- Compare normal development with what happens when obstacles are introduced to certain areas of deveopment
- Damage or remove areas of the brain and see what effect it has
- Implant electrodes to see what effect artificial stimulation has
- Observe normal behaviour and learning, and sometimes compare post mortem changes to the brain
Ethics of animal research
- Absolutists believe animal testing should never occur under any circumstances
- Relativists believe it is justified under certain circumstances
- Most people's reasons against animal testing include the pain caused to the animals, the indignity, the fact that animals often die during certain types of research, and the idea that we are exploiting those less able to express themselves for our own gain
- Most people feel more strongly about animal research done on animals we consider more intelligent or closer to ourselves - people don't care about sea slugs, but get very emotive about primate research
Ethics committees are in charge of deciding which research is allowed - they make relativist decisions based on whether the benefit to humanity outweighs the negative effects to the animals
Artificial stimulation of human brains
People undergoing brain surgery often agree to allow the scientists to artificially stimulate areas of their brain to see what happens.
Once the skull has been cut open the surgery is completed under just local anaesthetic because the brain tissue itself feels no pain - patients are awake and able to tell the doctors what effect different stimulations are having on their body!
This man played the banjo throughout his surgery to ensure the doctors weren't damaging areas involved in his ability to play! (See http://news.bbc.co.uk/1/hi/sci/tech/7665747.stm for video!)
Diseases or accidents that destroy or impair part of the brain have (sadly) provided us with the vast majority of our understanding of different regions and what they do.
Famously Phineas Gage had a lot of his left frontal lobe and midbrain destroyed in an accident and the fact that it completely changed his personality has shown us that these areas of the brain are involved in the control of emotions.
Dr Oliver Sachs chronicles many such stories from his time as a clinical neurologist, and his book, 'The man who mistook his wife for a hat' is an excellent and interesting read. Though not essential to this course it will engage you more with the topic and is not just written for pure scientists!
Computerised Tomography scans
Thousands of tiny X-ray beams passed through the head (or other parts of the body). They are reduced in strength (attenuated) by the density of tissue they pass through, and the strength of the ones that pass through is measured. The data is processed by computer into a cross sectional image of that part of the body. Used to identify major structures and detect larger problems eg tumours and aneurisms. Images are frozen in time.
Special dyes can be injected to make certain areas opaque so they show up more clearly
Magnetic Resonance Imaging
Finer detail than CT scans, produced using magnetic fields and radio waves to detect certain atoms, usually hydrogen. Different images form depending on the amount of water present in different areas, among other things. Lots of 2D images can be put together into a 3D structure. Used to diagnose damage, and show a snapshot of the brain.
Functional Magnetic Resonance Imaging
Allows scientists to watch the brain change with activity! Monitors uptake of oxygen in different areas, because deoxyhaemoglobin absorbs and then re-emits the signal, unlike oxyhaemoglobin. If an area of the brain is being used, it receives more blood flow, more oxyhaemoglobin is delivered, and less of the signal is absorbed - on the screen these areas appear to light up. Usually used to investigate normal brain function, but is now being considered as a diagnostic tool for things like Alzheimer's.
Problems with fMRI
So far it's the best that we've got, but there are still arguments about its usefulness:
- It's noisy, (like the others) which some patients find very stressful
- The patient's head has to remain completely still, which limits the use - any movement will reduce accuracy. Other parts of the body can be moved, which allows some flexibility
- There are also questions about its validity - some scientists argue that measuring the flow of oxygenated blood to certain parts of the brain only shows correlation, not cause (most scientists, however, are convinced that it is an effective tool).