The first person to study how electrical currents effected the brains of humans was Penfield in 1958. He operated on people whom had severe brain tumours or epilepsy. He decided to carry out an experiment on a group of his patients (with their consent) into how electrical stimulation affects the brain. He gave his patients small electrical shocks to various parts of their cerebral cortex during the operations and asked the patients to report what they experienced (as the brain has no pain receptors the patients were fully awake).
He found that when he stimulated different parts of the brain there were a series of different affects on the patients. E.g. when he stimulated the auditory sensory cortex of one of his patients brain the person reported that they suddenly could not hear. These discoveries where quite magnificent at the time and led the way for more research into the brain and then later development of PET and MRI scans. But there are still a great number of problems in this research and any research using electrical stimulation.
For a start in the above experiment there was a very small sample of people used and therefore the results cannot be generalised to the rest of the human population. Also all of the patients had either brain tumours or epilepsy and therefore their brains were “abnormal” anyway. So none of the findings can be generalised to people with “normal” functioning brains. All experiments using electrical stimulation on the brain also lack ecological validity due to the fact that the impulses are abnormal and artificial. Therefore they may not reflect the actual function of the cortex. Also no one really knows what affect theses impulses are having on the brain, i.e. they could be damaging to the patients.
- Describe and critically assess one non-invasive method of investigating the brain. (12)
All non-invasive methods of investigating the brain do not actually affect the brain but watch its naturally sending its own electrical impulses. This is one of the great advantages of non-invasive methods over invasive ones. The invasive method I am going to describe and assess is the EEG (electroencephalogram). Every neuron in the brain produces small electrical signals all of the time whether a person is asleep, awake, active, sitting down etc…These small signals are boosted and registered by around 30 electrodes glued to the head. The EEG is the only scan which shows the electrical activity of the brain. This has many advantages, especially for people whom have brain abnormalities.
Other scans show that the person has normal brain structure and no damage. But the EEG in many cases shows that the brain functioning is far from normal and this can explain the persons brain abnormalities. This is most important for sufferers of epilepsy. Most epileptics have normal brain structure and no brain damage yet suffer serious brain defects which can only be seen in the electrical functioning of the brain and hence be seen on the EEG scans. EEG’s can explain whether an epileptic has focal (one part of the brain affected) or multifocal (several areas affected). This can help a doctor decide if drugs are an appropriate treatment or whether neurosurgery might help.
Other people have used EEG in similar ways to the above. Othmer et al (95) used EEG as a biofeedback for improving Attention Deficit Hyperactivity Disorder (ADHD) and specific learning difficulties.
Although EEG are a very useful and important way of investigating the brain there are a number of disadvantages and problems. The scans can only measure the surface electrical activity of the brain and not the deeper activity (which may be important in a number of syndromes such as epilepsy). Also it is a very broad and wide-ranging scan. Although it can show whether a persons brain activity is normal or not, it cannot specifically pinpoint the region of the brain producing this activity.