When an object was felt by the left hand, it could be recognised by the left hand agin, but not named or recognised with the right hand.
This experiment supports the idea that each hemisphere has different functions (brain lateralisation) and the hemispheres are unaware of stimuli represented to the other hemisphere, without the corpus callosum.
This experiment had implications for learning more explanations for brain damage, in order to help patients in future. The experiment was also said to treat the individual epileptics, however the ethics of the experiment may be questioned; the patients did not necessarily volunteer for the experiment and they may have made a loss from the surgery. The method also had some issues – Only 11 people were tested, who were all epileptics, which does not provide a cross section of society. There was also no control group, for example epileptics without their corpus callosum severed.
Brain localisation has several cases of empirical evidence, including Wernicke ’s area (the place in the brain responsible for language comprehension), Brocca’s Area (the place in the brain responsible for speech), the case of Phineas Gage (who damaged the frontal lobe) and the case of HM (memory loss due to removal of hippocampus). There are some general cases of localisation in the brain, as listed above; however, there are several arguments against localisation, highlighting its limitations. The brain shows plasticity, which will be looked at later. Localisation is not the same for all people, there are many variations so it is not clearly cut. An example of this is lateralisation being more evident in one gender than the other. There are also several parts of the brain which interact to produce function, so the brain and neurons show emergent properties. Therefore localisation does control behaviour of the body in many ways as there are several direct connections between the brain and a certain bodily function or behaviour; however it is not the only contributor.
Plasticity of the brain (or neuroplasticity), is the ability of the brain and nervous system in all species, to change structurally and functionally as a result of input from the environment. Although localisation of parts of the brain for specific functions does exist, neuroplasticity also exists; the brain is flexible and can change the location of function in the brain, often in the case of brain damage or other environmental demands and localisation is not always fixed for individuals.
A case study relating to neuroplasticity is phantom limbs. Sometimes, after losing a limb, a person is still able to feel the sensations of the limb. One may also be able to feel sensation when touching another part of the body or feel sensation in another part of the body when touching the edge of the remaining limb. An example of this is Victor Quintero, whose cortex strip in the brain, which originally processed input from the face, took over the area that received input from the now missing hand. Therefore, when he touched his face, he could feel himself touching his missing hand.
Another example of plasticity is ‘Thinking about thinking’. It has been found that mind-sculpting can occur without input from the outside world. The brain can change by the thoughts we think, which is called ‘self-directed neuroplasticity’ by Schwartz. An example of this is when people imagine themselves playing a piano without moving their fingers. Their brain did change and they became better at playing the piece from simply imagining it.
Phantom limbs do support the fact that there is neuroplasticity; however they do not always occur when someone loses a limb. In the second example, of the mind being able to change the brain, Schwartz attempted to help patients with obsessive compulsive disorder and the information he received may have had implications for helping other patients in future. However only 18 patients were observed which is too small a number for strong reliability.
Other strengths of neuroplasticity involve of the following examples: taxi drivers in London, whose brain changes as they learn the structure of London and changes in the brain after meditation or juggling training. Therefore, neuroplasticity does change a person’s behaviour if there is exposure to a change, which may change the course of brain localisation.
The main limitation of neuroplasticity is the fact that there is brain localisation, which is the opposite of neuroplasticity). Noticeable changes in the brain do not always occur which decreases reliability, however recently neuroplasticity has been proved a factual process that occurs in the brain so we must accept that localisation and plasticity work together in the brain to determine a person’s behaviour.
It must be considered that to determine the behaviour of a person, one must at more than just the biological evidence. Neurophysiology in general ignores the changes that environmental experience cause. Methods in determining changes in the brain can have limitations which can decrease reliability of all the empirical evidence of both neuroplasticity and localisation. An example of this is electrical stimulation activating other parts of the brain as well. Finally, cognitive processes must be considered and by focusing on the physiology of the brain, researchers may ignore the implications of psychological findings and theories have for brain area functions. This stresses the limitations of both localisation and plasticity in contributing to behaviour.
Brain localisation works together with neuroplasticity in different areas of the brain, to contribute to a person’s overall behaviour. There is evidence for each idea, however neither can fully explain nor prove the actions of the brain. Furthermore, the brain uses localisation to control the body, as well as neuroplasticity, often in the case of changing external environments.