It is a technology that has remained firmly in the realms of science fiction, but new research has provided hope for those hoping to be revived after being cryogenically frozen.

The study claims to have shown for the first time that memories formed before an animal has been frozen can survive intact after it has been thawed.

While the experiments were carried out in an organism with a somewhat simpler brain than humans – nematode worms – they answer an important question about the cryogenic process.

Alcore Life Extension Foundation in Arizona (pictured above) is one of the cyrogenic preservation companies where people have had their bodies or heads frozen in liquid nitrogen. New research suggests the techniques used to preserve the bodies - should it ever be possible to revive them - leave memories in tact

Overall there are not many creatures capable of being revived after being cryogenically frozen, and it has never been successfully achieved with any mammal.

However, if they could be reanimated, scientists have questioned whether the memory and personality of someone who had gone through the process would remain the same.

The freezing process can cause damage to cells if not conducted without cryopreservative chemicals, and the effects of these is not well understood.

LEECH CAN SURVIVE BIG FREEZE A leech has been found to be able to survive after being submerged in liquid nitrogen. Ozobranchus jantseanus, a parasite found inside freshwater turtles, can be successfully reanimated after exposure to an astonishing -196°C for 24 hours. It can also survive in temperatures of -90°C for nearly three years. The discovery was made by a team of Japanese scientists who found a still-living leech attached to a frozen turtle. Most organisms expire after freezing because of the damage caused by the water in their cells when it freezes. Advertisement

The new findings, conducted by researchers working for the cyronics industry, reveal that, in worms at least, memories stored in the brain can survive the process.

Natasha Vita-More, a researcher for the Alcor Life Extension Foundation in Scottsdale, Arizona, said: 'This is the first evidence of preservation of memory after cryopreservation.

'Further research on larger organisms with more complex nervous systems could prove to be beneficial to the issue of cryopreservation, including, specifically, memory retention after reviving.'

Worldwide there are only an estimated 300 people who have undergone cryopreservation after they have died in the hope that they can be revived using future technology.

However, the industry is extremely controversial and has attracted criticism from scientists.

Although a popular theme in science fiction movies such as Forever Young, Demolition Man and Austin Powers, it has never been possible to successfully revive a human or any mammal.

The researches showed worms trained to react to a smell reacted could still remember their training after being cryogenically preserved using either a slow freezing process or vitrification with protectant chemicals

Cryogenic preservation features in several science fiction films, including Forever Young staring Mel Gibson, shown above, but in reality it has never been possible to successfully revive any mammal using the process

Some species of frog, arctic fish and insects are able to survive multiple freezing and thaw cycles because they have a naturally occurring antifreeze in their cells that protect them from ice.

In other animals, freezing causes the growth of ice crystals that can burst or damage their cells.

In an attempt to combat this the cryonics industry has developed chemicals to protect the cells. Using techniques like vitrification – rapid cooling – can also help reduce damage.

This has allowed scientists to preserve mammalian cells and even an entire organ from a rabbit before reviving them, but never for a whole body.

The impact of using these techniques on the delicate structures of the brain has also been a subject of increasing debate.

To answer this Dr Vita-More and Daniel Barranco of the University of Seville, and the CryoBioTech research group at the University of Seville, trained the nematode worm Caenorhabditis elegans to respond in specific ways when they smelled benzaldehyde.

In a series of experiments, published in the journal Rejuvenation Research, they placed trained and untrained worms through different cryopreservation methods.

The researchers trained nematode Caenorhabditis elegans worms, like the one shown above, to react to the smell of benzaldehyde and found that they retained their memory of this after being cryogenically frozen

They found that while only a third of the worms that were preserved using a slow freezing method compared to those frozen using vitrification, both groups retained memories of how to respond to the benzaldehyde smell.

The worms were left frozen for 30 minutes before they were thawed.

The results showed those worms which had been cryogenically frozen equalled those that had not been frozen at all in tests of their memory for the smell.

The researchers said: 'We demonstrated that cryoprotectants used in both the slow freezing and vitrification processes do not affect, alter, or change the mechanism that regulates the olfactory imprinting and long-term memory.

Secondly, we determined that the process of cryopreservation methods of slow freezing or vitrification do not affect, alter, or change this mechanism.'