This essay uses examples to examine how studies of people with brain damage or who suffer disruption to brain activity have provided evidence about the relationship between brain activity and behaviour in normal functioning.
There are several ways in which abnormal behaviour may be associated with a damaged or malfunctioning brain. These in turn may be used to describe the relationship between a normal brain and behaviour. Biological psychology argues that all elements of our individual psychological existence, including desires, moods, emotional responses, are biologically based upon neuronal activity within the brain. Emotions, for example are altered by neuronal system changes. Synaptic activity can change the neural system resulting in behavioural, cognitive and emotional changes under certain conditions. Amongst others, there are three specific examples that are of interest:
(a) Neurological diseases often cause a disruption to the transmission of certain chemicals, sometimes resulting in the failure to manufacture a required neurotransmitter. Parkinson’s disease, for example is associated loss of conscious control over motor functions. This is because of the deterioration or destruction of neurons dependent upon dopamine.
(b) Illnesses associated with neuroses and depression are sometimes treated with prescription drugs. These target specific synapses, which cause a change in certain areas of the brain, thereby altering the brain’s processing of information. For example, the part of the brain that generates anxiety in a person, may show inhibited activity through the effects of the chemical.
(c) So-called recreational drugs that may stimulate, depress or otherwise alter the neuronal system act by changing activity in the central nervous system. Synaptic changes affect information processing and consequently may affect behavioural, cognitive and emotional responses.
These examples illustrate the chemical intervention of neurotransmitters and synapses that may result in changes to behaviour. A synapse is a component of the nervous system where an electro-chemical signal passes from one nerve cell to another. People who suffer with schizophrenia often are diagnosed with a pathology associated with the behaviour of certain neurotransmitters in specific parts of the brain. When these neurotransmitters are monitored in people with schizophrenia, there is often over-activity recorded. This is also evidenced by the person being drawn to stimuli that would otherwise not receive attention. This is sometimes treated with chemicals that counteract this effect by reducing the brain’s overactivity in these areas.
The above examples demonstrate the link between what is observed in a malfunctioning brain and normal brain behaviour. In these specific cases it may be reasonable to make some cautious generalisations about normal electro-chemical brain behaviour from what is observed from a damaged brain. Knowledge gained from studying the behaviour associated with damaged or malfunctioning brains may help understanding of how behaviour is controlled by the complex intertwining of variables. The relationship between brain activity and observed behaviour are examples of this. Brain trauma caused by accident or invasive surgery may also have an impact on human behaviour. Surgery for brain cancer offers the opportunity to observe patient behaviour before and after the procedure.
Sperry pioneered a surgical technique for the treatment of epilepsy (Sperry,1969). Epilepsy is caused by regionalised, chaotic, electrical brain activity. The division of the brain into hemispheres separated by the corpus callosum provides the opportunity to compare right and left hemisphere activity. The corpus callosum integrates the activity of both hemispheres. Epilepsy in one hemisphere therefore tends to influence electrical activity in the other. Sperry showed that by severing the corpus callosum, epilepsy could be greatly reduced without negatively impairing the patient. Sperry also found that through training, specific learning could take place in one hemisphere with different learning taking place in the other.
The relationship between brain and behaviour can also be shown through the study of damage to the brain caused by other types of trauma, or cancer. Observing damage caused by strokes, which results in a loss of oxygen and nutrients to a part of the brain can also help the understanding of the brain and behaviour. Lesions caused by the destruction of neurons may cause behavioural changes which indicate changes in behaviour. This may help the understanding of how specific brain areas contribute to normal functioning.
The well-documented case of Phineas Gage ( Miell, Phoenix and Thomas p. 268) illustrates how partial brain damage may result in behavioural changes. Gage received a traumatic brain injury which he survived, but which resulted in extreme, aberrant behavioural changes. His ambulatory and motor functioning was however unimpaired. Through this and through subsequent research, it has been found that in the case of brain damage the workings of the remainder of the brain is revealed by the damage caused, and not the functioning of the damaged part itself.
Finally, clinical depression may illustrate development of the thinking in this area further. There is an argument that genetic predisposition may result in an individual’s susceptibility to develop depression. This is not to imply the inevitability that someone will suffer clinical depression. Early and later environmental factors may mitigate this. It may also be that someone with no genetic evidence to indicate a tendency towards depression might become depressed in extreme circumstances (Anisman and Zacharko, 1982).
It may be that certain genes influence depression and this may be evidenced in the nervous system.The effectiveness of drug-based therapy in some cases indicates the involvement of certain neurotransmitters in depression. It may be therefore suggested that there are anomalies in neurotransmission within certain neural systems. It might be inferred that certain genes might give an individual a tendency towards an abnormality in the density of neural receptors at a particular type of synapse.
It cannot, however be clearly argued that depression has a solely biological or social basis. Both elements have both subtle and profound effects on behaviour. Synaptic changes influence behaviour. Conversely, the environment can be seen to have an impact on the nervous system. Depression, as an illness can therefore be seen to have both biological and social influences.
Anisman, H. and Zacharko, R.M.(1982) ‘Depression: the predisposing influence of stress’, The Behavioural and Brain Sciences, vol. 5, pp. 89-137
Miell, D., Phoenix, A and Thomas K., (2002) Mapping Psychology, Open University, Milton Keynes.
Sperry, R. W. (1969) ‘Hemisphere deconnection and unity in conscious awareness’, American Psychologist, vol. 23, pp. 723-33