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By Miruna-Maria Cozma
The brain controls numerous cognitive functions, including memory, organizing and planning, decision-making, and much more. Our capacity for independent living and our ability to do daily duties are both impacted by these cognitive capacities.
Infancy:
Babies' brains are like sponges; they take up everything from their surroundings, especially knowledge from their parents or other primary caregivers. Babies may learn any language during their first year or two, for instance, but their vocabulary rapidly becomes limited to the sounds and signals they encounter. It can be far more challenging to acquire new languages later in life, especially if they are not one's original tongue, because of this quick fine-tuning. The enormous number of synapses, or connections between neurons, that are established during the first few years of life is partly responsible for this sponginess.
During the early years of life, crucial cellular and genetic processes unfold. While the majority of neurons are present at birth, other brain cells, like glia, undergo rapid development and maturation.
Glial cells, responsible for forming synapses, insulating connections, providing nutrients, and combating pathogens in the brain, continue to mature for several decades.
Both neurons and glia accumulate mutations over time, but those that occur during development appear to significantly influence the risk for diseases later in life.
Childhood: 2 to 10 years
Between 18 months and two years of age, the brain undergoes a shift towards learning by strengthening important connections and eliminating those that are not being utilized. To prioritize certain experiences, inhibitory connections, which serve as brakes for information processing, develop across brain circuits. Synaptic pruning occurs, resulting in babies losing about half of the synapses they had formed. On the other hand, myelination, the process of wrapping neuronal connections with myelin, rapidly increases to strengthen connections throughout childhood and beyond. This enhanced signal-to-noise ratio is crucial for processing emotions, social interactions, and communication skills.
The brain's sensitivity to interactions with caregivers and the environment during childhood makes it vulnerable to the effects of stress caused by trauma or neglect, which can significantly impact a child's brain development throughout life.
Adolescence: 10 to 19
During the developmental stage between 10 and 19 years old, significant transformations occur in the brain networks responsible for understanding emotions and motivations in various situations. As teenagers venture into the world beyond the comfort of their homes, they undergo a period of heightened sensitivity to their surroundings.
This sensitivity is evident through extensive synaptic pruning and myelination, particularly in the circuits related to processing emotions and rewards. This phenomenon explains why adolescents are driven to seek out new experiences, even if they may pose risks or challenges.
Young Adulthood: 20 to 39
The brain is often believed to reach its peak development in the mid-to-late 20s, with white matter volume peaking and information processing speed at its highest. However, neuronal networks continue to refine into young adulthood, particularly those related to rational thinking and future planning. Despite this, brain development is far from complete. As individuals enter their 30s and 40s, adult synaptic plasticity allows connections to adapt and reorganize in response to new activities, rather than decline.
Late adulthood: 40s and beyond
The human brain's capacity to respond to change, known as plasticity, does not diminish in the adult and aging brain, as believed in the past. New research has revealed the presence of "silent synapses" in the brains of adult mice, indicating the brain's ability to form new memories dynamically throughout adulthood. These previously inactive connections have long been associated with early development but have now been found to be widespread in adult human brains across different ages and regions. These findings are revolutionizing scientists' understanding of the aging brain, indicating that it can continue to change dynamically throughout adulthood.
40 to 65:
As we move into our 40s and beyond, life takes on more demanding responsibilities of adulthood — focusing on career, caring for family, and contributing to the next generation. Because each person's experiences differ greatly, pinpointing specific mental milestones in later life becomes more challenging.
Factors such as engagement in a community, lifestyle choices, and exposure to stress or toxins can significantly impact brain development and the aging process. For instance, a 50-year-old who is highly sociable and regularly engages in exercise, travel, or volunteering activities might have a "younger" brain compared to a 50-year-old who leads a more isolated lifestyle with fewer enriching activities.
Older adults who participate in memory training tasks, solve crossword puzzles or even play video games may enhance certain cognitive functions. However, the precise mechanisms behind these findings remain unknown.
65 years and beyond:
As people age, the brain tends to shrink and may start to degenerate. However, older individuals also possess the potential for enhanced wisdom derived from a lifetime of experiences.
Some experts have proposed that the brain's circuitry related to emotional processing and moral decision-making could play a role in various aspects of wisdom, although research in this area is still limited.
Older persons can continue to perform many of the things they have liked for their whole lives, even with potential changes in cognition that come with aging. Studies indicate that senior citizens may still acquire new abilities, create fresh memories, and enhance their language and vocabulary.
Also, some cognitive changes are typical. For instance, they may struggle to multitask, take longer to identify words and remember names, and have milder declines in their attention span.
Positive improvements in cognition may also accompany aging. For example, some individuals possess deeper word-meaning understanding and have bigger vocabularies than younger adults.
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