Damage to the memory centres of the brain can not only impair one's ability to remember past occurrences, but also to imagine future or fictitious scenes, according to U.K. researchers.

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SYDNEY: Amnesia can impair not only one's ability to remember, but also to imagine new situations, U.K. researchers have shown.

Their findings, published today in the U.S. journal Proceedings of the National Academy of Sciences, suggest that an important function of memory is that it creates a foundation on which our imagination builds.

Amnesiacs have trouble recalling past occurrences, but, said co-author Eleanor Maguire, "Until now it was not known if the difficulties amnesic patients have are restricted to the past, or whether they could imagine future experiences or even imagine fictitious experiences."

In order to investigate this question, the team, from University College London and Cardiff University in Wales, studied patients with amnesia cased by damage to the hippocampus - a region of the brain which is crucial to memory.

The patients were asked to imagine certain scenes, such as lying on a beach or strolling through a museum. Their imaginings were recorded and compared to those of a 'control' group of people whose memory was intact and who had similar age, education and IQ to the amnesiacs.

The researchers found that scenes described by the control group were significantly richer and more detailed than those without brain damage, even when the team accounted for the possibility that the control group was simply recalling specific episodes from their own pasts.

"We found that the role played by the hippocampus was far broader than merely reliving past experiences," Maguire said. "It also seems to support the ability to imagine any kind of experience, including possible future events. In that sense, people with damage to the hippocampus are truly forced to live in the present."

When they took a closer look at the way amnesic patients described their imaginings, the researchers were struck by a distinct lack of coherence. The pictures painted in their mind's eye seemed to consist of fragmented images, instead of a holistic representation of an environment or setting.

According to Maguire, this provides an additional clue about the role of the hippocampus. "We believe … that the findings suggest a common mechanism that might underpin both recalling real memories and how we visualise imaginary and future experiences, with the hippocampus providing the backdrop, or environmental setting, into which the details of our experiences are bound."

Although researchers still have a long way to go before truly understanding memory, the shift in perspective offered by these findings could lead to new research strategies.

"I hope [our findings] encourage people to look beyond memory as merely being a record of the past," Maguire said. "Instead I think we should be asking, why do we have a memory system, what is its purpose? Our results show that imagining and so planning the future might be one purpose."