A new study conducted by neuroscientists at Duke University explains how we can feel confident and certain about events that never occurred. It all depends upon the area of the brain that is processing the memory.

Whenever we retrieve any past event from our memory, two areas of our cerebral cortex are simultaneously activated – the medial temporal lobe (MTL) located at the base of our brain, and the frontal parietal network (FPN), located at the top. Whereas the former (MTL) recalls specific facts about the episode, the later (FPN) tries to retrieve a gist of the whole episode. What the researchers found appears striking : the area of the brain an individual approaches when he tries to recall the past event determines whether it is likely to be false or true. Human memory, as distinct from computer memory, is prone to situational recall errors, and many people are often wrong about past events and episodes; indeed they may feel quite strongly about them although they never happened.

In the current study by Cabeza, functional MRI scans of the brain confirmed that when volunteers were confidently recalling factually correct events, there was increased activity in the MTL region. Because of the association of this area of the brain with specific facts, these memories tend to be vivid and rich. By contrast, “impressionist” FPN memory lacks details, is often vague and sketchy, and quite often factually incorrect. Cabeza and his team provides a practical insight into the application of this research to clinical use.

As we get older, our “specific” detailed memory gets gradually replaced by more general or global impressions of things and events, representing a gradual switch from MTL to FPN processing. In patients with Alzheimer’s disease however, both types of memories are lost early, providing a potentially useful early diagnostic tool.

This study, published recently in the Journal of Neuroscience, was a collaboration between Robert Cabeza and his colleagues at Duke University and Hongkeun Kim at Daegu University in South Korea.

Reference

Hongkeun Kim and Roberto Cabeza. Trusting Our Memories: Dissociating the Neural Correlates of Confidence in Veridical versus Illusory Memories.The Journal of Neuroscience, November 7, 2007, 27(45):12190-12197.

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