Neurobiology of Aging and the Diagnosis of Generalized Degenerative Disease

At age two, most of the child's brain is not fully developed, it is seventy-five percent of adult weight. At age five the brain is ninety-five percent of adult weight. Based on solid scientific evidence, the brain is not a completed organ at birth. Post mortem studies reveal that myelination - one of the five basic processes that make up brain development begins in the brain stem and cerebellum before birth but is not completed in the frontal cortex of the brain until late adolescence period. Myelination process begins before birth, that is during the prenatal period - it is the first process to occur in brain development. Myelin, a fatty layer accumulates around nerve cells to allow nerve impulses to move more quickly - protecting the neuron and acting like an insulation for the human brain. The cerebral hemispheres are the first myelinated. By the second year, the cerebrum is completed. During the process of brain development, there is an increase in the axonal connection which contributes to the growth of the brain. According to neuroscientists, the brain is divided into two- the right hemisphere and the left hemisphere. The left side of the body is controlled by the right hemisphere, while the left side of the brain which is the dominant part controls the right side of the

The physical growth transformations infants undergo in stage two of lifespan development range from, brain, motor, to sensory/perceptual development, and infant’s overall body height and weight. During the first two years, brain

Babies grow and change so much in the first two years of life, and many of those growth are directly related to the brain. Brain grows so rapidly than any other organ and reaches 75% by the age of 2. Communication within the central nervous system and spinal cord begins with neurons. The final part of the brain prefrontal cortex matures.

By age two the brain has developed to two-thirds of what it will weigh by adulthood and has increased to five times the density it was at birth.

Age-related declines are not constant across brain regions. Moreover, patterns of brain aging differs among individuals. Post mortem (PM) studies cannot help in assessment of brain tissue and its components. Moreover, PM cannot provide information on dynamic process of adult brain development, and its connection with brain structure and function. MRI helps in in-vivo measurements of the brain. It was realized that there is cortical thinning as age progresses. . Some studies of cortical thickness failed to replicate stability of the primary sensory regions (e.g., calcarine cortex) (Fjell et al., 2009; Salat et al., 2004) while others found that cortical thinning in frontal and parietal lobes exceed that of the temporal and occipital regions (Thambisetty et al., 2010). It is suggested that myelin is related to shrinkage in cerebral cortex or responsible for loss of cortical volume. MRI has helped evaluate leukoaraiosis which is a change in white matter integrity that is displayed on a T2-weighted MR image as a high signal intensity area. This area is defined as white matter hyperintensities (WMH) which depicts pathological processes such as ischemic lesions, gliosis, axonal degeneration, loss of myelin, microinfarcts, and expansion of perivascular spaces (de Leeuw et al., 2001; Pantoni, 1998). WHM is observed around the borders of the ventricles and deep in the subcortical WM regions. WHM is not present in health adults until the age of 50-55 (Hopkins et al., 2006). Further,

It is full of comprehensive and engaging style; well reference and scientifically proven, summarizes the current revolution in neuroscience and neuroplasticity, and closes the gap that the old age or matured brain, which is unchangeable is changeable and malleable (plastic); extending it functions from one region to the other. Doidge engaging style of writing, scientific proves, and academic tone help to make the book persuasive.

Myelin is the protective sheath around axons in the nervous system, and is often referred to as 'white matter.' It acts as an insulator to the electrical signal that is conducted down the axon as a neuron fires, and can well be compared to the insulation around an electrical wire. The myelin sheath contains a variety of fatty substances (lipids), and contains at least ten distinct chemicals (2). . From what is known, axons are not fully myelinated at birth, but myelin is formed from birth on into the second decade of life (3). The way myelination takes place is through glial cells wrapping around the axons in a spiral fashion. The axons are originally embedded in these glial cells, and the

This paper will discuss the relationship between the aging process and key diseases associated with aging. Examples of aging-associated diseases include cancer, diabetes, cardiovascular disease, and neurodegenerative diseases (López-Otín, Blasco, Partridge, Serrano, & Kroemer, 2013, p. 1194). Of these, we will discuss in-depth recent studies that have linked aging with Alzheimer’s disease, cardiovascular disease, and diabetes. These diseases affect a significant proportion of the population over the age of 65 and place a considerable burden on the American health care system. Therefore, a better understanding of how they are related to aging and each other can result in the adoption of innovative treatments and declined risk for older adults.

