Monday, November 11, 2019

Psychological Basis Of Behavior Essay

Until recently the causes of psychological disorders were not so clearly defined. Then advanced imaging techniques made it possible to see various areas of the brain and pinpoint areas that control behavior. It has been long known that the brain uses chemical messengers called neurotransmitters for signaling during its various processes. Advances in neuromedicine revealed that a lot of neurological and psychological disorders have a basis in imbalances between various neurotransmitters in the brain. Diseases like Parkinson’s, Schizophrenia and Obsessive-Compulsive Disorder are only a few where administering drugs that controlled levels of various neurotransmitters in the brain could control the disease symptoms and in some cases even provide a cure. Indeed, it was the discovery of these pharmacological agents that led to the discovery of newer agents that could control various neurological disorders by manipulating levels of neurotransmitters. Development of various drugs for schizophrenia was done on the basis of the fact that they had the ability to block dopamine receptors. In addition it was noticed that there was also an increased number of dopamine receptors present in these patients1. Similarly, in patients who suffered form Obsessive-compulsive disorder (OCD) an abnormality in the neurotransmitter serotonin was implicated and it was shown that drug therapy that did not affect 5-HT receptors was ineffective in the treatment of OCD6. Parkinson’s disease like schizophrenia also is due to an abnormality in dopamine levels but in Parkinson’s dopamine levels become depleted4. Parkinson’s disease is a movement disorder caused by the depletion of dopamine produced in the substantia nigra, a part of the brain that is responsible for voluntary movements of the body11. Parkinson’s disease is a neurodegenerative disease that affects 1% of the population. Its pathophysiology involves degeneration of substantia nigra. This portion is responsible for movements in the body. Various hypotheses have been proposed concerning the causes of the disease and include genetic factors, environmental factors and viruses. Amongst these genetic factors are considered the most important and mutations in various genes have been identified that are linked to Parkinson’s disease. Genes that have been implicated are PINK-1, DJ-1, and LRRK2 and it is thought that in addition to hereditary viruses and toxins are thought to cause theses mutations4. Parkinson’s disease is characterized by a fine pin-rolling tremor of the hands, rigidity, bradykinesia, an expressionless face called a mask like face and a parkinsonian gait characterized by small steps and reduced swing of the arms. Additional symptoms may be present and include difficulty in chewing and swallowing, depression, fatigue, dementia, speech problems, constipation, urinary problems and orthostatic hypotension7. Symptoms vary from patient to patient and can also have drastic emotional consequences for the patient. Diagnosis is often difficult as there are no tests available and is usually made on history and examination of the nervous system. Various treatment options are available and are mainly aimed at increasing the levels of dopamine in the brain. These include Levodopa, which is a precursor of dopamine and the nerve cells use synthesize dopamine. Other drugs like bromocriptine, apomorphine and pramipexole act by imitating the activity of dopamine4. There is no definitive cure for this disease and the treatment is only symptomatic. Adjuvant therapy may be given to relieve symptoms such as depression. Schizophrenia is another disorder that is caused by an imbalance between dopamine levels. The difference is that high levels of dopamine are found and the disease has mainly psychiatric manifestations. The cause of schizophrenia still remains unknown and this has been hampered largely by the different subtypes of the disease presenting a large variety of symptoms and involving different areas of the brain. It is also a feature of diseases like Alzheimer’s and Huntington’s disease9. Schizophrenia is characterized by auditory and visual hallucinations, delusions in which the patient thinks that his thoughts are being controlled externally and paranoid behavior believing someone is poisoning him, disorders of movement, cognitive dysfunction and emotional symptoms such as lack of interest in surroundings and social withdrawal2. Newer research has suggested that people with schizophrenia may experience an inability to smell certain items suggesting a disorder in the orbitofrontal region of the brain and surprisingly this sensory deficit has also been found in patients with Parkinson’s disease10. Other studies indicate that abnormalities in the amygdalia a region of the brain dealing with psychological processes may cause schizophrenia and other psychiatric disorders8. Though the cause is still doubtful it has been seen that schizophrenia runs in families thus suggesting a genetic factor. Environmental factors and trauma during birth have also been suggested as causative factors. In the past agents used to treat schizophrenia like chlorpromazine and haloperidol blocked both D1 and D2 receptors and caused extra pyramidal side effects2. But the newer agents like clozapine have a high affinity for D1 receptors and thus do not cause unwanted extrapyramidal side effects. Other agents that have fewer side effects are risperidone and olanzepine and are very effective in controlling symptoms. All of these agents act by reducing levels of dopamine in the brain thus enabling the control of symptoms. The genetic predisposition to schizophrenia is now widely known. Family history of mental ailments such as schizoaffective disorders, bipolar disorders and depression, are a very strong indication and predisposition to developing schizophrenia. However, complex researches in the pattern of schizophrenic disorders among monozygotic twins have not been able to establish the full authenticity of the claim. The scientists claim that schizophrenia has been associated with the â€Å"shy gene† or 5-HTT gene. Currently, having a schizophrenic geneticity is only the first link; further development is dependant on other factors as well. (Schizophrenia. com, 2007)12 Many claim that there exists a link between schizophrenia and the environment. This is based on the fact that increased risk of schizophrenia within families cannot be singly attributed to the cause of it alone. The environmental factors that are thought to play an important role