Question: How did scientists, over 50 years ago, supposed to find out information about the brain without MRI scanners?

Tom Hartley answered on 22 Jun 2010:

Hi gioula,

Most of our knowledge about the nervous system came from experiments with animals. The basic properties of nerves were investigated in squid (mainly because they have very thick nerve fibres). Some of the important properties of synapses (the connections between nerve cells which are strengthened and weakened when we learn something) came from studies with sea slugs. Many important experiments were done with electrodes implanted in animals brains while they were alive. Although this might seem cruel, this doesn’t hurt, and it provides detailed information about what each cell does. We would know very little about how the brain works without these experiments. Squid and sea slugs don’t have brains in any way comparable to ours, so most of the experiments were done with mice and rats, with some studies using cats, rabbits and even monkeys. In fact some of these studies are now (very rarely) carried out in humans, because people with epilepsy sometimes need electrodes put into their brains (to determine where their seizures begin, so that they can have an operation on the correct part of the brain).

Brain imaging lets us find out directly about the human brain, without using animals or electrodes, but it doesn’t tell us much about how individual cells work, so some of the animal experiments still continue today.

Before the advent of brain imaging, most of our knowledge about the human brain came from studying patients with brain injuries, neuropsychology and neurology. People with brain damage often show an interesting pattern of symptoms where some abilities are seriously impaired, while others are almost unaffected. By looking carefully at a large number of patients, or at specially selected cases in detail it is possible to learn quite a bit about how the brain normally works from the different ways it can go wrong.

Cognitive psychology involves looking at the behaviour of healthy people with carefully designed tasks. By comparing what people do when faced with different tasks (for example how quickly or accurately they recognize a word) you can also figure out a lot about the how the brain works.