Question: is it easy to miss things from an mri scan and what do you do if you can't see something on the scan picture?

Carolyn McGettigan answered on 16 Mar 2010:

There are different ways in which we might ‘miss’ things in an MRI scan.

1. Scanners aren’t perfect, and there are some parts of the brain that don’t come out as well in functional MRI images, for reasons associated with the physics of how the scanner works. So, you can get what’s called ‘signal drop-out’. This means that it can be slightly harder to detect activity changes in some parts of the brain. This can be difficult if you expect these areas to be involved in your study but there are all sorts of techniques being developed to improve these ‘artefacts’.
2. Sometimes we might not see activity in an experiment because of weaknesses in the experimental design. These can range from problems with the participants not performing the task as we intended, or that we didn’t choose our experimental materials (in my case, sounds) very carefully, or that we didn’t set up another aspect of the experiment well enough to get the most from the fMRI data. We usually run a ‘pilot’ of each experiment – maybe with just 4 or 5 participants – to make sure that the experiment runs well and that the data from these initial participants is engaging ‘sensible’ parts of the brain that we would expect to be involved in the task.
3. Analysing fMRI data can be pretty complicated and it might take literally a few months of trying out different approaches before settling on the method that gets the best from the data. Sometimes the activation changes can be quite small, so we can occasionally ‘miss’ interesting activations because we haven’t yet found the best way of ‘modelling’ the data. This doesn’t mean that we interfere with the data – just that brain data is very complex and it takes time to analyse it thoroughly.