in causing schizophrenia include psychosocial, biological and physical factors, which are in effect from birth till maturity. It is now claimed that the interaction of the genetic and the social or environmental factors are very important in the development of disease in schizophrenic patients. (Tsuang, 2001) Many of the environmental effects that come into play do so in preterm and in early childhood. The highest contribution seems to be the state of labor, for example, hypoxia, CNS damage RH incompatibility of the mother and child etc. Also, other prenatal factors may include maternal depression, bereavement and flood and famine. Rubella infections and infections of the CNS are also thought to play a very important role in the development of schizophrenia. Schizophrenia. com, 2007)12 Obsessive-compulsive disorder is another psychiatric disorder that has at its cause an imbalance between neurotransmitters. In this case the neurotransmitter is serotonin. The areas of the brain thought to be involved in this disorder are the basal ganglia and the frontal lobe6. People with OCD have obsessional thoughts and t he compulsion to carry out those thoughts repeatedly3. Patients often have an awareness of their abnormal thought patterns and are distressed by them but are unable to control them. Common symptoms are patients exhibiting rituals and having unwanted thoughts and behavior patterns. Patients may have unwanted thoughts of a fear of germs or hurting someone called an obsession and compulsions are the acts of carrying out those obsessional thoughts like repeatedly washing and cleaning or repeatedly counting or checking things over and over again3. Sometimes it manifests in conjunction with other psychiatric disorders like schizophrenia and depression. It often resolves when these disorders are treated. It has also been seen with diseases like Parkinson’s disease and Huntington’s chorea6. This disorder usually starts in adolescence and the patient is usually aware that he has some psychiatric ailment. The etiology is uncertain but Obsessive-compulsive disorder also has a genetic component. Though environmental factors are also a major cause, head trauma has also been implicated in certain cases6. Various treatment options are available including behavioral therapy. Drugs called selective serotonin reuptake inhibitors act by delaying the uptake of serotonin into the neuron and thus prolonging it’s action. This controls the deficiency of serotonin thought to be involved in causing obsessional symptoms. Drugs that are being used include fluoxetine, sertraline, fluvoxamine, paroxetine and clomipramine. Drug therapy used to treat other anxiety disorders is not effective in obsessive-compulsive disorder since it may not target the 5-HT receptors that are used by serotonin. Adams et al (2005)14 reported an up-regulation of serotonin receptors in caudate nuclei of OCD patients. Administration of SSRI drugs was tested in OCD patients. When untreated patients were compared with healthy normal individuals, it was found that cerebral 5-HT (2A) receptors binding were high in these patients. However, this difference was diminished when SSRI drug was administered to the patients. Different studies have reported that 5-HT reuptake inhibitors (SRIs) are most successful in treatment of OCD (Mansari & Blier, 2006). This suggests serotonin depletion may be a vital cause of this disease. Normally, serotonin is actively involved in moderating flow of messages from orbital frontal cortex to thalamus via caudate nucleus. Various pharmacological studies have suggested 5-HT concentration in OFC is regulated by 5HT2 like receptors. SRI drugs modify 5-HT receptors regulation of serotonin and hence mostly used in treatment of OCD (Mansari & Blier, 2006)15. Delgado and Moreno (1998)16 also reported that these drugs binding potency is related to hallucinogens. Pitterger et al (2006) reported that drugs that reduce elevated glutamate levels in brain might be effective in treatment of OCD. Pitterger et al (2006)17 suggested antiglutamatergic agent riluzole (Rilutek) play vital role in reducing glutamate hyperactivity in the cortico-striato-thalamo-cortical circuitry. Conclusion Overall a link has been found among various mental illnesses. This is evident by the fact that obsessive-compulsive disorder may be present in people who already have Schizophrenia or Parkinson’s disease. This overlap suggests that similar areas of the brain are involved in the etiology of these diseases and also that similar neurotransmitters may also be involved. Also interesting is the similarity in the deficiency in the sense of smell in both Parkinson’s and schizophrenia. As research progresses and advanced neuroimaging techniques become available it will become possible to interlink these diseases to one another. Special areas of interest may be the basal ganglia and the amygdalia as they are seen involved in a variety of neurological disorders. Parkinson’s disease is a neurological disease, having a progressive nature. There are certain peculiar signs and symptoms that a Parkinson patient presents with; these include tremor, rigidity, akinesia or bradykinesia. Etiologically, Parkinson’s disease is found in 1% of the population above 60 years of age. The ratio increases in people above 70 years of age. Although, also found in women, predominantly affects male gender. The role of environment in causing Parkinsonism is worth mentioning. Carbon mono-oxide and manganese, apart from certain pesticides play the major role in causing the disease. Parkinsonism among old aged people is idiopathic, but familial inheritance can be possible. A lot is not known about the role of genetics and inheritance of this disease, but occurrence in younger ages carries a higher probability of familial inheritance. It has been found that schizophrenia and Parkinson disease may share similarity by showing dysfunction of the prefrontal cortical areas of the brain. Also, both these conditions are the result or excess of deficiency of the levels of dopamine, which in turn dictates the treatment plan for such conditions. Similarly, patients suffering from Parkinson’s disease may show the presence of obsessive compulsive disorders, and the severity depends upon the length of the disease progression. The relation between these three conditions presenting in close relation with each other raise many questions about the progress of each disease, and whether treatments of each condition contain treatments for others as well. (Maia, 2003)13

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