The present study examined the neurophysiological correlates of true and false memories in a reality monitoring paradigm.

We know from studies using the DRM paradigm that true and false memories sometimes differ in terms of their experiential content.

Research in the neurosciences suggests that true and false memories also differ in terms of the brain regions that are active during recognition. In particular research in the DRM paradigm has found differences in activation in the prefrontal cortex between true and false memories.

In reality monitoring paradigms participants imagine some events and perceive other events. False memories occur when participants believe that they perceived events that they only imagined.

Prior research has shown that visual imagery can activate some of the same brain regions as visual perception. This may result in memory traces for imagined events that are a lot like the memory traces for perceived events and may result in false memories.
 

• Participants saw a word for 2.5 seconds under the instructions that they were to imagine the referent of the word.
• On half the trials participants then saw a rectangle for 300 msec. On the other half of the trials the participant then saw a color photograph of the referent 300 msec. There were a total of 350 items presented 175 of each type.
• On the test participants presented with words auditorially and asked to indicate whether or not the picture had been previously shown--Note this means that you should make the same responses both to non-presented words and words that had been presented without pictures.
• During both the test phase and study phase ERPs were being collected from the subject from various scalp locations.

Imagined items that later resulted in false memories were accompanied by greater parietal and occipital activation at study than imagined items that later resulted in correct rejections.

Pictures that were later correctly remembered produced greater overall activation at study than did pictures that were later incorrectly rejected.

Test Phase Results

True memories were associated with greater activation at posterior electrode sites than false memories.

In particular true memories and false memories differed in terms of their occipital activation and parietal activation with true memories tending to show a greater positive deflection.

Parietal activation may reflect activation of the Precuneus, an area that prior neuroimaging studies have found to be related to visual imagery. The activation of the Precuneus may occur because of reactivation of visual memory traces or the activation of a visual buffer.

It is also interesting that neural activity at encoding predicted false memories. Greater occipital activation at encoding resulted in more false memories.

These findings show that visual imagery at study can result in false memories, and the more detailed the visual imagery the greater the risk.