Pinel highlights several types of research methods that are used within biological psychology. These include experiments which are used by scientists who want to determine cause and effect and nonexperiments which usually consist of quasiexperiments or case studies. Both human and nonhuman subjects can be used in research and rats, mice and primates are among the most common nonhuman subjects used. Research can also be either pure or applied. Pure research is conducted to gain knowledge about a specific area of interest and applied research is conducted to directly benefit humankind.
Pinel (2011) explains that there are six main divisions of biological psychology and the first is physiological psychology. This refers to the study of the neural mechanisms of behaviour through the manipulation of the nervous system. Silber & Wagner (2004) state that this can be done through methods such as lesioning, stimulation (using electrical currents or chemicals) and recording (using microelectrodes). The subjects of this research are usually animals and the research is pure.
The second division of biological psychology is psychopharmacology, which focuses on the manipulation of neural activity and behaviour with drugs. Methods used in this type of research include drug trials, and the subjects can be either human or nonhuman. The research is also usually applied. (Klein & Thorne, 2006)
Neuropsychology is another division, and Gross (2010) explains that it focuses on the effects of brain damage. This is usually done in human patients and is applied research. An influential study carried out in the area of cognitive neuroscience is DeGelder, Dolan, Morris & Weiskrantz’s (2001) study that investigated affective blindsight. The results from this study showed that people who are blind, due to damage to the primary visual cortex, still have some awareness of human emotion.
Psychophysiology studies the relation between physiological activity and psychological processes in human subjects. Usually, this is measured using methods such as the electroencephalogram (EEG) or eye tracking. Research is both pure and applied. (Pinel, 2011)
Cognitive neuroscience is concerned with the neural basis of cognition. Klein and Thorne (2006) state that it is the most current division of biological psychology and tends to involve using human subjects in non-invasive research that is both pure and applied.
Finally, the sixth division is comparative psychology. Comparitive psychologists aim to understand the evolution and genetics of behaviour by comparing the behaviour of different species. The subjects in this research tend to be nonhuman and psychologists often engage in ethological research, observing species in their natural environment. Research also tends to be pure. (Pinel, 2011)
As Gross (2010) explains, the biological perspective of psychology often comes under scrutiny and is involved in a number of key debates. However, trying to understand the brain through methods described above is extremely important for the development of knowledge about the brain and behaviour. Without it, people would not be able to develop interventions such as drugs to aid psychological disorders or problems brought on by Parkinson’s disease.
Describe the main components of a neuron and explain the function of two of them.
Pinel (2008) describes neurons as nerve cells that make up the nervous system and explains that they are specialised to receive, conduct and transmit electrochemical signals. Gross (2010) also explains that the nervous system is comprised of approximately 100 billion neurons and 80 per cent of these are found in the brain.
Neurons differ vastly in terms of their size and shape, but most share four main components. These are the cell body, dendrites, axon and terminal boutons. (Pinel, 2008)
Pinel (2008, p.32) describes the cell body as the “metabolic center” of the neuron. It contains organelles that coordinate the processes that are important for the cell’s survival. The dendrites are the fibres that branch out from the cell body and the axon is the long narrow fiber that extends from the cell body. Silber (1999) explains that the axon is covered by a protective coating called myelin and this coating has breaks along its length known as the nodes of Ranvier. There is usually only one axon for each cell body, but this single fiber may contain a small number of branches. Finally, the terminal bouton is the swelling at the end of each axon branch. Silber and Wagner (2004) state that within each terminal bouton are sacs known as vesicles which store neurotransmitter molecules
Pinel (2008) explains that the structures needed to keep a cell alive are found in the cytoplasm. In neurons, most of these structures are found in the cell body. The nucleus is the largest structure of the cell body and it contains the cell’s DNA, which directs the synthesis of proteins. The endoplasmic reticulum is also prominent in the cell body. This is a system of plate-shaped membranous sacs that is covered in ribosomes, where proteins are produced. The Golgi apparatus has a similar structure to the endoplasmic reticulum but does not contain ribosomes. Instead, it prepares proteins and other molecules to be either transported to other parts of the cell or released from the cell. Mitochondria supply the cell with energy and are scattered through the neural cytoplasm but are more prominent in the cell body. Neurofilaments and microtubules are also found in the neural cytoplasm. Neurofilaments provide skeletal like support for the neuron and microtubules transport substances within the neuron.
