Mixing Memory has a fantastic account of recent research on memory distortions in schizophrenia that might explain the unusual experiences and strange ideas that characterise the condition.
Memory distortions are often tested by the use of ‘source monitoring’ or ‘reality monitoring’ experiments (largely invented by Marcia Johnson), where participants are given a list of words and asked to read some of the words out loud, and imagine themselves reading the others out loud.
Afterwards, participants are given a recognition test where they are shown each word and asked whether they read it out, or imagined reading it out.
There are many variations on this theme, but a consistent finding is that those with symptoms of psychosis are more likely to confuse words they imagined reading out with those they said out loud.
The Mixing Memory article tackles a recent study which ran a similar experiment while brain-scanning participants to see which areas would be active when distortions were present.
It turns out that less activity in an area of the frontal lobe called the the medial anterior pre-frontal cortex was linked to more memory distortion errors.
One difficulty though, is that this form of memory distortion is also present in people who have no signs of mental illness but have some delusion-like ideas or experience sensory distortions, suggesting that this effect cannot explain psychosis completely.
Link to ‘Was it Real or Did I Imagine It? Source Monitoring, Schizophrenia, and Our Grip On Reality’