Even so, Professor W. Greenough (1970) reports that the brain will continue its growing regardless of the number of stimulation because of what he coined as experience-expectant behaviors, the idea that the brain assumes you will encounter the natural experiences such as seeing things and learning in general. Experience-dependent learning, unique cultural experiences, is what enhances brain growth to a further extent. Hence, one can learn that the more exposure to learning stimulation, the more development the brain undergoes and that even old brains are still plastic for change unless the individual is placed in a impoverished environment with complete isolation.
According to the study conducted by University College London; Maguire (2000), long term experience of spatial jobs, particularly taxi drivers, have more grey matter in the posterior hippocampus compared to non-taxi drivers from days of memorizing maps and the city’s geography to stimulate the growth of extra grey matter in the posterior hippocampus that deals with produce more neural circuitry in that specific region of the brain. One can conclude that the more exposure to that skill or experience, the more plastic the brain will be in creating new neuron pathways and developing itself. Other evidence prove similar results, Pascal-Leone (2002) reported that after instructing participants to practice a five-finger piano exercise for five days, their motor cortex had expanded, even more if they decided to practice outside of training sessions. These results suggest that training and imagination can alter brain physiology. One other example refers to Richard Held (1960) who ran a series of experiment testing sensory inputs and motor outputs. One group of participants were asked to stroll on a convoluted pathway while wearing goggles that warped their vision. The other group were asked to wear the same goggles but were carried down by a volunteers in a wheelchair. Those that engaged their tactile sensory with the environment scored higher on tests regarding brain activity and visually related tasks. The results prove that when forced to extendedly exercise one particular brain region it can improve that specific skill furthermore, again creating more neuron pathways.
Environmental factors, however, can also have a negative effect such that when often challenged with chronic stress, it has many physiology permanent harms. In the study of how chronic stress affects immunity, Kiecolt-Glaser et al., (1984) discovered that more t-cells, involved in the activation of the immune system were active in the blood sample before the final exams while very fewer were present during the blood sample taken during the exams. One must consider some health factors that were not put in account to such as drug use, sleep patterns, and general health.
When faced with stress, the sympathetic drive responses by having the mental or physical stimulus activates the central nucleus of the amygdala that particularly deals with anxiety and fear and triggers the hypothalamus to release the production of norepinephrine and glucocorticoids, primarily cortisol from the adrenal medulla and cortex. It is an adaptive response to prepare the body for a flight or fight response that shifts energy and nutrient rich blood to skeletal muscles for glucose metabolic change and physical rapid movement, deferring from mediating injuries. (Sternberg, 2000) supports that this temporary inhibition of immunity by suppressing the formation and decreasing the longevity of lymphocytes (B and T-cells) if faced with an invading agent, triggers negative feedback to allow a short burst of immune activity, one of the few benefits of stress, explicitly acute stress. However, it is still unsure as to why stress shuts down the immune system as a good cause.
Stress can also affect the way humans deposit fats in their body. Research done by White Hall Study (1985) observed that chronic stress in humans could alter the way they gain weight. It is dangerous because fat carried in the midsection or abdomen is much worst than anywhere else in the body.
In addition, stress increase blood cholesterol levels through the action of adrenaline on the release of fatty acids. These cholesterol particles will clump together and block pathways in artery walls that may result to atherosclerosis and further death if not stopped. A study by Epel et al., (2004) investigated that fragile telomeres were a result to chronic stress. Telomeres act as a protective cover for chromosomes for proper replication. As more stress hormones are released, the more consequence it has on physiology.
Environment has a profound affect on physiology that shapes our brains and body everyday. Stimulations and experiences that deal with learning enhances neuroplasticity and provoke a heavier more complex cerebral cortex, while common exposure to chronic stress provoke negative consequences of physiology. Thus with research, one can ascertained that the experience we face daily affect our body and mind, whether positively or negatively. The brain is an evolutionary organ that alters its structure according to your experiences.