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What is neuroplasticity?

This is an excerpt from Brain Health and Exercise by Ryan Glatt,Aimee Nicotera.

The remarkable feature that sets the nervous system apart, particularly the brain, is its inherent plasticity. Neuroplasticity, a distinctive quality of the nervous system, underlines the brain’s remarkable ability to adapt and transform. Neuroplasticity can manifest in functional or structural alterations and may be either adaptive or maladaptive. Functional neuroplasticity ­pertains to changes in synaptic activity, brain function, and neural ­connections, often preceding structural changes. In contrast, structural neuroplasticity involves modifications to the number of nerve cells, brain volume, and the structure of neurons, though it remains a less explored area in human neuroscience.

The dichotomy between positive (adaptive) and negative (maladaptive) neuroplasticity is crucial in understanding how the brain evolves over time. While the term neuroplasticity might imply positive change, it’s essential to recognize that it encompasses both constructive and detrimental alterations. The principle of “use it or lose it” aptly summarizes this dynamic, because our brains reinforce or diminish neural connections based on their utilization. Key concepts surrounding neuroplasticity and aging shed light on the potential for slowing cognitive decline, the relationship between effort and change, and the growing importance of maintaining effort and complexity as we age. Factors such as cognitively stimulating environments, nutrition, stress management, sleep, and physical activity come into play to foster favorable neuroplasticity. These factors are instrumental in shaping the interplay between cognitive reserve and neuroplasticity, illustrating the profound impact of lifestyle and environment on our brain’s ability to adapt and thrive (Been et al. 2022; Maharjan et al. 2020).

Functional Neuroplasticity Functional neuroplasticity refers to changes in synapses, brain activity, and connections within neuronal networks. Functional changes often precede structural changes in the brain.

Structural Neuroplasticity Structural neuroplasticity refers to changes in nerve cell number, brain volume, or modifications to nerve cell structures (like dendrites). There is still much unknown about structural neuroplasticity in humans (Smith 2013).

Positive Neuroplasticity Positive (adaptive) neuroplasticity refers to creating or strengthening synapses and neuronal connections, nerve cell structures, and brain volume. It is important to note that neuroplasticity is often falsely used to imply that all changes are positive and permanent.

Negative Neuroplasticity Negative (maladaptive) neuroplasticity is not a scientific term, but we use it to describe the weakening or degeneration of synapses and neuronal connections. In addition to behavioral, environmental, and experiential factors, mechanisms like neurotoxicity partially explain the more scientific concepts related to negative neuroplasticity.

Table 1.4 demonstrates the different ways in which the brain can be changed, summarizing functional, structural, adaptive, and maladaptive neuroplasticity.

Neuroplasticity is always in a degree of change and can be conceptually understood as bidirectional. Whether the change is positive or negative, our brain strengthens the synapses and neuronal connections we use most. When connections are not used, the brain will allow them to degenerate. This “use it or lose it” process was described by a neuroscientist named Dr. Donald Hebb, who posited the concept of Hebbian plasticity. Hebbian plasticity refers to two types of neuroplasticity. Long-term potentiation is when a series of neural signals create enough demand for a certain circuit of neurons to synchronize. Conversely, long-term depression refers to the downregulation of neural activity that eventually leads to lessened activity within a particular network or a loss of connections. This is also where the phrase neurons that wire together is from. Still, it is not necessarily literal, since networks of neurons do not need to be near each other for their activity to be synchronized (Smith 2013; Jellinger and Attems 2013).

There are several concepts surrounding neuroplasticity and the aging process to consider:

• Slowing cognitive decline: Positive experiences and healthy lifestyle behaviors in early life contribute to slower cognitive decline and greater cognitive reserve. Neuroplasticity is related to slowing cognitive decline by taking advantage of adaptive factors concerning ­maladaptive factors.
• Effort and change: The brain’s ability to change in response to experience is most available early in life. As age increases, the ability of the brain to change in response to experience decreases. At the same time, the amount of effort required to make these changes increases. This is important because many older adults may not engage in sufficient physical and cognitive activity to address this curve.
• More effort required: Individuals may be less eager to engage in more intense and frequent exercise as they age. However, neuroplasticity requires greater effort, frequency, and complexity of interventions to maintain significant benefits.

The following factors can facilitate positive or negative change based on individual behaviors, experiences, and environmental conditions (Maharjan et al. 2020):

• Cognitively stimulating environments that provide opportunities for learning and novel experience are highly conducive to positive neuroplasticity.
• Nutrition, stress, and sleep are all contributing factors to neuroplasticity. Various mechanisms underlie positive or negative changes in the brain, such as the glymphatic system, which can regulate brain toxicity and is related to sleep and exercise.
• Physical activity and exercise are contributing factors. Negative (or ­maladaptive) neuroplasticity can be induced by sedentary behavior. Some studies demonstrate that anywhere from a single session to several weeks of exercise can positively affect the brain. However, there are more significant benefits when we maintain consistent yet variable exercise and physical activity throughout our lifespan.

Positive neuroplasticity is elicited by a healthy lifestyle and environmental variables contributing to a high cognitive reserve. Negative neuroplasticity can be elicited by poor lifestyle and environmental variables, leading to maladaptive neuroplasticity and neurodegeneration. The next section will explore the concept of cognitive reserve in more detail.

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