Buzz
Engaging in physical activity not only boosts your physical health but may also enhance your cognitive abilities.
Recent studies reveal that exercise does more than release endorphins, known for creating the euphoric 'runner's high.' It may also foster the development of new neural connections and even the growth of fresh brain cells. Additional research highlights the strong link between regular physical activity and improved mental performance.
Activities like running, cycling, and other sports might activate an ancient 'fight or flight' response, potentially stimulating brain cell growth, similar to how it benefited early humans during hunting or evading predators. Alternatively, increased blood flow to the brain could be the key factor.
While experts note that the exact role of these new brain cells remains unclear, or whether they integrate into functional neural networks influencing thought and behavior, it is now certain that new cell growth occurs in brain regions responsible for thinking, learning, and memory.
Until recently, neuroscientists thought the brain ceased generating new neurons, or nerve cells, after birth. While they acknowledged that synapses, the links between neurons essential for memory and thought transmission, evolve and expand with age before declining later in life, they believed the total number of neurons could only decrease over time.
In recent years, scientists from institutions across the globe have revolutionized this perspective by studying neurogenesis, the process of new brain cell formation. Their findings, observed in various test subjects, including humans, reveal that neurons are continually generated, even in older individuals. Behavior plays a crucial role in determining the extent of this cell growth, leading to groundbreaking insights (refer to Mind-Body Exercise Connection Research).
"The remarkable discovery is that the rate of new cell generation in the brain is influenced by your engagement with the environment," explains neurobiologist Fred H. Gage. Physical activity appears to be a critical factor in this process.
"Exercise leads to an increase in the number of micro blood vessels in the brain," he notes. These vessels are closely tied to the creation of new cells. "This establishes a direct physiological connection between physical activity and neurogenesis," he adds.
During exercise, muscles consume oxygen at a higher rate, prompting the heart to deliver more oxygen-rich blood to the brain via the carotid artery. The brain utilizes approximately 25% of the oxygen you inhale. The release of endorphins during exercise also contributes to increased energy, mental alertness, a heightened sense of well-being, and improved memory retention for regular exercisers.
Before recent research, scientists believed that enhanced blood flow to the brain was the primary reason for the connection between exercise and improved cognitive function. However, we are now gaining deeper insights into the relationship between physical activity and brain health (refer to A Brain Primer).
In The Laboratory
In 1998, Gage from the Salk Institute and Peter Eriksson at Sahlgrenska University Hospital in Göteborg, Sweden, examined hippocampal tissue from deceased cancer patients aged 57 to 72. These individuals had been injected with bromodeoxyuridine (BrdU) during their lives for diagnostic purposes.
BrdU is only taken up by cells that are dividing, indicating the creation of new cells. In cancer patients, it helps identify multiplying cancer cells. The discovery of BrdU-labeled neurons in the hippocampus provided definitive evidence for Gage and Eriksson, confirming that neurogenesis was occurring.
"Detecting new neurons involves identifying whether they are undergoing cell division," Gage explains. Importantly, these newly formed cells were not idle but appeared to be functional.
"We observed that these newly formed neurons were acknowledged and integrated by surrounding cells. They appeared to be connected to the relevant regions, suggesting they could contribute to cognitive processes,"
At the same time, Gage and fellow researchers at Salk were conducting separate studies on how learning impacts the brains of mice. Their findings could hold significant implications for humans. The mice were placed in an enriched environment filled with toys, treats, and other stimuli designed to encourage mental activity.
As an additional variable, running wheels—essentially mouse treadmills—were introduced. The mice ran voluntarily, choosing their own pace and duration. Remarkably, the mice that ran developed twice as many new brain cells compared to those in the control group.
The Salk team remains uncertain why running has such a profound impact on neural growth. Some theories suggest that running may boost oxygen and nutrient delivery to brain tissues or trigger the release of growth factors that encourage neuron formation, according to Gage. Alternatively, running might prepare the nervous system to process new information as an animal navigates unfamiliar environments, whether hunting or evading predators.