The dendrites are attached to the cell body and appear as a system of branches that differ in denseness. Silber and Wagner (2004) explain that the amount of branching depends on the type of the neuron and each branch has various regions which are thicker than others. This is known as postsynaptic thickening and it is here that the postsynaptic receptors are located. The main purpose of the dendrites is to receive incoming signals from other neurons, and this is known as convergence. Kalat (2009) explains that some dendrites also have spines, which are short outgrowths that increase the surface area available for synapses. McAllister (2000) indicates that proper growth and branching of dendrites are crucial for nervous system function.
Briefly discuss how the monoamine theory accounts for depression.
The monoamine oxidase hypothesis is a major theory of clinical depression. The theory proposes that depression is caused by underactivity at serotonergic and noradrenergic synapses. Serotonin (5-HT) and norepinephrine (noradrenaline) are known as monoamine oxidase (MAO) transmitters. (Silber & Wagner, 2004)
There is a large amount of supporting evidence for this theory, including Leonard’s (2000) review of evidence that a biochemical lesion in the norepinephrine or serotonin neuronal systems in involved in depression.
Gross (2010) explains that the relationship between serotonin and depression was discovered in the 1950’s when the drug resperine was given to patients with high blood pressure. The drug causes a decrease of norepinephrine levels in the brain which can lead to depression.
Tricyclics were also found to be effective in relieving depression during the 1950s. Klein and Thorne (2006) explain that these work by blocking the reuptake of noradrenaline and serotonin, leaving more of the transmitter in the synaptic gap. This makes transmission of the next nerve impulse easier.
The newest class of antidepressants are called selective serotonin reuptake inhibitors (SSRIs). These raise the levels of serotonin in serotonergic synapses, but do not affect noradrenergic synapses. (Silber & Wagner, 2004)
MAOIs are antidepressant drugs that prevent the MAO enzyme from breaking down neurotransmitters that increase both 5-HT and noradrenaline in the brain. A study by Boovariwala et al (2001) found that a higher level of MAO-A in the brain is the primary monoamine-lowering process during major depressive episodes.
Evidence from post mortem studies have also shown increased numbers of serotonin and norepinephrine receptors in people who have had depression. Stockmeier (2003) found that several post mortem studies of serotonin receptors discovered a significant increase in serotonin-2A receptors in dorsolateral prefrontal cortex in people who had committed suicide after suffering with depressive illness.
Claridge and Davis (2003) state that monoamine hypothesis is the most prominent biological theory of depression. Gross (2010) also highlights that when a metabolite, which is a by-product of the breakdown of neurotransmitters found in urine , blood and spinal fluid has been tested, levels of 5-HT are lower in people with depression. However, Davison and Neale (2001) believe that the measurements of this metabolite could be a result of various biochemical abnormalities. Also, the lower concentrations found are not a direct indication of levels in the brain.
Davison and Neale (2001) have also proposed that an increase in neurotransmitter levels is not a sufficient explanation for why drugs alleviate depression. This is due to the prolonged period of time (usually 7-14 days) it takes for a patient’s symptoms to decrease after starting a course of antidepressants.
Klein and Thorne (2006) propose that due to the problems of the original monoamine hypothesis, it has evolved into a theory that concentrates on monoamine receptor sensitivity rather than reductions in monoamine levels. This enhanced theory proposes that the delay in the reduction of symptoms in depressed patients taking antidepressant drugs results from time-dependant adaptational changes in the neurotransmitter receptors. This leads to increased norepinephrine metabolite levels because the brain is attempting to compensate for the decreased receptor sensitivity.