IMPACT OF DAMAGE TO THE BRAIN’S PARTS ON ONE’S MENTAL PROCESSES AND BEHAVIOR
Brain, the vital component of the central nervous system (CNS), affects a person’s “mental process” which can be expanded to include behavior, thinking, learning, personality, and psychological aspects of the mind. Causes like prolonged hypoxia (shortage of oxygen), poisoning, infection, and neurological illness lead to widespread brain damage whereas physical trauma (traumatic brain injury), stroke, aneurysm or neurological illness lead to localized brain damage. Assessment of extent of brain injury is done by neurological examination, neuroimaging, and neuropsychological assessment techniques like magnetic resonance imaging (MRI), functional magnetic resonance imaging (FMRI), computed tomography (CT), positron emission tomography (PET), single photon emission computed tomography (SPECT) etc (“Brain damage,” n.d.). Some of the impacts on the metal processes due to damage of the brains parts like Medulla oblongata, Reticular formation, Cerebellum, Hypothalamus, Amygdale and Hippocampus have been discussed in the article below.
The medulla oblongata or the medulla, acts as a relay station transmitting the nerve signals between brain and the spinal cord. It controls autonomic functions like breathing, heart rate, swallowing, vomiting, defecation, urination etc. A person suffering from damage to medulla oblongata is considered to be brain dead or in a persistent vegetative state (when the body depends on a ventilator or other supportive equipment). Depending on the nature of the damage, the person may recover or die after this life support is removed. Smith (n.d.)
The reticular formation is a comprehensive network of nerve fibers located in the central area of the brain stem. Some of the vital functions performed by it include ability to obtain recuperative sleep, sexual arousal, and the ability to focus on tasks without being easily distracted. Effects of damage to the reticular formation include a constant feeling of fatigue, disturbed sleep pattern and lack of control on wakefulness leading a person to a coma state. It also shows a negative impact on a person’s ability to concentrate, as well as sexual arousal.
The cerebellum or the little brain is only 10% of the weight of the brain, but contains as many neurons as all the rest of the brain combined. It integrates visual, auditory, vestibular, and somatosensory information received from various channels. This integrated information is modified to promote coordination of voluntary motor movement, balance and equilibrium and muscle tone. Data from clinical and functional studies indicate that the cerebellum also regulates memory processes (Arriada-Mendicoa, Otero-Siliceo & Corona–Vázquez, 1999). Damage to cerebellum leads to multiple effects like:
1) loss of coordination of motor movement (asynergia)
2) inability to judge distance and when to stop (dysmetria)
3) inability to perform rapid alternating movements (adiadochokinesia)
4) movement tremors (intention tremor)
5) staggering, wide based walking (ataxic gait)
6) tendency toward falling
7) weak muscles (hypotonia)
8) slurred speech (ataxic dysarthria)
9) abnormal eye movements (nystagmus) (“Cerebellum”, n.d.)
Hypothalamus forms a critical link between autonomic nervous system and endocrine system. The primary function of hypothalamus is homeostasis i.e.: maintaining blood pressure, body temperature, fluid and electrolyte balance, and body weight to a precise value called the set-point. It maintains the four basic biological needs or four F’s of survival: fighting, fleeing, feeding, and reproduction. Damage to hypothalamus influences food intake, weight regulation, thirst, body heat, balance, sleep cycle, response to pain, levels of pleasure, sexual satisfaction, anger and aggressive behavior. Its damaging effect on autonomic nervous system is seen when homeostasis is disturbed.
The amygdale is a part of the limbic system (also referred to as emotional brain) and is found buried within the cerebrum. It is connected to hypothalamus and prefrontal cortex influencing the emotional feelings and related physiological responses to certain situations such as those that warn of pain or other unpleasant consequences or signify the presence of food, water, salt, potential mates or rivals, or infants in need of care. Stimulation of amygdale in humans primarily causes fear and fear-related responses leading to an increased heart rate and pupil dilation. The amygdala of male is a bit bigger than that of the female. Stimulation of the amygdala will produce penile erection, sexual sensation (lust), representations or memories of intercourse and orgasm including its important role in pregnancy in case of women. It also has the ability to respond to emotional stimuli conveyed through sound, or by facial expression. Damage to the amygdale hampers autonomic responses and also leads impairment of the ability to learn new emotions as well as to react appropriately in different situations. Due to this, the patient fails to recognize a dangerous situation.
The hippocampus, another part of the limbic system, is associated with long-term memory and spatial navigation. In the case of Alzheimer’s disease, hippocampus is one of the first regions of the brain to suffer damage, leading to memory problems. People with extensive hippocampal damage may experience amnesia – the inability to form or retain new memories. The hippocampus acts as a memory “gateway” through which new memories must pass before entering permanent storage in the brain. Thus people with damage to the hippocampus can remember the distant past but cannot form new memories (Catherine, 2006).
1) Arriada-Mendicoa, N., Otero-Siliceo, E., & Corona–Vázquez, T. (1999). Current concepts regarding the cerebellum and cognition. Rev Neurol, 29(11), 1075-82.
2) Brain damage. (n.d.). In Science Daily. Retrieved October 8, 2009, from http://www.sciencedaily.com/articles/b/brain_damage.htm
3) Catherine, E. (2006). Memory Loss and the Brain. Retrieved October 8, 2009, from http://www.memorylossonline.com/glossary/hippocampus.html
4) Cerebellum. (n.d.). Retrieved October 8,2009, from http://www.neuroskills.com/tbi/bcerebel.shtml
5) Smith, S. (n.d.). What is medulla oblongata? Retrieved from http://www.wisegeek.com/what-is-the-medulla-oblongata.htm