Meanwhile, at Princeton, neuroscientists Elizabeth Gould and Charles Gross from the psychology department advanced the study of neurogenesis. They discovered new neurons not only in the hippocampus but also in the more sophisticated cerebral cortex of adult rhesus monkeys.
To identify new neurons in the adult brain, Gould and Gross administered BrdU injections to the monkeys. They examined the cerebral cortex at intervals ranging from two hours to seven days post-injection, discovering BrdU in cells across three regions, all associated with advanced cognitive functions.
The scientists identified multiple neuron-specific proteins within these cells. Additionally, they confirmed that the BrdU-labeled cells exhibited the long axon extensions typical of neurons.
To achieve these findings, Gould and Gross employed a method known as fluorescent retrograde tracing. This involves applying a chemical dye to a specific brain area, which then travels along axons back to the cell body, rendering the axons visible under microscopic examination.
When the monkeys participated in various mentally stimulating activities, the production of new cells significantly increased.
Collectively, these discoveries indicate that neurogenesis occurs across a wide spectrum of mammalian species, including humans.
Gould and Gross emphasize that the role of new cells in the cortex remains unclear. However, if these newly formed neurons are proven functional, it could challenge existing theories about brain functionality.
Gage predicts that advanced brain imaging techniques will soon reveal how physical and mental exercise stimulates neural growth in humans. He notes that the brain is not a one-way system solely dictating behavior but is also shaped by it.
"We are discovering that human behaviors influence the brain's structure, including the number of cells and their connections, which in turn affects future behaviors,"
A study at the University of Illinois' Beckman Institute for Advanced Science and Technology, supported by the National Institute on Aging, provided stronger evidence of aerobic exercise's benefits for the human brain. The study analyzed the cognitive effects of walking versus toning exercises on 124 adults aged 60 to 75.
Both exercise groups improved in repetitive tasks, like pressing a button in response to visual cues. However, the walking group outperformed the toning group in filtering out irrelevant cues and completing tasks efficiently.
Effectively managing relevant information while filtering out distractions is crucial for 'executive control,' which encompasses planning, inhibition, and temporarily holding information in memory.
"Executive control processes are primarily governed by the frontal and prefrontal brain regions, areas that experience metabolic and structural decline with aging," explains Arthur F. Kramer, a psychologist and Beckman Institute researcher. "Cells shrink, and blood flow diminishes. Walking benefits cognitive functions most affected by age-related decline."
Brain Workout World
The key question is: What activities best stimulate cognitive development, and how can we measure their effectiveness? While sit-ups promise toned abs, and running or cycling brings temporary exhaustion or an endorphin boost, how do we gauge if we're sufficiently strengthening our brain?
If running is beneficial, what about sports that require strategic thinking, teamwork, and social interaction—factors psychologists have long associated with improved mental health?
While definitive answers may take time, some theories suggest that social interaction plays a significant role in neurofunctioning. Gage notes that sports involving social engagement could enhance neurogenesis, provided they include aerobic activity.
"Researchers often focus on running or walking in experiments because these activities can be isolated and analyzed independently of social interaction, learning experiences, or other variables. This allows them to confirm that exercise alone is sufficient," he explains. "However, this doesn't rule out other effective methods to achieve similar results."
Until more is known, the best approach is to continue running or begin an exercise regimen that boosts circulation. Such activities benefit the mind, body, and spirit.
Neurobics
Activities like running, cycling, and tennis increase blood flow to the brain, but neuroscientists believe that physical exertion isn't the sole path to maintaining mental sharpness.
Dr. Amir Soas from Case Western Reserve University Medical School in Cleveland emphasizes that the brain requires mental exercises to remain sharp. "Areas of the brain that remain inactive for extended periods tend to deteriorate, much like any other part of the body," he explains.
Complex tasks activate more synapses across various brain regions. Just as physical exercise builds blood vessels in muscles, mental workouts promote the growth and health of blood vessels in active brain areas. Studies suggest this can even help prevent Alzheimer's and Parkinson's in susceptible individuals.
Engaging in activities such as writing stories, learning chess or a new language, or solving crossword puzzles stimulates multiple brain regions, increasing synaptic activity (refer to Mind Games: Creating New Brain Cells).
