Question: i still dont understand how you test on brains?

Hannah Brotherton answered on 16 Jun 2013:

Hi travpro12

I test changes in the brain using a reflex in our ears. This reflex is similar to the one we have when we pull our hand away from a hot stove, it just involves muscles in our ears. We have small muscles in our ears, that have a reflex at a very high sound intensity, that is thought to protect us from loud noises. However, this reflex can be affected by our brain activity and how fast or slow it works. For example, if I put an earplug in a person’s ear, I am reducing the amount of sound going into the brain. The brain responds to this by increasing its activity, it is compensating for the reduced sound. This increased activity affects this reflex. By increasing its activity, the brain is more sensitive and is in a way more alert to sounds. Its on edge. So when I take the plug out and measure the sound intensity where the reflex occurs, it happens at a lower sound. So with a hot stove analogy, if our hands became more sensitive to heat because of extra nerve activity, we would pull away our hand from a stove that is only mildly hot. Our hand reflex is more sensitive to heat.

Why is this important? When people have a constant ringing in their ears, the brain is constantly on alert. The brain activity has been increased for such a long time, that the brain can hear this increased activity activity. Imagine our brains are like a car engine waiting at a traffic light. We can hear the engine but we are used to it and so ignore the sound, but if we rev the car (increasing the activity), we notice the sounds much much more. This is what is happening in people with ringing in their ears. Their brain is over active and they are hearing their own brain at work.

If I can understand how our brain increases its activity, it might be possible to learn how to decrease it…….leading to a treatment for people with constant ringing in their ears.

I hope this answers your question. Below I have also gone on to explain how we test brains in other parts of neuroscience/audiology.

You can test on brains in many different ways. So for instance, you can test on a brain in a human by using imaging techniques. In psychology and audiology, you can investigate which parts of the brain are involved in hearing. You can get a person to listen to sounds whilst imaging the parts of their brain that ‘light’ up during imaging. We can compare this to a person who has lost their hearing, do the same experiment and investigate the differences in which part of the brain is activated. The brain is in itself a living thing. It knows when it is damaged. For example, when a normal hearing person loses their hearing, the part of the brain normally involved in sound perception loses its function. However, the brain is clever enough to know this and tries to compensate for this. this is done by ‘recruiting’ other parts of the brain, which now become activated when a sound is presented. So what we notice in individuals that have lost their hearing, other parts of their brain, which are not normally involved in hearing, become activated when sound is present to the person.

This is just one of many ways we can test on brains. Other ways include brain slices and electrode placement (measuring the electric currents in the brain). Another more indirect way of testing on brains is through behavioural testing. Our brain is capable of learning and storing memories. This was first shown to occur in animals in the early 19th century. A scientist found that if you fed a dog and present a sound such as a bell whilst the dog was feeding, when you present the sound again without the food, the dog would start the ‘salivate’. The brain associated the sound with food and began to prepare the body for feeding. This is known as ‘pavlovian conditioning’ and forms the basic learning traits many animals show today. So, if you ever see a dog open a fridge after their owner says ‘fridge’, it is likely the dog gets a treat after this behaviour. So, the dog has associated this sound/word with the behaviour which leads to a treat. This forms the basis of animal training.