Why you can distinctly recall that school picnic after 20 years

Why is it that some people have a richly-detailed recollection of past experiences (episodic memory), while others tend to remember just the facts without details (semantic memory)?

Actually, these different ways of experiencing the past are associated with distinct brain connectivity patterns that may be inherent to the individual and suggest a life-long 'memory trait', a new study from Rotman Research Institute, Canada, shows.

"With ageing and early dementia, one of the first things that people notice is difficulty retrieving the details of events," said study's senior author Brian Levine from Rotman Research Institute.

"Yet no one has looked at how this relates to memory traits. People who are used to retrieving richly-detailed memories may be very sensitive to subtle memory changes as they age, whereas those who rely on a factual approach may prove to be more resistant to such changes," he said.

In the study, 66 healthy young adults (average age 24) completed an online questionnaire describing how well they remember autobiographical events and facts.

Their responses fell between the extremes seen in people with Highly Superior Autobiographical Memory (HSAM) or Severely Deficient Autobiographical Memory (SDAM) recently described by memory researchers.

The participants had their brains scanned at Baycrest with resting state functional magnetic resonance imaging.

The researchers focused on connections between the brain's medial temporal lobes and other brain regions.

Those who endorsed richly-detailed autobiographical memories had higher medial temporal lobe connectivity to regions at the back of the brain involved in visual processes, whereas those tending to recall the past in a factual manner (minus the rich details) showed higher medial temporal lobe connectivity to areas at the front of the brain involved in organisation and reasoning.

The study was published online in the journal Cortex.