • The brain is likened to a playground with children engaged in diverse activities.

    • If one area (e.g., the jungle gym) is removed, the children (neurons) adapt by finding new activities rather than disappearing.

    • Similar to neurons, when certain functions are damaged, remaining cells either die from lack of stimulation or adapt to take on new roles.

Mechanisms of Neuroplasticity

  • Neuroplasticity involves both structural and functional changes:

    • Structural Changes:

    • These changes include the formation of more synapses, axonal growth, and the recruitment of additional receptors within the nervous system.

    • Neurogenesis can also occur, which was not fully acknowledged until recent years.

    • Functional Changes:

    • The nervous system can develop increased excitatory postsynaptic potentials, indicating a heightened level of activity and excitability in the nervous system.

  • Compensation is acknowledged as a form of neuroplasticity where the nervous system reorganizes, but it is considered maladaptive if it inhibits relearning the usage of the affected parts.

Consequences of Compensation

  • Compensation can lead to conditions where the central nervous system does not engage in necessary motor control processes critical for recovery.

  • Patients often learn not to use their affected limbs due to slower or painful movement experiences, leading to the concept of "learned non-use."

  • According to Rebecca Lewthwaite (PhD researcher), "Patients often can only make short-term solutions that eliminate the long-term possibilities," emphasizing that while compensation may appear easier in the short term, it can undermine long-term recovery potential.

Summary Points on Recovery and Compensation

  • Recovery can take multiple forms, with neuroplasticity being a shared experience for all individuals, including those without pathology as they learn new skills.

  • Recovery and compensation are distinct but interconnected aspects of neuroplastic change; as therapists, the goal is to encourage recovery-focused neuroplasticity over compensatory mechanisms.

  • The ultimate objective is to restore pre-morbid level function, allowing patients to use the affected parts as they did prior to their injury, rather than compensating through alternative means.