Neuroplasticity and Alzheimer’s Disease

Writers: Prahalad Srinivasan, Aayan Subzwari, and Vijaya Varadarajan

An etymological excursion: neuro-plastic; with “plastic” coming from the Greek term “plastikós” indicating “suitable for molding”. [1] Now, are neurons made of plastic? Um, not quite, but the ability for neurons and “the nervous system to change its activity in response to intrinsic or extrinsic stimuli by reorganizing its structure, functions or connections after injuries.” [2] is what we call neuroplasticity. Transcranial magnetic stimulation (TMS) is used to detect the brain’s decline by measuring neuroplasticity and the brain’s ability to respond to stimuli. It plays an extremely important role in the early identification of Alzheimer’s disease.

Neuroplasticity is the ability of the brain to respond to external and internal stimuli, often leading to small changes in the structure and function of the organ. When patients contract Alzheimer’s disease and the onset of Aβ peptides and tau proteins begins, the expression of synaptic plasticity begins to degrade. Often, the decline of neuroplasticity is one of the first signs that the patient has Alzheimer’s, and tests often check for signs of neuroplasticity design when testing for Alzheimer’s. 

Recent research shows that there are indeed ways to improve and track declining neuroplasticity in a patient’s brain, one of which being TMS - Transcranial magnetic stimulation By using magnetic fields, TMS can stimulate nerve cells within the brain to form connections, allowing the brain to restore some of its abilities to respond to external stimuli.

Transcranial Magnetic Stimulation (TMS), is a non-invasive procedure approved by the U.S Food and Drug Administration (FDA) to alleviate symptoms of major depression. The FDA has also endorsed TMS for treating obsessive-compulsive disorder (OCD), and migraines, and aiding smoking cessation when standard methods have not been successful, but has recently been tested for patients of Alzheimer’s. When used for Alzheimer’s patients, it is often first used to measure the level of existing neuroplasticity in the brain using biomarkers. 

Figure 1: The effects of DBS and rTMS in the brain.

Scientists and clinicians have long believed that the brain couldn’t mold and possibly better its function. Modern research has crossed out that way of thinking, suggesting that the brain is subject to change. Neural pathways are continually altering and responding to stimuli. Due to the large role of neuroplasticity in brain function, early decline in its function can have more severe effects. In the beginning stages of Alzheimer’s a slight decline in neuroplasticity and the brain’s ability to respond to stimuli is observed. However, as the neuroplasticity worsens, so do many other important features of the brain, one of the main reasons that AD is significantly worse in the later stages. Major declines occur in the spine, the brain’s neural network, and the condition of cells in the central nervous system. 

As Alzheimer’s onsets and progressively worsens, several chemical changes occur within the brain, specifically the buildup of proteins as they are unregulated. Some of the unregulated proteins during Alzheimer’s include GAP-43, MARCKS, and spectrin, all of which reflect and could eventually prevent attempts to respond to stimuli. Along with the upregulation of these proteins, various other changes also occur in the brain affecting neuroplasticity, such as sprouting which results in neuron loss as well as damage to the cytoskeleton resulting in build-up of plague. 

As we continue exploring the effects of neuroplasticity in the brain, it is important to remember that neuroplasticity decline is often one of the first signs of Alzheimer’s. This means it is one of the most crucial factors for researchers to consider when developing a treatment for the disease. Hopefully, new research in neuroplasticity will help researchers progress in their understanding of the disease and lead to more potential cures.

Citations:

“Transcranial magnetic stimulation.” Mayo Clinic, 6 January 2023, https://www.sciencedirect.com/science/article/pii/B9780128194102000278. Accessed 5 March 2024.

“Chapter 31 - Alzheimer disease and neuroplasticity.” ScienceDirect, 6 January 2023, https://www.sciencedirect.com/science/article/pii/B9780128194102000278. Accessed 5 March 2024.

“Plasticity in Early Alzheimer's Disease: An Opportunity for Intervention.” NCBI, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3419487/. Accessed 5 March 2024.

“Non-pharmacological treatment changes brain activity in patients with dementia.” Nature, 6 January 2023, https://www.nature.com/articles/s41598-020-63881-0. Accessed 5 March 2024.