Until recently, most of our knowledge of the functions of the Nervous System was obtained through research using animals. However, this research provided psychologists with a firm understanding about the causes and the treatments of neurological and mental disorders. This research also led to the development of the use of drugs to help people with neurological disorders, and then finally to the use of surgical techniques. These techniques resulted in the treatment of disorders such as Schizophrenia and Parkinson’s disease.
Today there are many other research methods available to Psychologists that allow them to study the brain in more depth that would have been impossible to imagine many years ago. Today, methods have been devised to allow Psychologists to identify neurons that contain particular chemicals, and to take photographs of particular ions entering neurons when the appropriate ion channels are open.
One of the first research method used was Lesioning. This involves correlating a behavioural deficit with damage to a specific part of the nervous system. There are two ways to study this. The first way would be for a neuropsychologist to examine the effects brain damage, for example to the occipital lobe, which is situated at the back of the brain, and the effect has on brain damage has on the individuals visual perception.
The second way would be for the neuropsychologist to produce an experimental brain lesion. This is when an injury to a particular part of the brain is induced and is only ever practiced on the brain of animals for research purposes. As a result of this research it is now possible for surgeons to lesion parts of the brain to alleviate some forms of suffering. A recent revelation in Lesioning is the treatment of Parkinson’s Disease. In Parkinson’s Disease, cells using the neurotransmitter, dopamine, in the basal ganglia and other areas of the brain die and this results in the patient having tremors when they are resting. By Lesioning a small structure deep within the brain, these symptoms are prevented. This type of Lesioning is known as direct Lesioning because the surgeons already know the outcome of the treatment due to past research carried out in laboratories with animals.
When an animals brain is experimentally lesioned, the investigator hypothesises that the lesion will have specific consequences on the animals behaviour. If particular behaviours are disrupted, this suggests that the damaged part of the brain is involved in theses behaviours. To reach the region of the brain that requires Lesioning, the experimenter uses a device called a Stereotaxic apparatus to insert an electrode into the specific location of the brain. The experimenter passes an electrical current through the electrode, which produces heat and destroys the small portion of the brain around the tip of the electrode.
A Stereotaxic apparatus can also be used to insert wires for recording the electrical activity of neurons in particular regions of the brain. An electrical current can also be passed out of the brain using this technique. If an electrical connector on an animals skull is attached to an electrical stimulator, current can be passed to a portion of the animals brain. This current activates neurons located near the tip of the electrode. This allows the experimenter to determine how this artificial stimulation of the brain affects the behavior associated with it.
Stereotaxic apparatus is also used on Humans. An example of this is the Lesioning used to relieve the tremors in Parkinson Disease. Surgeons can also insert electrodes into the human brain and record the electrical activity of particular regions to try an find out which areas of the brain are responsible for triggering epileptic seizures. After the brain lesion is made and the behaviour has been observed, the researcher must then verify the location of the lesion. To do this the brain has to be removed, and special histological procedures are used to slice the brain, dye the relevant cells and fiber tracts and examine the sliced under a microscope. This technique has led to an enormous understanding of the anatomy of the brain, and its related functions. Research has proven that the Cerebellum is involved in motor control and the temporal lobe is involved in auditory perception. Without the use of this technique, these facts would be unknown.
Neorusurgery origins date back to the late 1930s when two chimpanzees, Becky and Lucy had frontal lobectomies performed on them. The surgery resulted in an increase in calmness and passivity. Egas Moiz thought that this technique might be generalized to humans. In 1935 the first frontal lobotomy operations were performed. While treating some symptoms such as chronic schizophrenia, the prefrontal lobotomies were found to have serious side effects, such as apathy and severe intellectual impairments. A few surgeons refined the technique of psychosurgery and now perform a procedure called a Cingulotomy, which involves cutting the cingulum bundle, a small band of nerve fibers that connects the prefrontal cortex with parts of the limbic system.
