Question: you said you\\\\\\\'re interested in how we get lost and recognise places, so why do we and how do we?

Tom Hartley answered on 20 Jun 2010:

Hi Leamma,

I could talk about this for a long time, but it would get boring, so I am going to try to keep it short for you (it’s not the whole story).

The brain, as you probably know, is made up of billions of tiny cells called neurons which send signals to one another and can represent different types of information. Part of the brain called the hippocampus is important for finding your way around and knowing where you are (as well as forming new memories). Signals sent by neurons in this part of the brain are related to where you are in the world. For example one cell might fire when you are in the North East corner of your kitchen, another might fire when you are in the middle of the room, and another in the South East corner and so on. It is thought (by some scientists at least) that these cells are used to form a map of the world, and your position within it.

If your hippocampus is badly damaged, you may lose your ability to form new memories – this is a very devastating condition (amnesia) affecting many aspects of everyday life – to get a better idea of this you can watch a video here. Fortunately cases of dense hippocampal amnesia (like Clive Wearing’s in the clip) are quite rare. They are still able to remember many things because we have lots of different kinds of memory, not all of which depend on the hippocampus (for example, they would be able to remember phone numbers for a short period of time, or how to play the piano. because these are different types of memory). But they do have problems with places and with getting lost.

We invented a new memory test where we ask peolpe to recognize places (actually computer generated landscapes – I made this picture to answer another question from Jade). Patients with damage to the hippocampus cant remember places, even for a short time, if they’re asked to recognize them from a different point of view . They can do it from the same point of view, because then you don’t need to recognize the place, just the picture and that doesn’t need your hippocampus.

One reason we want to understand how the hippocampus works is to help with a much more common problem, Alzheimer’s Disease which affects over 700000 people in the UK at the moment. Maybe someone you or one of your friends knows has the illness, which hits many people as they get into old age, impairing their memory, communication and movement. There is no cure for Alzheimer’s, but there are some treatments which can stabilize the worst symptoms for a time in its earlier stages (unfortunately this is only temporary). We hope that our memory test might help spot these people earlier on, as the disease often starts in or near the hippocampus, spreading later to other parts of the brain.

So not a very short answer after all, but there’s a lot more I could say (I didn’t even mention my brain imaging work, but you can read about that on my profile or in my blog).