Life span developmental psychology takes a scientific approach to human growth and change, focusing on change during the life span. There are three main aspects to life span development: cognitive, social, and physical development. This class is not simply a discussion of nature vs. nurture, it explores the interaction between genetic and environmental factors that orient us towards specific behaviors. Initially, my views on life span development were limited to more sociological factors, and did not take into consideration physical developments of the brain. In relation to my personal and professional identity this course has made me realize that development occurs on a spectrum and that not everyone develops at the same time, in the same ways, making me more understanding and compassionate towards those who developed differently than me. The three most important lessons I have learned from this class are that development occurs throughout the entire life span, infants begin learning at a very young age, and that senescence begins as early as young adulthood.

al.’s (2012) study later demonstrated the relationship between premature birth and brain volume. Premature infants at 5 months after birth who were small for gestational age had lower brain structure measurements than the premature infants with an appropriate gestational age. However, as development progresses after birth their brain volume catches up to those of AGA infants, but still remained less. The MRI measurements that were calculated in SGA infants was 10% less than those of AGA infants. Lower brain volume can be a possible predictor of chronic lung disease. The results also showed a difference in the pituitary gland. It was showed to be larger in height in the infants with the lowest birth weight. This suggests that it is caused by an increased secretion of the growth hormone. Additionally, it was also found that the corpus callosum of SGA infants was thinner than the other groups. This is associated with other MRI measurements of the brain that showed to be less than AGA

Areas of high neuroplasticity also tend to be areas of scarce myelination. As mentioned earlier in this paper, these areas both tend to reside within the evolutionarily new neocortex. Neocortical areas exhibit an early and brief myelination cycle as compared to older and deeper brain areas, which exhibit later and extensive myelination. The axons of the neocortex are long, thin, and sparingly myelinated compared to other regions of the brain, as observed through Nissl staining. These Nissl stains verify a pattern of myelination in which the highest cortical areas are the most sparsely myelinated. Perhaps unsurprisingly, the pattern of neural damage, such as neurofibrillary tangles associated with AD, follows the pattern of myelination. In other words, these tangles develop in the areas that are most sparsely myelinated. In contrast, areas of heavy myelination are much more resistant to stressors that cause neuronal degeneration5. It is believed that areas of decreased myelination are characteristic of cells retained in their juvenile state. Without the structural encasing of myelin, these cells are more flexible to changes, and thus have higher plasticity than cells that are heavily myelinated. Therefore, neurons of the neocortex are likely highly plastic largely because of their lower degree of myelination.

Why does the human brain age? Brain aging is a part of human life and a big part of society as the awareness for brain aging increases. Over time memory tends to become less efficient as we age and the neurons in the brain decreases (Bendheim, P.E. (2009). By 2050 in the US, 20 percent of the population will be 65 years or older. And as the elderly population increases, so will the incidence of age-related neurological disorders (Perlmutter, David. (2004). Therefor it is important to understand the aging brain, and how to keep the brain functioning as one ages.

As discussed before since infants are usually born with cortical development, the subtypes of cortical neurons amounts at 24 and 96 hours get investigated using organoids grow

According to Crawford and Walker(2010), the life course is defined in literature as, “The progression and path an individual takes from conception to death.” (Crawford and walker, 2012, p.3). The study of the life course and human development is extremely complex and could be described as interdisciplinary as it encompasses many fields of study. When examining the life course of individuals it is necessary to consider all of the various factors that affect human behaviour. These may include; psychological, biological, social, behavioural, cognitive or culture factors. Age can also be considered as a factor that influences lifespan development. In the early 19th century, the term “age related change” was regarded as only applicable to the early childhood stage but in recent years, psychologists have come to accept that age related changes occur throughout the entire life span. According to Boyd and Bee (2014), other earlier theories included Charles Darwin’s suggestion that, “the wide variety of life forms that exist on earth evolved gradually as a result of the interplay between environmental factors and genetic process.” (Boyd and Bee, 2014, p.3) Therefore Darwin proposed that it was either solely, “nature” or “nurture” that influenced the human development, but instead, a combination of both. In this assignment, I am going to focus on the specific psychological factors that influence human behaviour during the life course. I will compare two different psychological

It is clear to neurobiologists that aging results in a decrease in brain size as well as a decrease in the efficiency of brain functions. It has been a widely held belief that aging causes neurons to die and for the overall number of neurons to decrease as one reaches old age. Studies