Critical Assessment of an Invasive Method of Investigating the Brain
There are many different invasive ways of investigating thee brain
including chemical stimulation, ablation and lesioning. All invasive
methods artificially stimulate, and actually affect the brain. For my
example I am going to look at electrical stimulation.
The first person to study electrical stimulation on the brain was by
Olds and Milner in 1954. They applied a weak current to the pleasure
centre of the brain to a number of rats using small electrodes. The
rats themselves could trigger the electrical stimulation themselves by
pressing a lever. They found that apart from eating and sleeping the
rats would press the lever for hours of end. This was very important
research at the time and showed how electrical impulses affect the
brain, but it has a number of weaknesses. It is difficult to
generalise these findings to humans. As we have conscious thought, and
our brains are much more complex. Therefore what affects a rat's brain
may have no effect, or even increased affect on a human brain.
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...