Cingulotomies have been shown to be effective in helping some people who suffer from severe compulsions. In a recent study, Baer et al (1995) conducted a long-term follow up study of 18 people who underwent cingulotomy for severe obsessive-compulsive disorder. For each of these people, other forms of therapy had been unsuccessful. It was found that after their surgeries, the people in Baer’s study showed marked improvements in their functioning and the symptoms of depression and anxiety had decreased. Baer concluded that by removing the section of brain believed to be associated with compulsion, you therefore eliminated the behaviour associated with it.
Although psychologists can record the electrical activity of the brain from deep inside, it is a very invasive structure. Until recently, recording the electrical activity of the neurons in the brain involved inserting electrodes in to the brain. A new technique has now evolved that involves attaching electrodes to the scalp. This method is known as electroenephalography (EEG). Using this method it is now possible to record the brains electrical impulses without causing any harm or distress to the individual. These electrodes are positioned in a specific way so the researchers who are recording the activity from the electrodes will be recording them from consistent positions. EEG activity is seen in the form of line-tracing or electroencephalogram (EEG or ‘brainwave’). These can be coloured or in grayscale, which means there are areas of high and low activity that can be represented by darker or lighter colours. The EEG or brainwaves represent the different psychological states.
A benefit of using the EEG technique is that as well as being non-invasive; it provides a measure of the brains activity in real time. This allows psychologists to match the presentation of stimulus or a task with the brains activity. It allows psychologists to measure how the brain responds while it is engaged in tasks such as deciding whether tow figures rotated in a three-dimensional space are the same or difference (Williams et al., 1995).
The development of several different diagnostic machines which can be used to investigate the brain’s structure and activity has revolutionalised neuropsychology. This technique is called Neuroimaging. They are called this because they allow psychologists to visualize and obtain images of the brain. For example the CT scanner has the ability to produce a picture that looks like a slice of the brain. This scanner sends a narrow beam of X-Rays through a person’s head.
The beam is moved around the patient’s head and a computer calculates the amount of radiation that passes through it at various points along each angle. This results in a two dimensional image of a ‘slice’ of the patients head. This allows surgeons to determine the exact location of a brain lesion in a patient. Knowing the results of behavioural testing and the location of the lesion allows the surgeon to compare them and make inferences about the normal function of the damaged tissue.
A Magnetic Resonance Imaging (MRI) scanner provides pictures of the structure of the brain in much greater detail than the CT scanner. This is possible because it uses magnetic fields and radio waves instead of X-Rays. When a magnetic field is passed over the head, reverberations are produced by hydrogen molecules. These reverberations are picked up by the scanner which can then convert the activity into structural image. It is also possible to use the MRI in a functional capacity, that examines the brains functions as well as its structure. This is called Functioning Magnetic Resonance Imaging (fMRI). MRI and fMRI are non-invasive which means they can be used to investigate the development of function, e.g. Language, attention, vision and memory.
Bartels & Zeki (2000) recruited 17 healthy participants who were “truly, deeply and madly in love” to take part in their experiment in which they monitored the brains activity under different conditions. Using fMRI, they aimed to see whether distinctive patterns of brain activity would be produced by watching pictures of a loved one. They showed each participant pictures of partners and of three friends who they had known for a similar length of time.
They found a mixed pattern of brain changes, with activation and deactivation found when participants viewed pictures of their lover. Activity was significantly high in the insula, a part of the brain involved in visual interpretation of emotional information, and in the caudate nucleus and putamen, sub cortical structures which become active during positive and negative emotion. Deactivation was seen in the right prefrontal, parietal and middle temporal cortices, a finding similar to that reported in studies of expressed happiness.
Bartels & Zeki concluded that they, “have shown that underlying one of the richest experiences of mankind is a functionally specialized system of the brain.” By studying the brain and its anatomy, it has allowed many psychologists to conclude how function and location in the brain interact. Research has made it possible for psychologists to determine which behaviours are associated with specific areas of the brains anatomy. By doing this it has allowed psychologists to treat and cure many disorders, that without research and scientific advances, would never have been possible.
References
Smith, E. S., Nolen-Hoeksema, S., Fredrickson, B. L., & Loftus, G. R. (2003). Introduction to Psychology. London, Thomson Wadsworth. Green, S (2004) Principle of Biopsychology. New York, Psychology Press.